Mars Express Status Report - December 2009 and January 2010
In the course of December the pericentre latitude of the spacecraft's orbit increased from 71°N to 87°N, close to Mars' northern pole. After 1 January it decreased again to lower latitudes and reached 71°N at the end of the reporting period.
Mission performance has been good, with an average of 1.5 science pointings and 3.2 observations per orbit. There were 216 orbits with pericentre in December and January, corresponding to MTP-72, MTP-73 and MTP-74.
|Spacecraft distance to Earth||142 million km||99 million km|
|One-way signal travel time||7m 53s||5m 32s|
|Sun elevation at pericentre||+26°||-1°|
The instruments performed nominally during the reporting period. As part of the routine operations all instruments were operated regularly: ASPERA on 68% of the orbits, HRSC on 12%, MARSIS on 43%, OMEGA on 21%, PFS on 38%, and SPICAM on 100% of the orbits. Also 33 VMC observations were made, including the instrument's first Mars limb observation, which has captured clouds over the planet's limb. Together, for all instruments, 100% of the planned observations were executed successfully. The daily amount of returned science data was 1.1 Gbit.
Spacecraft status and performance
End December, the friction torque of reaction wheel #3 increased and showed slightly more jitter than usual. It remained, however, well below the allowed maximum. This has occurred on occasion in the past when it was observed to last for a few weeks to a few months. The behaviour had no negative impact on the spacecraft's pointing accuracy and towards the end of January 2010 the effect had already reduced significantly.
Several tests were performed with the internal mass memory of the PFS instrument. These tests were part of the ongoing analysis to check whether the spacecraft's overall on-board data handling (OBDH) bus usage can be increased by retarding the PFS data delivery.
Thermal and Power sub-systems
Both sub-systems are performing nominally. Like in all solar opposition seasons, the power consumption for the spacecraft's thermal control currently is higher due to the unfavourable illumination by the Sun. Outside the Mars observation pointings and ground station contact periods the spacecraft assumed a warm-up attitude.
The measured power demand and battery discharge during the current eclipse/aphelion season remained within predictions.
Telemetry, Tracking & Command (TT&C)
The TT&C sub-system is performing nominally. The telemetry bit rate was 228 kbps (maximum) over all ground stations throughout the reporting period.
In MTP-72 to MTP-74, general usage of the spacecraft S-Band link for radio science was not supported due to power constraints (to avoid battery discharge before eclipses). To mitigate the science loss, an “opportunistic radio science” approach has been implemented during this period, with the recording on ground of all X-Band data.
On 30 January, at a minimum Mars-Earth distance, both S-Band low gain antennae (LGAe) were tested successfully. The New Norcia ground station was used for downlink (signal only) and uplink (with telecommands), while mimicking the spacecraft rotation in Sun Acquisition Mode. This has confirmed the ability to use the LGAe for emergency commanding, has re-commissioned the S-Band transmitter 2 that hadn't been used since 2005, and calibrated the capability and limitations of the ESA tracking station network for such emergency commanding.
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 19 per week, with 33 passes completed over New Norcia (ESTRACK), 54 over Cebreros (ESTRACK), 11 over Madrid (DSN), 56 over Goldstone (DSN) and 2 over Canberra (DSN). More than 99.4% of the data available on-board the spacecraft has been received on ground.
- 16 February to 26 March 2010: Phobos flyby campaign
- 3 March 2010: Phobos closest ever approach (at 62 km from the moon's centre, or 50 km from its surface)
- March 2010: Orbit change to 88:25 resonance
- 31 March 2010: Mars at aphelion
- 19 April 2010: End of 8th eclipse season (started on 10 November 2009)
- April 2010: Test of Radio Frequency Distribution Unit (RFDU) switch #3
- 15 August 2010: End of 8th occultation season (started 20 September 2009)