Mysterious misalignments between geomagnetic and stellar reference frames seen in CHAMP and Swarm satellite measurements

2015 ◽  
Vol 203 (3) ◽  
pp. 1873-1876 ◽  
Author(s):  
Stefan Maus
Keyword(s):  
Magnetic Field ◽  
Reference Frames ◽  
European Space Agency ◽  
Processing System ◽  
Field Measurements ◽  
Low Earth Orbit ◽  
Space Agency ◽  
Order Of Magnitude ◽  
Stellar Aberration ◽  
Star Camera

AbstractThe orientation of a spacecraft in Low Earth Orbit can be determined accurately from either magnetic field measurements or star camera images. Ideally, the independently computed spacecraft attitudes should agree. However, we find that the German CHAMP and European Space Agency triple-satellite Swarm geomagnetic satellites exhibit consistent misalignments between the stellar and geomagnetic reference frames, which oscillate with the local time of the orbit. Having an amplitude of 20 arcsec, these oscillations are more than an order of magnitude larger than the stability of the optical bench, which cohosts the magnetometers and star cameras. The misalignments could originate either from the magnetometer or star camera measurements. On one hand, as-yet-unknown external magnetic field contributions could appear as a rotation of the geomagnetic reference frame. On the other hand, the observed misalignments agree in amplitude and phase with the effects of stellar aberration, caused by the movement of the star cameras relative to the light rays emitted by the stars. This is surprising because stellar aberration is allegedly already corrected for by the star image processing system. Resolving these mysterious misalignments is key to fulfilling the measurement accuracy requirements and science objectives of the ongoing Swarm mission. If caused by stellar aberration, fully correcting for this effect could significantly improve the attitude accuracy not only of CHAMP and Swarm, but also of several other past and ongoing scientific satellite missions.

Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby

2021 ◽  
Author(s):  
Wei-Jie Sun ◽  
James Slavin ◽  
Rumi Nakamura ◽  
Daniel Heyner ◽  
Johannes Mieth
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
European Space Agency ◽  
Flux Rope ◽  
Transfer Event ◽  
Flux Transfer Events ◽  
Space Agency ◽  
Flux Ropes ◽  
Flux Transfer ◽  
Magnetospheric Multiscale Mission

<p>BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the  flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees.  As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.</p>

End effects in the magnetic field of free electron lasers with sheet electron beams

1990 ◽  
Vol 68 (11) ◽  
pp. 1227-1236
Author(s):  
G. Pocobelli
Keyword(s):  
Magnetic Field ◽  
Free Electron ◽  
Electron Beams ◽  
Field Measurements ◽  
End Effects ◽  
Direction Parallel ◽  
Additional Degree ◽  
Order Of Magnitude ◽  
Three Space ◽  
The Magnetic Field

We calculate the magnetic field of a free-electron-laser's wiggler of a recent design (Granatstein et al. Appl. Phys. Lett. 74, 643 (1985)) using sheet electron beams. We did not assume periodic boundary conditions, as was done in their work, and we obtained analytical expressions in two of the three space variables. We found various irregularities in the field behavior that were dependent on the size of the wiggler in the x direction (parallel to the beam's wide size), and that increased up to a width an order of magnitude greater than the height of the beam channel. These irregularities had been observed in field measurements. A method consisting of making the end magnets thinner worked effectively to reduce the irregularities. We also studied a similar magnetic configuration with free and independent currents and no magnets, and added the additional degree of freedom of programming the currents to further reduce the irregularities.

scholarly journals Field Intercomparison of Radiometers Used for Satellite Validation in the 400–900 nm Range

2019 ◽  
Vol 11 (9) ◽  
pp. 1129 ◽  
Author(s):  
Viktor Vabson ◽  
Joel Kuusk ◽  
Ilmar Ansko ◽  
Riho Vendt ◽  
Krista Alikas ◽  
...  
Keyword(s):  
Ocean Color ◽  
European Space Agency ◽  
Field Measurements ◽  
Stray Light ◽  
Radiometric Calibration ◽  
Space Agency ◽  
Systematic Effects ◽  
Funded Project ◽  
Field Intercomparison ◽  
Reference Measurements

