Images of the Earth

The small camera on the bottom side of the satellite can be commanded from ground to take color pictures of the earth. Several images have been downloaded yet and some of them are shown below. The resolution is 640x480 pixels in 8bit resolution. Unfortunately the automatic brightness adjustment is not active long enough when a picture is taken, which results in  overexposed pictures with insufficient contrast.

From top left : the very first picture downloaded; picture of earth horizon with satellite antenna clearly shown; picture of half earth half space; picture of earth surface with clouds

GPS Receiver

The GPS receiver has already been activated several times. It initializes and operates without malfunction but fails to establish contact to any GPS satellites. The problem is traced back to an improper integration of the patch antenna at the front panel that, combined with a mismatch in the antenna connection, causes a severe limitation of the antennas field of view such that a link to four satellites at the same time for several minutes can hardly be established. It has not yet been achieved and the chances for success are very low.

Three-Axis Attitude Control

The implementation of an attitude control system is highly complex, partly due to the fact that its proper operation cannot be fully verified on earth. It is therefore disappointing to report that due to a software problem (bug) in the attitude determination software for reading and processing the analog sun sensors measurements correctly, the on-board process does not achieve a useful estimate of the satellite's actual attitude. This affects the attitude control seriously, as the control law will not be activated if attitude estimation is not successful. Hence, the advanced attitude controller based on magnetic actuation can not be evaluated on COMPASS-1 because the attitude estimation process fails. Only the detumbling controller had been activated (to slow down the satellite spin), which does not require information on the satellite's attitude.

Technology Demonstration

Up to this very date, the satellite is still doing well in space and shows no sign of significant degradation. The power system is constantly supplying energy to the on-boards electronics and, after the heaters have been deactivated for good, produces enough excessive power to charge the batteries for the eclipse times. The communication system is also working just fine. It is remarkable that the COMPASS-1 spacecraft comprises of a total of nine (9) microcontrollers (one on EPS, COM, ADCS, and CDHS, and one on each sun sensor), all of whom apparently work very well in space. No single-point failure or malfunction appeared that resulted in a significant degradation of the mission operation. This is particularly a great success, as most of the systems are engineered with COTS components, which were designed for use in terrestrial applications, most dominantly in industrial applications. The fact that the satellite up to present still operates nominally, verifies that the spacecraft is well suitable for low earth orbit missions.

Mission Data Evaluation

This section is to be updated. Some main results can be found in the paper "Flight Results of the COMPASS-1 Mission" in the "Publications" section.



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