Title: Accurate Mars Express orbits to improve the determination of the mass and ephemeris of the Martian moons
Authors: Rosenblatt, P. ×
Lainey, V.
Le Maistre, S.
Marty, J.C.
Dehant, D.
Pätzold, M.
Van Hoolst, Tim
Häusler, B. #
Issue Date: May-2008
Publisher: Pergamon Press
Series Title: Planetary and Space Science vol:56 issue:7 pages:1043-1053
Abstract: The determination of the ephemeris of the Martian moons has benefited from observations
of their plane-of-sky positions derived from images taken by cameras
onboard spacecraft orbiting Mars. Images obtained by the Super Resolution Camera
(SRC) onboard Mars Express (MEX) have been used to derive moon positions
relative to Mars on the basis of a fit of a complete dynamical model of their motion
around Mars. Since, these positions are computed from the relative position
of the spacecraft when the images are taken, those positions need to be known
as accurately as possible. An accurate MEX orbit is obtained by fitting two years
of tracking data of the Mars Express Radio Science (MaRS) experiment onboard
MEX. The average accuracy of the orbits has been estimated to be around 20-25
meters. From these orbits, we have re-derived the positions of Phobos and Deimos
at the epoch of the SRC observations and compared them with the positions derived
by using the MEX orbits provided by the ESOC navigation team. After fit of the
orbital model of Phobos and Deimos, the gain in precision in the Phobos position
is roughly 30 meters, corresponding to the estimated gain of accuracy of the MEX
orbits. A new solution of the GM of the Martian moons has also been obtained
from the accurate MEX orbits, which is consistent with previous solutions and, for
Phobos, is more precise than the solution from the Mars Global Surveyor (MGS)
and Mars Odyssey (ODY) tracking data. It will be further improved with data from
MEX-Phobos closer encounters (at a distance less than 300 km). This study also
demonstrates the advantage of combining observations of the moon positions from a
spacecraft and from the Earth to assess the real accuracy of the spacecraft orbit. In
turn, the natural satellite ephemerides can be improved and participate to a better
knowledge of the origin and evolution of the Martian moons.
ISSN: 0032-0633
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Non-KU Leuven Association publications
× corresponding author
# (joint) last author

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