Mars Express: Spacecraft and Payload Operations Were Nominal, Except for the OMEGA Anomaly Reported Below

4th SSEWG Meeting 26-27 October 2010

Report on Solar System Missions in Operations Gerhard Schwehm; Head, Solar System Science Operations Division (SRE-OS)

General: The most important event in the reporting period was the flyby of Rosetta at asteroid Lutetia on 10 July, at 15:44:54.75 UTC at a closest distance of 3168 km. Spacecraft and most of the payload elements performed nominally during the flyby and provided a wealth of data. All payload operations linked to the flyby had been completed successfully on 14 July.

As the first step in the Mission Extension Process the overall status of the spacecraft, payload and ground segment of the missions to be extended was reviewed during a dedicated Mission Extension Operations Review (MEOR) at ESOC on 30-Jun-2010 for Cluster, Mars Express, Venus Express and PROBA 2. This review was successful completed for all missions with Board concluding that all missions have demonstrated that their operations could be continued through 2014. For the missions not operated by the Agency, SOHO and Hinode, a similar more restricted review was held at ESTEC on 3 June. These missions and their status will be presented in detail as part of the discussions on mission extensions during this meeting of the SSEWG.

SOHO: Operations of SOHO continued nominally during the past months. The exception was one event on 20 August at 13:55 UT when SOHO went into Emergency Sun Reacquisition (ESR) mode. Cause was a false Coarse Sun Pointing Attitude Anomaly Detection (CSPAAD), as in the ESR’s of December 2004 and July 2009. ESR recovery was smooth, and transition back to Coarse Roll Profile (CRP) mode was achieved at 22:28 UT on 20 August. The next day the NASA SOHO Mission Director and ESA’s Mission Manager implemented the necessary momentum management and roll manoeuvre. Technical support was in stand-by remotely. The spacecraft was back in Normal Mode on 21 August at 23:03 UT. Instrument recoveries proceeded over the rest of the weekend into Monday, August 23. This was the first ESR without ESA engineering support on site and without a Science Operations Coordinator (SOC) to coordinate the instrument recovery a realistic test of how SOHO will be operated in future in order to minimize operations cost.

Cluster: The spacecraft and the instruments were operated nominally according to the master science plan. Only a small number of minor anomalies were recorded, e.g. a solid state recorder anomaly occurred on 29 June on C3. Data recording had stopped and a warm restart was done during the next pass. About 30 hours of data were lost. In September C4 recovered from a controller failure of the Solid State Recorder, which had caused the corruption of all stored data. Science data worth about 50 hours could not be recovered. In July the 5-month eclipse season had ended and all spacecraft came through it in a healthy state. However, already on 22 October a new eclipse season was entered that will last about 9 months.

1 For the current eclipse season an agreement with XMM-Newton was reached to allow for additional Perth passes - XMM normally has priority for this station. Cluster 4 has been experiencing radio interference at Perth due to the installation of a commercial service around Perth (WiMax internet access). Until the implementation of a filter has been completed, C3 and C4 have been allocated to MSP (Maspalomas) and C1 and C2 to Perth (as their frequencies are far enough away from commercial frequencies). The C2 perigee was raised in July. Two orbit trim manoeuvres have been performed on C2 in August and two more were be performed on C1, C2 and C3 in September.

The CAA (Cluster Active Archive) development has been continuing smoothly and successfully. In August the CAA had reached 1075 registered users (user statistics can be found in //caa.estec.esa.int/caa/user_stats.xml). The re-processing of Double Star has been continuing despite some computer interface issues in China, which are being addressed by the Cluster Project Scientist directly with our Chinese partners. A media and Cluster community event was held 1 September at ESOC to celebrate 10 years in orbit operations of the mission.

