Space research in Finland

Aalto University
PO Box 13000
FI-00076 Aalto
Finland
http://www.aalto.fi/en

Space research at Aalto University spans the School of Electrical Engineering (Aalto-ELEC), School of Science (Aalto-SCI) and School of Engineering (Aalto-ENG). Activities at ELEC cover radio astronomy, plasma physics of planetary and Earth space environments, Earth observation by remote sensing methods, and small satellite technologies. Aalto-ENG covers GPS techniques, photogrammetry and remote sensing. Aalto-SCI activities focus on solar and stellar dynamo processes and the development of related numerical methods and data analysis tools, extending the space science and astronomy to a new realm of astroinformatics.

In the past few years, three new professors have been recruited and two new Academy of Finland -funded Centers of Excellence started operation at Aalto. Renewal of faculty has strengthened earlier research areas and expanded activities to cover new fields. Aalto MSc and PhD majors offer a full curriculum in space science and technology. Aalto is the only university offering a major in space technology.

Aalto space activities are nationally and internationally networked. National partners include the capital area research organizations, most notably University of Helsinki, the Finnish Meteorological Institute, and the VTT Technical Research Centre of Finland, as well as the Universities of Turku, Helsinki and Oulu under the auspices of the Finnish Centre for Astronomy with ESO (FINCA). Technology collaboration with the European Space Agency (ESA) has strengthened by the location of the ESA Business Incubation Centre (ESA-BIC) in the premises of the Aalto startup center A Grid.

The Metsähovi Radio Observatory hosts several radio telescopes dedicated to radio astronomical measurements. The largest telescope (14 meters), previously used for coordinated observations with ESA’s Planck mission, focuses on long time series of active galaxy variability and solar activity. It is also used in several networks to make high-resolution VLBI observations and dedicated geodetic VLBI measurements, as well as for high-precision tracking of spacecraft. Smaller telescopes are dedicated to solar monitoring.

Nanosatellite technologies have been developed in several CubeSat missions: Aalto-1, Aalto-2, Suomi 100 and Foresail-1. Both Aalto-1 and Aalto-2 satellites were successfully launched during 2017 and Suomi 100 satellite in December 3, 2018. The student satellite program continues to train multi-disciplinary engineers capable of designing, building, testing and operating spacecraft and its instrumentation under the auspices of the newly started center of excellence Sustainable Space, with Foresail-1 launched in May 2022. The satellite projects are conducted in wide national collaboration.

Space physics research covers topics ranging from space weather and space climate at Earth to plasma environments around solar system bodies. The work ranges from instrument design and building to satellite and ground data analysis and numerical modelling of space plasmas and their interactions with solar system bodies. Aalto is involved in European Space Agency missions such as Rosetta, Mars Express, Venus Express, BepiColombo and the upcoming JUICE, HERA and Comet Interceptor missions. The modelling tools serve as state-of-the-art interpreters of the complex interactions between solar wind particles and the studied solar system object. Combination of satellite data analysis and numerical simulations target key space physics questions such as plasma and energy transfer across plasma boundaries (especially reconnection) or interaction with planetary atmospheres especially pick-up ions). Long-term studies on magnetic disturbances in the Sun, solar wind and ground are proceed within centre of excellence ReSoLVE and geoscientific infrastructure G-EPOS.

Remote sensing research focuses on development of methods and microwave sensors for space-borne monitoring of Earth surface, especially phenomena typical of the northern boreal forest and sea ice. The photogrammetry and remote sensing activities cover dynamic phenomena of the environment through space borne, aerial, and terrestrial sensing systems. Methodology development includes electromagnetic imaging systems, especially their radiometric and geometric calibration. These multisensory imaging methods are applied to dynamic environmental modeling and geographic visualization of local and global physical phenomena. Aalto is also part of the Academy of Finland Center of Excellence in Laser Scanning Research.

Unique cubesat observations with the Suomi 100 satellite

Suomi 100 composite — A composite image of the aurora taken by the Suomi 100 satellite’s camera (top left corner insert) and the observations by the satellite’s radio instrument above the EISCAT heater facility (top right corner insert). The solid lines illustrate the view direction of the camera and the dot at the end of a dashed line the position of the heater.

Suomi 100 nanosatellite has made unique small satellite observations of the ionosphere and auroras (Figure ). The satellite made joint measurement with the EISCAT heater facility, which is located in Tromsø, Norway. Satellite’s HEARER radio spectrometer observed the transmitted 8 MHz radio waves on the low-Earth orbit above the heater (Kallio et al., 2022a; submitted). The observed signal provided information about the response of the ionosphere to energy input. Satellite’s camera instrument, in turn, took a unique photo of aurora in Northern Europe (Kallio et al., 2022b; submitted).

Modelling, analyzing, and visualizing turbulent, magnetized astrophysical flows

Solar dynamo simulations — A volume rendering of global convective dynamo simulations. Colors on the two spherical surfaces represent the radial velocity close to the surface and the bottom of the simulation domain. The meridional cuts show the azimuthal component of the inductive effect arising from turbulent convection for a previous lower-resolution run (left slice) and the new high-resolution run (right slice), red indicating positive, and blue negative values. The background image is from an instrument onboard the Solar Dynamics Observatory. Image credit Ameya Prabhu and the INTERDYNS PRACE project.

Understanding turbulent, magnetized plasmas is vital in many research areas, ranging from astrophysical research to fusion reactor optimization. The astroinformatics group develops high-performance computing tools for large-scale simulations and data analysis methods for magnetized plasmas, and performs cutting-edge modelling, for example of the solar magnetism and turbulence within the solar convection zone. The research of the group is funded mainly by the European Reseach Council through the Consolidator Grant UniSDyn (grant holder M. J. Käpylä). The recent research highlights include the completion of the upgrade of the test field data analysis suite to accommodate to situations, where strong magnetic background turbulence takes place (Käpylä et al. 2020, https://dx.doi.org/10.3847/1538-4357/abc1e8), and the completion of a high-order finite-difference solver fully adapted to run on multi-node GPUs in heterogeneous architectures (Astaroth repository, https://bitbucket.org/jpekkila/astaroth). During 2020, the group was awarded 57 Million CPU hours through PRACE to the INTERDYNS project, to compute turbulent transport coefficients in solar-like stars (see ), for the first time in the regime, where a small-scale dynamo instability occurs simultaneously with the large-scale dynamo generating the global magnetic field of the Sun. The results show that deeper “inversion layers” of the inductive effect arising from turbulent convection are formed, which may help to solve the controversies related to explaining the solar dynamo mechanisms.

Geospace research with the Suomi 100 CubeSat

The Aalto carries out space weather and aurora research with their Suomi 100 geospace cubesat using its radiospectrometer and white light camera instruments. The satellite was launched in December 3, 2018. After the initial testing phase, the first science phase started in early 2019 with an emphasis on the camera observations (), especially, on taking photographs of auroras. The second science phase started in the summer 2019 with the radiospectrometer being used to make both global and local measurements in the frequency range 5–8 MHz. The local measurements include also joint active measurements with the EISCAT ionospheric heater.

Space environment studies

Studies of the Earth's space environment focus on one hand on the long-term variability of the solar activity and space climate, and on the other hand on the short-term response of the space environment to the variable solar wind driving force. The long-term variability studies are conducted in collaboration with the University of Oulu, under the auspices of the ReSoLVE Center of Excellence. The Aalto activities focus on modeling the solar dynamo including both centennial and decadal variability, as well as on long-term variability of the geomagnetic activity, while the Oulu activities complement these by examining the larger-scale heliospheric processes.

Space environment studies have been performed with the GUMICS-4 global magnetohydrodynamic simulation (see ). Studies include examination of energy transfer from the solar wind through the plasma boundaries to the near-Earth space environment, and the corresponding dynamic processes and variability that occurs both in the magnetosphere and in the ionosphere. Recent focus of the studies has been on the critical role of the Mach number of the incoming solar wind flow in the capacity of the magnetopause to shield the energy flux ().

Cross-polar cap potential versus Ey — The cross-polar cap potential (CPCP) as a function of the interplanetary electric field Y component (E_Y) in GUMICS-4 (see Lakka et. al. 2018 for the details of the study). Red (blue) dots represent data points for which the solar wind Alfven Mach number M_A is larger (lower) than four. Both the colour of the points and the response of the CPCP on E_Y changes at E_Y=5 mV/m and suggests that the CPCP saturates with a dependence on the solar wind M_A.

Global hybrid plasma modelling

Global hybrid modeling of solar wind interactions with solar system objects is carried out by the space research group at the School of Electrical Engineering of the Aalto University in collaboration with the Finnish Meteorological Institute. The focus in the modeling work is on space physics and space weather phenomena and planetary and cometary plasma physics. Especially, we study Earth and Mercury, i.e. planets with strong intrinsic magnetic field and the magnetosphere, and the induced magnetospheres and ion erosion of comet 67P and Mars and Venus.

Overview of the Hermean plasma environment — A hybrid plasma simulation of the Hermean magnetosphere.

shows an example of a global 3-dimensional hybrid model simulation of the Hermean solar wind interaction (Jarvinen et al., 2020a). Coloring on the polar plane gives a snapshot of the solar wind proton number density. The increase of the density at the bow shock is seen in bright yellow. Lower densities (black and magenta colors) are found in the Hermean magnetotail. Magnetic field lines are shown near the ecliptic plane. Upstream of the bow shock the field lines are mostly oriented along the undisturbed interplanetary magnetic field (IMF) vector, which has a strong flow-aligned component due to the 17-degree Parker spiral angle. The field lines drape around Mercury’s magnetosphere downstream of the bow shock. In the northern cusp region, the IMF is found to connect with the intrinsic planetary magnetic field. Coloring on the field lines shows the north-south component of the magnetic field, which is perpendicular to the undisturbed IMF. Strong foreshock fluctuations are evident ahead of the quasi-parallel region of the bow shock.

illustrates the interaction of the solar wind with Venus in our global hybrid model. The blue-white coloring gives the solar wind proton density in the polar plane while the equatorial plane with green-yellow-red coloring shows the propagating foreshock ULF waves, and their interaction with the energization and escape of planetary heavy ions shown in red volumetric plot (Jarvinen et al., 2020b). Aalto team is extensively involved in the BepiColombo Mercury mission (e.g. Milillo et al., 2020; Karlsson et al., 2020; Bunce et al., 2020; Orsini et al., 2021) and, therefore, the model is also used to predict and analyze observations on BepiColombo. An example of the BepiColombo cruise phase analysis during the first Venus flyby on Oct 15, 2020 is shown in the figure.

Figure Y — A comparison between a global hybrid simulation of the Martian plasma environment and multi-spacecraft observations. Jarvinen R., Brain D.A., Modolo R., Fedorov A., Holmström M., Oxygen ion energization at Mars: Comparison of MAVEN and Mars express observations to global hybrid simulation, J. Geophys. Res., 123, 1678-1689, http://dx.doi.org/10.1002/2017JA024884, 2018.

shows an example of a comparison of a global 3-dimensional hybrid simulation of the Mars-solar wind interaction with multi-spacecraft observations on the Mars Express and MAVEN orbiter missions at Mars (Jarvinen et al., 2018). Oxygen ions escaping from the Mars upper atmosphere through the heavy ion plume experience strong finite larmor radius effects, which is seen in the spacecraft ion spectrometer measurements as well as in the model.

Simulation illustrating the effect of different cometary ion production processes around the comet 67P/Churyumov-Gerasimenko. Streaming content.

demonstrates the relative impacts of different physico-chemical processes around the comet 67P/Churyumov-Gerasimenko (Alho et al., 2019). Aalto team has developed a comprehensive 3D numerical space plasma model, which enables studies of cometary space plasma environment and its response to varying solar wind conditions. Especially, the team evaluated the atmospheric loss rate of the 67P/CG and its dependence on the distance from the Sun.

Metsähovi Radio Observatory

Metsähovi Radio Observatory, located 30 km west of the Otaniemi campus, is the only radio-astronomical observatory in Finland. The primary instrument is the 14-metre radio telescope, used mainly for observing the Sun and extragalactic radio sources (so called quasars), and for international very long baseline interferometry (VLBI) campaigns. The main products are the data collected with various radio telescopes and other instruments. Observations are carried out on a “24/7/365” basis, and observing time is scheduled for 97 % of the hours of the year.

Metsähovi Radio Observatory primary 14-metre telescope during daytime observations. Video by Metsähovi: Niko Lavonen and Niko Kareinen; streaming content.

The backbone of the Metsähovi observing programme is the very long timescale monitoring of quasars (a special type of radio-loud active galaxies), whose data sets, going back to early 1980s, are among the most extensive and best sampled in the world. Similarly, radio maps of the Sun have been made in Metsähovi since 1978.

Asolar radio map — A solar radio map at 37 GHz. Photo: Merja Tornikoski, Metsähovi Radio Observatory.

One of the by-products of our solar studies (three different observing systems, various wavelength ranges) is the study of space weather, which has some impact on everyday life on Earth. Also studying water in the solar system or gaining information about our planetary system by spacecraft tracking experiments that we participate in, give us more information about the conditions in our own Solar system.

The vast majority of the data is used for scientific research by researchers and research groups around the world. In a typical year, 50-60 users (65 % of them from abroad) use Metsähovi data for roughly 120-160 peer-reviewed publication. Most of the use is astronomical, but e.g. the VLBI measurements enable also extremely accurate positioning and distance measurements. For this reason, the Finnish Geospatial Research Institute (FGI) leases the 14-metre telescope and MRO’s technical staff for their own research and services.

Metsähovi staff participates in teaching space science and technology (B.Sc., M.Sc. and doctoral levels, as well as LuMa activities with high schools, and public outreach). Because MRO is the only radio astronomy observatory in the country, courses and students from other universities use Metsähovi for their own hands-on education. In addition to course and project work, the staff at Metsähovi also supervise thesis work in various fields.

Metsähovi has recently gone through major infrastructure upgrades. The protective radome of the 14-metre radio telescope was replaced in June 2020, and the renovation and extension of the premises were completed around the end of the year. In the near future, the main receiver will be updated to allow for simultaneous multifrequency observations and participation in new international Very Long Baseline Interferometry networks. Finally, we are looking into possibilities to better support the growing Finnish nanosatellite ecosystem by providing ground station and downlink services.

Radome swap — Switching the radome in the early hours of June 24, 2020. Photo: M. Tornikoski, Metsähovi Radio Observatory.

Image of the supermassive black hole in the centre of the Milky Way

EHT image of a black hole — Image of the supermassive black hole in the centre of the Milky Way. Credit: EHT collaboration.

Metsähovi researchers are part of an international Event Horizon Telescope (EHT) Collaboration that released the first image of the supermassive black hole in the centre of galaxy Messier 87 in 2019 and the first image of the supermassive black hole Sgr A* in the centre of our own Milky Way in 2022. EHT uses very long baseline interferometry at short millimetre wavelengths to create an instrument that has angular resolution of 20 microarcsecond and can thus make event horizon scale images of these two supermassive black holes. For details, see the special issue of the Sgr A* results in The Astrophysical Journal Letters at https://iopscience.iop.org/journal/2041-8205/page/Focus_on_First_Sgr_A_Results.

Two supermassive black holes in the centre of the quasar PKS 2131-021

Two supermassive black holes orbiting around one another in the centre of the quasar PKS 2131-021. Animation: Caltech/R. Hurt (IPAC); see also https://www.aalto.fi/en/news/radio-observations-reveal-the-dance-of-two-black-holes

Observations made by Metsähovi and Owens Valley Radio Observatory (OVRO) revealed that radiation from the quasar PKS 2131-021 is subject to periodic variation, created by two orbiting supermassive black holes in the centre. Long time series are required for understanding such behaviour and the rare periodicity that follows the sine curve with a cycle of around five years. It is anticipated that the two black holes will merge in approximately 10 000 years from now. (O'Neill et al., 2022, https://iopscience.iop.org/article/10.3847/2041-8213/ac504b)

RadioAstron Black Hole Jet Observations

An international team has made ultra-high angular resolution images of the black hole jet at the centre of the giant galaxy NGC 1275, also known as radio source Perseus A or 3C 84. The researchers were able to resolve the jet structure ten times closer to the black hole than what has been possible before with ground-based instruments, revealing unprecedented details of the jet formation region.

A schematic figure of interferometric observations with RadioAstron. http://www.aalto.fi/en/current/news/2018-04-03-004/.

Supermassive Black Holes seen with Gravitational Lensing

An international research team with heavy involvement from Finland found an peculiar gravitational lense that magnified the supermassive black hole jet in a distant active galaxy. The lense, estimated to be a star cluster weighting about 1000-10000 solar masses in a spiral galaxy between the Earth and the and the active galaxy, was found in the radio monitoring data of the Owens Valley Radio Observatory (Caltech) and Metsähovi Radio Observatory (Aalto).

