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| Titel |
Mars Express Bistatic Radar Observations 2016 |
| VerfasserIn |
Tom Andert, Richard A. Simpson, Martin Pätzold, Daniel S. Kahan, Stefan Remus, Kamal Oudrhiri |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143682
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| Publikation (Nr.) |
 EGU/EGU2017-7428.pdf |
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| Zusammenfassung |
| One objective of the Mars Express Radio Science Experiment (MaRS) is to address the
dielectric properties and surface roughness of Mars, which can be determined by means of a
surface scattering experiment, also known as bistatic radar (BSR). The radio subsystem
transmitter located on board the Mars Express spacecraft beams right circularly polarized
(RCP) radio signals at two wavelengths – 3.6 cm (X-Band) and 13 cm (S-Band) – toward
Mars’ surface. Part of the impinging radiation is then scattered toward a receiver at a ground
station on Earth and both the right and left circularly polarized echo components (RCP and
LCP, respectively) are recorded. The dielectric constant can be derived in this configuration
from the RCP-to-LCP power ratio. This approach eliminates the need for absolute end-to-end
calibration in favor of relative calibration of the RCP and LCP ground receiver channels.
Nonetheless, accurate relative calibration of the two receiving channels remains
challenging.
The most favorable configuration for bistatic radar experiments is around Earth-Mars
opposition, which occurs approximately every two years. In 2016 the minimum distance of
about 0.5 AU was reached on May 30th; eleven BSR experiments were successfully
conducted between the end of April and mid-June. The specular point tracks during two
experiments over the Syrtis Major region were very similar on April 27th and June 2nd, and
the data were collected using the same Earth-based antenna. The separation in time and the
different observing angles provide an opportunity to check reproducibility of the calibrations
and analysis methods.
The paper will illustrate the general spacecraft-to-ground BSR observation technique and
describe in detail the calibration procedures at the ground station needed to perform the
relative calibration of the two receiving channels. Results from the calibrations and the
surface observations will be shown for the two MaRS experiments over Syrtis Major. |
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