No. 144 - Solar array testing
01 October 2010 16:26
Report for the period 28 August to 24 September 2010
This report covers 28 days of Rosetta mission operations. On 3 September, the performance of the solar arrays was tested by tilting them with respect to the Sun direction, simulating deep-space conditions. Data have been acquired and are being processed; a preliminary analysis indicates that performance was nominal.
During the reporting period, mission operations were conducted using the ESA New Norcia (NNO) ground station.
At the end of the reporting period on 24 September, Rosetta was 627 million km from Earth (4.19 AU); the one-way signal travel time was 34 min 52 sec (2092 sec). The spacecraft's distance from the Sun was 483.5 million km (3.23 AU).
On 9 September, the procedure to switch over to the redundant reaction control system (RCS) pressure regulator was completed, unfortunately revealing that the pressurant leak is in a section of piping that is common between the two regulators and cannot be isolated. In the light of this failure, it has been decided not to repressurise the RCS for the rest of the mission. This implies that the system will be used in 'blow-down' mode. This increases operational uncertainties, but the margins remain comfortable. A precise estimation of the overall effect will be possible at the time of the first rendezvous manoeuvre in January 2011; however, the impact on the comet arrival timeline is expected to be only of the order of one week.
The spacecraft will enter a superior conjunction phase that will last from 2 to 31 October; the deepest conjunction condition will occur between 10 and 23 October and will affect the telemetry link to such an extent that dumping of the mass memory will not be attempted during this period. The detailed results of the solar arrays test will be fed into the spacecraft configuration for deep space operations and thereby incorporated into the mission planning.
After this phase, spacecraft activities will focus on the final payload checkout and preparation of the instruments for the hibernation phase. These activities will be conducted between mid-November and mid-December.