Schematic image of gravitational lens radio astronomy. — A schematic image of gravitational lens radio astronomy. http://www.sci-news.com/astronomy/gravitational-milli-lens-05134.html

Long-term variability of solar activity and solar wind disturbances

Solar data from SOHO, SDO and ground-based facilities such as Metsähovi and other ground-based telescopes are analysed to better understand the complex structure of the solar active regions and their variability over the solar cycles and grand minima and maxima. The Sun - Earth magnetic coupling is studied by the modern tools of machine learning, statistics and data analytics.

The evolution of solar wind over the decades and its effect to the magnetospheric dynamics is studied by the satellite and ground-based data. Magnetic activity in the magnetosphere and on ground was found to be strongly driven by the external conditions in yearly and monthly time-scales. High-speed streams and embedded magnetic fluctuations are found to best modulate magnetic disturbances at the high latitudes. Solar wind Alfvénic fluctuations are found throughout the solar cycle but most strongly they power geomagnetic activity in the declining solar cycle phase. The known rapid increase of geomagnetic activity in 2003 is reported to be related to the transition from Alfvénic fluctuations being embedded in slow solar wind until 2002 and in fast wind after that (Tanskanen et al., 2017a).

The yearly occurrence of the solar wind Alfvénic fluctuations within slow solar wind (< 400 km/s) and fast solar wind (> 600 km/s). The yearly solar wind speed is shown by a green line.

Geomagnetic activity and instrument development

Geomagnetic activity varies in time-scales from seconds and minutes to years and solar cycles. The seasonal variation of high-latitude geomagnetic activity has been recently found to closely follow the solar wind speed. The seasonal pattern of the high-latitude geomagnetic activity is modulated by the solar wind structure in addition to the equinoctial mechanism, heliographic latitude and the Russell-McPherron effect. Geomagnetic activity maximizes, on average, around the two equinoxes in spring and fall. Although the two-equinox pattern in geomagnetic variation is seen in multiyear averages, only one fourth of individual years since 1966 show this pattern. For the rest of the years, the two peaks in geomagnetic activity are seen purely during solstice months or as an equinox-solstice combination. The rare winter dominance in geomagnetic activity is reported for the declining phase of the solar cycle 23. That is found to be due to the elongated coronal holes in the southern solar hemisphere. Tanskanen et al., 2017b.

Rapid geomagnetic fluctuations are known to be closely linked to the high-latitude geomagnetic activity such as pulsations and substorms. There are latitudinal differences on magnetic fluctuations amplitude and fluctuation coverage. Midnight hosts most fluctuations below and noon above 72 deg. geomagnetic latitude. Latitudinal differences are larger in fluctuations coverage than in fluctuations amplitude. The largest differences in seasonal variation between midnight and noon are seen in the polar cap. Peitso et al., High-frequency geomagnetic fluctuations at auroral oval and polar cap, accepted to Space Weather, 2018.

Latitudinal variation of geomagnetic fluctuation coverage from 65 to 85 Mlat. The fractional derivative rate (FDR) measures the portion of the time that is covered by the magnetic fluctuations exceeding 0.2 nT/s. The largest fluctuation coverage below 72 GMlat is at midnight and above 72 GMlat at noon.

Geomagnetic activity has been monitored at high, mid and low-latitudes for more than a century by ground-based magnetometers. A new concept of small magnetometers, CubeMAG, has been developed enabling the detection of magnetic field disturbances at exosphere by small satellites and under water by seafloor magnetometers.

Modelling the long-term evolution of the solar dynamo

The Sun, aside from its eleven year sunspot cycle, is additionally subject to long-term variations (such as the Gleissberg cycle which manifests itself as amplitude modulation of the basic cycle) and irregular disruptions (such as the Maunder minimum) in its activity. The astroinformatics group at Aalto-SCI has made a huge computational effort to capture such behavior in global-scale convection dynamo simulations. The first ever solar-like solutions, covering a few magnetic cycles with the toroidal magnetic field showing clear equatorward migration in low latitudes and a poleward branch at higher latitudes, were obtained in wedges of compressible turbulent magnetoconvection by the group members in 2012 (Käpylä et al. 2012, ApJL, 775, 22). These models have since that time been extended considerably in time to be able to investigate the solutions on a scale of a millennium in solar time units (Käpylä et al. 2016, A&A, 589, 56, the “Pencil-Millennium” simulation). Our longest model produced so far covers 200 magnetic cycles, and reveals extremely complex behavior, including multiple dynamo modes, strong short-term hemispherical asymmetries, and epochs of disturbed and even ceased surface activity. Surprisingly, the most prominent epoch with suppressed surface activity (see , 25-50 yrs) is actually a global magnetic energy maximum; during this epoch it is particularly the bottom toroidal magnetic field, which reaches a maximum, demonstrating that during grand-minima-type events the magnetic field can be hidden in the deep parts of the convection zone, making the interpretation of such events non-trivial.

Time-latitude diagram of the azimuthally averaged toroidal magnetic field near the surface (upper panel) and at the bottom of the convection zone (lower panel), from Käpylä et al., 2016a.

Finnish Environment Institute
PO Box 140
FI-00251 Helsinki
Finland
http://www.syke.fi/en-US

Finnish Environment Institute SYKE is both a research institute, and a center for environmental expertise under the Ministry of Environment. SYKE is responsible for carrying out environmental research, monitoring and assessment, publishing and disseminating the results, and maintaining the appropriate information systems. As a national center of environmental information, SYKE provides expert services and takes care of diverse statutory tasks. There is a strong emphasis at SYKE on providing support to the decision-making process, including scientific and technical advice and through the development of methods to combat harmful environmental changes.

The Data and Information Centre of SYKE compiles and manages data systems, provides technical support and training on information technology, harmonizes and develops SYKE international reporting, and deals with other centralized aspects of data management. In addition, the center is responsible for the development of the Finnish Environmental Administration geographic information systems (GIS) and Earth Observation (EO) information systems. The EO research and development concentrates on operational monitoring of snow cover, lake ice cover, water quality, land use, land cover and phenology. The research includes validation of EO products with in-situ observations. Additionally, theoretical and experimental research on the optical characteristics of water, snow and land cover is performed in cooperation with national and international partners.

The customers of SYKE are researchers in environmental administration, governmental and municipal authorities, general public and private industry. Data are also delivered to the international research community in collaborative projects and upon requests.

The EO research and development at SYKE focuses on the utilization of the Sentinel satellites of the EUs Copernicus programme and other satellites such as the Landsat series for environmental monitoring and dissemination of EO based information in user friendly manner. We currently provide openly available and quality controlled EO based information for water quality, cryosphere (snow cover and lake ice extent), land cover and phenology applications. Through our TARKKA (www.syke.fi/TARKKA/en) service users can browse true color satellite images and various materials based on satellite observations for environmental monitoring and status assessment (maps and station site timeseries).

More information about SYKE’s EO data and services is available through the following links:

Satellite observations -homepage:: www.syke.fi/en-US/Open_information/Satellite_observations
EO examples:: www.syke.fi/EOstorymap
Open information services: www.syke.fi/en-US/Open_information
TARKKA - High resolution satellite images: www.syke.fi/tarkka/en

Finnish Meteorological Institute
PO Box 501
FI-00101 Helsinki
Finland
http://www.fmi.fi
http://space.fmi.fi

The Finnish Meteorological Institute is a governmental research institute responsible for the national weather service in Finland. It is the largest space research organization with about 130 staff members working in space research and Earth observation (within Space and Earth Observation Centre, FMI-SPACE). FMI is known for its scientific modeling capabilities including meteorological, climatic, and space plasma models and simulations. FMI expertise in space instruments dates back more than three decades and includes instrumentation for planetary atmospheres and plasma environments and general solar system research. FMI has a competitive record of building space instruments for planetary, space research and Earth Observation purposes, gathering and analyzing data, developing theoretical models for data interpretation, and publishing the results in leading peer-reviewed journals. FMI provides space & satellite technology services like project management, quality assurance and flight hardware manufacturing for space instrument projects of various research institutes and companies, and also analysis of satellite mission proposals per request by the Government.

FMI-SPACE includes three units: 1) Earth Observation Research, 2) Space Research and Observation Technologies and 3) Arctic Space Centre.

The expertise of FMI in Earth Observation (EO) is manifested by our participation on several satellite mission core science teams by ESA, NASA and EUMETSAT and active role in proposing new satellite missions. The research focuses on developing methods to interpret satellite observations of the Earth’s environment. This is an essential component in advancing further the utilization of the satellite infrastructures, like the EU’s expanding Copernicus programme. FMI’s ground-based observations in Sodankylä are used as key reference observations for satellites in Arctic and boreal areas. Increased focus in the EO research is given for climate research including carbon cycle and water cycle, high latitude monitoring, societal applications with international policy component in climate change mitigation, ozone layer protection, clean air and health. A new research component is identified in linking Earth observation more strongly to economic applications.

The northern location of Finland is optimal for monitoring space weather phenomena with ground-based instrumentation. In collaboration with the University of Oulu FMI operates networks of magnetometers, auroral cameras and Beacon receivers whose data are used both in research and services. The services include contributions to the ESA Space Situational Awareness program and the national 24/7 space weather service. Starting from 2019 FMI coordinates the PECASUS Global Space Weather Center, a service of ICAO to provide advisories for the international civil aviation. In research FMI’s main interests are in ionospheric tomography, near-Earth particle environment modelling and magnetosphere-ionosphere coupling processes. The institute has a long record in development of MHD simulations including operational codes for ensemble runs and 24/7 operations.

The FMI Arctic Space Centre operates in Sodankylä Northern Finland using cutting-edge technologies, developing techniques and leveraging its northerly location, to provide understanding of Earth's environment, developing services and infrastructure for society and the international community. The Centre’s three satellite antennas are used mostly for downlinking Earth Observation satellite data from spacecraft to Earth. The Arctic Space Centre also operates National Satellite Data Centre (NSDC) that is a central hub of providing and disseminating satellite data to Finnish users. The main data set NSDC distributes is the free and open Copernicus Sentinel data from all currently orbiting Sentinel spacecraft.

Perseverance rover mission for the exploration of Mars

FMI is among the scientific partners that provided measurement equipment for the NASA’s Perseverance rover, launched on July 30 and planned to land on Mars in February 2021. The pressure and humidity measurement devices developed by the FMI are based on Vaisala’s sensor technology and are similar but more advanced to the ones sent to Mars on the first Curiosity rover in 2012. A Spanish-led European consortium provides the rover with Mars Environmental Dynamics Analyzer (MEDA); a set of sensors that provides measurements of temperature, wind speed and direction, pressure, relative humidity, and the amount and size of dust particles. FMI’s pressure and humidity sensors are part MEDA. The new mission equipment complements the Curiosity rover. While working on Mars, the Curiosity and Perseverance rovers will form a small-scale observation network. The network is only the first step, anticipating the extensive observation network planned on Mars in the future.

First accurate assessment of the Earth’s seasonal snow mass

FMI-SPACE researchers, together with Environment and Climate Change Canada (ECCC), made a major step in climate research by giving the first reliable estimate on the Northern Hemisphere snow mass. The article “Patterns and trends of Northern Hemisphere snow mass from 1980 to 2018” was published in Nature 21 May 2020, https://www.nature.com/articles/s41586-020-2258-0.

Read the article: https://rdcu.be/b4mE2

Distribution of seasonal maximum snow mass on the Northern Hemisphere during the period from 1980 to 2018 based on GlobSnow approach that assimilates space-borne microwave radiometer data with ground-based observations of snow depth. Snow Water Equivalent (SWE) gives the depth of water released by instantaneous snow melt.

Ground conductivity plays an important role when estimating geomagnetically induced currents during space weather storms

Rapid variations in geomagnetic field during space weather storms are known to induce harmful currents in long man-made conductors, like power networks or natural gas pipelines. The time derivative of the horizontal component of magnetic field as measured by ground-based magnetometers (dH/dt) is widely used to estimate spatial distribution and intensity of these geomagnetically induced currents (GICs). Such magnetometer measurements are known to be affected both by the primary currents in the ionosphere and magnetosphere and by induced currents in the conducting ground (telluric currents). The impact of telluric currents becomes large with increasing dH/dt, but this fact is often neglected in GIC modelling by estimating primary currents with the total measured dH/dt. Juusola et al. (2020) show that such negligence can lead to significant errors particularly at coastal sites close to high-conducting ocean water and close to near-surface conductivity anomalies. This finding is based on 25 years of data from the northern European International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network as analyzed with the method of Spherical Elementary Current Systems (SECS), which enables separating the primary and telluric parts from dH/dt measurements. The IMAGE-SECS combination revealed dramatic differences particularly in the spatial distribution of the two current systems. Field separation into the two parts is therefore highly recommended always when magnetic data from dense observation networks are available.

Reference: Juusola, L., H. Vanhamäki, A. Viljanen and M. Smirnov, Induced ground currents due to 3D ground conductivity play a major role in the interpretation of geomagnetic variations, Ann. Geophys., 38, 983–998, 2020 https://doi.org/10.5194/angeo-38-983-2020.

A new method to reconstruct volumetric images on ionospheric electron density

Electron density variations are strong particularly in the Arctic ionosphere, where the variability is not controlled just by solar illumination but also by particle precipitation. Arctic region poses therefore an extra challenge for applications that rely on radio wave propagation in or through the ionosphere. Instead of statistical electron density models ray-tracing codes would need information on real, three-dimensional variations in the electron density.

FMI and the Sodankylä Geophysical Observatory have developed a computationally efficient statistical tomography method, called TomoScand (http://space.fmi.fi/MIRACLE/tomoscand/), for regional volumetric imaging of ionospheric electron density. As advancement to previous similar tools, the priors for the TomoScand inversion can be parametrised with physical units and understood as a probability distribution for realistic electron density profiles. In addition, comparisons of prior and posterior distributions provide an easy way to distinguish the regions of large uncertainties in the results.

TomoScand inversion is able to process electron density information from several different measurement concepts. The primary input data sources are Global Navigation Satellite Systems (GNSS) with their dense receiver networks and the Finnish network of ground-based receivers for Beacon signals (150 and 400 MHz) from Low Earth Orbit satellites. Occasionally available in-situ electron density measurements by space-based Langmuir probes (e.g. on-board the ESA Swarm mission) can be utilized in the reconstructions, as well. shows an animation of TomoScand results and time evolution of the measurements that have been used in the reconstructions. Validation of the TomoScand outputs with EISCAT Incoherent Scatter Radar measurements (Norberg et al., 2016) have demonstrated the capability of the new tool to provide electron density estimates consistent with the radar measurements. TomoScand can therefore be considered as a useful extension for the future EISCAT_3D system.

Still from unsupported video. — An animation of the receiver network, data points and results of statistical ionospheric tomography above Scandinavia.

Norberg, J., Virtanen, I. I., Roininen, L., Vierinen, J., Orispää, M., Kauristie, K., Lehtinen, M. S. (2016). Bayesian statistical ionospheric tomography improved by incorporating ionosonde measurements. Atmospheric Measurement Techniques, 9(4), 1859–1869. https://doi.org/10.5194/amt-9-1859-2016

Mars Curiosity detects seasonal variation of Mars atmospheric methane

FMI scientists have been part of the NASA Curiosity Rover science team and provided atmospheric pressure and humidity devices for the Curiosity mission. These devices were also used in correlation studies when Curiosity found evidence that methane in the Martian atmosphere has seasonal variation. Higher concentrations appear in late summer and early autumn in the northern hemisphere and lower concentrations in the winter and spring.

After having monitored the Martian atmosphere for two full Martian years (five Earth years), it can be concluded that the annual average concentration of methane in Mars’ atmosphere is 0.41 ppb. The seasonal variation of methane abundance seems to range from 0.24 ppb in winter to 0.65 ppb in summer. Also high methane spikes up to about 7 ppb occurring randomly were detected.

Methane could be produced through geologic or biologic processes, but the source still remains a secret. A plausible explanation for the methane seasonal variation is suggested to be slow seepage from an underground reservoir varied by seasonal changes of solar heating of the surface.

Seasonal variation of the average amount of methane in the Martian atmosphere.

Reference: Webster, C. et al., Background Levels of Methane in Mars' Atmosphere Show Strong Seasonal Variations, Science, 8.6.2018. http://science.sciencemag.org/content/360/6393/1093.

Improving the global picture of carbon cycle and greenhouse gases by satellites

The greenhouse gas emissions are driving the climate change which affects strongly the societies and political decision making. Reduction in uncertainties related to natural carbon cycles and global monitoring of greenhouse gas emissions, both natural and anthropogenic are urgently needed. Global satellites time series provide information that can be used to better understand regional changes and to quantify their effect globally.

Finnish Meteorological Institute (FMI) is on of the leading institutes in developing and utilizing satellite remote sensing to study the cryosphere. The unique ground-based reference site hosted by FMI and located in Sodankylä provides ground truth for numerous satellite missions. Joint analysis of satellite and ground-based data has recently resulted in new findings related to increased carbon uptake in boreal regions due to earlier spring recovery. This work was published in the PNAS journal (Pulliainen et al, 2017, PNAS).

