THE MAPPING PERFORMANCE OF THE HRSC / SRC IN MARS ORBIT 
J. Oberst ?, T. Roatsch *, B. Giese *, M. Wählisch 2 F. Scholten ?, K. Gwinner *, K.-D. Matz ? E. Hauber ^, R. Jaumann ®, J. Albertz P 
S. Gehrke ^, C. Heipke *, R. Schmidt *, H. Ebner 
1 os E D > 
4 M. Spiegel ¢, S. vanGasselt ©, G. Neukum ©, 
and the HRSC Co-Investigator Team. 
? Institute of Planetary Research; German Aerospace Center; Rutherfordstr. 2; D-12489 Berlin; Germany 
(Juergen.Oberst@dir.de) 
? Technical University, Institute of Photogrammetry and Cartography, Berlin, Germany 
* University Hannover, Institute of Photogrammetry and Geolnformation, Germany 
4 Technical University, Institute of Photogrammetry and Remote Sensing, Munich, Germany 
© Freie Universitit, Institute of Geosciences, Berlin, Germany 
Commission IV, WG IV/9 
KEY WORDS: Extra-terrestrial, Planetary, Pushbroom, Imagery, Photogrammetry, Cartography, Remote 
Sensing, Exploration 
ABSTRACT: 
The images obtained by the HRSC (High Resolution Stereo Camera) on Mars Express show excellent potential for topographic 
mapping of the planet. 
The derived stereo models agree with topographic data obtained earlier by MOLA (Mars Orbiter Laser 
Altimeter) on the Mars Global Surveyor: For the image scenes from the Mars-Express commissioning phase that were studied, 
we find absolute differences in heights as small as 50 m and lateral positional differences along MOLA tracks of about 100 m. 
We show that HRSC effectively fills the gaps left between the MOLA tracks. SRC (Super Resolution Channel) images are well 
placed at their nominal geometric positions and reveal further detail within the HRSC context images. However, many of the 
images, fall short of the expected image quality for reasons to be examined. 
1. INTRODUCTION 
The ESA (European Space Agency) spacecraft Mars Express 
was successfully launched from Baikonur on June 2, 2003, 
entered Mars orbit on December 25, 2003, and has begun 
surface mapping. The spacecraft is equipped with HRSC 
(High-Resolution Stereo Camera), a multiple line scanner 
operated in the pushbroom mode. The camera, which gathers 
images of very large size, has been specifically designed for 
3-D-mapping of the planet with high precision. In addition, 
the SRC (Super Resolution Channel) is designed to take 
very high resolution array images. With these two cameras 
in combination, there is an unprecedented mapping 
experiment in Mars orbit. This paper represents a first 
assessment of the performance of HRSC and SRC, judging 
from data obtained in the commissioning phase. 
2. HRSC/SRC CAMERA 
The HRSC-camera (Fig. 1) is equipped with nine line 
sensors, 5184 pixels each (Table 1), oriented perpendicular 
to the spacecraft motion. One of these sensors is oriented 
towards nadir (ND), 2 others oriented forward and backwards 
(+/-18.9°) with respect to the flight direction to obtain 
images with perspective effects for 3-D mapping (SI, S2). 
Two more sensors, equipped with panchromatic filters (Table 
2), normally for photometric mapping, however, can be used 
for 3-D mapping as well (P1, P2). There are four additional 
sensors equipped with filters for multispectral mapping (IR, 
GR, BL, RE). All 9 sensors of the camera are operated 
simultaneously, to obtain large-size images at high 
resolution, in stereo, and in color. From a nominal orbit 
height of 250 km, images with a ground pixel size of 10 m 
can be achieved. Stereo, photometry, and color channels are 
usually operated in a pixel summation mode of 2x2, 4x4, or 
8x8 to reduce data volume. 
The SRC (Super Resolution Channel) is a framing camera, 
equipped with a 980 mm telescopic lens (Table 1) for 
imaging at highest resolution (up to 2.3 m from the nominal 
orbit height) to show details within the large HRSC context 
frames. Typically, images are obtained in a series, with or 
without overlap (Fig. 2). 
At the time of writing (April 27, 2004), HRSC has obtained a 
total of 69 orbit swaths covering a Mars surface area of 10.9 
mill. kn? (in which 7.6 mill. km” were covered at resolutions 
better than 50 m/pixel). A total of 853 SRC frames were 
acquired. 
  
Fig. 1: Imaging scheme of HRSC on Mars-Express with its 9 
sensors 
1318 
Internatic 
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The five | 
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