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No. 59 - Recharging Philae's Secondary Battery

No. 59 - Recharging Philae's Secondary Battery

Report for Period 28 April - 12 May 2006The 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.

Date DOY

Main Activity

790 28.04.06 118 Monitor pass
794 02.05.06 122 Monitor pass - TM bit rate to 22 853 bps
795 03.05.06 123 Monitor pass
796 04.05.06 124 Monitor pass
801 09.05.06 129 Monitor pass - WOL
802 10.05.06 130 Monitor pass

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).

Spacecraft Status

The thermal behaviour of the spacecraft is nominal and stable. Its configuration is, since DOY 230/2005, ACM1, with tank gauge heater 7A switched off.

The spacecraft is slowly warming up as the spacecraft to Sun distance decreases.

The only instruments operated in the reporting period were SREM and the Lander. SREM remains active in the background for radiation monitoring. SREM's data collection rate is currently reduced to cope with the limited ground contacts during solar conjunction and the upcoming near Sun Hibernation period.

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.

Ground Facilities

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.

Future Milestones

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.

Last Update: 1 September 2019
24-Apr-2024 15:35 UT

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