After 20 days of intensive effort by CNES, Thales Alenia Space (TAS), and JPL, the Jason-1 spacecraft has now recovered from the <link http: www.aviso.oceanobs.com en news-storage _top external-link-new-window>safe mode event of 28 February 2013, and routine geodetic mission operations have resumed.  All Jason-1 payload science instruments were returned to operation by 10:55 UT on Monday, 18 March 2013, and <link http: www.aviso.oceanobs.com en news-storage _top external-link-new-window>full science and NRT operational data production was restarted shortly thereafter.

While comprehensive diagnostics did not detect any permanent loss of redundancy, or any loss of single-string systems required to continue the mission, there were several issues with the power and battery management subsystems that prolonged this safe mode recovery effort.  

During this safe hold period, due to the fact that Jason-1 is currently in a full-Sun period (no eclipses), the solar panels are constantly illuminated. 

When the payload instruments were off, CNES observed that the power management subsystem was beginning to overcharge the battery and that the battery temperatures were rising rapidly.  To increase the power draw on the battery and thus prevent the overcharging, several heaters were turned on in the payload compartment.  At present, one heater in the region of the inoperable TRSR instruments remains on and is operating at about 20°C.  This has stabilized the battery situation, but the net result is that the ambient temperature in the payload compartment is about 6-10°C warmer than before the safe hold.  This may impact instrument behavior, particularly for the JMR which has experienced calibration shifts in the past related to thermal regime changes.

CNES will continue to closely monitor the thermal, battery, and power subsystems in the days ahead.  The instrument teams are also closely monitoring the payload behavior.

We would also offer a note of caution about using the initial science products from Cycle 529 onward until better characterizations of possible instrument calibration shifts are available and corrections are made to the science processing algorithms.

The Jason-1 mission was interrupted on 28 February 2013 at 16:13 UT, during Geodetic Cycle 527.  Cycle 528 was almost entirely lost.  

Routine science operations resumed prior to Cycle 529, which began on 19 March 2013 at 20:28 UT. 

Very best regards.

Thierry Guinle & Glenn Shirtliffe

CNES & NASA/JPL Jason-1 Project Managers