ESA Science & Technology - No. 11 - First Scientific Activity

The second slot of OSIRIS commissioning was completed on the first day of the reporting period. Overall the activities of this long OSIRIS commissioning slot were successful and most of the objectives achieved. However, some of the data collected in the previous passes were lost due to a suspected instrument software crash at the end of the period; for this reason a delta OSIRIS commissioning of about two days will be scheduled in the near future.

The covers of the two ROSINA sensors, DFMS and RTOF, were successfully opened after having released the locks via pyro firing.  This was done in preparation for the upcoming commissioning operations, planned for the second half of May. The new version of the on-board software for ROSINA was uplinked and successfully verified. The second slot of RSI (Radio Science Investigation) commissioning was successfully completed according to plan.

On the subsystem side an important activity was the pressurisation of the Reaction Control Subsystem in view of the upcoming deep-space manoeuvre. The firing of the 12 pyro valves that connected the high-pressure helium tank to the fuel tanks via the pressure regulators was successfully executed on 6 May and the regulated pressure of 17 bar was achieved shortly after. Monitoring of the pressure evolution is still continuing at the end of the reporting period.

Close monitoring of the thermal environment continues. The temperature of the thruster modules on the +X side of the spacecraft continues to slowly increase with the decreasing distance to the Sun. At the end of the reporting period the hottest thruster module, number 7, had reached 65 °C. Adjustments to the on-board thermal control table, to cope with the increasing spacecraft temperature, were uplinked to the spacecraft.

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 128, 02:26) Rosetta was at 27.5 million km from the Earth. The one-way signal travel time was 1 min 31 seconds.