L.H. Svedhem
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7 records found
1
Journal article
(2026)
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Jacob Parrott, Beatriz Sánchez-Cano, Håkan Svedhem, Olivier Witasse, Dikshita Meggi, Colin Wilson, Alejandro Cardesín-Moinelo, Ingo Müller-Wodarg
Solar energetic events can have considerable effects on planetary ionospheres. However, the erratic nature of these solar energetic events make observations difficult. Here we show a mutual radio occultation observation, which serendipitously occurred just 10 minutes after a large solar flare impacted Mars. This resulted in the largest lower ionospheric layer ever recorded, where it was 278% its typical size. We used in-situ soft x-ray irradiance measurements to show a threefold increase in flux. This infers a different relation of soft X-ray to this layer's density than previously thought, with variations depending on the amount of spectrum 'hardening' leading to the increase of ionisation from secondaries.
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Solar energetic events can have considerable effects on planetary ionospheres. However, the erratic nature of these solar energetic events make observations difficult. Here we show a mutual radio occultation observation, which serendipitously occurred just 10 minutes after a large solar flare impacted Mars. This resulted in the largest lower ionospheric layer ever recorded, where it was 278% its typical size. We used in-situ soft x-ray irradiance measurements to show a threefold increase in flux. This infers a different relation of soft X-ray to this layer's density than previously thought, with variations depending on the amount of spectrum 'hardening' leading to the increase of ionisation from secondaries.
Journal article
(2026)
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Harald Krüger, Masanori Kobayashi, Hiroshi Kimura, Tomoko Arai, Håkan Svedhem, Sho Sasaki
Nozomi was Japan’s first space mission to Mars, launched on 3 July 1998 UT. It was equipped with the Mars Dust Counter (MDC) which was an impact ionisation dust detector. MDC detected 96 dust particle impacts when the spacecraft was in Earth orbit and later in interplanetary space, before its operation ended in April 2002 due to a technical failure on board. We compare the Nozomi dust measurements with the dust measurements obtained with the dust detector on board the Ulysses spacecraft. Impact speeds and masses of dust particles measured by Nozomi MDC are overall consistent with the measurements obtained by Ulysses in the same region of interplanetary space. Based on the impact speeds measured while Nozomi was in Earth orbit, MDC detected neither dust particles of natural origin that were bound to the Earth nor space debris. The dust impact rate measured in interplanetary space varied by approximately a factor of 2, consistent with theoretical predictions by the Interplanetary Meteoroid Engineering Model. The particle impact direction was concentrated towards the ecliptic plane, in agreement with an interplanetary origin of the majority of the measured dust particles. No impacts of cometary trail particles could positively be identified during known cometary trail crossings of Nozomi. The Nozomi dust data may become a valuable reference for the dust measurements to be obtained in the same region of interplanetary space with future space missions like, for example, MMX and DESTINY+.
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Nozomi was Japan’s first space mission to Mars, launched on 3 July 1998 UT. It was equipped with the Mars Dust Counter (MDC) which was an impact ionisation dust detector. MDC detected 96 dust particle impacts when the spacecraft was in Earth orbit and later in interplanetary space, before its operation ended in April 2002 due to a technical failure on board. We compare the Nozomi dust measurements with the dust measurements obtained with the dust detector on board the Ulysses spacecraft. Impact speeds and masses of dust particles measured by Nozomi MDC are overall consistent with the measurements obtained by Ulysses in the same region of interplanetary space. Based on the impact speeds measured while Nozomi was in Earth orbit, MDC detected neither dust particles of natural origin that were bound to the Earth nor space debris. The dust impact rate measured in interplanetary space varied by approximately a factor of 2, consistent with theoretical predictions by the Interplanetary Meteoroid Engineering Model. The particle impact direction was concentrated towards the ecliptic plane, in agreement with an interplanetary origin of the majority of the measured dust particles. No impacts of cometary trail particles could positively be identified during known cometary trail crossings of Nozomi. The Nozomi dust data may become a valuable reference for the dust measurements to be obtained in the same region of interplanetary space with future space missions like, for example, MMX and DESTINY+.
Journal article
(2026)
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Dmitrij Titov, Patrick Martin, Gerhard Kminek, Agustin Chicarro, Colin Wilson, Olivier Witasse, Alejandro Cardesín-Moinelo, Håkan Svedhem, Claire Parfitt, Daniel Paardekooper, Jorge L. Vago, Elliot Sefton-Nash
Mars Express (MEX) is one of the most productive planetary missions of the European Space Agency (ESA). This low cost (∼150 M€) mission has been instrumental in shaping the planetary community in Europe and has contributed to paving the way for many subsequent ESA endeavours. During more than two decades, Mars Express has collected a wealth of data in all disciplines of Martian science. This paper concludes the Topical Collection “Mars Express: Pioneering Two Decades of European Science and Exploration of Mars” prepared under the auspices of the International Space Science Institute. It briefly describes various aspects of the mission (leaving details to dedicated articles), summarizes the major science achievements, discusses the lessons learned from 20 years of Mars Express operations, and bridges with future Mars science and exploration.
