No. 12 - Latest Rosetta Commissioning Activities
18 May 2004 17:57
Report for week 7 to 14 May 2004
The most important activity in the reporting period was the execution of the first deep-space manoeuvre on 10 May. This was the most critical spacecraft activity executed since LEOP, involving a change in velocity (delta-V) of 152.8 ms-1, achieved through a continuous burn of the four on-board axial thrusters for a duration of about 3.5 hours. The manoeuvre was executed successfully and the performance of the spacecraft was excellent, with an estimated inaccuracy of about 0.05%.
Payload commissioning activities continued in the reporting period, with the execution of the second RPC commissioning slot, the first activation of SREM and the beginning of the third commissioning slot for the Lander PHILAE. A repeat of specific MIDAS test scanning sequences, requested by the PI to investigate problems detected during the MIDAS commissioning slot in April, was executed on DOY 133 but did not produce satisfactory results.
On the subsystems side the thermal environment is stable, but with high temperatures due to the vicinity of the Sun. The temperatures of the thruster modules on the +X side of the spacecraft are still high, reaching 65 °C for thruster module 7, but they are still within the operational limits and did not rise above the limit of 70 °C even after the end of the delta-V execution.
Stability problems with the Mission Control System were experienced twice during the reporting period and led to interruption of support. Fortunately, this did not impact on the real-time operations, but reduced the availability of the Data Disposition System during the week (due to recovery actions and further investigation activities).
Throughout the reporting period additional ground station support was provided by DSN stations as planned, to increase the amount of tracking data in order to improve orbit determination and manoeuvre optimisation activities.
The table below shows a chronology of the main activities in the reporting period:
At the end of the last New Norcia pass in the reporting period (DOY 135, 02:00) Rosetta was at 31.6 million km from the Earth. The one-way signal travel time was 1 minute 45 seconds.