J/A+A/580/A28 Astrometric observations of Phobos (Pasewaldt+, 2015)
Astrometric observations of Phobos with the SRC on Mars Express:
New data and comparison of different measurement techniques.
Pasewaldt A., Oberst J., Willner K., Beisembin B., Hoffmann H., Matz K.D.,
Roatsch T., Michael G., Cardesin-Moinelo A., Zubarev A.E.
<Astron. Astrophys. 580, A28 (2015)>
=2015A&A...580A..28P 2015A&A...580A..28P
ADC_Keywords: Planets ; Positional data
Keywords: Astrometry - ephemerides - planets and satellites: individual: Phobos
Abstract:
Mars Express (MEX) carried out 74 Phobos flybys at distances between
669 and 5579km from April 2008 to August 2011. Images taken with the
Super Resolution Channel (SRC) were used to determine the Martian
moon's spacecraft-centered right ascension and declination.
Image positions of Phobos were measured using the control point and
limb fit measurement techniques. Camera pointing and pointing drift
were controlled by means of background star observations that were
compared to the corresponding positions from the Tycho-2 catalog.
Blurred and noisy images were restored by applying an image-based
point spread function in a Richardson-Lucy deconvolution.
Altogether, we provide 158 astrometric observations of Phobos with
estimated uncertainties between 0.224 and 3.405km circular about the
direction to the satellite. Control point measurements yield more
accurate results than limb fit observations.
Description:
The data is given in the form of two tables. Each table contains the
same set of observations: Data in tablea1.dat has been reduced using
MEX navigation orbits and predicted attitude by the European Space
Operations Centre (ESOC). tablea2.dat data has been derived using MEX
accurate orbits by the Royal Observatory of Belgium (ROB) and measured
attitude by the European Space Astronomy Centre (ESAC).
From 158 astrometric observations 103 were determined by means of both
methods, 27 using only control point measurements, and 28 performing
only limb fit observations. Hence, each data table contains 261
entries, namely 130 control point measurements and 131 limb fit
observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 104 261 Astrometric observations of Phobos reduced with
ESOC navigation orbits and ESOC predicted attitude
tablea2.dat 104 261 Astrometric observations of Phobos reduced with
ROB accurate orbits and ESAC measured attitude
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See also:
J/A+A/487/755 : CCD observations of Martian Satellites (Veiga+, 2008)
J/A+A/488/361 : Phobos Mars Express astrometric observations (Willner+, 2008)
J/A+A/572/A104 : Astrometric obs. of Phobos and Deimos in 1971 (Robert+, 2014)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Img Image name
13- 22 A10 "Y-M-D" Date Image date (UTC)
23 A1 --- --- [T]
24- 35 A12 "h:m:s" Time Image mid-time (UTC)
36 A1 --- --- [Z]
39- 40 A2 --- Meth Measurement method (1)
43- 50 F8.4 deg RAdeg Right ascension in the spacecraft-centered ICRF
53- 60 F8.4 deg DEdeg Declination in the spacecraft-centered ICRF
63- 70 F8.4 deg ePos [0.002/0.04] 1-σ uncertainty in right
ascension and declination
73- 74 I2 --- Np [3/50] Number of measured control points/
percentage of measured limb points
76- 84 F9.2 km Xpos [-6987/8684] X coordinate of Mars Express
spacecraft in the Mars-centered ICRF
86- 94 F9.2 km Ypos [-12538/13427] Y coordinate of Mars Express
spacecraft in the Mars-centered ICRF
96-104 F9.2 km Zpos [-9140/9796] Z coordinate of Mars Express
spacecraft in the Mars-centered ICRF
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Note (1): Measurement method as follows:
CP = Control point measurements
LF = Limb fit observation
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Acknowledgements:
Andreas Pasewaldt, andreas.pasewaldt(at)tu-berlin.de
(End) Patricia Vannier [CDS] 30-Apr-2015