Another highlight by FMI satellite remote sensing group is the development of a analysis method to detect emission regions of carbon dioxide globally using solely satellite observations. This methodology was applied to NASA’s OCO-2 satellite’s observations of carbon dioxide and have resulted so far two highly valued publications (Hakkarainen et al., GRL, 2016 and Eldering et al, Science 2017).

From Eldering et al, Science, 2017. Maps of the OCO-2 XCO2 anomaly. — From Eldering et al, Science, 2017. Maps of the OCO-2 XCO2 anomaly (mean in each grid box of the daily anomaly from the regional median) in 1° by 1° cells between September 2014 and April 2016.The anomalies are only plotted for the regions identified as clusters of enhancements due to fossil fuel burning.

Increased societal impact using air quality observations of OMI

The Dutch-Finnish Ozone Monitoring Instrument launched in 2004 on-board NASA’s EOS-Aura satellite has turned out to be highly successful mission with exceptionally stabile performance and low instrument degradation. The scientific use of the data is increasing along with the growing time series and the OMI observations have opened new possibilities for applications, thanks to the operational, near-real-time or quasi-near-time services, running also at the National Satellite Data Centre in Sodankylä. Such services include e.g. monitoring volcanic emissions and other air quality episodes.

During the last years, specific activities have taken place to support in increasing amount the societal needs related to utilizing and benefitting from the satellite data, e.g. to support environmentally sustainable solutions. This has resulted in closer collaboration with FMI and authorities, ministries, cities, industry and general public. The recently published overview paper of OMI summarizes the 14 years of OMI observations and research findings and demonstrates the societally important application areas including air quality monitoring, trends, air quality forecasting, pollution events, top-down emission estimates and support for Montreal protocol (Levelt et al., 2018, ACP).

Another highlight by FMI satellite remote sensing group is the development of a analysis method to detect emission regions of carbon dioxide globally using solely satellite observations. This methodology was applied to NASA’s OCO-2 satellite’s observations of carbon dioxide and have resulted so far two highly valued publications (Hakkarainen et al., GRL, 2016 and Eldering et al, Science 2017).

From (Levelt et al, ACP, 2018). OMI mission averages (2004–2016). — From (Levelt et al, ACP, 2018). OMI mission averages (2004–2016) for NO2 (a), absorbing aerosol index (AAI; b), HCHO (c), and SO2 (d). Total ozone column (O3; e) and surface UVB amount (f) are shown for 24 September 2006, the day with a record size ozone hole.

National Land Survey (NLS)
Finnish Geospatial Research Institute (FGI)
FI-02431 Masala
Finland
https://www.maanmittauslaitos.fi/en/research

Finnish Geospatial Research Institute (FGI) is a research and expert institute that carries out research and development for spatial data infrastructures. The FGI provides a scientific basis for Finnish maps, geospatial information and positioning and carries out research and development on methods for the measurements, data acquisition, processing and exploiting of geospatial information. FGI conducts innovative research and expert work within the field of spatial data. The esteemed international research institute offers reliable information for the benefit of society.

The strategic research areas of the FGI are Spatial Data Solutions Supporting Digitalisation, Dynamic Earth, Smart Environments and Interaction and Robotics and Intelligent Transportation Systems.

Space Geodesy

Started in 2012, all major space geodetic instruments at Metsähovi Geodetic Research Station has been under renewal, the last ones to be completed are the Satellite Laser Ranging (SLR) system (estimated commissioning 2021-2022) and the VGOS (VLBI Geodetic Observing System) radio telescope system (in commissioning phase). Due to the increasing demands for, e.g., GNSS satellite tracking and following the recommendation by the International Satellite Laser Ranging Service (ILRS), a modern kHz-capable SLR system is being built. The new system includes a fast-moving 0.5m telescope with a 2kHz laser as the light source housed in a modern observatory building with an automated dome. In addition to providing geodetic products, such as the position of the centre of the mass of the Earth, it can track both low orbit Earth exploring satellites and navigation satellites like European Galileo for enhancement of their orbits. The VGOS system consists of a 14-m dish radio telescope and a broadband receiver system to be used 24/7 for geodetic VLBI. Telescope was built in 2018 and the complete system is planned to be operational 2022. As a part of a global network, observations are used for determining the Earth orientation in space and maintenance of global reference frames, both vital for use of navigation satellites. GNSS Stations at Metsähovi are part of the national array of 47 GNSS stations called FinnRef. All the stations were built between 2012-2019 and have geodetic GNSS receivers and calibrated antennas. 20 stations belong to the European EPN Network and two, including Metsähovi, to the global IGS network.

A panorama of Metsähovi — Metsähovi Geodetic Research Station

FGI performs various research related to the abovementioned space geodetic techniques. FGI is developing techniques to observe satellite tracks and rotation states by active SLR and passive optical measurements. This is used, in addition to geodesy, to identify satellite types, to pick out-of-control-cases, to map space debris, and to predict risks for falls and collisions.

In an Academy of Finland -funded ALBEDO project (ended in 2020) FGI/GEOGEO was, together with University of Helsinki, developing novel techniques for estimating the Earth's time variable albedo from Earth's radiation pressure forces experienced on satellites. An online real-time Earth albedo web service is being commissioned, led by University of Helsinki, based on NOAA DSCVOR EPIC camera images.

In Academy of Finland Finnish Research Infrastructures (FIRI) project FLEX-EPOS (started in 2020) a high-precision and low-noise time and frequency link between Metsähovi Geodetic Research Station and the Finnish realization of UTC housed at VTT MIKES is being refined. This already established 60+km link over optical fibre enhances the performance of all space geodetic measurements in Metsähovi.

Earth-Space research ecosystem (E2S) was accepted as a FIRI infrastructure by Academy of Finland starting 2020. The VLBI, SLR and GNSS at Metsähovi Geodetic Research station, as well as the 20 FinnRef GNSS stations are part of this infrastructure. Other participating organizations are Sodankylä Geophysical Observatory of Oulu University (consortium leader), Metsähovi Radio Observatory of the Aalto University and the Finnish Metrological Institute.

From quasars to geodesy: how astronomy can enable a new era in ultra-precise geodetic measurements (NT-VGOS) is an Academy of Finland funded project in consortium with Aalto University Metsähovi Radio Observatory. The aim of the NT-VGOS is to bring together expertise from astronomy and geodesy to develop a new method to foster the ultra-precise Very Long Baseline Interferometry (VLBI) observations. The project reinforces and supports exploring the full capacity of new global geodetic observing network VGOS (VLBI Global Observing System) – a global infrastructure project in which Finland takes part.

Intelligent Shipping Technology Test Laboratory (ISTLAB) is an EU funded project, the goal of which is to build a jointly used laboratory and innovation environment for the study and development of smart maritime transport, with extensive use of GNSS navigation-based applications. The project focuses on the Port of Rauma and its smart navigation fairway. Consortium is led by the Satakunta University of Applied Sciences; the project’s main partners are the Finnish Meteorological Institute and the FGI.

Geodetic SAR for Baltic Height System Unification and Baltic Sea Level Research (SAR HSU) is an ESA funded consortium of German, Polish, Estonian, Swedish and Finnish partners. Within the project geodetic SAR (Sentinel 1) is used for connecting tide gauges to the GNSS network with active SAR transponders and GOCE based high resolution geoid.

Support Grant for the Galileo Reference Centre (GRC) is a coordinated effort among four partners from Netherlands, Sweden and Finland to provide GRC access to a range of facilities (permanent GNSS networks, and two radio telescopes) and expertise at the member state level for Galileo service performance monitoring.

Planetary spectrometry is an Academy of Finland funded consortium with the University of Helsinki where numerical methods and experiments are developed for scattering and emission by media of cosmic and terrestrial particles. The project culminates, in preparation for the ESA/JAXA BepiColombo mission, in the synoptic interpretation of X-ray fluorescence emission spectra as well as ultraviolet, visible, and near-infrared reflection spectra and images of Mercury obtained by the NASA MESSENGER mission.

Carte du Ciel (ended 2020) was an ESA funded project to digitize and measure photographic plates obtained during the Carte du Ciel -project in Helsinki 1890-1910. By combining the data with ESA Gaia astrometric satellite star catalogue, we can study the proper motions and brightnesses of stars over a timespan of about 100 years.

Orbital Laser Momentum Transfer (OLaMoT) was an ESA funded project, coordinated by Thales Alenia Space, France. The idea is to study, if satellites can be protected from colliding space debris by deflecting the debris particle orbit using the light pressure of laser. FGI analysed the effectivity of the momentum transfer and monitoring techniques. The project concluded that the technique is feasible and created a system concept and roadmap. As a spin off, it was also showed that by controlling the polarisation of the laser, the debris particle can be steered several degrees.

Navigation and Positioning

The research related to navigation and positioning currently covers both radio and sensor based navigation and their hybridization as well. The most topical and important topics in satellite positioning are the security and resilience of GNSS as well as improving its accuracy for location based services such as those related to intelligent transport in both land and sea.

The FGI coordinates activities in an H2020 project EGNSS-ENABLED SMART ROAD INFRASTRUCTURE USAGE AND MAINTENANCE FOR INCREASED ENERGY EFFICIENCY AND SAFETY ON EUROPEAN ROAD NETWORKS (ESRIUM), which aims at setting up a service to foster greener and smarter road usage, road maintenance, and to increase road safety. This will be done by means of an accurate and recent digital map of road surface damage and road wear. FGI ’s activities in this collaborative project are related to precise and secure EGNSS based localization for user vehicles.

The FGI contributes to the security of GNSS in national level by offering signal quality information in multiple frequencies for all four Global constellations: GPS, Galileo, GLONASS and BeiDou. This is carried out by means of a GNSS-Finland platform initially developed for Traficom, which uses the location data provided by the FinnRef reference network to provide real-time information on the quality of the GNSS signals close to each FinnRef station. Alert messages will be provided to Traficom in case of detection of signal anomalies, such as GNSS interference. There is a map based application showing the signal quality in terms of traffic lights. This development started in 2019 and was finished by the end of 2020. The GNSS Finland service is now operational. The resilience of GNSS positioning and timing in Finland will also be improved in a new project funded by the Academy of Finland security of supply specific funding.

In addition, FGI is involved in developing maritime AI based navigation and situational awareness and most recently, cubesat based PNT (Positioning, Navigation, and Timing) in indoor and challenging conditions together with the universities of Vaasa, Tampere, and Aalto.

Earth Observation

Sentinel satellites of the European Copernicus programme have supplied a large amount of Earth Observation (EO) free and open data to various thematic applications since 2015. They offer continuous measurement about the earth’s surface, and enable the extraction of time series data for environmental monitoring. In order to more efficiently make use of time series data approach in environmental applications, we have developed our own toolkit for the automated processing of EO data. The Earth Observation Data Information Extractor (EODIE) toolkit is based on command line (bash) and Python scripts that call several python libraries and ESA open access software, like SNAP and sen2cor. Several open Python libraries are utilized, among others, to read and reproject the shapefile, read and write raster files, calculate per polygon statistics and visualize the results. The toolkit can be used on both Linux and Windows systems, and on virtual computers such as the CSC environment.

Currently, we are participating in two European Space Agency projects related to the EODIE development.

ESA Sentinel-1 for Science Amazonas, project consortium consist of four partners: GISAT (Czech), Agresta (Spain), Norwegian University of Life Sciences, and the Finnish Geospatial Research Institute. The project aims at publicly releasable forest loss and gain maps produced using Multi-temporal forest Change Detection. The change maps will incorporate spatially and temporally explicit estimates of change, the type of change (e.g. deforestation, degradation, areas of natural or assisted regrowth), and provide data and tools for the scientific community for the future research. Project www site: http://project.gisat.cz/s14scienceAmazonas/.
Dragon5 project, which is a cooperation between the ESA and the Ministry of Science and Technology (MOST) of the P.R. China. Our Dragon 5 focuses on the exploitation of Copernicus Sentinels, Chinese, ESA and ESA Third Party missions EO data for geo-science and applications development. We have a collaborative project with the China University of Geoscience, Wuhan. The aim is to develop automatic tools for analysing satellite time-series data. ESA also provides opportunities for young researchers, training and research visits, within the Dragon5 project co-operation. Project www site: http://dragon5.esa.int/projects/automated-identifying-of-environmental-changes-using-satellite-time-series/.

Example of the EODIE toolkit output, with a three years of Sentinel-2 NDVI time series for one test forest stand in Finland, showing a clear cut in early 2018.

The Natural Resources Institute Finland (Luke)
Latokartanonkaari 11
FI-00790 Helsinki
Finland
http://www.luke.fi/en

Researchers and specialists working at Luke provide new solutions towards the sustainable development of the Finnish bioeconomy and the promotion of new biobased businesses. Together with its partners, Luke will build a society based on bioeconomy. This is done in four research programmes, concentrating on forests (Boreal Green Bioeconomy), food production (Innovative Food Systems), fisheries (Blue Bioeconomy), and societal ascpects (BioSociety). In addition to research programmes, Luke also carries out statutory government work. We monitor natural resources, certify plant production, inspect control agents, store genetic resources, produce data on greenhouse gases, support natural resource policies and produce Finland’s official food and natural resource statistics. The volume of work in Luke was in 2019 about 1300 person years, including about one person year of work on satellite-based remote sensing. In addition to this, several person years of work is done on airborne remote sensing and terrestrial laser scanning.

For monitoring forest resources, Luke conducts National Forest Inventory (NFI). NFI is based on statistical sampling, i.e. measuring of a large set of sample plots representing the whole Finland, all land use classes and all forest ownership categories. The most prominent application of satellite-based remote sensing in Luke is the Multi-Source National Forest Inventory (MS-NFI). It is currently producing numerical raster maps about 45 forest resource themes and municipality level statistics. MS-NFI uses high-resolution satellite images, the NFI field data, and numerical map data. The first MS-NFI results were produced in late 1980's. It is the first satellite image aided nation-wide inventory based on statistical framework.

New nation-wide products are currently made every second year. The latest forest resource maps, describing the forests in 2017 and the corresponding municipality statistics were published in 2019. The results for year 2019 will be ready in the first quarter of 2021.

The results are freely available. MS-NFI products are employed as input information in forest management planning by forestry authorities and for timber procurement planning by forest industries. Furthermore, the results have been used in ecological studies, e.g., in analyzing the quality of the habitats of key-stone species, for assessing the habitat and landscape values for nature conservation planning, and for other research purposes, and also in planning sampling designs.

Image of forest resource maps. — An example of the forest resource maps from MS-NFI-2015. The red colour channel is the volume of birch, the green channel the volume of pine, and the blue channel is the volume of spruce. They grey areas are not forest. The map overlay is based on the National Land Survey of Finland Topographic Map 2016.

The MS-NFI method is under continuous development to decrease the estimation errors at different spatial levels and to increase the temporal accuracy. Methods for comparing the different MS-NFI are also being developed. In the current method, the estimates are made to describe the forest resources as accurately as possible at a target date (July 31, 2019 for the next published products). New satellite sensors are used as they become available. The Sentinel-2A and 2B satellites have increased the availability of images with sufficiently low cloud cover during one growing season. Landsat 8 data is also used to make the cloud-free data set for the target year as complete as possible. The field data is updated from field work dates to the target date. This includes using growing models and finding large changes (usually clear-cuts) between the field work date and the image date.

The MS-NFI team is firmly established in the field of forest remote sensing. The MS-NFI method has been successfully tested or employed also outside of Finland. Its variation is in use Sweden and USA. Examples of other countries with collaborative work are Austria, China, Germany, Ireland, Italy, New Zealand, Norway, and Poland.

University of Helsinki
Department of Physics
POBox 64
FI-00101 Helsinki
Finland
http://www.physics.helsinki.fi/

Space research at the University of Helsinki is carried out mostly at the Department of Physics. Furthermore, the Department of Geosciences and Geography is active in analysis of meteorite materials and utilizes space facilities in geoinformatics. The newly established Institute of Atmospheric and Earth System Research (INAR) uses remote sensing data in climate and weather research. The multidisciplinary environment includes materials researchers involved in planetary geophysics, and the particle physics and astrophysics community cover a continuum from particle cosmology, observational cosmology, astrophysics, planetary research, and space environments of the Earth and planets. Space activities comprise at the beginning of 2020 approximately 100 FTE, of which some 50 FTE are in astronomy and space physics. We produce annually about 100 peer-reviewed articles.

The Finnish Centre for Astronomy with ESO (FINCA) is an important national organizational framework. In space research, we have active co-operation the Finnish Meteorological Institute (FMI) and with the Finnish Geospatial Institute (FGI) of the National Land Survey of Finland.