An intercomparison of radiance and irradiance ocean color radiometers (the second laboratory comparison exercise—LCE-2) was organized within the frame of the European Space Agency funded project Fiducial Reference Measurements for Satellite Ocean Color (FRM4SOC) May 8–13, 2017 at Tartu Observatory, Estonia. LCE-2 consisted of three sub-tasks: (1) SI-traceable radiometric calibration of all the participating radiance and irradiance radiometers at the Tartu Observatory just before the comparisons; (2) indoor, laboratory intercomparison using stable radiance and irradiance sources in a controlled environment; (3) outdoor, field intercomparison of natural radiation sources over a natural water surface. The aim of the experiment was to provide a link in the chain of traceability from field measurements of water reflectance to the uniform SI-traceable calibration, and after calibration to verify whether different instruments measuring the same object provide results consistent within the expected uncertainty limits. This paper describes the third phase of LCE-2: The results of the field experiment. The calibration of radiometers and laboratory comparison experiment are presented in a related paper of the same journal issue. Compared to the laboratory comparison, the field intercomparison has demonstrated substantially larger variability between freshly calibrated sensors, because the targets and environmental conditions during radiometric calibration were different, both spectrally and spatially. Major differences were found for radiance sensors measuring a sunlit water target at viewing zenith angle of 139° because of the different fields of view. Major differences were found for irradiance sensors because of imperfect cosine response of diffusers. Variability between individual radiometers did depend significantly also on the type of the sensor and on the specific measurement target. Uniform SI traceable radiometric calibration ensuring fairly good consistency for indoor, laboratory measurements is insufficient for outdoor, field measurements, mainly due to the different angular variability of illumination. More stringent specifications and individual testing of radiometers for all relevant systematic effects (temperature, nonlinearity, spectral stray light, etc.) are needed to reduce biases between instruments and better quantify measurement uncertainties.

scholarly journals The e-ASTROGAM space mission: a major step forward for supernova physics

2017 ◽  
Vol 12 (S331) ◽  
pp. 351-356
Author(s):  
Vincent Tatischeff ◽  
Roland Diehl ◽  
Alessandro De Angelis
Keyword(s):  
Gamma Ray ◽  
European Space Agency ◽  
Space Mission ◽  
Medium Size ◽  
Major Step ◽  
Space Agency ◽  
Broad Energy Range ◽  
Order Of Magnitude ◽  
Energy Gamma ◽  
Broad Energy

Abstracte-ASTROGAM is a gamma-ray observatory operating in a broad energy range, 0.15 MeV – 3 GeV, recently proposed as the M5 Medium-size mission of the European Space Agency. It has the potential to revolutionize the astronomy of medium-energy gamma-rays by increasing the number of known sources in this domain by more than an order of magnitude and providing gamma-ray polarization information for many of these sources. In these proceedings, we discuss the expected capacity of the mission to study the physics of supernovae, both thermonuclear and core-collapse, as well as the origin of cosmic rays in SN shocks.

scholarly journals First observations of magnetic holes deep within the coma of a comet

2018 ◽  
Vol 618 ◽  
pp. A114 ◽  
Author(s):  
F. Plaschke ◽  
T. Karlsson ◽  
C. Götz ◽  
C. Möstl ◽  
I. Richter ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
European Space Agency ◽  
Time Frame ◽  
Fluxgate Magnetometer ◽  
Space Agency ◽  
First Time ◽  
Comet 67P

