| Date: | 2004-06-09 09:28:00 | |
| Sender: | Granier Jean-Pierre <Jean-Pierre.Granier@cnes.fr> <slrmail@dgfi.badw.de> | |
| Subject: | [SLR-Mail] No. 1219: TOPEX IN Safe Hold Mode from 26 May 2004 | |
| Author: | Granier Jean | |
| Content: | ******************************************************************************** SLR Electronic Mail 2004-06-09 09:28:00 UTC Message No. 1219 ******************************************************************************** Author: Granier Jean-Pierre Subject: TOPEX IN Safe Hold Mode from 26 May 2004 Subject: TOPEX IN Safe Hold Mode from 26 May 2004 Subject: TOPEX IN Safe Hold Mode from 26 May 2004 Dear colleagues, Here is a status provided by Lee-Lueng Fu, from JPL about the TOPEX incident. DESCRIPTION OF INCIDENT: The T/P satellite entered safehold mode (SHM) on 26 May 2004 at 18:58 UTC due to a roll reaction wheel (RW) failure. Although the three remaining RWs are functional, all are continuing to experience intermittent halts when passing through zero wheel-speed crossings. On June 1 at 11:16 UTC, an erroneous hardware interrupt caused the On-Board Computer (OBC) to halt autonomously. This anomaly does not appear to have any direct correlation to the current RW problems. On June 3, the computer memory was reloaded and reinitialized, and nominal OBC operations were restored. CORRECTIVE ACTION: Activities to investigate the RW problems and determining the cause of the OBC anomaly are ongoing. Analysis of both the RW anomalies and options to return to a normal mission science mode is in progress by teams from both JPL and the T/P Guidance and Navigation Control contractor Swales Aerospace, with additional support from Honeywell (wheel contractor). IMPACT ON PROJECT AND SCHEDULE: T/P is continuing to operate in a power-positive sun pointing SHM, with contingency procedures implemented as required to maintain a nominal satellite attitude orientation. Overall health of the satellite remains good, and science data recovery operations have been suspended as a result of SHM operations. DORIS is always ON, SSALTO receive DORIS TM. Sincerely yours Jean-Pierre Granier ”/DGFI3/home/slrmail/mbox” complete From: slrmail@dgfi.badw.de ******************************************************************************** |