While strategic focus is in ESA and ESO activities, research utilizes observations from a variety of international observatories and spacecraft through collaboration and utilizing open databases. Particularly in training of new generation of space researchers, smaller-scale facilities are very useful, one important tool being the Nordic Optical Telescope. We also contributed to Aalto University’s student satellite Aalto-1’s radiation monitor in collaboration with University of Turku and plasma brake in collaboration with FMI.

Very important progress took place in 2017. From the beginning of the year the development of the world-wide unique space plasma simulation tool Vlasiator moved from the FMI to the University when Minna Palmroth started as a professor in computational space physics. A major success was the inclusion of the Centre of Excellence in Research of Sustainable Space, FORESAIL, in the CoE programme of Academy of Finland, 2018 – 2025. The UH led consortium has partners from Aalto University, University of Turku and FMI. Our space research is also the most successful in Finland in terms of ERC funding. At the end of 2020, our researchers had one Advanced Grant (Karri Muinonen) and three Consolidator Grants (Emilia Kilpua, Minna Palmroth, and Peter Johansson). Finally, Karri Muinonen will start a five-year term as Academy Professor in Sept. 1., 2021.

We have major contributions to ongoing and future large space missions and instruments. The Solar Intensity X-ray and particle Spectrometer (SIXS), together with the Mercury Imaging X-ray Spectrometer (MIXS), are on their way to Mercury on board the BepiColombo mission by ESA and JAXA, launched in 2018. Through the Foresail Centre of Excellence, a series of small geospace satellites (Foresail-1 to Foresail-3) is being prepared. We participate in the Science Ground Segment of ESA’ dark energy mission Euclid, to be launched most likely in 2022. The ESA Safety & Security program's Hera near-Earth asteroid mission (launch in 2024) carries a microsatellite Milani with the Finnish ASPECT hyperspectral imager payload co-developed by VTT and University of Helsinki. The ESA F-class mission Comet Interceptor (estimated launch in 2029) is carrying the Multispectral InfraRed Molecular and Ices Sensor (MIRMIS) payload co-developed by VTT and University of Helsinki with partners from the U.K. and U.S.A. Our experimental high-energy astrophysics scientists have pursued a Finnish participation in ESA’s planned X-ray satellite Athena (see below). There is also a strong interest in the future space-based gravitational wave observatory LISA.

Research Fields

Our research activities include interstellar medium and star formation, extragalactic astrophysics, cosmology, stellar astrophysics, solar activity and its consequences on planetary environments via magnetospheric and ionospheric physics and the physics of space weather, including terrestrial planets and small solar system bodies, as well as planetary geophysics.

In studies of the interstellar medium our focus is in the early stages of the star formation process. Here we use observations from the ground (e.g., ESO’s telescopes) and the satellites (e.g., ESA’s Herschel and Planck). In theoretical extragalactic research we study the formation and evolution of galaxies using both numerical simulations performed on high-performance computing facilities and analytical calculations. Our research in cosmology forms a seamless continuum from theoretical particle cosmology to space-based utilization of Planck observations where our team has contributed to the core of data analysis of cosmic microwave background observations. In planetary research our focus is on the orbital determination, shape, structure, and composition of asteroids and comets, e.g., by using the observations by the revolutionary ESA Gaia space mission, as well as the surface regolith, atmospheres and magnetospheres of solar system bodies.

With establishment of the new Centre of Excellence our space physics activities are now organized under its umbrella. The scientific emphasis is on Solar-Terrestrial relations, including both solar processes driving the space weather phenomena and the near-Earth response to them. The FORESAIL CoE is preparing for three CubeSatellites during its funding period focussing on radiation belts, controlled re-entry of satellites and electric sailing outside of the magnetosphere.

Our major contributions to future large space missions are the Solar Intensity X-ray and particle Spectrometer (SIXS), together with the Mercury Imaging X-ray Spectrometer (MIXS), onboard the Mercury mission BepiColombo by ESA and JAXA, to be launched in 2018, and the participation in the Science Ground Segment of ESA’s dark energy mission Euclid, to be launched most likely in 2022. Our experimental high-energy astrophysics scientists have pursued a Finnish participation in ESA’s planned X-ray satellite Athena. There is also a strong interest in the future space-based gravitational wave observatory LISA.

Meanwhile, in the Helsinki Computational Field Theory group we use simulations to study the properties and dynamics of early universe phase transitions, including the production of a stochastic gravitational wave background. Several years ago we showed (Hindmarsh et al., 2014) that sound waves in the plasma of the early universe are, for many scenarios, the most significant source of gravitational waves. This was a key result in making LISA a viable probe of cosmological phase transitions.

The First Global 6D Magnetosphere Vlasov simulation

Space is the richest reachable plasma laboratory, hence many of the fundamental and universal physics discoveries of the fourth state of matter – plasma – root in space physics. The near-Earth space is the only place one can send spacecraft to study plasmas. But: Normally one can send only a few satellites, leaving gaps in observations – and demanding modelling of space.

Modelling space plasmas has three broad categories from computationally feasible to almost impossible. The easiest is to assume that plasmas are a fluid, allowing using a coarse grid, where each cell are like pixels in a 3D camera picture. The computationally most demanding is to model electrons and protons as particles, in which case the simulation volume needs to be filled with tiny grid cells capturing electron physics. Since space is big electron-scale physics cannot extend to the entire near-Earth space.

There is a midway, in which protons are particles and electrons are fluid. Even this hybrid method is so demanding computationally that it has been feasible only in two spatial dimensions. Until now: the Vlasiator group at UH was able to extend the world’s most accurate space environment simulation Vlasiator to cover all six dimensions (Palmroth et al., in preparation.).

With the help of PRACE Tier-0 grant and the HLRS supercomputer Hawk in Stuttgart, the Vlasiator group completed the world’s first 6D simulation of one of the most mysterious questions in space physics: what causes the Earth’s magnetospheric tail to erupt plasma clouds at times? This question has not been answered by observations nor by previous fluid models, because the decisive physics occurs at ion-scales.

The world’s first 6-dimensional simulation of ion-scale dynamics within the near-Earth space. The solar wind flows into the simulation from the right. The Earth’s magnetic field is an obstacle to the solar wind flow, and hence a bullet-shaped magnetosphere is formed. A similar process makes water circulate a rock in a river. The latest Hawk runs are effectively making 4 million self-consistent spacecraft observations of the ion-scale physics within the near-Earth space, making it possible to study long-standing mysteries in space physics.

Observational prospects for phase transitions at LISA

Recently, Chloe Gowling and Mark Hindmarsh used an analytical model of the sound waves from phase transitions to investigate how much LISA would be able to tell us about the physics of the early universe. They used a Fisher matrix analysis to estimate the likely uncertainty in several key phase transition parameters, taking into account compact binary foregrounds (Gowling and Hindmarsh, 2021).

Predicted signal to noise ratios ρ for observing a stochastic gravitational wave background from a first-order phase transition at LISA. The parameters are the phase boundary speed v_w, the phase transition strength α and the mean bubble spacing relative to the Hubble radius r_*. The two plots at left include the LISA instrument noise and the foreground of unresolved stellar origin black hole binaries, while the two plots at right also include the unresolved galactic binary foreground. Also shown (turquoise dashed line) is the Jouguet detonation speed, the minimum speed at which the reaction front forms a detonation.

Analyzing solar eruptions from Sun to Earth

Coronal mass ejections (CMEs) are gigantic magnetized plasma clouds that propagate from the Sun into interplanetary space. Earth-directed CMEs can interact with our planetary magnetic field and drive various space weather disturbances. These disturbances can have wide-ranging impacts, from generating auroral displays to damaging communications satellites, making reliable forecasting important. The University of Helsinki space physics team uses advanced data-driven modeling and a variety of state-of-the art observations, including ground-based radio observations to analyze CMEs from the low corona to Earth’s orbit and beyond. The key focus is on the magnetic structure of the CMEs, which is crucial information for space weather forecasting. The UH team develops inner coronal simulations for realistic modeling of CMEs and the background solar wind they propagate into. The heliospheric component is provided by the 3-dimensional and time-dependent EUropean Heliospheric FORecasting Information Asset (EUHFORIA) model that is developed and tested in cooperation with e.g., KU Leuven. Observations from the recently launched Solar Orbiter, Parker Solar Probe, and BepiColombo spacecraft are used for revealing how CMEs evolve during their propagation and understanding turbulence and other embedded small-scale features.

The First Global 6D Magnetosphere Vlasov simulation

Researchers in the Vlasiator team made an impressive leap forward in modelling the near-Earth space accurately for the first time within the entire global regime including parts of the solar wind, magnetosphere and ionosphere. The run was made possible by adding an adaptive mesh to the Vlasiator's spatial grid (see ). A highly competitive computational grant through PRACE Tier-0 utilising one of Europe's largest supercomputers made it possible to achieve the world’s first global six-dimensional description of the near-Earth plasma state. This run is accurate both in space and in velocity space, representing a significant leap in space physics, as it can be used to study the grand challenges of Solar-Terrestrial research. The run was achieved in summer 2019, and the first results were presented in an oral presentation at 14th International Conference on Substorms, 30 Sep – 4 Oct, 2019 in Tromso, Norway.

Slices of plasma density along the midday meridional plane and the equatorial plane from a global 6D Vlasiator simulation, overlaid with the newly added refined spatial simulation grid.

Solar Superstorm of AD 774 accurately dated

Researchers at the University of Helsinki in cooperation with e.g. the Natural Resources Institute and the Sodankylä Geophysical Observatory conducted research on historic solar particle events. By analysing ¹⁴C records in Lapland pine trees, conclusive evidence was found, that the increase in the ¹⁴C abundances of tree rings dated to AD 774-775 was caused by a solar superstorm (Uusitalo et al., 2018). Furthermore, the separate analysis of early- and latewood enabled a timing considerably more accurate than previously, i.e. to June AD 774. Similar analysis are conducted for other historical solar particle events. This research is important for evaluating the risk solar superstorms cause on e.g. space instruments. The AD 774 superstorm can serve as an estimate of a worst-case scenario.

Early- and latewood ¹⁴C measurements for the event. The horizontal axis represents the calendar year of the growing season, and the vertical axis represents the age-corrected Δ¹⁴C. To visualize the average temporal difference between early- and latewood growth, the data points are set to June and August, respectively, for each calendar year. The baseline is defined as the average ¹⁴C of AD 770–773. The uncertainties represent a 1 σ error (Uusitalo et al., 2018).

Black hole mergers in a full cosmological setting

In the Helsinki Theoretical Extragalactic Research group, we have been simulating the dynamics of binary supermassive black holes found in the centres of massive elliptical galaxies undergoing mergers. Using the newly developed KETJU code we can now resolve the black hole merging process accurately for the first time in galaxies forming in a full cosmological setting. The calculation of the resulting gravitational wave signal provides predictions for the upcoming LISA mission to be launched by ESA in the early 2030s.

Sequence of illustrative example snapshots of simulation run A (5:1 mass ratio galaxy merger). The main images show the projected stellar density, while the insets show the stellar particles (blue), supermassive black holes (SMBHs, black), and sections of their trajectories in the regularised region (gray). The snapshots illustrate different characteristic phases of the SMBH binary evolution: the SMBHs first sink to the centre of the merging galaxy due to dynamical friction (left panel) and form an eccentric bound binary (middle panel) that shrinks due to stellar scattering, finally entering the strongly relativistic regime (right panel) where the binary shrinks due to gravitational wave emission, and where other relativistic effects such as precession of the orbit are apparent as well. The corresponding timescales and spatial scales are indicated on the figure. Mannerkoski et al., 2019.

University of Oulu
PO Box 8000
FI-90014 University of Oulu
Finland
http://www.oulu.fi/english

Space-related research in the University of Oulu is conducted in the Space Physics and Astronomy Research Unit (https://www.oulu.fi/spacephysics-astronomy/), consisting of three research groups, and at the Sodankylä Geophysical Observatory. Research areas include space climate and space weather research, solar effects on atmosphere and climate and other solar-terrestrial connections, ionospheric and magnetospheric physics, cosmic rays, astronomy, and planetology. About 60 researchers are working in these units, including 6 full professors and about 20 PhD students.

Space Climate research group

Space Climate group (SCG) concentrates on the long-term change (years to thousands of years) in solar magnetic fields and their effects in the whole heliosphere, including the near-Earth space, atmosphere and climate. Space climate has, during the last 20 years, grown to a central focus area in space physics, a topic of collaboration at the widest international level, e.g., within the PRESTO (Predictability of Variable Solar-Terrestrial Coupling) program of SCOSTEP (Scientific Committee on Solar-Terrestrial Physics). Space Climate group is one of the main originators of space climate and has had a leading role from the start of this field. SCG has one of the widest research programs in Space climate research in the world. SCG hosted the Centre of Excellence on Research on Solar Long-term Variability and Effects (ReSoLVE, http://www.spaceclimate.fi/resolve/) funded by the Academy of Finland in 2014-2019. The research is supported by several research grants, e.g., from Academy of Finland (PROSPECT, 2019-2023; and a post-doc project) and University of Oulu Kvantum Institute.

Recent research conducted under the ReSoLVE Centre of Excellence (2014-2019) by the SCG considered the past evolution of solar activity variations since the last 150 years and their influence in the heliosphere, near-Earth space, atmosphere and the climate system. These variations were studied with a wide array of data, e.g., observations of the solar magnetic field and spectral line emissions at several observatories from ground (WSO, MWO, KP, SOLIS) and satellites (SOHO/MDI, SDO/HMI); historical geomagnetic observations; historical satellite observations of energetic particles at low-Earth orbit (NOAA/POES) as well as several climate reanalysis datasets.

The research after ReSoLVE CoE has concentrated on making use of the past findings to develop new prediction methods for space climate (PROSPECT project). One of the most interesting developments is to use long-term solar wind predictions to improve long-term predictions of climate variations. These are connected to the topical research on the effects of solar wind driven energetic particle precipitation in the winter time middle-atmosphere and the climate system of the northern hemisphere. This research is done in collaboration with the international HEPPA-SOLARIS community. Recently the unique corrected dataset of energetic particle precipitation from POES satellites developed at SCG has been included in latest climate model intercomparison studies within the international HEPPA-SOLARIS community (Nesse-Tyssoy et al., 2021; Sinnhuber et al., 2021).

New results on the influence of energetic particle precipitation on polar vortex dynamics

It is now well established that energetic particle precipitation (EPP) from space into the upper atmosphere can lead to significant ozone loss in the mesosphere and stratosphere during wintertime. Changes in ozone lead to changes in the atmospheric heating/cooling rates and this has been thought to ultimately influence the strength of the stratospheric polar vortex, the strong westerly wind that forms each winter around the cold polar stratosphere. However, the mechanisms connecting the EPP to dynamical variations of the polar vortex have long been ambiguous especially because the connection seems to depend on the internal state of the atmosphere.

We have studied the atmospheric response of EPP from ground to upper stratosphere using ERA-Interim/ERA-40 re-analysis data and calibrated satellite measurements of EPP. We found that the strong EPP indeed causes ozone loss with associated thermal changes and enhances the stratospheric polar vortex, but that this connection appears much stronger during times when the equatorial stratospheric winds (so called QBO winds) are easterly (Salminen et al., 2019). We hypothesised that this might be because easterly QBO guides more planetary waves into the polar vortex, and that this makes the vortex more sensitive to EPP-related changes which are amplified by planetary wave feedback mechanisms.

We proved this hypothesis in subsequent studies by specifically concentrating on times preceding sudden stratospheric warmings, large breakings of the polar vortex, which are characterized by strong preceding planetary wave activity (Asikainen et al., 2020). We showed that the EPP influence takes place almost exclusively during such times. A closer analysis (Salminen et al., 2022) revealed that the enhanced planetary wave activity into the stratosphere concentrated on the equatorward side of the polar vortex is a key component enabling the EPP influence. It allows the small initial changes related to EPP-caused ozone loss to be strongly amplified into observable dynamical changes by so-called wave-mean-flow interactions.

These results highlighted the importance of planetary waves as an amplifier for the EPP effect on the polar vortex, but they also suggested that because of this amplification the EPP-influence could work both ways, i.e., while strong precipitation could enhance the vortex weak precipitation could potentially even lead to breaking of the entire vortex. We examined this possibility by conducting a statistical analysis of all sudden stratospheric warmings (SSW) occurring since 1957 (Salminen et al., 2020). We considered the influence of EPP, sunspots, QBO and El Niño Southern Oscillation on SSW frequency and found that EPP together with QBO phase strongly influences the occurrence probability of SSWs. The highest, over 80% probability of SSW occurrence was obtained when QBO is easterly and EPP level is lower than average. This important finding paves the way for improved long-term predictions of average winter weather in arctic regions, which is strongly influenced by SSWs.

