Auroral imaging with combined Suomi 100 nanosatellite and ground-based observations: A case study

Auroras can be regarded as the most fascinating manifestation of space weather and they are continuously observed by ground-based and, nowadays more and more, also by space-based measurements. Investigations of auroras and geospace comprise the main research goals of the Suomi 100 nanosatellite, the first Finnish space research satellite, which has been measuring the Earth's ionosphere since its launch on Dec. 3, 2018. In this work, we present a case study where the satellite's camera observations of an aurora over Northern Europe are combined with ground-based observations of the same event. The analyzed image is, to the authors' best knowledge, the first auroral image ever taken by a cubesat. Our data analysis shows that a satellite vantage point provides complementary, novel information of such phenomena. The 3D auroral location reconstruction of the analyzed auroral event demonstrates how information from a 2D image can be used to provide location information of auroras under study. The location modelling also suggests that the Earth's limb direction, which was the case in the analyzed image, is an ideal direction to observe faint auroras. Although imaging on a small satellite has some large disadvantages compared with ground-based imaging (the camera cannot be repaired, a fast moving spinning satellite), the data analysis and modelling demonstrate how even a small 1-Unit (size: 10 cm x 10 cm x 10 cm) CubeSat and its camera, build using cheap commercial off-the-shelf components, can open new possibilities for auroral research, especially, when its measurements are combined with ground-based observations.Comment: Accepted manuscript 34 pages, 17 figure

Radar—CubeSat Transionospheric HF Propagation Observations: Suomi 100 Satellite and EISCAT HF Facility

Radio waves provide a useful diagnostic tool to investigate the properties of the ionosphere because the ionosphere affects the transmission and properties of high frequency (HF) electromagnetic waves. We have conducted a transionospheric HF-propagation research campaign with a nanosatellite on a low-Earth polar orbit and the EISCAT HF transmitter facility in Tromsø, Norway, in December 2020. In the active measurement, the EISCAT HF facility transmitted sinusoidal 7.953 MHz signal which was received with the High frEquency rAdio spectRomEteR (HEARER) onboard 1 Unit (size: 10 × 10 × 10 cm) Suomi 100 space weather nanosatellite. Data analysis showed that the EISCAT HF signal was detected with the satellite's radio spectrometer when the satellite was the closest to the heater along its orbit. Part of the observed variations seen in the signal was identified to be related to the heater's antenna pattern and to the transmitted pulse shapes. Other observed variations can be related to the spatial and temporal variations of the ionosphere and its different responses to the used transmission frequencies and to the transmitted O- and X-wave modes. Some trends in the observed signal may also be associated to changes in the properties of ionospheric plasma resulting from the heater's electromagnetic wave energy. This paper is, to authors' best knowledge, the first observation of this kind of “self-absorption” measured from the transionospheric signal path from a powerful radio source on the ground to the satellite-borne receiver

COSIMA-Rosetta calibration for in-situ characterization of 67P/Churyumov-Gerasimenko cometary inorganic compounds

20 pages, 3 figures, 5 tablesInternational audienceCOSIMA (COmetary Secondary Ion Mass Analyser) is a time-of-flight secondary ion mass spectrometer (TOF-SIMS) on board the Rosetta space mission. COSIMA has been designed to measure the composition of cometary dust grains. It has a mass resolution m/{\Delta}m of 1400 at mass 100 u, thus enabling the discrimination of inorganic mass peaks from organic ones in the mass spectra. We have evaluated the identification capabilities of the reference model of COSIMA for inorganic compounds using a suite of terrestrial minerals that are relevant for cometary science. Ground calibration demonstrated that the performances of the flight model were similar to that of the reference model. The list of minerals used in this study was chosen based on the mineralogy of meteorites, interplanetary dust particles and Stardust samples. It contains anhydrous and hydrous ferromagnesian silicates, refractory silicates and oxides (present in meteoritic Ca-Al-rich inclusions), carbonates, and Fe-Ni sulfides. From the analyses of these minerals, we have calculated relative sensitivity factors for a suite of major and minor elements in order to provide a basis for element quantification for the possible identification of major mineral classes present in the cometary grains

Carbon-rich dust in comet 67P/Churyumov-Gerasimenko measured by COSIMA/Rosetta

Cometary ices are rich in CO2, CO and organic volatile compounds, but the carbon content of cometary dust was only measured for the Oort Cloud comet 1P/Halley, during its flyby in 1986. The COmetary Secondary Ion Mass Analyzer (COSIMA)/Rosetta mass spectrometer analysed dust particles with sizes ranging from 50 to 1000 μm, collected over 2 yr, from 67P/Churyumov-Gerasimenko (67P), a Jupiter family comet. Here, we report 67P dust composition focusing on the elements C and O. It has a high carbon content (atomic |${\rm{C}}/{\rm{Si}} = 5.5{\rm{\ }}_{ - 1.2}^{ + 1.4}\ \ {\rm{on\ average}}$ |⁠) close to the solar value and comparable to the 1P/Halley data. From COSIMA measurements, we conclude that 67P particles are made of nearly 50 per cent organic matter in mass, mixed with mineral phases that are mostly anhydrous. The whole composition, rich in carbon and non-hydrated minerals, points to a primitive matter that likely preserved its initial characteristics since the comet accretion in the outer regions of the protoplanetary disc.</p

