Double Star Status Report - February 2005
10 Mar 2005 17:51During the largest geomagnetic storm of 2004, the redundant attitude computer failed on TC-1 spacecraft. Now both spacecraft have non functioning attitude computers. The consequences are no attitude control of the spacecraft. Fortunately, both spacecraft are spinning at 15 rpm and are therefore stable. A slow drift of the spin axis is observed about 0.9 degrees per month on TC-1 and 1.5 degrees per month on TC-2. This means that we should not have problems up to end of nominal mission lifetime (31 July 2005).
In addition, initial computation from China shows that the drift of TC-1 will reverse in a few months and go back to post launch attitude. An investigation is on-going in China to find the cause of the problem. Memory chips failure seems to be the cause of the failure. Attitude information can be derived from the magnetometer data at perigee and the routine processing has started.
The European instruments are operating nominally. Resets on PEACE (electron sensor) are still occurring. Some of them are related to the Sun pulse not being provided at regular interval to the instrument. Investigation continues with the Chinese. Work around are being used like regular resets of the instrument and switch-off inside radiation belts. Other instruments are not sensitive to this problem and are working nominally.
The European Payload Operation System (EPOS) co-ordinates the operations for the seven European instruments on TC-1 and TC-2 and is running smoothly. A few problems still occur on the ground stations but the data return has improved, especially after avoiding period of antenna interferences on TC-2. The return for the month of November for the magnetometer on TC-1 was above 94%.
The Double star workshop held at the beginning of November 2004 was a great success and we can clearly see the complementarity of Cluster and Double Star. Many new results have been presented. Among them a few highlights are:
A special issue of Annales Geophysicae is in preparation to present the first Double Star results.