Influence of By component of interplanetary magnetic field on solar wind-magnetosphere coupling

Recent research (e.g., Holappa et al., 2020; Holappa et al., 2021) has shown magnetospheric response to solar wind driving is significantly different for positive and negative IMF By when the Earth’s magnetic dipole axis is tilted (NH summer or winter). We have shown auroral electrojets, precipitation of magnetospheric electrons and protons to the ionosphere and the ring current are stronger for By < 0 than for By > 0 in NH summer, while the By-dependence is reversed for NH winter. This is demonstrated in Figure 1, which shows that for a constant value of the Newell coupling function , precipitation of energetic (>30 keV) electrons (measured by NOAA POES satellites) is stronger for By < 0 than for By > 0 in Northern hemisphere summer (or for positive dipole tilt angle).

While the physical mechanism of the explicit By-effect is still not fully understood it was shown (Holappa and Buzulukova, 2022) that the By-dependence can be captured by global MHD models. This promising result suggests that further MHD modeling might reveal the underlying physical mechanism.

Precipitation vs IMF and Newell — . The flux of precipitating energetic (>30 keV) electrons measured around dawn (04-12 MLT) auroral zone (50-70 geomagnetic latitude) by NOAA POES satellites in Northern Hemisphere summer (positive dipole tilt). Measurements are sorted by the Newell coupling function and IMF By (Holappa et al., 2020).

Cosmic Ray research group

The Cosmic Ray research group (CRG) is led by prof. Ilya Usoskin and focuses on full-range research, from direct ground-based and space-borne measurements to scientific data analysis and theoretical modelling, of cosmic rays and their atmospheric effects. With the advance in technological development, our civilization is more and more vulnerable to space-weather/space-climate radiation hazards, and the cosmic-ray induced effects become increasingly important. The group operates ground-based neutron monitors in Oulu (Finland) and Concordia (Antarctica) and is involved in AMS02 cosmic-ray experiment onboard the International Space Station. The group possesses top-level expertise in ground-based cosmic-ray measurements, analysis of solar-particle storms and long-term variability and provides reference data and analyses. The group is actively involved in many international research organizational activities, including IAU (International Astronomical Union), ISWAT (International Space Weather Action Teams) under COSPAR umbrella, IUPAP, etc. The group leads several research grants by the Academy of Finland (ESPERA project, 2019-2023; QUASARE project 2020-2024), Horizon Europe (ALBATROS project, 2023-2026), etc.

Extreme solar events and the worst-case scenario of a radiation storm

Sporadic bursts of solar energetic particles (SEP) are produced by solar eruptive phenomena such as flares or coronal mass ejections. During the Space Era, thousands of SPE events have been recorded including tens of strong ones that affect the Earth's atmosphere and environment, in particular by destroying the ozone layer in the Earth's atmosphere or posing serious hazards for space-borne electronic and even space- and aircraft crew. However, the question of the worst-case SEP event remained open until the discovery, employing the cosmogenic proxy data, of extreme SEP events, a factor of 100 stronger than the events of the Space Era, on the multimillennial time scales (e.g., Usoskin et al., 2013). Presently, five extreme events and three candidates are known (Cliver et al., 2002). The strongest known extreme SEP events occurred in 774 AD, 5259 BC and 7176 BC. The group coordinates the international efforts in a systematic study of these events, e.g., via leading an ISSI Internationa team on extreme events (https://www.issibern.ch/teams/solextremevent), and taking an active part in the discovery and verification of new events (e.g., Brehm et al., 2022; Usoskin et al., 2021). The group is also at the forefront of research on the terrestrial effects caused by such extreme events (e.g., Golubenko et al., 2020).

Despite many new datasets for the extreme SEP events being obtained, their nature is still unclear and the question is still open whether they are similar to ‘normal’ SEP events but stronger, representing a tail of the distribution, or a new unknown type of solar events as illustrated in Figure XX. The cosmic-ray group actively work in this direction, involving also data of super-flares on sun-like stars, to reveal the nature of extreme and set up a paradigm of the worst-case scenario of an extreme solar eruptive event.

Complementary cumulative occurrence probability distribution of solar events with the SEP fluence (over 200 MeV) exceeding the given value — Complementary cumulative occurrence probability distribution of solar events with the SEP fluence (>200 MeV) exceeding the given value. The open circles and stars denote the space-era measurements and proxy-based reconstructions, respectively. Blue, red and grey curves depict the best-fit Weibull/exponential distributions for the observed, extreme and combined statistics, respectively. The green bar denotes the EEE detection threshold (Usoskin et al., 2020). The plot is modified after Usoskin & Kovaltsov (2021)).

Ionospheric Physics research group

The Ionospheric Physics research group studies ionospheric physics and the geospace environment by utilizing different ground-based and satellite measurements. One of the key questions is to understand how space weather phenomena affect the coupled magnetosphere-ionosphere-thermosphere system, producing electric currents and fields in the ionosphere. Joule heating causes expansion of the atmosphere and geomagnetically induced currents on the ground (GICs) may affect technological systems like power transformers and pipelines. The group has led and participated in several projects funded by Academy of Finland, ESA and EU.

One of the most important research infrastructures used in ionospheric research is the international EISCAT incoherent scatter (IS) radar facility. With these radars, located on the mainland of Scandinavia and on Svalbard, researchers can study the Earth's ionosphere up to 1000 kilometer altitude. The mainland radars will be replaced in 2023 with phased-array EISCAT_3D radar facilities, with stations distributed in Norway, Sweden and Finland. This infrastructure (ESFRI Landmark) will be the world-leading facility of its kind providing volumetric observations of the high-latitude ionosphere. In addition, several other ground-based equipment such as all-sky cameras, magnetometers, riometers etc. are utilized which are operated by the Sodankylä Geophysical Observatory (SGO) and the Finnish Meteorological Institute (FMI). Satellite missions, e.g., ESA’s SWARM play also an important role in the research (see the science highlight below). We have developed several advanced analysis methods for ground-based and satellite measurements and participated in related international projects, including ESA’s 10th Earth Observation satellite candidate, Daedalus Phase 0 science and requirement consolidation study.

Auroral Current are Stronger in the Northern Hemisphere

Auroral current systems in the high-latitude ionosphere are concentrated to the auroral ovals that circle Earth’s magnetic poles. They consist of field-aligned currents (FAC) that connect Earth’s magnetosphere and ionosphere, their closure currents, and the eastward and westward electrojets. In a series of three papers we analyzed 6 years of magnetic field measurements from the European Space Agency’s Swarm satellites and concluded that while the auroral currents in the Northern and Southern hemispheres are very similar, they are not completely symmetrical. When averaged over all seasons, currents in the Northern hemisphere are 10-15% stronger than their southern counterpart (Workayehu et al., 2019), but the hemispheric asymmetry is modulated by the overall level of geomagnetic activity, so that the asymmetry is stronger during quiet than disturbed conditions.

In a further study (Workayehu et al., 2020) we discovered that there are large seasonal variation, with the hemispheric asymmetry being largest during local winters and statistically insignificant during local summers. Finally, by studying the effect of interplanetary magnetic field (IMF) on the hemispheric asymmetry (Workayehu et al., 2021, J. Geophys. Res. Space Phys., 126, e2021JA029475, https://doi.org/10.1029/2021JA029475), we found that the auroral currents are larger for IMF By>0 in the Northern Hemisphere (By<0 the Southern Hemisphere) than vice versa. The strongest asymmetry occurs in local winter and autumn for IMF By>0 in the Northern hemisphere and IMF Bz>0, when the north/south ratio of integrated field aligned currents is about 1.18.

Swarm FAC and electrojet currents — Analysis of Swarm satellite field-aligned currents (top row) and electroject currents (bottom row) during quiet conditions (planetary activity index Kp<2), when the asymmetry between North (left column) and South (right column) is most prominent.

The physical mechanism producing the hemispheric asymmetry is currently unknown, but our model calculations indicate that differences in the background electrical conductivity, affected by sunlight and magnetic field strength, or asymmetries in the convection electric field cannot explain the observations. Other possible reasons, to be investigated in the future, include or auroral conductance enhancements caused by energetic particle precipitation or asymmetries in the solar wind - magnetosphere coupling.

Astronomy Research group

The Astronomy research group investigates dynamical processes at many different scales, starting from the Solar System and extending to our Milky Way Galaxy and nearby galaxies in general. The extragalactic research focuses on galaxy formation and evolution. The group is particularly interested in the morphology and mass distributions of local redshift-zero galaxies, representing the endpoints of diverse evolutionary pathways starting from primordial dark matter fluctuations. This approach, called galactic archeology, is capable of answering the question in which level the galaxies formed in mergers of dark matter halos at high redshifts, and to what extent they formed due to slower processes related to internal galaxy evolution, or due to interactions with the galaxy environment.

The Milky Way Galaxy is a point of reference for the extragalactic work performed in the group. In order to understand the dynamical and star formation processes in other galaxies, knowledge is needed also of our own Galaxy. There is an ongoing research of dynamics of binary stars, in particular Cataclysmic Variables, which provides an excellent way to study how stellar evolution is affected due to accretion of gas onto compact objects. Members of the group play a leading role in the field of galaxy morphology, having a strong background in dynamical N-body modeling with their own codes. The group is involved in several international networks, i.e. the Spitzer Survey of Stellar Structure (S4G), the Fornax Deep Survey (FDS), and currently to SUNDIAL, a H2020 Innovative training network. S4G, a legacy Spitzer survey of about 3000 galaxies observed at infrared, and its ground-based optical extension on ESO-telescopes, is currently the most complete survey of the nearby universe. The ultimate goal of SUNDIAL is to train astronomy/computer science PhD-students to use EUCLID satellite data (totaling several petabytes), which will be the largest extragalactic database in the coming years: Oulu group is leading the Finnish participation to OU-EXT work package dedicated to combination of ground-based survey data to Euclid.

Artist's conception of the Europa Clipper spacecraft performing a flyby at Jupiter's moon Europa. (IMAGE:NASA/JPL).

Another focus of research in the Astronomy group are small particles found in the environment of the solar system planets (circumplanetary dust), which are detected by in-situ instruments on spacecraft. The grains carry information on the physical and chemical conditions at their points of origin, like the surfaces or even the interiors of the moons of the giant planets. For instance, the Cosmic Dust Analyzer instrument on board the Cassini mission at Saturn identified salts in water ice particles expelled from the active Saturnian moon Enceladus, revealing that this icy moon harbors a subsurface water ocean. Also Europa, one of the moons of Jupiter, is known to possess a subsurface ocean. The habitability of the moons of the giant planets is a central theme of the ESA Cosmic Vision programme and the NASA Decadal Survey, which makes Enceladus and Europa prime targets for future spacecraft exploration, because they may support astrobiological processes in their oceans. The astronomy group is involved in two space missions that will explore the Jupiter system. One of them is the ESA mission JUICE (JUpiter ICy moons Explorer), that will perform two close flybys at Europa after arrival of the spacecraft in 2029. The other spacecraft is the NASA Europa Clipper Mission, which will focus on the exploration of Europa and its habitability with a sequence of about 45 close flybys (see figure). The spacecraft carries, among other instruments, the SUrface Dust Analyzer (SUDA), an instrument that will detect dust particles that are released continuously from the surface of Europa when micrometeoroids strike the surface at large velocities. This process creates a dust envelope around Europa that will allow SUDA to directly measure the composition of particles lofted from the surface. The non-ice compounds, minerals and organics, are very interesting. Because of the fairly rapid geologic processes on Europa, recorded in its abundant surface structure (see figure), these substances give witness of the ocean composition. Thus, SUDA will be a key instrument to constrain the subsurface conditions on Europa.

The Sodankylä Geophysical Observatory (SGO), located about 120 km north of the Artic circle and 350 km from Oulu, conducts geophysical measurements of the ionosphere, atmosphere, magnetosphere, and solid Earth at 20 different locations in Finland, Sweden, Norway, and Svalbard. The SGO data archive spans more than 100 years allows studying the long-term evolution of the geospace environment. The Radio Science Laboratory of SGO has a long history of developing innovative measurement methods culminating in the recent construction of Finland’s largest radio telescope, the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA). KAIRA is a multi-purpose radio receiver used for atmospheric research and prototyping for the future EISCAT_3D incoherent scatter radar system. SGO has been granted 2,5 million euro of infrastructure funds from the Academy of Finland for the construction of the EISCAT_3D site in Karesuvanto, Finland. These funds are part of a 12,8 million euro allocation of funds by the Academy for the construction of the large international EISCAT_3D distributed incoherent scatter radar.

Abrupt shrinking of solar corona in the late 1990s

We have derived the longest uniform record of rotational intensities of the solar coronal magnetic field since 1968 using the Mount Wilson Observatory (MWO) and Wilcox Solar Observatory (WSO) observations of the photospheric magnetic field and the PFSS model of the coronal field. We found that the time evolution of the coronal magnetic field during the last 50 years agrees with the heliospheric magnetic field observed at the Earth only if the effective coronal size, the distance of the coronal source surface, is allowed to change in time. We calculated the optimum source surface distance for each rotation and found that it experienced an abrupt decrease in the late 1990s. The effective magnetic volume of the solar corona shrunk to less than one half during a short period of only a few years. This abrupt shrinking of the solar corona coincides with simultaneous changes in sunspots that are all likely related to the decrease of the overall solar activity, i.e., the demise of the high-activity period of the Sun during most of the 20th century.

Field lines — Figure shows one typical sample of a simulated coronal magnetic field configuration during four sunspot minima in 1976, 1986, 1996 and 2008 using Mount Wilson Observatory VSM instrument data. Corresponding values of the optimum source surface radius are noted above each plot. Figure shows that the structure of the coronal magnetic field has notably changed from the minima in 1976 and 1986 to the minimum in 2008. In the early decades, the typical minimum-time structure consisted of long magnetic fields lines connecting the high and mid-latitudes of the opposite solar hemispheres. During the recent minimum field lines are typically much shorter, closing mostly within the same hemisphere. This change reduces the radial extent of coronal magnetic field lines and the volume covered by closed coronal field lines. Ref: I. I. Virtanen, J. Koskela, and K. Mursula, Abrupt shrinking of solar corona in the late 1990s, 2020, https://doi.org/10.3847/2041-8213/ab644b.

Systematic re-analysis of major solar energetic particle events of the space era

Solar energetic particles (SEP) affect the Earth's atmosphere and environment, in particular by destroying the ozone layer in the Earth's atmosphere or posing serious hazards for space-borne electronic and even space- and aircraft crew. Understanding of these phenomena forms a major challenge in Space Physics. The era of direct measurements of SEPs by ground- or space-based detectors covers several decades and provides a large amount of information, which was, however, not systematically and consistently analysed earlier. We have made a major revision of the available information of 70 major SEP events for the last 60 years. The revision was made in the following directions: full revision of the GLE database including the correction of the variable background level (Usoskin et al., 2020a, https://doi.org/10.1051/0004-6361/202038272); update of the neutron-monitor yield function with improved accuracy in the low-energy range (Mishev et al., 2020, https://doi.org/10.1029/2019JA027433); Development of a new effective-energy method of spectrum reconstruction (Koldobskiy et al., 2019, https://doi.org/10.1007/s11207-019-1485-8); Revised analysis of major SEP events for the last decades (Usoskin et al., 2020b; https://doi.org/10.1029/2020JA027921).

This has greatly reduced the level of uncertainty and also corrected several essential errors in the previous analyses of major SEP events. The revised datasets and results are publicly available at the International GLE database (https://gle.oulu.fi).

GLE sample — Example of the integral SEP fluences reconstructed for GLE 38 (8 December 1982). Blue points with error bars depict reconstructions of the integral fluence from individual NMs, while red arrows denote the upper limits (no statistically significant response in the NM). Error bars represent the full-range uncertainties. The thick blue curve represents the best-fit spectral approximation with 1σ uncertainties. Ref: Usoskin, I., S. Koldobskiy, G.A. Kovaltsov, et al., Revised GLE database: Fluences of solar energetic particles as measured by the neutron-monitor network since 1956, 2020a, https://doi.org/10.1051/0004-6361/202038272.

New results on the influence of energetic particle precipitation on polar vortex dynamics

It is now well established that energetic particle precipitation (EPP) from space into the upper atmosphere can lead to significant ozone loss in the mesosphere and stratosphere during wintertime. Changes in ozone lead to changes in the atmospheric heating/cooling rates and this has been thought to ultimately influence the strength of the stratospheric polar vortex, the strong westerly wind that forms each winter around the cold polar stratosphere. However, the mechanisms connecting the EPP to dynamical variations of the polar vortex have long been ambiguous especially because the connection seems to depend on the internal state of the atmosphere.

We have studied the atmospheric response of EPP from ground to upper stratosphere using ERA-Interim/ERA-40 re-analysis data and calibrated satellite measurements of EPP. We found that the strong EPP indeed causes ozone loss with associated thermal changes and enhances the stratospheric polar vortex, but that this connection appears much stronger during times when the equatorial stratospheric winds (so called QBO winds) are easterly (Salminen et al., 2019, https://doi.org/10.1029/2018JD029296). We hypothesised that this might be because easterly QBO guides more planetary waves into the polar vortex, and that this makes the vortex more sensitive to EPP-related changes which are amplified by planetary wave feedback mechanisms.

