Mars Express Status Report - February 2010
The eighth Mars Express occultation season, which started 20 September 2009, as well as the eighth Mars Express eclipse season, which started 10 November 2009, both are ongoing. Over the course of the reporting period, the eclipse durations decreased from 40 minutes to 29 minutes.
Mission performance has been good, with an average of 1.9 science pointings and 4.0 observations per orbit. There were 97 orbits with pericentre in February, corresponding to medium term planning MTP-74 and MTP-75. The Sun elevation at pericentre is now continuously below 0° (in the reporting period it moved from -1° to -11°). These night conditions are favourable for radar observations of Mars.
|Spacecraft distance to Earth||99 million km||116 million km|
|One-way signal travel time||5m 32s||6m 26s|
|Sun elevation at pericentre||-1°||-11°|
Phobos flyby campaign
Between 16 February and 26 March Mars Express performs a series of twelve flybys of Phobos, the larger of the two Martian moons. During the campaign all instruments on board Mars Express are used to study Phobos. The first four flybys in the campaign were completed on 16, 22, 25 and 28 February with the spacecraft passing progressively closer to the moon (at altitudes from 991 kilometres down to 226 kilometres).
The campaign's closest flyby of Phobos will be on 3 March, when the spacecraft will pass just 67 km from the moon's surface. During this closest approach radio investigations will provide the most precise measurements to date of the moon's gravity field.
For more details and for first results from the Phobos flyby campaign, see the links in the right-hand menu.
The instruments performed nominally during the reporting period. As part of the routine operations all instruments were operated regularly: ASPERA on 76% of the orbits, HRSC on 16%, MARSIS on 95%, OMEGA on 18%, PFS on 41%, and SPICAM on 100% of the orbits. Also 22 VMC observations were made. Together, for all instruments, 99.2% of the planned observations were executed successfully. The daily amount of returned science data was 1.5 Gbit.
Spacecraft status and performance
On 1 February the Inertial Measurement Unit (IMU) of the AOCS was switched from B (nominal) to A (redundant) for a regular check; the IMU-A accelerometers and gyros will be monitored over a period of several weeks.
A season of long star tracker occultations (more than 1.5 hours) has started and will last a few weeks. The star tracker behaviour is nominal.
Thermal and Power sub-systems
Both sub-systems are performing nominally. Around the Mars solar opposition on 29 January, the spacecraft's thermal power demand peaked at 190W as predicted and started to decrease again afterward. Outside the Mars observation pointings and ground station contact periods a warm-up attitude continues to be used for the spacecraft.
The measured power demand and battery discharge during the current eclipse/aphelion season remained within predictions. They are also close to the behaviour corresponding to a battery degradation of 30% relative to the nominal capacity (which was the estimated degradation level in November 2009, prior to the eclipse season). Slightly lower battery voltages at the end of the regular battery discharges hint at some degradation during the eclipse season, to be confirmed after the season's last eclipse in April.
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.
From 8 February onwards, the more favourable power situation allowed to resume the nominal planned radio science including usage of the S-Band. The “opportunistic radio science” scheme implemented last month (involving the recording of all X-Band data) has been discontinued.
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 14 per week, with 14 passes completed over New Norcia (ESTRACK), 15 over Cebreros (ESTRACK), 4 over Madrid (DSN) and 23 over Goldstone (DSN). All of the science data available on-board the spacecraft has been received on ground.
- 3 March 2010: Phobos closest ever approach (at 77 km from the moon's centre, or ~67 km from its surface)
- March 2010: Orbit change to 88:25 resonance
- 26 March 2010: End of Phobos flyby campaign
- 31 March 2010: Mars at aphelion
- April 2010: Test of Radio Frequency Distribution Unit (RFDU) switch #3
- 19 April 2010: End of 8th eclipse season (started on 10 November 2009)
- 15 August 2010: End of 8th occultation season (started 20 September 2009)