Mars Express: Spacecraft and payload operations were nominal, except for the OMEGA anomaly reported below. In August MEX successfully completed two tests related to a routine end-to-end verification of the NASA-ESA communication chain between MEX and MER. Agreement was reached on possible dates for the next, routine, MEX-MELACOM – MER test campaign. The last very close (108 km) Phobos flyby for some time to come will take place on 9-Jan-2010. During this flyby special observations will be planned. Preparations for the upcoming solar conjunction season (17-Jan-2010 – 24-Feb-2010) are proceeding well. Although this conjunction season overlaps with a Mars Express eclipse season, no special measures are necessary. During the conjunction no science operations are possible. An anomaly was detected during two OMEGA observations end-Aug-2010. In both cases an overcurrent protection device was switched off. The OMEGA IR band is split over two detectors, L and C, and the anomaly detected occurred in the C-channel. Following a number of successful tests using only the remaining L- and VIS-channel, operations were resumed using these channels. Currently it is assumed that the anomaly is due to some form of short-circuit related to an end-of-life on the cryocooler for the C-channel, although this still needs to be confirmed. This would be consistent with the previously observed degradation of the C-detector cooler. The impact of this anomaly on the science return from the instrument is reported elsewhere. During July and August a number of science data losses occurred, partly caused by ground stations being down, the mass memory being full and also by HRSC data overproduction due to excellent imaging conditions. NASA HQ has requested MEX support to its Mars Surface Laboratory (MSL) mission, similar to what had been provided for the Phoenix Lander. The request is to provide support for both EDL coverage and for MEX to provide backup relay support during MSL surface operations.

2 Rosetta: Spacecraft operations during the Lutetia flyby on 10 July, at 15:44:54.75 UTC at a closest distance of 3168 km were performed nominally. Payload operations linked to the flyby had been completed on 14 July. By end July the large amount of science data that had been accumulated during the Lutetia fly was linked to ground and distributed to the Experiment teams. Since 12 July Rosetta is the solar-powered spacecraft that has been operating at the largest heliocentric distance. In August the spacecraft passed the 3 AU heliocentric distance and has entered the regime were we can monitor the spacecraft performance under conditions as for the start of the nominal comet operations phase. Therefore starting in August a number of tests to prepare for the spacecraft hibernation were performed successfully, e.g. RF strobing tests with the New Norcia Deep Space Antenna. This was followed by the characterisation of the solar arrays at low intensity and low temperature. The analysis of the test data is ongoing with the experts at ESTEC, however, from the initial results it has been confirmed that the solar array output meets the predictions. We had to perform a number of detailed thermal characterisation runs to see if we could get reach for large heliocentric distance the new switch on temperature limits for OSIRIS make the operations more robust. As this will be a major challenge for heliocentric distances beyond 3 AU an intensive consultation process has been put in place to define the best approach out of a number of options that were identified. On 15 July the AOCS was switched to a 3 reaction wheels mode to allow the switch off reaction wheel B to minimize its operations time. The final test of the RCS system has been prepared by the SOM and iterated with the experts in D/TEC and the Projects Department. The activities to switch over to PR 2 for the Rosetta RCS were completed on 9 September. Unfortunately the pressure in the system started immediately to decay from the expected nominal reading of 3.77 bars to 0 bars within 5hours. This is an unambiguous indication that there is a leak in the section that was opened and exposed to pressure in the test. At the same time COPS the ROSINA subsystem that monitors the ambient pressure around the spacecraft detected an increase in pressure with a subsequent decay that followed the reading of Pressure Transducer 2. One can only conclude that the RCS has an unrecoverable and permanent leak in the regulated section. The RCS anomaly and the implications were analysed in close collaboration with ESOC. We want to recall that we had tested and characterized the thruster performance at low pressure levels and that ESOC had studied the tank temperatures under realistic conditions now that the spacecraft is far away from the Sun and therefore we had all critical parameters available to assess the mission baseline under the new constraints. ESOC Flight Dynamics could demonstrate that we will achieve the nominal mission without re-pressurization by delaying the start of the post- hibernation rendezvous manoeuvre by only 1 week.