We proved this hypothesis in a subsequent study by specifically concentrating on times preceding sudden stratospheric warmings, large breakings of the polar vortex, which are characterized by strong preceding planetary wave activity (Asikainen et al., 2020, https://doi.org/10.1029/2019JD032137). We showed that the EPP influence takes place almost exclusively during such times. A closer analysis revealed that the enhanced planetary wave activity into the stratosphere is a key component of the EPP influence. It allows the small initial changes related to EPP-caused ozone loss to be strongly amplified by so called wave-mean-flow interactions.

EPP example — Schematic of the components of energetic particle influence on polar vortex depicted on top of the background distribution of zonal wind (red indicates westerly wind and blue easterly wind). A key component is enhanced planetary wave activity which enables wave-mean-flow amplification in the polar vortex.

These results highlighted the importance of planetary waves as an amplifier for the EPP effect on the polar vortex, but they also suggested that because of this amplification the EPP-influence could work both ways, i.e., while strong precipitation could enhance the vortex weak precipitation could potentially even lead to breaking of the entire vortex. We examined this possibility by conducting a statistical analysis of all sudden stratospheric warmings (SSW) occurred since 1957 (Salminen et al., 2020, https://doi.org/10.1029/2019GL086444). We considered the influence of EPP, sunspots, QBO and El Niño Southern Oscillation on SSW frequency and found that EPP together with QBO phase strongly influences the occurrence probability of SSWs. The highest, over 80% probability of SSW occurrence was obtained when QBO is easterly and EPP level is lower than average. This important finding paves the way for improved long-term predictions of average winter weather in arctic regions, which is strongly influenced by SSWs.

Auroral Current are Stronger in the Northern Hemisphere

Auroral current systems in the high-latitude ionosphere are concentrated to the auroral ovals that circle Earth’s magnetic poles. They consist of field-aligned currents (FAC) that connect Earth’s magnetosphere and ionosphere, their closure currents, and the eastward and westward electrojets. We analyzed 5 years of magnetic field measurements from the European Space Agency’s Swarm satellites and concluded that while the auroral currents in the Northern and Southern hemispheres are very similar, they are not completely symmetrical: On average, currents in the Northern hemisphere are 10-15% stronger than their southern counterpart (Workayehu, Vanhamäki, and Aikio, J., 2019, https://doi.org/10.1029/2019JA026835).

Auroral currents example — The degree of the hemispheric asymmetry depends on the level of geomagnetic activity. The figure shows the FAC (top row) and electroject currents (bottom row) during quiet conditions (planetary activity index Kp<2), when the asymmetry between North (left column) and South (right column) is most prominent.

In a further study (Workayehu, Vanhamäki, and Aikio, J. Geophys. Res. Space Phys., 2020, https://doi.org/10.1029/2020JA028051) we found that there is also large seasonal variation, with the hemispheric asymmetry being largest during local winters and statistically insignificant during local summers. The physical mechanism producing the asymmetry is currently unknown, but our model calculations indicate that differences in the background electrical conductivity, affected by sunlight and magnetic field strength, cannot explain the observations. Other possible reasons, to be investigated in the future, include asymmetries in the convection electric field or auroral conductance enhancements caused by energetic particle precipitation.

Department of Physics and Astronomy
FI-20014 University of Turku
Finland
http://www.physics.utu.fi
http://www.astro.utu.fi

Finnish Centre for Astronomy with ESO (FINCA)
FI-20014 University of Turku
Finland
http://www.finca.utu.fi

Space research at the University of Turku is conducted at the Tuorla Observatory and the Space Research Laboratory (SRL) both being parts of the Department of Physics and Astronomy. The largest groups at the Tuorla Observatory are the High-Energy Astrophysics group and Astrophysical Transients group. In addition, research is done on active galaxies, solar system, astrobiology and simulations of large scale structures in the Universe. Research on solar physics is done in collaboration with SRL and on astronomical instrumentation in collaboration with the Finnish Centre for Astronomy with ESO (FINCA, and below). The total number of staff members and PhD students is about 50.

Space Research Laboratory (SRL)

The research at SRL is focused on heliophysics. Alpha Magnetic Spectrometer (AMS-02) on-board the International Space Station and a number of instruments on-board ESA-led missions are carrying experiments delivering data: Energetic and Relativistic Nuclei and Electron experiment (ERNE) on-board Solar and Heliospheric Observatory (SOHO) and Solar Intensity X-ray and particle Spectrometer (SIXS) on-board BepiColombo mission are PI/co-PI-level SRL instrument projects. SRL also participates in the Solar Orbiter mission at co-I level in the Magnetometer and Energetic Particle Detector experiments. At national level SRL-led RADMON-instrument on-board the Aalto-1 CubeSat has delivered data on energetic protons and electrons in Low Earth Orbit since 2017. Together with the Embedded Electronics research group in the Department of Future Technologies, SRL forms the Instruments team of the Finnish Centre of Excellence in Research of Sustainable Space (FORESAIL), which develops energetic particle instrumentation for three CubeSats to be launched starting in 2021. Experimental research is supported by numerical model development on energetic particle transport and acceleration in turbulent plasmas and shocks.

Particle Telescope (PATE) for Foresail-1 satellite

One of the main activities of SRL over the years 2018-2020 has been the design, manufacturing and qualification of the Particle Telescope (PATE) for the Foresail-1 satellite. PATE () is an energetic particle instrument capable of measuring the energy spectrum and angular distribution of 80–800 keV electrons and 0.3–10 MeV hydrogen atoms and ions. The spacecraft will be launched in a polar low-Earth orbit in 2021. The main scientific objectives of the experiment are to characterize precipitating near-relativistic electron populations at very high angular resolution and to measure energetic neutral hydrogen from the Sun during strong solar flares. The instrument has two perpendicularly mounted particle telescopes that both operate with the same principle: measuring the energy losses of incident particles in a silicon detector stack and using the energy deposit pattern in the detector layers to identify the particle species and to determine their energy. Neutral atoms are ionized in the thin foils covering the detector stack and leave an identical energy dissipation pattern to ions of the same species in the detectors. PATE, however, uses the geomagnetic field as a filter to determine whether the particles arriving from the solar direction are charged or neutral. In addition to these key observations, PATE will measure the fluxes of protons and electrons in the radiation belts as well as solar proton fluxes while the satellite is above the polar regions. The instrument qualification model has been delivered to Aalto University for integration to the satellite in late 2020. The flight model is under construction and will be delivered to Aalto in spring 2021.

High-Energy Astrophysics group

The high-energy astrophysics group works on accreting black holes and neutron stars. We develop atmosphere models for rapidly rotating neutron stars in low-mass X-ray binaries with the aim to determine the equation of state (EoS) of cold dense matter of neutron stars and to understand the physics of accretion in these objects. We also construct atmosphere models for rotation-powered millisecond pulsars that are used by the NICER team to constrain the EoS. We work on hydrodynamical models of boundary/spreading layers on weakly magnetized neutron stars to understand the nature of kHz quasi-periodic oscillations. We also study X-ray pulsars and ultra-luminous X-ray pulsars, both observationally and theoretically. Here we construct models for the accretion column and for the accretion disc around magnetized neutron stars as well as monitor the sources to study the transition to the propeller regime to measure the neutron stars magnetic field. Another direction of research is accreting black holes of all scales. We model broadband spectra and timing properties of accreting black holes both in the optical/infrared and the X-rays. We are also doing optical polarimetric studies with the in-house built high-precision DIPol-2 and DIPol-Ultra Fast (UF) polarimeters with the aim to determine the accreting black hole emission mechanisms. The group uses both ground-based ESO VLT and the Nordic Optical Telescope (NOT) as well as space telescopes (XMM-Newton, Chandra, RXTE, INTEGRAL, Fermi, Swift, NuSTAR). We are also involved in preparation for the new X-ray missions being science group members of the NASA’s Imaging X-ray Polarimeter Explorer (IXPE) and of the Chinese enhanced X-ray Timing and Polarimetry (eXTP) missions. In particular, we develop models for X-ray polarization from X-ray pulsars, accounting for relativistic motion of the emission region in the case of millisecond pulsars.

Rapidly Rotating Neutron Stars

Neutron stars (NSs) contain the most extreme forms of matter available in the Universe. They also serve as astrophysical laboratories to study physics under extreme conditions of strong gravity, ultrahigh densities, super-strong magnetic fields and high radiation densities. The densities in NS interiors can exceed the density of saturated nuclear matter (about 3 x 10¹⁴ g/cm³) by a large factor. One of the goals of modern physics is to understand the nature of the fundamental interactions. NSs serve as excellent natural laboratories to study strong interactions and to determine the most important properties of matter in atomic nuclei and NSs. The theory of quantum chromodynamics, which can, in principle, treat strong interactions, is computationally intractable for multi-nucleon systems at NS densities. Instead, physicists have developed empirical models of nucleonic interactions, which make conflicting predictions. Laboratory experiments and NS observations are vital to test these theories and drive the progress.

NSs observations can be used to place constraints on strong interactions because the forces between the nuclear particles set the stiffness of NS matter. This is encoded in the equation of state (EoS), the relation between pressure and density. For a given NS mass M, the EoS sets its radius R via the stellar structure equations. By measuring the M-R relation, we can recover the EoS at supranuclear densities, which is of major importance to both fundamental physics and astrophysics. It is central to understanding NSs, supernovae, and compact object mergers including at least one NS. To distinguish among the models of strong interactions one needs to measure NS M and R to a precision of a few per cent for several NSs. Our group has developed state-of-the-art neutron star atmosphere models and methods to measure NS parameters from the evolution of X-ray spectra observed during thermonuclear explosions at the NS surface known as X-ray bursts (), from pulse profiles of rotation-powered and accreting millisecond pulsars (AMPs), from X-ray polarization to be observed from AMPs by the Imaging X-ray Polarimeter Explorer (IXPE) to be launched in the end of 2021.

Rotating neutron star figure — Images of a neutron star rotating at 700 Hz. Upper panels: blackbody case of local isotropic intensity. Lower panels: electron-scattering dominated atmosphere. Panels from the left to the right correspond to the inclinations i = 0°, 45°, and 90°. The lines of constant latitudes (every 10°) and longitudes (every 15°) are shown in black. From Suleimanov et al., 2020, Observational appearance of rapidly rotating neutron stars. X-ray bursts, cooling tail method and radius determination, A&A, 629, A33. doi:10.1051/0004-6361/202037502

X-ray Pulsars at Low Luminosities

X-ray pulsars is a subclass of accreting NS, possessing an extremely strong magnetic field (10¹²-10¹⁵ G). Studies of these objects allow us to probe physical processes happening under conditions of the magnetic fields exceeding the values achieved by mankind by 10 orders of magnitude. Historically, due to the limited sensitivity of existing instrumentation, broadband X-ray spectra of accreting pulsars have been studied at comparatively high luminosities and accretion rates. Under these conditions, most X-ray pulsars appear to have quite similar spectra with a characteristic cutoff power-law continuum presumably associated with the comptonization of seed thermal emission within the optically thick emission region close to the neutron star magnetic poles. In a few exceptional cases that were known until recently, however, the origin of the observed spectra was not clear. The situation changed in 2019, when we were able to detect a dramatic spectral transition in transient X-ray pulsars GX 304-1 and A 0535+262. The typical cutoff power-law continuum observed at high fluxes transformed to a two-component spectrum peaking in the soft (<10 keV) and the hard (>20 keV) bands at low luminosity (see ). We proposed the model where these spectral characteristics can be explained by the emission of cyclotron photons in the atmosphere of the neutron star caused by collisional excitation of electrons to upper Landau levels and further comptonization of the photons by electron gas. The latter is expected to be overheated in a thin top layer of the atmosphere.

X-ray pulsar spectrum — Spectra of low-luminosity persistent X-ray pulsar X Per (green, based on the INTEGRAL data), and low-state NuSTAR spectra of 1A 0535+262 (blue/red) and GX 304-1 (gray) modeled with the same two-component comptonization model. From Tsygankov et al., 2019, Cyclotron emission, absorption, and the two faces of X-ray pulsar A 0535+262, MNRAS Letters, 487, L30. doi:10.1093/mnrasl/slz079

Transitional Millisecond Pulsars

Transitional millisecond pulsars constitute a subclass of neutron stars that swing between the radio-pulsar state (when there is no active flow of matter from the companion star) and accretion state (when the matter dragged from the companion comes close to the neutron star). They provide strong evidence for the recycling scenario, where occasional accretion episodes can spin-up the neutron star to millisecond periods. Transitional millisecond pulsars also provide a unique set of observational data for understanding accretion at low rates onto magnetized neutron stars. For one of these sources, PSR J1023+0038, the pulsations at millisecond timescales have been found both in the X-rays and at optical wavelengths. This discovery challenged all previous low-rate accretion models, as the optical emission has to be coming from a very compact region. We proposed that the multiwavelength emission in this system originates from the area of interaction between the relativistic pulsar wind and the accretion stream (). Powerful wind is capable of stopping the stream, preventing its penetration towards the neutron star surface, and creating a standing shock. As the neutron star rotates, the shock slides along the matter leading to variations of the optical and X-ray fluxes with the period equal to half of the neutron star spin period, consistent with the observations. This scenario opens new prospects to study microphysical processes of interaction between the low-density relativistic beam with the matter.

Optical Polarimetry of Compact Objects

High-precision optical polarimetry is a powerful tool to study geometry and orientation of astrophysical objects. It can be used for determination of inclination and orientation of binary orbit and helps to locate various gaseous structures, such as streams, disks and jets.

Observatory possesses a unique expertise in developing high-precision instruments for optical polarimetry. Two such instruments, DIPol-2 and DIPol-UF (, left), have been built during the last decade in collaboration with the Institute of Solar Physics (Freiburg, Germany). Both polarimeters are currently employed for studying various polarization mechanisms, including polarization in exoplanets, binary systems and interstellar polarization with the accuracy up to 10^-5 and better. Our latest results obtained with the DIPol-2 for the high-mass gamma-ray binary LS I+61^o 303 revealed for the first time the presence of a variable, and synchronous with the orbital motion, linear polarization. From analysis of polarization data with the model of Thomson scattering by a cloud that orbits the Be star, we obtained new constraints on orbital parameters, including a small eccentricity (e < 0.2) and periastron phase 0.6, which coincides with the peaks in the radio, X-ray, and TeV emission (, right).

DIPol-UF polarimeter — Left: New high-precision optical polarimeter DIPol-UF built at the University of Turku and installed at the NOT (see Piirola et al., 2021, Double Image Polarimeter—Ultra Fast: Simultaneous Three-color (BVR) Polarimeter with Electron-multiplying Charge-coupled Devices, AJ, 161, 20. doi:10.3847/1538-3881/abc74f). Right: Orbit of a compact object in LS I+61o 303 around Be star (yellow circle), which lies at the ellipse focus. The red dashed line is the major axis of the orbit. The black dots on the orbit are spaced by the phase interval ∆φ = 0.1. Phases of apoastron (0.12) and periastron (0.62) are shown by asterisks. From Kravtsov et al., 2020, Orbital variability of the optical linear polarization of the gamma-ray binary LS I +61^o 303 and new constraints on the orbital parameters, A&A, 643, A170. doi:10.1051/0004-6361/202038745.

Compact object orbit — Left: New high-precision optical polarimeter DIPol-UF built at the University of Turku and installed at the NOT (see Piirola et al., 2021, Double Image Polarimeter—Ultra Fast: Simultaneous Three-color (BVR) Polarimeter with Electron-multiplying Charge-coupled Devices, AJ, 161, 20. doi:10.3847/1538-3881/abc74f). Right: Orbit of a compact object in LS I+61o 303 around Be star (yellow circle), which lies at the ellipse focus. The red dashed line is the major axis of the orbit. The black dots on the orbit are spaced by the phase interval ∆φ = 0.1. Phases of apoastron (0.12) and periastron (0.62) are shown by asterisks. From Kravtsov et al., 2020, Orbital variability of the optical linear polarization of the gamma-ray binary LS I +61^o 303 and new constraints on the orbital parameters, A&A, 643, A170. doi:10.1051/0004-6361/202038745.