Nitrogen-to-carbon atomic ratio measured by COSIMA in the particles of comet 67P/Churyumov–Gerasimenko

The COmetary Secondary Ion Mass Analyzer (COSIMA) on board the Rosetta mission has analysed numerous cometary dust particles collected at very low velocities (a few m s−1) in the environment of comet 67P/Churyumov–Gerasimenko (hereafter 67P). In these particles, carbon and nitrogen are expected mainly to be part of the organic matter. We have measured the nitrogen-to-carbon (N/C) atomic ratio of 27 cometary particles. It ranges from 0.018 to 0.06 with an averaged value of 0.035 ± 0.011. This is compatible with the measurements of the particles of comet 1P/Halley and is in the lower range of the values measured in comet 81P/Wild 2 particles brought back to Earth by the Stardust mission. Moreover, the averaged value found in 67P particles is also similar to the one found in the insoluble organic matter extracted from CM, CI and CR carbonaceous chondrites and to the bulk values measured in most interplanetary dust particles and micrometeorites. The close agreement of the N/C atomic ratio in all these objects indicates that their organic matters share some similarities and could have a similar chemical origin. Furthermore, compared to the abundances of all the detected elements in the particles of 67P and to the elemental solar abundances, the nitrogen is depleted in the particles and the nucleus of 67P as was previously inferred also for comet 1P/Halley. This nitrogen depletion could constrain the formation scenarios of cometary nuclei.</p

Radar – CubeSat Transionospheric HF Propagation Observations: Suomi 100 Satellite and EISCAT HF Facility

Radio waves provide a useful diagnostic tool to investigate the properties of the ionosphere because the ionosphere affects the transmission and properties of High Frequency (HF) electromagnetic waves. We have conducted a transionospheric HF-propagation research campaign with a nanosatellite on a low-Earth polar orbit and the EISCAT HF transmitter facility in Tromsø, Norway, in December 2020. In the active measurement, the EISCAT HF facility transmitted sinusoidal 7.953 MHz signal which was received with the HEARER radio spectrometer onboard 1 Unit (size: 10 cm × 10 cm × 10 cm) Suomi 100 space weather nanosatellite. Data analysis showed that the EISCAT HF signal was detected with the satellite’s radio spectrometer when the satellite was the closest to the heater along its orbit. Part of the observed variations seen in the signal was identified to be related to the heater’s antenna pattern and to the transmitted pulse shapes. Other observed variations can be related to the spatial and temporal variations of the ionosphere and its different responses to the used transmission frequencies and to the transmitted O- and X-wave modes. Some trends in the observed signal may also be associated to changes in the properties of ionospheric plasma resulting from the heater’s electromagnetic wave energy. This paper is, to authors’ best knowledge, the first observation of this kind of "self-absorption" measured from the transionospheric signal path from a powerful radio source on the ground to the satellite-borne receiver.Peer reviewe

Variations in cometary dust composition from Giotto to Rosetta, clues to their formation mechanisms

International audienceThis paper reviews the current knowledge on the composition of cometary dust (ice, minerals and organics) in order to constrain their origin and formation mechanisms. Comets have been investigated by astronomical observations, space missions (Giotto to Rosetta), and by the analysis of cometary dust particles collected on Earth, chondritic porous interplanetary dust particles (CP-IDPs) and ultracarbonaceous Antarctic micrometeorites (UCAMMs). Most ices detected in the dense phases of the interstellar medium (ISM) have been identified in cometary volatiles. However, differences also suggest that cometary ices cannot be completely inherited from the ISM. Cometary minerals are dominated by crystalline Mg-rich silicates, Fe sulphides and glassy phases including GEMS (glass with embedded metals and sulphides). The crystalline nature and refractory composition of a significant fraction of the minerals in comets imply a high temperature formation/processing close to the proto-Sun, resetting a possible presolar signature of these phases. These minerals were further transported up to the external regions of the disc and incorporated in comet nuclei. Cometary matter contains a low abundance of isotopically anomalous minerals directly inherited from the presolar cloud. At least two different kinds of organic matter are found in dust of cometary origin, with low or high nitrogen content. N-poor organic matter is also observed in primitive interplanetary materials (like carbonaceous chondrites) and its origin is debated. The N-rich organic matter is only observed in CP-IDPs and UCAMMs and can be formed by Galactic cosmic ray irradiation of N2- and CH4-rich icy surface at large heliocentric distance beyond a ‘nitrogen snow line’