10 Mar 2005 17:21

On 9 December, a scheduled switch-over of the on-board computer of spacecraft-1 was successfully performed to check that the main computer was OK following a switch-over to the redundant computer on 14 June 2004. This confirms that the computers on all four spacecraft are fully redundant.

Operations and Archiving

JSOC and ESOC operations are continuing nominally. During the September-December period we observed the usual AGC fluctuations due to ionospheric effects. When the fluctuations are too strong, the dump of data is interrupted and the spacecraft is switched to recording mode. The data return from September to December 2004 was above 98.8%.

The final case for the 2nd Cluster mission extension has now been prepared. Several iterations have taken place with the PIs/JSOC and ESOC to decrease the cost of the operations. A proposal to extend for 4 years with a mid-term review to check the status of the spacecraft is being proposed for the February 2005 SPC.

The Cluster Active Archive is progressing well. All interface documents, except two, have been received from the PIs and ESOC and are under internal review. The next review of the archive will take place in spring.

Science Highlights

Solar wind discontinuities have been studied with Cluster. It was shown that the minimum variance analysis (MVA), a widely used data analysis technique with one spacecraft, is much less reliable than previously thought to determine the type of interplanetary discontinuity. In addition, the classification between tangential and rotational discontinuities could be revisited and show different results than previous studies with single spacecraft methods.

An ISSI book compiling all results obtained by Cluster on the dayside boundaries of the magnetosphere is in the final stage of editing. It contains chapters on the bow shock, magnetopause, and cusp and presents the crucial advantage to have four spacecraft as compared to previous single or two spacecraft missions. An ISSI sponsored science team has furthermore prepared and submitted a comprehensive review of the outcome of the Cluster Ground-Based initiative.