Une autre session a été acquise quelques heures plus tôt,
ainsi que quelques courtes observations. Toutes ces fenêtres sont
étroites (un seul pixel de large) et certaines sont contaminées
par la lumière réfléchie par Mars.
The main image cube on Phobos,
at 700 m pixel size. About 400 spectra cover Phobos, which represents ~15%
of the surface (external trailing hemisphere). Another 200 pixels cover
the dark sky, and are not plotted here. The data are represented in "image
projection", and are superimposed on a topological model of Phobos
oriented as Phobos was during observations (T. Duxbury's model, 1991, from
Mariner 9 and Viking observations). The parameter coded in color is the
amount of solar light reflected by the surface (radiance factor). It depends
on both surface properties and orientation. It is highly correlated to the
incidence angle relative to the normal (ie. to the topographic slope) which
implies that albedo is almost constant and this region of Phobos is uniformly
dark.
Another session was acquired a few hours earlier, and several other
short sessions exist. All are very narrow (one-pixel wide) and some are
contaminated by Marsshine.
Name |
Date |
Spectra |
Window size |
Estimated local time |
Phase angle |
Solar Meridian |
Ls |
Mars-Sun dist (au) |
PAVonis |
08/2 |
2365 |
296 x 8 |
10:15-12:30 |
2.8° - 4.2° |
100° |
350.5° |
1.547 |
BIBlis |
11/2 |
2189 |
274 x 8 |
13:00-14:50 |
2.7° - 4.1° |
100° |
352.0° |
1.551 |
ARAbia |
21/2 |
2432 |
98 x 25 |
8:50-12:40 |
0.5° - 5.2° |
335° |
2.0° |
1.563 |
DAEdalia |
27/2 |
3013 |
121 x 25 |
11:30-15:45 |
5.5°-10.1° |
165° |
4.5° |
1.570 |
SYRtis-Isidis |
01/3 |
3005 |
121 x 25 |
8:50-13:20 |
1.7° - 6.3 |
270° |
5.9° |
1.572 |
Valles Marineris |
07/3 |
3008 |
121 x 25 |
10:10-14:10 |
0.9° - 5.5° |
100° |
8.3° |
1.580 |
AURorae |
12/3 |
3007 |
121 x 25 |
11:30-15:10 |
0.9° - 5.5° |
70° |
11.2° |
1.585 |
OLYmpus |
13/3 |
2275 |
91 x 25 |
12:10-15:10 |
14.5° - 19° |
165° |
11.7° |
1.586 |
GORdii |
14/3 |
3000 |
120 x 25 |
11:30-16:10 |
4.0° - 8.6° |
160° |
12.2° |
1.588 |
ASCraeus |
21/3 |
2999 |
120 x 25 |
10:20-14:50 |
13.3°-19.7° |
115° |
15.6° |
1.596 |
HEBes |
26/3 |
2983 |
120 x 25 |
9:45-13:40 |
6.2°-10.9° |
110° |
18.0° |
1.601 |
PHObos |
25/3 |
600 |
24 x 25 |
_ |
~30° |
~160° |
17.5° |
1.599 |
Elysium |
22/2 |
3025 |
121 x 25 |
_ |
_ |
~220° |
2.5° |
1.564 |
Phobos Track |
25/3 |
298 |
298 x 1 |
_ |
~20° |
~160° |
17.5° |
1.599 |
Characteristics of the main sessions
The names of the sessions are
derived from remarkable features in the area, avoiding as much as possible
names already affected to USGS quadrangles. The number of spectra given
here is the number of calibrated spectra; they includes only spectra
for which both data blocks are present, without spatial integration (ie.,
acquired at maximum resolution), and in some instances spectra that can
be interpolated from neighbouring pixels. The window size is the size of
the acquisition grid (lines x samples), including all measurements; this
is the number of records in the data files. The last three columns give
the longitude of the subsolar meridian, the areocentric longitude of the
Sun, and the solar distance in astronomical units at the time of observation.
The first two sessions are
acquired at high resolution from the pericenter of an elliptical orbit;
the next nine sessions are medium resolution sessions acquired from a circular
orbit at the distance of Phobos (plotted on the map above). The two Phobos
observations are acquired during Phobos approach (quasi-synchronous orbits).
The last two sessions are not calibrated in the data base but contain meaningful
information (the "Elysium" session is acquired when the specacraft
is not stabilized, and pointing geometry is unknown; the Phobos track is
acquired with Mars in the background, and data are contaminated by Mars
reflected light). Other short sessions acquired at the limb of Mars and
on Mars and Phobos are included in the data base.
Detailed sessions characteristics and all data files are accessible through this page.
ISM
a été développé avec le soutien du CNES
Dernière mise à jour : 11 mai 2001
Adresse : http://www.ias.u-psud.fr/ism/