J/A+A/488/361 Mars Express astrometric observations of Phobos (Willner+, 2008)
New astrometric observations of Phobos with the SRC on Mars Express.
Willner K., Oberst J., Waehlisch M., Matz K-D., Hoffmann H., Roatsch T.,
Jaumann R., Mertens V.
<Astron. Astrophys. 488, 361 (2008)>
=2008A&A...488..361W 2008A&A...488..361W
ADC_Keywords: Planets ; Positional data
Keywords: astrometry - ephemerides - planets and satellites: individual: Phobos
Abstract:
New astrometric measurements for Phobos are reported on the basis of
69 SRC (Super Resolution Channel) images obtained during 28 Mars
Express Phobos flybys executed between 2004 and 2007. The measurements
have been made using a newly developed technique which involves
positional measurements of surface control points and verification of
camera pointing by background stars. The astrometric positions are in
excellent agreement with currently available Phobos orbit models.
However, we find remaining systematic offsets of 1.5-2.6km, with
Phobos ahead of the predicted position along its track. Our
observations will be a basis for further improvements in the Phobos
ephemeris. The methods we have developed will be useful for
astrometric tracking of planetary or asteroidal targets and spacecraft
optical navigation in future planetary missions.
Description:
Astrometric measurements were obtained from frame images of the SRC on
Mars Express. Camera pointing was controlled and corrected with
background star observations, made just before and after the Phobos
encounter.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 95 69 Astrometric observations of Phobos with respect
to Mars Express spacecraft position
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Image Image name
13- 22 A10 "Y-M-D" Obs.Date Date of image acquisition/observation
23 A1 --- --- [T]
24- 35 A12 "h:m:s" Obs.Time Time of image acquisition/observation
36- 45 F10.4 deg RAdeg Right ascension (J2000.0) wrt spacecraft
position
46- 55 F10.4 deg DEdeg Declination (J2000.0) wrt spacecraft position
56- 65 F10.4 deg ePos One sigma error of Right ascension/Declination
66- 75 F10.2 km Xpos X coordinate of Mars Express spacecraft in
Mars centered J2000.0 frame
76- 85 F10.2 km Ypos Y coordinate of Mars Express spacecraft in
Mars centered J2000.0 frame
86- 95 F10.2 km Zpos Z coordinate of Mars Express spacecraft in
Mars centered J2000.0 frame
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Acknowledgements:
Konrad Willner,
(End) Patricia Vannier [CDS] 23-May-2008