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Mars Express (MEX) is one of the most productive planetary missions of the European Space Agency (ESA). This low cost (∼150 M€) mission has been instrumental in shaping the planetary community in Europe and has contributed to paving the way for many subsequent ESA endeavours. During more than two decades, Mars Express has collected a wealth of data in all disciplines of Martian science. This paper concludes the Topical Collection “Mars Express: Pioneering Two Decades of European Science and Exploration of Mars” prepared under the auspices of the International Space Science Institute. It briefly describes various aspects of the mission (leaving details to dedicated articles), summarizes the major science achievements, discusses the lessons learned from 20 years of Mars Express operations, and bridges with future Mars science and exploration.
Journal article
(2025)
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Jacob Parrott, Håkan Svedhem, Beatriz Sánchez-Cano, Olivier Witasse, Colin Wilson, Ingo Müller-Wodarg
This study presents a comprehensive analysis of the Martian ionosphere using Mutual Radio Occultation (RO) observations between Mars Express and Trace Gas Orbiter, featuring 71 full vertical profiles out of a total of 124 measurements. Among these, 35 measurements were taken from regions with Solar Zenith Angles lower than 40°. The profiles also represent the largest data set for the lower M1 ionospheric layer during the midday ever measured. This paper has also been submitted with a comprehensive data set, which marks the first time MEX-TGO RO data has been made available to the community. Additionally, neutral temperature profiles have been extracted from the measurements. We find unexpected features in the lower thermosphere temperature behavior which we conclude is likely due to the effects of local circulation and associated dynamical heating rather than solar-controlled.
...
This study presents a comprehensive analysis of the Martian ionosphere using Mutual Radio Occultation (RO) observations between Mars Express and Trace Gas Orbiter, featuring 71 full vertical profiles out of a total of 124 measurements. Among these, 35 measurements were taken from regions with Solar Zenith Angles lower than 40°. The profiles also represent the largest data set for the lower M1 ionospheric layer during the midday ever measured. This paper has also been submitted with a comprehensive data set, which marks the first time MEX-TGO RO data has been made available to the community. Additionally, neutral temperature profiles have been extracted from the measurements. We find unexpected features in the lower thermosphere temperature behavior which we conclude is likely due to the effects of local circulation and associated dynamical heating rather than solar-controlled.
First Results of Mars Express
ExoMars Trace Gas Orbiter Mutual Radio Occultation
Journal article
(2024)
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Jacob Parrott, Håkan Svedhem, Olivier Witasse, Colin Wilson, Ingo Müller-Wodarg, Alejandro Cardesín-Moinelo, Peter Schmitz, James Godfrey, Olivier Reboud, More authors...
Spacecraft-to-spacecraft radio occultations experiments are being conducted at Mars between Mars Express (MEX) and Trace Gas Orbiter (TGO), the first ever extensive inter-spacecraft occultations at a planet other than Earth. Here we present results from the first 83 such occultations, conducted between 2 Nov 2020 and 5th of July 2023. Of these, 44 observations have to-date resulted in the extraction of vertical electron density profiles. These observations are the successful results of a major feasibility study conducted by the European Space Agency to use pre-existing relay communication equipment for radio science purposes. Mutual radio occultations have numerous advantages over traditional spacecraft-to-ground station occultations. In this work, we demonstrate how raw data are transformed into electron density values and validated with models and other instruments.
...
Spacecraft-to-spacecraft radio occultations experiments are being conducted at Mars between Mars Express (MEX) and Trace Gas Orbiter (TGO), the first ever extensive inter-spacecraft occultations at a planet other than Earth. Here we present results from the first 83 such occultations, conducted between 2 Nov 2020 and 5th of July 2023. Of these, 44 observations have to-date resulted in the extraction of vertical electron density profiles. These observations are the successful results of a major feasibility study conducted by the European Space Agency to use pre-existing relay communication equipment for radio science purposes. Mutual radio occultations have numerous advantages over traditional spacecraft-to-ground station occultations. In this work, we demonstrate how raw data are transformed into electron density values and validated with models and other instruments.
Journal article
(2023)
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Beatriz Sánchez-Cano, Olivier Witasse, Elise W. Knutsen, Dikshita Meggi, Shayla Viet, Mark Lester, Marco Pinto, Peter Schmitz, Håkan Svedhem, More Authors...
Despite the growing importance of planetary Space Weather forecasting and radiation protection for science and robotic exploration and the need for accurate Space Weather monitoring and predictions, only a limited number of spacecraft have dedicated instrumentation for this purpose. However, every spacecraft (planetary or astronomical) has hundreds of housekeeping sensors distributed across the spacecraft, some of which can be useful to detect radiation hazards produced by solar particle events. In particular, energetic particles that impact detectors and subsystems on a spacecraft can be identified by certain housekeeping sensors, such as the Error Detection and Correction (EDAC) memory counters, and their effects can be assessed. These counters typically have a sudden large increase in a short time in their error counts that generally match the arrival of energetic particles to the spacecraft. We investigate these engineering datasets for scientific purposes and perform a feasibility study of solar energetic particle event detections using EDAC counters from seven European Space Agency Solar System missions: Venus Express, Mars Express, ExoMars-Trace Gas Orbiter, Rosetta, BepiColombo, Solar Orbiter, and Gaia. Six cases studies, in which the same event was observed by different missions at different locations in the inner Solar System are analyzed. The results of this study show how engineering sensors, for example, EDAC counters, can be used to infer information about the solar particle environment at each spacecraft location. Therefore, we demonstrate the potential of the various EDAC to provide a network of solar particle detections at locations where no scientific observations of this kind are available.
