****************************************************************************** DORISMail 16-Nov-2004 16:57:15 Message No 0356 ****************************************************************************** Author: Tavernier Gilles Subject: DORIS/TOPEX incident on November 1, 2004 Dear colleagues, The DORIS/TOPEX receiver encountered an incident on November 1, 2004 at 3:21:10 UTC. The problem looks very similar to the incident that happened in December 1998 with the DORIS chain 1. The only difference is that the DORIS chain 1 incident occured over the South Atlantic Anomaly whereas the last one (Doris chain2) occured over Antarctica. The review committee concluded in 1999 that 2 possible causes could explain the incident : a 80C86 microprocesseur failure, or a PROM failure. > In case of a PROM failure, the DORIS chain 2 would have broken down very quickly. This was not the case. So a microprocessor failure is the most likely. > > In such a case the review committee concluded in favor of a possible return of the chain 1 to good health, should it remain OFF for a long time. It was thus recommended to switch back to chain 1 in case of a DORIS chain 2 failure. > Until now the procedures run to restart chain 2 were not sucessfull. We now intend to switch back to chain 1. We will keep you informed about the status of DORIS on-board TOPEX/POSEIDON. Best regards, Gilles TAVERNIER _____________________________________________________ CNES DCT/PO/AL - Bpi 2002 Phone : 33 - (0)5 61 27 37 76 18, avenue Edouard Belin Fax : 33 - (0)5 61 28 25 95 31 401 TOULOUSE CEDEX 9 Email : Gilles.Tavernier@cnes.fr _____________________________________________________ Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr