No. 59 - Recharging Philae's Secondary Battery
16 May 2006 14:31Report for Period 28 April - 12 May 2006
The reporting period covers two weeks of cruise, in which all scheduled ground station passes were used to recover telemetry stored during the solar conjunction. The level of activities remains minimal. The spacecraft will remain configured for solar conjunction until 18 May.
Upon a request by the Lander Team, the Lander has been activated on 9 May to recharge the probe's secondary battery. This activity was required due to an unexpected high self-discharge of the Lander secondary battery observed since commissioning. The last monitoring performed during Passive Checkout 2 (3-7 March 2006) confirmed the need to recharge the battery before the next planned Payload operation slot.
On 10 May, the attitude guidance was changed as required for Near Sun Hibernation entry (X axis Earth pointing without bias, Y axis perpendicular to Sun-Spacecraft-Earth with South direction option). This resulted in particular in a change of the actual Y-axis direction, such that the Sun is shining on the +X/+Z spacecraft quadrant after the guidance change.
A total of 6 New Norcia passes were taken during the reporting period to recover solar conjunction telemetry. TM/TC links with the OCC have been established for all passes.
At the end of the reporting period (DOY 132/2006) Rosetta was at 369.9 million km from Earth (2.47 AU; one-way signal travel time was 19 minutes 46 seconds). The distance to the Sun was 221.8 million km (1.48 AU).
The spacecraft is slowly warming up as the spacecraft to Sun distance decreases.
The Lander has been activated for 21 hours on DOY 128-129/2006 to recharge the probe's secondary battery. This activity was required in order to keep the battery state of charge above 10%. It had been originally scheduled during the first Active Checkout in December 2006, but telemetry from the last Passive Checkouts outlined a higher than expected level of self discharge for this battery. The Lander team therefore requested to advance this maintenance operation.
A total of 6 New Norcia passes were taken over the reporting period, to support spacecraft monitoring and intensive RF signal tracking during the solar conjunction. During the reporting period, a few incidents at the New Norcia ground station caused temporary degradation of the service.
On 23 May 2006, the spacecraft will be configured into Near Sun Hibernation Mode for a period of about 2 months, until end July 2006.
Operations for the Mars swing-by (February 2007) will start in August 2006, with another payload passive checkout (PC3), an intense tracking campaign around the Trajectory Correction Manoeuvre (DSM-2) in September, and the first payload Active Checkout (PC4) in November/December.