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DLR-TUBSAT
The Project
DLR-TUBSAT is a joint project of the DLR and the Institute of Aeronautics and Astronautics at the Technical University of Berlin. Based on the experience gained with TUBSAT-A and TUBSAT-B an attitude control unit of minimal dimensions has been developed for the DLR-TUBSAT microsatellite.
The satellite has a mass of approximately 45kg and a cubic shape of 32cm length. It is mainly used for high resolution earth observation tasks. This is done in a live TV mode with a three head camera system with different focal lengths, resulting in a resolution of 370 meter down to six meter per pixel. The pictures can be received with a standard satellite dish with a minimum of three meter diameter. The mission scenario implies, that the users transmits the coordinates of a point on the earth and the satellite computes the needed attitude control actions to track this point during the crossing.
Normally a television satellite is a satellite which retransmits an incoming TV signal from one source to many destinations. DLR-TUBSAT is more a "tele vision" satellite. It transmits a TV signal of its own view.
As you can see in the pictures the S-Band antenna (white cylinder on the right) has the same direction as the optics. The antenna is a helix antenna and has an opening of 70 degrees. To receive the signal of the satellite you will have to be within a 70 degree cone around the optical axis. This means you can only make pictures of an area within aproximatly 1000 km range of your receiving ground station.
The control is done by transmitting ground coordinates to the satellite. Attitude control is done with three reaction wheels and three fibre optic laser gyros. After the contact is over, the satellite disables all its systems but the TTC and the OBDH and goes into what we call "barbeque mode": It is tumbeling freely without attitude control so that it is warmed up by the sun from all sides.
On the 11th of December 1997 the DLR (Deutsches Zentrum für Luft- und Raumfahrt) signed a contract with the Indian Space Research Organisation (ISRO/ANTRIX) for a launch of DLR-TUBSAT on a PSLV-C2 as piggyback payload. Main payload is the Indian Remote Sensing Satellite IRS-P4 and as a second piggyback payload the Korean built KITSAT-3.
DLR-TUBSAT was launched on the 26th of May in 1999 into a polar sun-synchronus 12:00 o'clock orbit with an altitude of 720 km from the Indian SHAR launch complex on the eastern coast of the subcontinent.
More information: ILR, TU-Berlin
Project Managers: M. Steckling (1994-1998 TU-Berlin)
S. Schulz (1995-2000 TU-Berlin)
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