Astrophysical Transients group

The research interests of the astrophysical transients group (https://sites.utu.fi/sne/) cover extragalactic transients ranging from supernovae and their progenitor stars to tidal disruption events of stars by supermassive black holes and electromagnetic counterparts of gravitational wave sources. The group makes use of wide field imaging surveys that are detecting thousands of supernovae each year in addition to other types of astrophysical transients not studied in detail before. They are part of the Gravitational wave Optical Transient Observer (GOTO) collaboration currently deploying on La Palma and at the Siding Springs Observatory in Australia arrays of 40 cm astrographs on heavy-duty robotic mounts to achieve large instantaneous field of views on both hemispheres. The group carries out observations at a wide range of wavelengths from radio to infrared and optical using in particular the telescopes of ESO and the Nordic Optical Telescope (NOT), and also data from space telescopes such as the NASA Spitzer and WISE and the ESA/NASA HST. The group actively participates in large international collaborations such as the Electromagnetic counterparts of gravitational wave sources at the Very Large Telescope (ENGRAVE) and the extended Public ESO Spectroscopic Survey of Transient Objects (ePESSTO+) which is a large programme running at ESO. Members of the group have also key roles in astronomical instrumentation projects: the Son of X-Shooter (SOXS, see ) for the New Technology Telescope (NTT) of ESO and Multi-Adaptive Optics Imaging Camera for Deep Observations (MICADO) for the Extremely Large Telescope (ELT) of ESO.

The calibration unit of the SOXS spectrograph, which is currently in the test and verification stage at University of Turku. The SOXS spectrograph for the ESO NTT will be dedicated for transient and variable objects and covers a wide wavelength range 350-2000 nm. The first light is expected in late 2022 and subsequently NTT+SOXS will be almost exclusively used for transient and variable objects observations. A calibration unit employing seven different calibration lamps will be used to remove instrumental signatures and to provide wavelength calibration for the data. See Kuncarayakti et al., 2020, Design and development of the SOXS calibration unit, SPIE, 11447, id. 1144766 for the optical, mechanical, and electrical design of the SOXS calibration unit.

Late-phase spectroscopy of supernovae

Supernovae are stellar explosions that eject stellar material with velocities of several thousands km/s. Several months after the explosion, the continuously expanding ejecta become optically thin and thus reveal the inner parts of the stellar core where the explosion took place. This provides a rare opportunity to peer deep into the heart of the exploding star and study the chemical yields and explosion geometry. In an ongoing survey of late-time supernova spectra using the ESO VLT supplemented with Gemini and Subaru observations, it was found that the supernova SN 2016gkg exhibits a peculiar spectrum dominated by narrow emission lines, corresponding to velocities around 300 km/s, which is ten times slower compared to what is typically observed in other supernovae (see ). The presence of such slow-moving material in the core suggests significant explosion asymmetry, and is not predicted in typical standard-energy explosion models.

XIFS imaging for a supernova — Integral field spectroscopy (IFS) with ESO VLT was employed in the study of SN 2016gkg, to simultaneously capture the supernova and surrounding environment. This helped ascertain that the narrow emission lines originated from the supernova itself, not background. IFS-generated images of the supernova site, in various wavelengths, are shown (left panels). The spectrum of SN 2016gkg in the [OI]6300,6364 doublet region, showing multiple components including a pair of blue and red narrow lines superposed on a broad base (right panel). From Kuncarayakti et al., 2020, Direct Evidence of Two-component Ejecta in Supernova 2016gkg from Nebular Spectroscopy, ApJ, 902, 139. doi:10.3847/1538-4357/abb4e7

Observations of Electromagnetic Counterparts of Gravitational Wave Sources

The discovery of gravitational wave (GW) signals from merging binary black holes by the LIGO and Virgo collaborations opened up a new and very exciting era in astrophysics. This was followed by the detection of the signal from the merger of two neutron stars GW170817 in a galaxy at the distance of only 40 Mpc. Thousands of astronomers all over the world were involved in the campaign to search for and study the electromagnetic counterpart signal (so called kilonova) that was discovered to be associated with GW170817. The astronomers from Turku contributed to the spectrophotometric study of the counterpart with ESO telescopes (Abbott et al. 2017; Smartt et al. 2017). The multi-wavelength dataset showed that the emission was powered by radioactive decay of elements formed through the rapid neutron capture (r-process) nucleosynthesis confirming neutron star mergers as important sources of r-process elements. This extraordinary event marks the dawn of an era where electromagnetic radiation is now used together with GW detections to advance our understanding of the Universe. The electromagnetic counterpart of GW170817 still remains the only one confirmed for a GW source and therefore all future discoveries (and restrictive upper limits) will be very important and exciting. A deep search for an electromagnetic counterpart was carried out for the GW source S190814bv by the ENGRAVE consortium with a number of astronomers from Turku involved (Ackley et al. 2020, see ). S190814bv resulted from a likely merger of a compact binary system formed by a black hole and a neutron star but was almost ten times more distant than GW170817. Future improvements in the detection sensitivity and localisation precision of GW sources together with the capabilities of very wide field optical telescopes will provide new opportunities for characterising electromagnetic counterparts.

HAWK-I imaging — A near-infrared image from the HAWK-I instrument on the ESO’s VLT showing with insets individual galaxies within the sky localization area and redshift range of the gravitational wave source S190814bv resulting from a likely merger of a compact binary system formed by a black hole and a neutron star. The absence of any variable sources is evident from the subtractions between the two epochs of observations. From Ackley et al., 2020, Observational constraints on the optical and near-infrared emission from the neutron star-black hole binary merger candidate S190814bv, A&A, 643, A113 (including T. Heikkilä, E. Kankare, R. Kotak, H. Kuncarayakti, S. Mattila, S. Moran, T. Reynolds, K. Wiik). doi:10.1051/0004-6361/202037669

Tidal Disruption Events

Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). The TDEs were predicted theoretically more than thirty years ago. In this event, roughly half of the star’s mass is ejected whereas the other half is accreted onto the SMBH, generating a bright flare that is normally detected at X-ray, ultraviolet, and optical wavelengths. TDEs are also expected to produce radio transients, lasting from months to years and including the formation of a relativistic jet, if a fraction of the accretion power is channelled into a relativistic outflow. TDEs provide a means of probing central black holes in quiescent galaxies and testing scenarios of accretion onto SMBHs and jet formation. We have observed a transient source in the western nucleus of the merging galaxy pair Arp 299 that radiated >1.5×10⁵² erg in the infrared and radio, but was not luminous at optical or X-ray wavelengths. We interpret this as a TDE with much of its emission re-radiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs. The radio observations resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH ().

The astrophysical transient Arp 299-B AT1 in the luminous infrared galaxy Arp 299 shown as a colour-composite optical image from the HST (A). The insets B and C show the infrared brightening of the nucleus B1 that was interpreted as a thermal ‘infrared echo’ by interstellar dust of the shorter wavelength emission from a tidal disruption event. The evolution of the radio morphology at 8.4 GHz as observed with VLBI (D) was found consistent with emission from a relativistic jet launched by a tidal disruption of a star and for the first time resolved in high resolution radio observations. From Mattila S., 2018, A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger, Science, 361, 482. doi:10.1126/science.aao4669

Finnish Center for Astronomy with ESO (FINCA)

The research at FINCA concentrates on observational astronomy carried out using radio to gamma-rays, multi-wavelength data from large ground-based and space telescopes. Especially, use is made of ESO’s large ground-based facilities in the optical and infrared (the four 8 m ESO Very Large Telescopes; VLT) and in (sub)millimetre (Atacama Large Millimeter Array; ALMA), together with the Nordic Optical Telescope (NOT) on La Palma, in the northern hemisphere. Observational research is supplemented by modelling, computer simulations and theoretical work, that are essential in understanding the physics behind the observations. The science topics at FINCA cover a large range in contemporary astronomy from observational cosmology, distant active galaxies, and galaxy formation and evolution, through properties of nearby galaxies, to supernovae and their progenitor stars, stellar activity and star formation in our own Galaxy. Some of our recent research highlights are described below.

FINCA participates in one of the ESO’s ELT first light instrument consortia, MICADO (near-infrared adaptive optics imager), and a new instrument to the ESO 3.5 m New Technology Telescope (NTT), the Son Of X-Shooters (SOXS). Both involve in-kind contributions, participation in PSF reconstruction for MICADO, and building the calibration unit subsystem for SOXS. Our instrumentation work is performed in collaboration with Tuorla Observatory.

The disc-like host galaxies of radio-loud narrow-line Seyfert 1s

Until recently, relativistic jets were ubiquitously found to be launched from giant elliptical galaxies. However, the detection by the Fermi-LAT of gamma-ray emission from radio-loud narrow-line Seyfert 1 (RL-NLS1) galaxies raised doubts on this relation. J. Kotilainen (FINCA) and collaborators have morphologically characterized a sample of 29 RL-NLS1s (including 12 gamma-emitters, gamma-NLS1s) in order to find clues on the conditions needed by active galactic nuclei (AGN) to produce relativistic jets. They use deep near-infrared images from the NOT and the ESO VLT to analyse the surface brightness distribution of the galaxies in the sample. They detected 72% of the hosts (24% classified as gamma-NLS1s). Although it cannot be ruled out that some RL-NLS1s are hosted by dispersion-supported systems, these findings strongly indicate that RL-NLS1 hosts are preferentially disc galaxies. 52% of the resolved hosts (77% non-gamma-emitters and 20% gamma-emitters) show bars with morphological properties (long and weak) consistent with models that promote gas inflows, which might trigger nuclear activity. The extremely red bulges of the gamma-NLS1s, and features that suggest minor mergers in 75% of their hosts, might hint to the necessary conditions for gamma-rays to be produced. Among the features that suggest mergers in the sample, there are six galaxies that show offset stellar bulges with respect to their AGN. In the nuclear versus the bulge magnitude diagram (), RL-NLS1s are located in the low-luminosity end of flat spectrum radio quasars, suggesting a similar accretion mode between these two AGN types.

NLS1s K-band signals — The nuclear K-band magnitude versus the bulge K-band magnitude for the NLS1 host galaxies. Overlaid is a sample of blazars from Olguin-Iglesias et al. (2016). For the blazars sample we show the best linear fits (dashed blue line for FSRQs and dashed red line for BL Lacs) and the 95% prediction bands (dotted black lines). The 99% confidence intervals are shown for FSRQs (blue shade) and NLS1s (yellow shade). For the NLSy1s sample we show the best linear fit (green solid line). Adapted from Olguin-Iglesias, Kotilainen & Chavushyan, 2020, The disc-like host galaxies of radio-loud narrow-line Seyfert 1s, MNRAS, 492, 1450. doi:10.1093/mnras/stz3549

Connecting high-energy neutrinos with active galactic nuclei

Identifying the most likely sources for high-energy neutrino emission has been one of the main topics in high-energy astrophysics ever since the first observation of high-energy neutrinos by the IceCube Neutrino Observatory. Active galactic nuclei with relativistic jets, blazars, have been considered to be one of the main candidates due to their ability to accelerate particles to high energies. Previously, observational evidence has been found for one particular blazar, TXS0506+056, to be the origin of the astrophysical neutrino IC-170922A (see ). In a follow-up study led by T. Hovatta (FINCA), the connection between high-energy neutrinos and radio emission in a sample of blazars was studied. Using radio light curves of blazars from Aalto University Metsähovi Radio Observatory and Caltech’s Owens Valley Radio Observatory they found indications of a connection between large radio flares and high-energy neutrinos detected by the IceCube Neutrino Observatory. This has a major impact on the modeling of the emission of blazars, which would need to account for the existence of protons in the jets to be able to produce neutrinos. Several follow-up studies have been initiated, including obtaining observing time with the XMM satellite (PI Y. Liodakis, FINCA) to follow some candidate sources in X-ray energies.

VTT Technical Research Centre of Finland
PO Box 1000
FI-02044 VTT
Espoo
Finland
http://www.vtt.fi

VTT is one of the leading research and technology organisations in Europe. We use our research and knowledge to provide expert services for our domestic and international customers and partners. We cooperate with our customers to produce technology for business and build success and well-being for the benefit of society. VTT personnel is 2,103 (31.12.2019) and Net turnover 147 M€. VTT is part of Finland's innovation system and operates under the mandate of the Ministry of Employment and the Economy.

VTT has a long history from 1980’s on space projects with EC, ESA and private and public companies. These space instrumentation and remote sensing projects link to all the strategic research areas of VTT: Climate action, Resource sufficiency, Good life, Safety and security, and Industrial renewal. Below examples on current space instrumentation and remote sensing projects.

VTT Hyperspectral imaging technology

Small satellite industry is growing rapidly and making leaps in technological advancements in comparison to the traditional space industry. VTT’s hyperspectral imaging technology has potential to allow development of novel applications and services from large nanosatellite constellations to provide real-time situational awareness.

VTT hyperspectral imager flying on Aalto-1 satellite.

In recent years, VTT has developed several hyperspectral imager payloads for small satellite missions based on tunable spectral filters, which can be realized for various different wavelengths from ultraviolet to thermal infrared to enable different application needs. Instrument size is typically very small (0.5U) and light-weight (< 600 g). VTT’s unique 2D snapshot hyperspectral imagers are especially suitable for nanosatellite missions, as the whole 2D scene is imaged at once and the spectral data cube is constructed by taking multiple images of the same target at different wavelengths. Thus, this method is more spatially robust than traditional push-broom instruments in larger satellites. Another key advantage of the technology is that it is software programmable - same spectral sensing hardware can adapt to different application needs through programming of the wavelength selection even after launch.

VTT has already realized three payloads: The first visible - VNIR demonstrator for imaging between 500 nm and 900 nm has been launched on-board the Aalto-1 and a similar concept has also been develop for sun occultation mission on nanosatellite on board Belgian PICASSO nanosatellite, launched in fall 2020. VTT has also realized world’s first CubeSat-compatible miniaturized hyperspectral imager for SWIR region, for the wavelengths between 925 - 1400 nm (1000 - 1600 nm), launched to space in the Reaktor Hello World CubeSat mission in 2018. Due to the small size, it is easy to combine multiple different wavelength ranges into single satellite, from 500 up to 3000 µm range. This makes it possible in future to map composition of asteroids, which is future interest of the potential ASPECT mission. Currently, VTT is building the Asteroid Spectral Imager for ESA's Hera-mission, to be launched in 2024, as well as the UV-range spectral filters for ESA ALTIUS mission to allow gathering essential time-series data about atmospheric gas composition. Another recent project is the near and mid-infrared channels of the MIRMIS instrument (Modular Infrared Molecules and Ices Sensor) for ESA Comet Interceptor.

VTT Remote Sensing

The on-going earth observation programs, in particular the European Copernicus program and commercial satellite missions that provide imagery with sub-meter accuracy, offer global image acquisitions more often than weekly. Huge data volumes make it possible to get information from the state of the forest anywhere in the world from satellite images with the help of machine learning and AI tools.

We develop advanced interpretation methods and image analysis systems mainly related to forestry. The results are introduced to user community. We are leading the Forestry Thematic Exploitation Platform (http://forestry-tep.eo.esa.int/), which is designed to answer the needs that have emerged from the dramatically increased data supply. The cloud platform offers an online working environment and services, with a broad spectrum of means to turn satellite data to value adding information products. The platform can be used by academic, public and commercial sectors to offer readily made products, services or tools to their customers.

On operational forest monitoring side, we have been developing EO based forest change detection together with Finnish SME called Satellio (http://www.hakkuut.fi). The project is funded by Finnish Ministry of Agriculture and Forestry. Below an is example of change detection result in Finland.

Forest remote sensing by VTT and Satellio.

MillliLab
FI-02044 VTT
Finland
http://www.millilab.fi
Phone: +358 20 722 7219

Millimetre Wave Laboratory of Finland – MilliLab, established in 1995, is a joint laboratory between VTT, Technical Research Centre of Finland and Aalto University. MilliLab is also a European Space Agency, ESA, External Laboratory on Millimetre Wave Technology. Its main purpose is to support European space industry to meet the demands of future ESA missions, which will include an increasing number of millimetre wave instruments for astronomical and remote sensing applications.

MilliLab supplies services at millimetre wave frequencies in the field of device modelling, device characterisation, measurements, testing, research, and development. The parent organisations of MilliLab, VTT and Aalto University have a substantial amount of experience and expertise in the field of microwave and millimetre wave technology. The total research personnel with experience in millimetre waves is over 50.

MilliLab organised in June 2016 an international joint conference of 9^th Global Symposium on Millimeter Waves GSMM2016 and 7^th ESA Workshop on Millimeter-Wave Technology and Applications in AALTO university, Espoo.

MilliLab has continued to work in MetOp Second Generation activities. The MetOp main three instruments together contain a large number of micro to millimetre wave channels from 23 to 664 GHz. MilliLab is currently involved in several channels from 50 GHz upwards in a supporting role. MilliLab’s work in MetOp-SG concentrates on activities related to RF performance and reliability testing of the critical LNA and diode components. Furthermore, MetOp Microwave Sounder and Microwave Imager 89 GHz radiometer front-end receivers are being built in Finland by DA-Design Ltd. MilliLab performs the RF performance testing of the units for DA-Design. In 2017, the work concentrated on the Breadboard model receiver characterisation, and it has continued with the Engineering Qualification Model during 2018. In addition to MetOp work, MilliLab is participating in the European Components Initiative via ESA projects together with European space industry.

