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Rosetta Enters Near Sun Hibernation Mode European Space Agency June 2, 2006

Report for Period 12 May - 2 June 2006

The reporting period covers three weeks of cruise, in which telemetry stored during solar conjunction was recovered and the spacecraft reconfigured to Near Sun Hibernation Mode (NSHM).

On 24 May the spacecraft entered Passive Cruise Mode, including transition to NSHM, telecommunications reconfiguration to MGA with low telemetry and telecommanding bit rates and configuration of all subsystems for the new spacecraft mode. This completed the activities related to entry in Passive Cruise Mode. Two more passes were taken on 25 and 26 May, to confirm the correct behaviour of the new spacecraft mode. The spacecraft will remain in this low activity, low bit rate mode until 26 July.

No payload operations were carried out in the reporting period. SREM was kept active in the background for the entire period, and configured for a lower data collection rate to cope with the reduced visibility periods and bitrates available during the passive cruise period.

A total of 7 New Norcia passes of 8 hours commanding were taken during the reporting period. TM/TC links with the OCC have been established for all passes.

NNO Date DOY Main Activity Pass

808 16.05.06 136 Monitor pass - Solar Conjunction TM Recovered 809 17.05.06 137 Monitor pass - Prepare NSHM Entry 814 22.05.06 142 Monitor pass - Prepare NSHM Entry 815 23.05.06 143 NSHM Entry - TTC reconfigured to MGA-X, TM bit rate to 148 bps, TC bit rate to 250 bps 816 24.05.06 144 NSHM monitor pass 817 25.05.06 145 NSHM monitor pass 823 31.05.06 151 NSHM monitor pass

At the end of the reporting period (DOY 153) Rosetta was at 354.0 million km from Earth (2.37 AU; one-way signal travel time was 18 minutes 58 seconds). The distance to the Sun was 209.8 million km (1.40 AU).

Spacecraft Status

Thermal The thermal behaviour of the spacecraft is nominal and stable. Its configuration is NSHM1 since DOY 144/2006.

As expected after NSHM entry, the temperature of the spacecraft internal units, such as batteries, tanks, CDMUs and reaction wheels, has decreased by a few degrees. Apart from this mode-related adjustment of the on-board temperatures, the spacecraft is slowly warming up as the Sun distance is decreasing.

Power The subsystem is in its nominal configuration and performing nominally. All three batteries are in active configuration, at full state of charge.

Future Milestones

The spacecraft will remain in Passive Cruise Mode until 26 July 2006. During the entire period, the spacecraft will be monitored on the basis of weekly ground station passes.

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.