Mars Express Status Report - October 2009
During the reporting period mission performance has been nominal, with an average 1.6 science pointings and 5.2 observations per orbit. There were 107 orbits with pericentre passage in October, corresponding to the operations medium term plans MTP-70 and MTP-71.
|Spacecraft distance to Earth||211 million km||177 million km|
|One-way signal travel time||11m 45s||9m 51s|
|Sun elevation at pericentre||+33°||+35°|
During the course of the reporting period the Sun elevation at pericentre increased to the seasonal maximum of +35°.
The instruments performed nominally during the reporting period. As part of the routine operations all instruments were operated regularly: ASPERA on 100% of the orbits, HRSC on 73%, MARSIS on 56%, OMEGA on 33%, PFS on 88%, and SPICAM on 96% of the orbits. Also 11 VMC observations and 3 MELACOM sessions were performed. Overall, for all instruments, 99.5% of the planned observations were executed successfully. The daily amount of returned science data was 3.2 Gbit.
The software patch to improve the performance of the ASPERA instrument has been uplinked on 13 October and tested on 27 October, with excellent results. It is now ready for operational use.
Spacecraft status and performance
Thermal and Power sub-systems
Both sub-systems are performing nominally.
On 21 October, Deep Discharge Test #4 was performed. It showed that the capacity of the batteries has degraded by 25-29% with respect to their nominal (nameplate) capacity. This is better than three months ago, which confirms a chemical recovery effect on Li-Ion batteries when they are not used and kept below maximal charge. Independent methods yield a slightly different absolute capacity but all conclude to a 3% recovery.
In preparation of the forthcoming 2009-2010 eclipse/aphelion season, a meeting was held on 22 October dedicated to the spacecraft's power management. The sub-system's readiness was confirmed for this season, during which an extensive set of science observations will be performed. No other spacecraft set-up is required for energy management than the usual conservative planning measures in eclipse season.
Telemetry, Tracking & Command (TT&C)
The TT&C sub-system is performing nominally. The telemetry bit rate over the 34m ground stations was increased from 152 to 182 kbps on 7 October, and from 182 to 228 kbps (maximum) on 26 October.
Radio science investigations using the spacecraft's radio links took place 14 times per week, including 2 Bistatic Radar experiments. These investigations are part of the Mars Radio Science experiment (MaRS).
On 26 and 20 October, two relay tests took place with the NASA Rover Spirit, including return of test data and delivery of a test command. The link was stable for half the first test (up to 3600 km) and excellent for the whole second test (up to 4600 km). It is planned to verify the relay capability twice a year.
Ground segment status and performance
Mars Express operations were supported by ground stations from the ESA tracking station network (ESTRACK) and the NASA Deep Space Network (DSN).
The number of tracks was on average 18 per week, with 30 passes over New Norcia (ESTRACK), 17 over Cebreros (ESTRACK), and 32 over Goldstone (DSN). More than 99.8% of the data available on-board the spacecraft has been received on ground.
The Chinese VLBI Network reported good results for their Mars Express tracking experiment on 7-8 August 2009. They have been provided with the Mars Express transmission times for the next experiment in November.
- 10 November 2009 - 19 April 2010: The 8th eclipse season
- 3 March 2010: Phobos closest approach ever (at 62 km from the moon's centre and 50 km from its surface)
- 15 August 2010: End of 8th occultation season (started 20 September 2009)