The new launch date of the US space shuttle Endeavor is February 11, 2000. The shuttle is scheduled to depart at 18.30 CET for the Shuttle Radar Topology Mission (SRTM). The company had been postponed several times, most recently due to bad weather and computer problems. The Endeavor is to photograph the Earth in a new way: Two cameras are to capture a three-dimensional image of the earth. The data obtained will be more accurate than any topographic measurement results collected so far on civilian missions. The data will be the basis for infrastructure measures in many, until today poorly mapped countries of the world. At the same time, it is the basis for many applications ranging from environmental research to geology, from glacier science to agriculture.

Among the six crew members of the Endeavor is the German physicist and ESA astronaut dr. Gerhard Thiele as "mission specialist". The main task of the crew will be to secure the enormous data flood of 225 million bits per second on magnetic tapes. Overall, about 10 terabytes of information should be recorded.

"Stereo View" of the Earth During the SRTM mission Earth is being targeted for the first time from two different perspectives with radar. The Space Shuttle turns its back on the measurements at an altitude of 230 kilometers. The open cargo bay gives the twelve-meter-long main radar device (inboard antenna) the view of the globe.

A second, slightly smaller outboard antenna is deployed on a 60 meter long mast. By this constellation one can look at the earth with two "radar eyes" at the same time. display

The main radar sends microwaves to the ground where they are reflected. Main and Outboard antennas "stereo" receive the returning signals. Due to the different position of the two receiving antennas results in a time difference in the received signals, from which the terrain height can be calculated with complex calculation and correction procedures. The simultaneous "stereo" reception is the essential innovation of this mission. In previous missions, as in 1994, only the inboard antennas were used, looking one-eyed at the earth. In order to still be able to see spatially, it was necessary to compile the data from two consecutive passes (repeat-pass interferometry). Since there was always some time left between two overflights, the surface of the earth could have changed in the meantime and thus influenced the radar backscatter. If, for example, wind moves the vegetation, rain humidifies the ground or transported air masses influence the atmosphere, then the backscatter properties of vegetation, soil and atmosphere change, and so do the radar echoes. The calculation of a digital height model would then not be possible. These problems are eliminated by the simultaneous reception with two simultaneously receiving radar systems.

SRTM is a joint project of NASA, NIMA (National Image and Mapping Agency, USA), DLR and ASI (Italian Space Agency). Dornier Satellitensysteme GmbH, which belongs to DaimlerChrysler Aerospace (Dasa, Munich), is the main industrial contractor for the development of the radar system.

The Top Six for the mission:

  • German Aerospace Center - Special page of the DLR with up-to-date information on the mission
  • SRTM Live Webcast - The mission live on the Internet
  • NASA / JPL - The Control Center
  • NASA Quest - NASA comes into the classroom
  • Shuttle Reference Manual - Technical description of the space shuttle
  • The Earth - facts about the blue planet


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