The Rosetta spacecraft of the European Space Agency made ground-breaking observations of comet 67P/Churyumov-Gerasimenko and of its cometary environment. We search for magnetic holes in that environment, i.e., significant depressions in the magnetic field strength, measured by the Rosetta fluxgate Magnetometer (MAG) in April and May 2015. In that time frame of two months, we identified 23 magnetic holes. The cometary activity was intermediate and increasing because Rosetta was on the inbound leg toward the Sun. While in April solar wind protons were still observed by Rosetta near the comet, in May these protons were already mostly replaced by heavy cometary ions. Magnetic holes have frequently been observed in the solar wind. We find, for the first time, that magnetic holes exist in the cometary environment even when solar wind protons are almost absent. Some of the properties of the magnetic holes are comparable to those of solar wind holes; they are associated with density enhancements, sometimes associated with co-located current sheets and fast solar wind streams, and are of similar scales. However, particularly in May, the magnetic holes near the comet appear to be more processed, featuring shifted density enhancements and, sometimes, bipolar signatures in magnetic field strength rather than simple depressions. The magnetic holes are of global size with respect to the coma. However, at the comet, they are compressed owing to magnetic field pile-up and draping so that they change in shape. There, the magnetic holes become of comparable size to heavy cometary ion gyroradii, potentially enabling kinetic interactions.

Activities of the International Space Organization and Station

2021 ◽  
pp. 140-152
Keyword(s):  
International Space Station ◽  
Artificial Satellite ◽  
European Space Agency ◽  
Space Station ◽  
Low Earth Orbit ◽  
Joint Project ◽  
Intergovernmental Organization ◽  
International Space ◽  
Space Agency ◽  
Space Organization

This chapter describes the establishment process, purpose of establishment, mission, exploration plan, activities of the European Space Agency (ESA) and International Space Station (ISS), and an explanation of the contents of the treaty that is legal basis for its establishment. The European Space Agency (ESA) is an intergovernmental organization of 22 member states dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a worldwide staff of about 2,200 in 2018 and an annual budget of about € 6.68 billion (US $ 7.43 billion) in 2020. ESA also works closely with space organizations outside Europe. ESA has missions planned for Jupiter (JUICE, 2022) and others that will seek dark matter (Euclid, 2020) and observe the energetic universe (Athena, 2028). The International Space Station (ISS) is a space station (habitable artificial satellite) in low Earth orbit. The ISS programme is a joint project between five participating space agencies: NASA (United States), Roscomos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada).

scholarly journals Implementation of a Cryogenic Facility for Space Debris Analysis

2021 ◽  
Vol 11 (3) ◽  
pp. 948
Author(s):  
Paulo Gordo ◽  
Tiago Frederico ◽  
Rui Melicio ◽  
António Amorim
Keyword(s):  
Space Debris ◽  
Vacuum Ultraviolet ◽  
European Space Agency ◽  
Space Missions ◽  
Low Earth Orbit ◽  
Material Degradation ◽  
Pressure Sensitive Adhesive ◽  
Material Evaluation ◽  
Space Agency ◽  
Earth Orbits

This paper has resulted from a continued study of spacecraft material degradation and space debris formation. The design and implementation of a thermal vacuum cycling cryogenic facility for the evaluation of space debris generation at a low Earth orbit (LEO) is presented. The facility used for spacecraft external material evaluation is described, and some of the obtained results are presented. The infrastructure was developed in the framework of a study for the European Space Agency (ESA). The main purpose of the cryogenic facility is to simulate the LEO spacecraft environment, namely thermal cycling and vacuum ultraviolet (VUV) irradiation to simulate the spacecraft material degradation and the generation of space debris. In a previous work, some results under LEO test conditions showed the effectiveness of the cryogenic facility for material evaluation, namely: the degradation of satellite paints with a change in their thermo-optical properties, leading to the emission of cover flakes; the degradation of the pressure-sensitive adhesive (PSA) used to glue Velcro’s to the spacecraft, and to glue multilayer insulation (MLI) to the spacecraft’s. The paint flakes generated are space debris. Hence, in a scenario of space missions where a spacecraft has lost the thermal shielding capability, the failure of PSA tape and the loss of Velcro properties may contribute to the release of the full MLI blanket, contributing to the generation of space debris that presents a growing threat to space missions in the main Earth orbits.

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