D/SRE was briefed 23 September and he approved the recommendation to continue the mission in ‘blow-down mode, i.e. not to re-pressurize the fuel tanks.

The Hibernation Readiness Review has been confirmed for 5 November at ESOC.

The spacecraft is now cruising towards the aphelion of its current orbit that it will reach in October 2012 with a heliocentric distance of 5.29 AU.

3 With the Lutetia flyby successfully completed the pre-comet science operations have come to and end and the payload complement will be activated only for a final check- out, the PC 13, before the hibernation phase. Most of these activities will be conducted in the allocated slot in December 2010 with few exceptions required by the mission profile. The first Deep Space Rendez-vous Manoeuvre will be performed in January 2011. Following this the spacecraft will be prepared for the Hibernation that will be entered in June. The Science Ground Segment Team has visited during the reporting meeting all PI teams individually to discuss the science operations concept for Rosetta. These detailed discussions were extremely valuable as we will introduce a new concept how to operate the payload during the extremely complex and challenging near comet phase. A synthesis of the results from these meetings will be presented to the Rosetta SWTM during its next meeting on 7/8 December at ESOC.

Venus Express: Operations of spacecraft and payload continued nominally. From 21-July until 26-Aug Venus Express successfully went through a, so-called, “quadrature” phase during which the spacecraft has to be flipped and the smaller high- gain antenna is used, which results in a much reduced data rate. Such phases are operationally fairly complicated. On 29-July-2010 a number of SSMM anomalies were observed on Venus Express. It was decided to stop the execution of the on-board command timeline. During a later pass it was noticed this had not happened, and it was decided to command the spacecraft into safe mode using the S-band link. Following this successful commanding into safe mode the spacecraft was recovered nominally and has functioned nominally since. The impact on science was limited. As a result of the analysis of this anomaly, some doubt has been cast on the reliability of the (then in use) mechanism involving so-called ‘delayed telecommand (TC) files’. The use of such files was anticipated for quadrature and aerobraking phases as a safety measure. The next quadrature phase (Jan-2011) will be planned without the use of these delayed TC files. This has a limited impact on the planned science observations. During October, when the Venus Express pericenter was rather low (down to 165 km – after which the pericenter is raised again), a very successful aerodrag campaign was executed. This campaign uses specially developed operations to measure the atmospheric density between 160 and 190 km altitude. The ESOC - JAXA interface for a MEX – AKATSUKI collision avoidance protocol, once this mission arrives at Venus, has been set up. This mechanism follows the same approach as between ESOC and JPL for spacecraft at Mars.

Hinode: S/C operations were nominal with data downlink through S-band. The ESA funded ground segment provided all required downlink passes. All Hinode data with usage statistics are available to the community through the Hinode Science Data Centre

Europe: HUhttp://sdc.uio.no/sdc/UH. E.g. in August 2010 the Hinode SDC was accessed by 548 distinct hosts and 49 GB of data were down-loaded.

Chandrayaan 1: The SPICE consolidated dataset for the mission was released by ISRO on 2 September. Now the C1XS/XSM, SARA and SIR-2 teams will be able to produce their final datasets, which are to be released to ISRO end of November pending the final technical review at ESAC. In addition to this, the C1XS team will provide calibrated datasets in the same time frame.

PROBA 2: Ground Segment performance, science operations and data handling were nominal. The work on finalizing the Lyra calibration pipeline is still on-going. The nominal operations of all solar payloads were interrupted in the second week of September for the preparation of the propulsion experiment, a technology demonstrator. The experiment should have shown the functioning of the Cool Gas Generators (COGEX) technology that offers easy to use, leak free and long term storage for gasses on board of spacecraft by producing gasses through decomposition of a solid propellant inside a gas generator. The operations of the COGEX will include the firing of a small thruster in flight direction and in anti-flight direction. Although the possible orbital change is minimal, great care is taken not to endanger instruments or the spacecraft. However, the need to clarify a number of small technical issues related to the pyro valves was one of the reasons that the test was postponed.