****************************************************************************** dorismail 10-Apr-2012 12:19:42 Message No 0807 ****************************************************************************** Author: Ferrage Pascale Subject: TR: Jason-1 Status and Future Mission Options ----------------------------- Message forwarded from Lee-Lueng Fu to the Ocean Surface Topography Science Team (OSTST) comunity --------------------------------- Dear OSTST Members: As you have been previously informed, Jason-1 has suffered from two Safe Hold Mode (SHM) events since February 16. The first event took place on February 16, involving an anomaly of Gyro#3 related to a single event upset in the region of the South Atlantic Anomaly. After corrective actions the mission returned to nominal mission mode (NOM) on February 29 with nominal operation of Gyro#3. On March 3, Jason-1 again entered SHM following a double anomaly detected in the onboard computer's RAM ("double EDAC error"). A major consequence of this systematic "double EDAC error" anomaly will be that after any future SHM reconfiguration, there will be a loss of the dual reconfiguration capability that allows for a robust SHM should Jason-1 lose an additional reaction wheel (RW). This loss of this reconfiguration capability has significantly increased the risk of losing control of the spacecraft if there is a loss of one of the three remaining RWs. Taking these risks into account, CNES, in agreement with JPL, decided to remain in the current stable and controllable safe hold configuration, thus interrupting the altimetry science mission since 3 March 2012. Although it is likely that Jason-1 can still provide valuable data for some time, these events triggered the need to revisit the "end of life" planning strategy that was discussed at the Lisbon OSTST and endorsed by the agencies in late 2011. The following are two options under consideration by the joint CNES/NASA mission management team (ie., the Joint Steering Group, or JSG) for the mission to proceed: * Option 1: Continuation of the mission in the current tandem altimetry orbit (1336km) - If done immediately, this implies accepting the increased risks of losing control of the Jason-1 spacecraft and jeopardizing the current reference orbit occupied by Jason-2, and the future Jason-3 and Jason-CS missions, (as well as the uncontrolled T/P spacecraft.) - Or wait in safe mode for an undetermined period of time for potential flight software modifications to be developed to bypass the systematic double reconfiguration anomaly. * Option 2: Continuation of the mission in a new geodetic orbit (-12.6km / 1324km) - This would return Jason-1 to the nominal operation mode and allow for maneuver operations to begin to vacate the reference orbit. - This would then permit: 1. Resumption of the science mission in the geodetic orbit by late-May. 2. Retire the risk of Jason-1 failing in the current altimetric reference orbit. 3. The new geodetic orbit would eventually become the safe and final graveyard orbit when Jason-1 is decommissioned. The mission and operation teams are working hard on the mission recovery schedule. The objective is to resume the mission as soon as possible, taking into account the different constraints. We will let you know as soon as we can. Given the significant risks involved in Option 1 and the fact that Cryosat data have been processed for oceanographic applications and made available to the user community, the joint mission management team is inclined to adopt Option 2, which will collect valuable data for geodetic applications in a safe orbit that will also be used for final decommissioning. The JSG is planning to have a decision meeting during the week of April 16. The intent of this message is to provide the OST Science Team with the status of the mission and outline the decision making process regarding the future of Jason-1, as well as to provide the Science Team with an opportunity to provide inputs to this process before the JSG decisional meeting. Best regards and best wishes for the future of Jason-1 ! Rosemary Morrow and Pascal Bonnefond - CNES Jason-1 Project Scientists Lee-Lueng Fu and Josh Willis - JPL Jason-1 Project and Deputy Project Scientists Thierry Guinle and Glenn Shirtliffe - CNES and JPL Jason-1 Project Managers ********************************************************** Lee-Lueng Fu llf@jpl.nasa.gov Jet Propulsion Laboratory M/S 300-329 4800 Oak Grove Dr. phone: (818) 354-8167 Pasadena, CA 91109 fax: (818) 354-1178 ********************************************************** Cliquez sur l'url suivante https://www.mailcontrol.com/sr/36ucecisFCHTndxI!oX7UnSTKdEpakD!GTXL4ILy+3hI!j1esjxbuuo1cyLgyJpdgggfmPdeQSejfskgLULbMA== si ce message est indésirable (pourriel). Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr