****************************************************************************** dorismail 27-Feb-2009 13:34:43 Message No 0586 ****************************************************************************** Author: "Frank G. Lemoine" Subject: Status of Jason-1 and Availability of DORIS data Subject: No 0586 : Status of Jason-1 and Availability of DORIS data Authors: Frank Lemoine (NASA Goddard Space Flight Center) Pascale Ferrage (CNES) Dear Colleagues- The purpose of this message is to provide an update on Jason-1 and summarize the availability of DORIS data for this satellite following the end of the tandem flightoperations between Jason-1 and Jason-2. On Monday, 26-January, 2009, Jason-1 began a series of paired transfer maneuvers to move to a new orbit that has a 162-degree on-orbit phase lag between Jason-1 and OSTM/Jason-2.  The maneuvers involved successively lowering the Jason-1 semimajor axis by 20 km, allowing the orbit to drift, and finally raising the semimajor axis back up to the nominal altitude.  The sequence of these maneuvers was completed by February 14, 2009, with  a single-burn orbit trim maneuver performed on February 19, 2009. The Jason-1 altimeter was reactivated on Tuesday February 10, 2009 (the Altimeter did not collect data for most of the time while the major orbit Maneuvers were occurring). The full dates and times of the maneuvers are summarized below: FIRST MANEUVER (delta-a of -10 km) 1st burn:  2009/01/26 at 21:10 UTC : Dv = -2.33m/s, duration = 351.1 secs 2nd burn: 2009/01/26 at 23:59 UTC : Dv = -2.33m/s, duration = 364.8 secs SECOND MANEUVER (delta-a of -10 km, no correction needed for very slight over-burn) 1st burn: 2009/01/27 at 21:30:20 UTC :   Dv = -2.33m/s, duration = 376.2 secs 2nd burn: 2009/01/28 at 00:18:23 UTC : Dv = -2.33m/s, duration = 389.7 secs THIRD MANEUVER (delta-a of +10 km) 1st burn: 2009/02/04 at 10:39 UTC  DV  = 2.33m/s, duration = 395 secs  2nd burn: 2009/02/04 at 13:39 UTC DV = 2.33m/s, duration = 408 secs  FOURTH  MANEUVER 1st burn: 2009/02/06 at 03:49 UTC  DV  = 2.01m/s, duration = 356 secs  2nd burn: 2009/02/06 at 06:42 UTC DV  = 1,95 m/s, duration = 354 secs  Slight over burns wich  put Jason-1 only 469 m below the nominal operational orbit, instead of the expected 1000 m below, this led Jason-1 to drift longer than foresee to the rendezvous point for the final maneuver. FIFTH MANEUVER: final maneuver 1st burn: 2009/02/14 at 18:02 UTC DV  = 0,125 m/s, duration = 22 secs  2nd burn: 2009/02/14 at 20:46 UTC DV  = 0,107 m/s, duration = 19 secs  Observed delta-a = +480 m  (+500m targeted);  Efficiency: 96%. This placed Jason-1 well within the new station-keeping control box (+/- 1 km) on 14 February 2009 at 20:51 UTC. ORBIT TRIM MANEUVER 2009/02/19  21:45 to 2009/02/19 21:46 UTC, DV= 0,011 m/s, duration = 4.5 secs   ===================================================================== Availability of DORIS data for Jason-1 ------------------------------------------- DORIS data are available until cycle 259  (prior to the initiation of orbit change operations  on January 26, 2009) No DORIS data will be delivered between January 26th to February 10th, so the  next delivery will start for cycle 262 (after the fourth manoeuver) Nevertheless, the Jason1 files relative to manoeuver, mass and cyle number have normally been updated during that orbit change manoeuver period: URL: ftp://ftp.cls.fr/pub/ids/satellites/ja1man.txt URL: ftp://ftp.cls.fr/pub/ids/satellites/ja1mass.txt URL: ftp://ftp.cls.fr/pub/ids/satellites/jason_cycle_dates/ Cautionary Note ---------------------- The model of J. M. Lemoine and H. Capdeville to correct the Jason-1 DORIS data for the perturbations caused by the South Atlantic Anomaly (SAA) [JM Lemoine &  H. Capdeville, Journal of Geodesy, November 2006] is optimized for the nominal (TOPEX/Jason1/Jason2) repeat ground track configuration. Work is underway  to possibly improve this model for use in the new Jason-1 phasing orbit. Note  that the raw data files delivered to the IDS data centers are uncorrected for the SAA effect and this model must be applied ex post facto prior to  processing the data for POD analyses. Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr