DETERMINATION OF CONJUGATE POINTS OF STEREOSCOPIC THREE LINE SCANNER DATA
OF MARS 96 MISSION
Franz Wewel
Technical University of Berlin, Department for Photogrammetry and Cartography
Sekr.: EB9, Straße. des 17. Juni135, D-10623 Berlin, Germany
Tel.: +49 30 314 23338, Fax.: +49 30 314 21104, E-mail: franz 0 fpk.tu-berlin.de
Commision lll
KEY WORDS: Correlation, Matching, Resolution, Extraterrestial, Three_Line
ABSTRACT:
In November 1996 a Russian spacecraft starts to the planet Mars. The spacecraft will carry two German cameras: The
High Resolution Stereo Camera (HRSC) and the Wide Angle Optoelectronic Stereo Scanner (WAOSS). Both cameras
are three line stereo cameras. Besides other tasks the image data will be applied to obtain digital terrain modells. Due to
the camera design an to the proposed orbit the image data will be really complex. Especially the image matching process
is affected by varying ground pixel resolutions. Software to handle these problems is under development.
KURZFASSUNG:
Im November 1996 startet eine russisches Raumfahrzeug zum Mars. An Bord sind zwei deutsche Kameras, die
Hochauflósende Stereokamera (HRSC) und der Optoelektronische Weitwinkel-Stereoscanner (WAOSS). Beide Kameras
sind als Stereokameras konzipiert. Aus den Bilddaten der Kameras sollen unter anderem globale digitale
Oberfláchenmodelle abgeleitet werden. Aufgrund des Kamerakonzeption und der gewáhlten Umlaufbahn werden die
Bilddaten sehr komplex sein und hohe Ansprüche an die photogrammetrische und kartographische Software stellen. Die
Bildzuordnung hat insbesondere das Problem, von sich ständig wechselnde Bodenpixelauflösungen zu bewältigen.
1. INTRODUCTION
1.1 General aspects of the determination of conjugate
points for the Mars 96 mission
Scheduled for launch in November 1996 a Russian
spacecraft will reach the planet Mars in fall 1997. The
main tasks of this mission are obtaining global views of
the Martian surface and atmosphere and the systematic
examination of morphological feature with high resolution
imagery for geoscientific and cartographic purposes.
Besides other sensors the spacecraft carries two German
cameras: the High Resolution Stereo Camera (HRSC)
and the Wide Angle Optoelectronic Stereo Scanner
(WAOSS) (Albertz J. et al., 1992). Similar to the MOMS-
02 sensor HRSC and WAOSS work with the pushbroom
principle and have a nadir, a forward and a backward
looking stereo channel. Thus permanent along track
stereo data acquisition is provided.
At the Technical University of Berlin a working group
develops photogrammetric and cartographic software
(Scholten F., 1996) to process the data of the HRSC and
WAOSS scanners. Among other products, the data of the
stereo cameras will be used to generate a global Martian
elevation model as well as terrain models (Uebbing R.,
1996) with high spatial resolution of feature of high
interest. The generation of these terrain models requires
the determination of a great amount of corresponding
points.
The special properties of the image data, as a result of
camera design and operation, the proposed orbit and the
particular conditions of the Martian surface, have a great
influence on the data processing and the matching
strategy. Especially the highly elliptical orbit leads to
unconventionally looking image data and affects the
image correlatability and the determination of stereo
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996
disparities. Inorder to illustrate this, here the main
aspects.
1.2Stereo cameras and platform system of the Mars
96 mission
The HRSC and WAOSS cameras are single optic
instruments working with the pushbroom method. The
scanning of both cameras based on an along track triple
stereo concept.
parameter HRSC WAOSS
focal length 175 mm 21.7 mm
number of CCD's 9 3
active pixel per CCD 5184 5184
field of view (FOV) 11.9? 80.0?
FOV per pixel 8.3" 67.4"
stereo angle 18.9? 25.0°
duration of imaging
sequence 3 min 1h
line scan frequency «450 Hz < 240 Hz
min ground resolution 12 m 96 m
exposure time 2.2-54.5 ms 12.5-15 ms
Table 1: HRSC and WAOSS camera parameter
Due to an inertially fixed spacecraft the cameras are
mounted on a manceuvrable platform (ARGUS) which has
a three axial suspension (Schwarz G., 1994).
Besides the three stereo CCD's the HRSC camera has
four multispectral and two photometry channels. The main
technical characteristic of both cameras are listed in Table
1.
around pixel size Im]