Related to MetOp SG receiver technology, in 2016-17 MilliLab has characterized low-barrier Schottky diodes for millimeter-wave mixer application in collaboration with ACST GmbH. Low-barrier Schottky diodes have recently been intensively studied and developed especially for detector applications. When operating as mixers, these diodes require only very little LO power, but have the drawbacks of poor conversion efficiency and noise temperature. In this research activity, with some low-barrier diodes fabricated by ACST, good conversion loss performance was achieved at 183 GHz with LO power as low as 100 microwatts; however, the mixer noise performance was not as low as desired.

LNA modules under mechanical tests during preliminary reliability assessment for MetOp-SG radiometers.

University of Jyväskylä
PO Box 35
FI-40014 University of Jyväskylä
Finland
http://www.jyu.fi

The University of Jyväskylä with its six faculties is one of the largest Universities in Finland. The Accelerator Laboratory (JYFL-ACCLAB) is an integral part of the Department of Physics within the Faculty of Mathematics and Science. JYFL-ACCLAB is multi-user facility hosting four accelerators providing ion, electron and photon beams for a large national and international user base. The users of JYFL-ACCLAB represent a multidisciplinary range of fields, addressing research into nuclear and atomic physics, nuclear astrophysics and fundamental interactions, radiation effects in electronics and materials, ion source development and plasma physics, nanoscience, materials characterization and thin-film research. JYFL-ACCLAB also provides a wide range of analysis, irradiation and expert consultancy services to industrial partners.

JYFL-ACCLAB is one of 29 high-level Research Infrastructures selected in the latest update to the Finnish Research Infrastructure (FIRI) Roadmap. JYFL-ACCLAB has also been designated a National Task by the Ministry of Education and Culture as a centre of expertise in radiation- and ion-beam research, education and applications. It operates in close collaboration with the Helsinki Institute of Physics (HIP), and it has been supported as a Transnational Access Facility in a number of European programs from EU-FP4 to Horizon2020 since 1996. JYFL-ACCLAB also operates the RADiation Effects Facility (RADEF), recognised as an External European Component Irradiation Facility by the European Space Agency (ESA).

Radiation Effects Facility (RADEF)

Radiation Effects Facility
PO Box 35
FI-40014 University of Jyväskylä
Finland
http://www.jyu.fi/accelerator/radef

The increased demand in radiation testing for European satellite projects attracted ESA to the JYFL-ACCLAB in 2004, when an ESTEC/Contract No. 18197/04/NL/CP: "Utilization of the High Energy Heavy Ion Test Facility for Component Radiation Studies” between ESA and JYFL was signed. After the upgrade, RADiation Effects Facility (RADEF) was qualified to one of ESA’s External European Component Irradiation Facilities (ECIF) serving ESA and the European satellite and aerospace industry for irradiations and research projects in these fields. This contract has been extended several times, and the latest extension continues until the end of 2022. A layout of the RADEF facility is shown in .

A layout from the RADEF beam lines with LINAC cave and control barrack.

RADEF is specialized in applied research related to nuclear and accelerator based technologies, to study of radiation effects in electronics and related materials. Our specialty is to provide high penetration heavy ion cocktail beams, protons in wide energy range and energetic electrons. For these beams the RADEF group utilizes combination of JYFL's ECR ion sources and K-130 cyclotron, and the LINAC electron accelerator. Because in the emerging technologies the integrated circuits have become more susceptible to radiation, the group is expanding its research activities toward the radiation effects in avionics and ground level systems (see the RADSAGA project below). RADEF has a wide network of collaborators worldwide, e.g. ESA, NASA/GSFC, CNES, JAXA, Vanderbilt University (USA), CERN, AIRBUS, TAS and STMicroelectronics, to name a few. RADEF provides its services to companies, institutes and universities in the radiation effects community. Since the start of the activities over 100 different collaborators have tested their electronic components at RADEF. Each year, more than 30 different international groups are visiting us, totalling with more than 40 individual test campaigns. The beam time used in radiation effects testing is about 800 hours annually, i.e. about 13% of the total accelerator beam time at JYFL-ACCLAB.

Heavy ion cocktails at RADEF

The growing complexity in modern electronic technologies raises the requirements for beam energies as the ion beams have to penetrate deeper into the devices in order to reach the sensitive layers. Due to this ESA provided funding for RADEF to develop higher energy beams for electronics testing.

A new 18 GHz ECR ion source HIISI was developed at the JYFL-ACCLAB. The main purpose of HIISI is to increase the energy of high-energy beam cocktails from 9. 3 MeV/u to above 15 MeV/u for radiation effects testing of electronics with the K130 cyclotron. After commissioning of HIISI ion source, three new ion cocktails were developed with beam energies of 10, 16.3 and 22 MeV/n. The basic properties of the cocktails are given in Tables -. See more information from the RADEF-web-pages (http://www.jyu.fi/accelerator/radef).

**10 MeV/n** ion cocktail. Changing time from ion to ion is about 15 min. The changing time between this and 16.3 Me/n cocktail is about 30 min.

**16.3 MeV/u** ion cocktail. The changing time from ion to ion is less than 15 min. Changing time between this and 10 Me/n cocktail is about 30 min.

**22 MeV/u** ion cocktail. Changing time from ion to ion is about 15 min.

Linear electron accelerator

Another recent ESA-funded development project at RADEF was the introduction of a LINAC electron accelerator (see ). One main objective for this equipment is to test electronics for ESA’s JUICE mission. With the LINAC accelerator both high energy electron (from 6 to 20 MeV) and gamma-ray beams can be produced.

Ongoing EU projects at RADEF

EU MSCA-Horizon-2020 ITN project, RADSAGA (GA#721624)

The project RADSAGA (RADiation and Reliability Challenges for Electronics used in Space, Aviation, Ground and Accelerators) will, for the first time, bring together the European industry, universities, laboratories and test facilities to educate 15 PhD’s about electronics exposure to radiation. Three of these PhD students will graduate from JYFL, two are hosted by RADEF and one by CERN. The project spans over the years 2017-2021, and the kick-off meeting was held in April 2017. This project was granted with total of 3.9 M€, and it is coordinated by CERN. The RADEF group is one of the seven beneficiaries. Fourteen other partners, mainly companies and research laboratories, take part in the RADSAGA consortium.

Erasmus Mundus Joint Master Degree programme – RADMEP

University of Jyväskylä is part of the consortium, coordinated by University of St. Etienne (France), with KU Leuven (Belgium), and University of Montpellier (France) that will provide 2-year master degree studies for the next 4 consecutive years starting in fall 2021. The project RADMEP – “Radiation and its Effects on MicroElectronics and Photonics Technologies” offers multidisciplinary and innovative programme covering studies in the interactions between Radiation and MicroElectronics and Photonics, two Key Enabling Technologies for the future of Europe. RADMEP’s objective is to educate students in those advanced technologies, providing methodologies and introducing practical applications for their implementation in a variety of natural or man-made radiation-rich environments.

Erasmus Mundus Joint Master Degree programme – RADMEP

EU Horizon-2020 project called “RADiation facility Network for the EXploration of effects for indusTry and research” (RADNEXT) was granted funding in 2020. This 4-year and 5Meur project is coordinated by CERN with 31 participants in 12 countries. The implementation of the project will start in the spring of 2021. The primary objective is to create a network of facilities and related irradiation methodology for responding to the emerging needs of electronics component and system irradiation for New Space, automotive, IoT, nuclear dismantling and civil applications, medical and accelerator applications; as well as combining different irradiation and simulation techniques for optimizing the radiation hardness assurance for systems, focusing on the related risk assessment. RADEF is providing Transnational Access for the users for radiation effects testing through this project.

Ongoing EU projects at RADEF

Estimation of proton induced Single Event Effect rates in very deep submicron technologies

In order to improve standard methods to characterize proton SEE sensitivity by direct ionization, and then estimate the SEE rates in orbit, in 2020 ESA granted funding for a 2-year project to Alter Technologies Ltd (France) and RADEF to study low energy proton effects in modern memory technologies. In addition to providing proton and ion beam for this study, RADEF will also perform simulation and numerical studies to complement the experimental results. The objective is to build models and calculation methods to estimate soft error rates in space that will take into account contributions of low and high energy protons, but also heavy ions present in radiation environments.

Radiation Characterisation of EEE components for ESA space applications

Commercial Off The Shelf (COTS) electronics have become increasingly popular for space applications in the recent years due to their advantages in price and performance over radiation hardened technologies. The radiation sensitivity of COTS parts can vary and before using them in radiation environments (like space) they need to be tested using radiation sources. RADEF is part of ESA-funded project with RUAG Space Finland in order to perform radiation effects tests on various electronics devices that are candidates for ESA space missions.

Thermal nanophysics group at Nanoscience Center (NSC)

The thermal nanophysics group at NSC led by prof. Maasilta has been at the forefront of superconducting bolometric radiation detection for some time now, starting with several ESA funded projects in the mid 2000’s, followed by several TEKES funded projects in 2010s. The focus has been on transition edge sensor (TES) technology, both sensor and application development, in collaboration with JYFL accelerator laboratory, the Quantum Sensors Group at NIST Boulder laboratories and VTT Micronova. In particular, we successfully designed and fabricated large 256 pixel X-ray TES arrays with novel designs from Mo/Cu bilayers (Fig. 4), on 6-in wafers at VTT’s Micronova clean room facilities. Such large X-ray TES arrays can only be fabricated at a couple of national laboratories around the world.

(a) A photograph of the JYU/VTT 256 pixel X-ray TES array and (b) micrograph of one pixel.

TES bolometers and calorimeters are currently the most widely used and most developed ultrahigh sensitivity and resolution technology, with many projected applications in future space science missions for far-infrared and X-ray satellite missions such as SPICA (ESA/JAXA), ATHENA (ESA), Origins Space Telescope (NASA). We have also recently initiated a study of advanced superconducting detector technology based on phononic crystal structures in collaboration with NASA Goddard Space Flight Center, with targeted applications for far-IR bolometry. These promising developments are still in the early phase and are based on the groundbreaking demonstrations of coherent modification of heat transport performed in our group earlier. In addition to working on the more developed TES technology, the group is also a member of an ongoing EU FET-open project SUPERTED (2018-2022), where a totally new type of thermoelectric superconducting bolometer will be demonstrated, with also potential for space applications.

University of Eastern Finland
PO Box 1627
FI-70211 Kuopio
Finland
http://www.uef.fi

The University of Eastern Finland (UEF) is one of the largest universities in Finland, with campuses In the cities of Kuopio and Joensuu. The research that can be attributed to space research at UEF belongs primarily in the field of satellite remote sensing and is located at the Faculty of Science and Forestry. At the Department of Applied Physics, several research teams work in the field of Computational Physics and Inverse Problems. The research teams have belonged to the Centre of Excellence in Inverse Problems Research since 2006 granted by the Academy of Finland. In particular, the Bayesian approximation error approach as well as machine learning methods are extensively used by the group to construct efficient algorithms that provide real world solutions to inverse problems. The problems that are studied in Kuopio include for example various forms of tomography, wave propagation and satellite observations of atmospheric aerosols.

Recently, in collaboration with the Finnish Meteorological Institute's Unit in Kuopio and NASA, significant progress has been made in improving the inversion algorithms related with satellite remote sensing of aerosol optical depth. Another important field utilizing satellite remote sensing is forest bioeconomy, where the methodology is developed as a collaboration between the Department of Applied Physics and the School of Forest Sciences. These techniques are especially important in forest inventory studies.

University of Vaasa
PO Box 700
FI-65101 Vaasa
Finland
https://www.univaasa.fi

The University of Vaasa is an academic institution that has four Schools (Technology and Innovation, Management, Marketing and Communications, Accounting and Finance) and three multidisciplinary research platforms on strategically chosen topics - digitalisation, innovation and entrepreneurship as well as energy technology business.

The University of Vaasa has space-related activities in several of its units. Its Digital Economy research platform and School of Technology and Innovations develop space technology in the form of small satellite design, satellite remote sensing methods using computer vision methodology, and satellite positioning technologies especially for logistics and supply chain monitoring needs. The School of Management has expertise in geospatial analysis in the field of regional studies, among other things as a basis for urban and regional development and rural planning. The Schools of Marketing and Communications as well as Accounting and Finance have expertise in the field of space business models and innovation ecosystems, especially in the development of new space data innovations, new business models in the space economy and space-based data utilization in economic forecasting.

Multidisciplinary space-related expertise has grown in the past years at the University of Vaasa, especially with the university's EU-funded Finnish-Swedish Kvarken Space Economy project (http://www.kvarkenspacecenter.org), which aims to develop methods for utilizing satellite data and GNSS in, for example, agriculture and forestry, fisheries, nature conservation, logistics, energy transmission (synchronization) and sustainable transport. One of the important tasks of the project is to help companies use the information available from space in their business development and to create a space information center in the Kvarken region of the Gulf of Bothnia of the Baltic Sea. This “Kvarken Space Center” created data and expertise will be disseminated to companies, educational institutions and other actors in the area to create novel space-based competencies and innovations. The project is also building a satellite data ground station for the university on two frequencies, and also plans to register a cubesatellite called KvarkenSat and launch it in Nordic collaboration from Kiruna, Sweden in late 2022 as a technology demonstration mission.

In addition, the University of Vaasa's recent research opening “Everyday Space” by regional studies looks far into the future and towards the everyday life of space colonies, as the project maps people's reactions, views and perceptions in everyday talks on future extraterrestrial communities.

National Public and Private sector launches

Launch Programme and Finnish participation

Launch Programme and Finnish participation

Schedule Programme and Finnish participation

Finnish Centre for Astronomy with ESO (FINCA)

Finnish Participations

Unique cubesat observations with the Suomi 100 satellite

Modelling, analyzing, and visualizing turbulent, magnetized astrophysical flows

Geospace research with the Suomi 100 CubeSat

Space environment studies

Global hybrid plasma modelling

Metsähovi Radio Observatory

Image of the supermassive black hole in the centre of the Milky Way

Two supermassive black holes in the centre of the quasar PKS 2131-021

RadioAstron Black Hole Jet Observations

Supermassive Black Holes seen with Gravitational Lensing

Long-term variability of solar activity and solar wind disturbances

Geomagnetic activity and instrument development

Modelling the long-term evolution of the solar dynamo

Perseverance rover mission for the exploration of Mars

First accurate assessment of the Earth’s seasonal snow mass

Ground conductivity plays an important role when estimating geomagnetically induced currents during space weather storms

A new method to reconstruct volumetric images on ionospheric electron density

Mars Curiosity detects seasonal variation of Mars atmospheric methane

Improving the global picture of carbon cycle and greenhouse gases by satellites

Increased societal impact using air quality observations of OMI

Space Geodesy

Navigation and Positioning

Earth Observation

Research Fields

The First Global 6D Magnetosphere Vlasov simulation

Observational prospects for phase transitions at LISA

Analyzing solar eruptions from Sun to Earth

The First Global 6D Magnetosphere Vlasov simulation

Solar Superstorm of AD 774 accurately dated

Black hole mergers in a full cosmological setting

Space Climate research group

New results on the influence of energetic particle precipitation on polar vortex dynamics

Influence of By component of interplanetary magnetic field on solar wind-magnetosphere coupling

Cosmic Ray research group

Extreme solar events and the worst-case scenario of a radiation storm

Ionospheric Physics research group

Auroral Current are Stronger in the Northern Hemisphere

Astronomy Research group

Abrupt shrinking of solar corona in the late 1990s

Systematic re-analysis of major solar energetic particle events of the space era

New results on the influence of energetic particle precipitation on polar vortex dynamics

Auroral Current are Stronger in the Northern Hemisphere

Space Research Laboratory (SRL)

Particle Telescope (PATE) for Foresail-1 satellite

High-Energy Astrophysics group

Rapidly Rotating Neutron Stars

X-ray Pulsars at Low Luminosities

Transitional Millisecond Pulsars

Optical Polarimetry of Compact Objects

Astrophysical Transients group

Late-phase spectroscopy of supernovae

Observations of Electromagnetic Counterparts of Gravitational Wave Sources

Tidal Disruption Events

Finnish Center for Astronomy with ESO (FINCA)

The disc-like host galaxies of radio-loud narrow-line Seyfert 1s

Connecting high-energy neutrinos with active galactic nuclei

VTT Hyperspectral imaging technology

VTT Remote Sensing

Radiation Effects Facility (RADEF)

Heavy ion cocktails at RADEF

Linear electron accelerator

Ongoing EU projects at RADEF

EU MSCA-Horizon-2020 ITN project, RADSAGA (GA#721624)

Erasmus Mundus Joint Master Degree programme – RADMEP

Erasmus Mundus Joint Master Degree programme – RADMEP

Ongoing EU projects at RADEF

Estimation of proton induced Single Event Effect rates in very deep submicron technologies

Radiation Characterisation of EEE components for ESA space applications

Thermal nanophysics group at Nanoscience Center (NSC)