...
Despite the growing importance of planetary Space Weather forecasting and radiation protection for science and robotic exploration and the need for accurate Space Weather monitoring and predictions, only a limited number of spacecraft have dedicated instrumentation for this purpose. However, every spacecraft (planetary or astronomical) has hundreds of housekeeping sensors distributed across the spacecraft, some of which can be useful to detect radiation hazards produced by solar particle events. In particular, energetic particles that impact detectors and subsystems on a spacecraft can be identified by certain housekeeping sensors, such as the Error Detection and Correction (EDAC) memory counters, and their effects can be assessed. These counters typically have a sudden large increase in a short time in their error counts that generally match the arrival of energetic particles to the spacecraft. We investigate these engineering datasets for scientific purposes and perform a feasibility study of solar energetic particle event detections using EDAC counters from seven European Space Agency Solar System missions: Venus Express, Mars Express, ExoMars-Trace Gas Orbiter, Rosetta, BepiColombo, Solar Orbiter, and Gaia. Six cases studies, in which the same event was observed by different missions at different locations in the inner Solar System are analyzed. The results of this study show how engineering sensors, for example, EDAC counters, can be used to infer information about the solar particle environment at each spacecraft location. Therefore, we demonstrate the potential of the various EDAC to provide a network of solar particle detections at locations where no scientific observations of this kind are available.
Aerobraking is an effective technique to save significant
amounts of fuel while lowering an orbit around a planet. It was first
applied by NASA at Venus, with Magellan during its extended mission, in
1993. The first aerobraking at Mars was done, also by NASA, with Mars
Global Surveyor, in 1999. ESA did its first experimental aerobraking
with Venus Express, near the end of its mission, at Venus in 2014. ESA’s
ExoMars Trace Gas Orbiter, TGO, was the first ESA spacecraft to do
aerobraking as a part of its nominal mission. TGO reduced its apocentre
attitude to near 400 km, to achieve a near circular orbit, during one
full year of aerobraking, finishing in April 2018.
Remote measurements of atmospheric parameters are difficult at
high altitudes due to the tenuous medium. However, atmospheric drag
experienced during aerobraking is directly proportional to the local
atmospheric density and this drag can be measured accurately by on board
accelerometers and so provide precise data on the local atmospheric
density along the s/c trajectory. Additional, even more sensitive data,
averaged along the trajectory, can be acquired by precise tracking of
the s/c orbit. Large data sets have been collected from both the Venus
Express and the TGO aerobraking campaigns. Both these data sets show
larger than expected day to day variations of the atmospheric densities
of the two planets throughout these campaigns. In spite of the large
differences in the surface pressure/density at the two planets, the
upper atmospheres are surprisingly similar, albeit highly variable.
This talk will focus these atmospheric differences and similarities,
and comparisons with existing models will be made. Potential
improvements in the method and optimisation of measurements will be
evaluated, and applications to ESA’s next Venus mission, ENVISION, will
be discussed.
...
Aerobraking is an effective technique to save significant
amounts of fuel while lowering an orbit around a planet. It was first
applied by NASA at Venus, with Magellan during its extended mission, in
1993. The first aerobraking at Mars was done, also by NASA, with Mars
Global Surveyor, in 1999. ESA did its first experimental aerobraking
with Venus Express, near the end of its mission, at Venus in 2014. ESA’s
ExoMars Trace Gas Orbiter, TGO, was the first ESA spacecraft to do
aerobraking as a part of its nominal mission. TGO reduced its apocentre
attitude to near 400 km, to achieve a near circular orbit, during one
full year of aerobraking, finishing in April 2018.
Remote measurements of atmospheric parameters are difficult at
high altitudes due to the tenuous medium. However, atmospheric drag
experienced during aerobraking is directly proportional to the local
atmospheric density and this drag can be measured accurately by on board
accelerometers and so provide precise data on the local atmospheric
density along the s/c trajectory. Additional, even more sensitive data,
averaged along the trajectory, can be acquired by precise tracking of
the s/c orbit. Large data sets have been collected from both the Venus
Express and the TGO aerobraking campaigns. Both these data sets show
larger than expected day to day variations of the atmospheric densities
of the two planets throughout these campaigns. In spite of the large
differences in the surface pressure/density at the two planets, the
upper atmospheres are surprisingly similar, albeit highly variable.
This talk will focus these atmospheric differences and similarities,
and comparisons with existing models will be made. Potential
improvements in the method and optimisation of measurements will be
evaluated, and applications to ESA’s next Venus mission, ENVISION, will
be discussed.