****************************************************************************** dorismail 08-Jan-2009 20:30:26 Message No 0572 ****************************************************************************** Author: "Frank G. Lemoine" Subject: Proposed Jason-1 Orbit Change: Jason-1 to move to interleaved (Message forwarded from the Ocean Surface Topography Mission Project Scientist, L.L. Fu) ------------------------------------------------------------ ..... ..... Pending approval by the Joint Steering Group scheduled for meeting on Jan 12, the Jason-1 satellite will be moved to a new ground track on January 26, 2009 after the end of repeat cycle 259, after more than 7 years of service on the nominal ground track. The OSTM/Jason-2 satellite will continue the long term climate data record on the primary Topex/Jason-1/OSTM/Jason-2 ground track. The Jason-1 satellite will be moved to the same interleaved orbit that was used by Topex from 2002-2005. Several maneuvers will be performed beginning on January 26, 2009, with the interleaved orbit achieved by February 9, 2009. Please note the following regarding the new Jason-1 orbit. 1) Jason-1 will use the same pass numbering scheme adopted by Topex in the interleaved ground track. However, the start time of the Jason-1 and Jason-2 repeat cycles will differ by approximately 5 days. 2) The first Jason-1 repeat cycle on the new interleaved ground track will be numbered repeat cycle 260. 3) The Jason-1 altimeter will be placed in standby mode during the transition to the new ground track. This may have some impact on the calibration of the JMR, due to changes in the spacecraft thermal environment.  Re-calibration of JMR will be performed if necessary. 4) After achieving the new ground track there may be some delay in the availability of the Precise Orbit Ephemeris (POE) for Jason-1, which as a result will delay GDR availability. This is due to the required tuning of the POE orbit determination strategy and models. (e.g. Doris USO correction model). Best Regards, Lee-Lueng Fu ------------------------------------------------------------- Lee-Lueng Fu JPL 300-323 4800 Oak Grove Drive Pasadena CA 91109 FAX:818-393-6720. VOICE: 818-354-8167 Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr