No. 151 - Spacecraft ranging and trim burn
The trim manoeuvre (ΔV 17.3 ms-1) of RDVM#1 was initiated on 10 February, but was aborted when the spacecraft entered safe mode a few seconds into the burn due to an attitude pointing error that exceeded the failure detection isolation and recovery (FDIR) system limit of four degrees for the first 100 seconds of the manoeuvre. The attitude pointing error was due to an operational oversight that caused a command to adjust the spacecraft attitude before the burn not to be uplinked. The safe mode was promptly recovered and the spacecraft is back on track for the required trim manoeuvre. During the few seconds that the burn lasted, the reaction control system (RCS) branch A behaviour was consistent with the commands issued by the attitude and orbit control system.
During the reporting period, mission operations were conducted using the ESA New Norcia (NNO) ground station and the DSS-14 (Goldstone, 70 metres), DSS-24 (Goldstone, 34 metres), DSS-25 (Goldstone, 34 metres), DSS-26 (Goldstone, 34 metres), DSS-34 (Canberra, 34 metres), DSS-54 (Madrid, 34 metres), DSS-55 (Madrid, 34 metres) and DSS-65 (Madrid, 34 metres) NASA Deep Space Network (DSN) antennas.
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Main activities during reporting period | |||
| DoY | Date | Pass | Activity |
| 025 | 25-Jan-2011 | DSS-54 2527 NNO 2527 |
Monitor |
| 026 | 26-Jan-2011 | DSS-54 2528 NNO 2528 CEB 2528 DSS-25 2528 DSS-34 2528 |
Monitor Monitor + DDOR DDOR DDOR DDOR |
| 027 | 27-Jan-2011 | DSS-25 2529 NNO 2529 |
Monitor |
| 028 | 28-Jan-2011 | DSS-65 2530 NNO 2530 |
Monitor |
| 029 | 29-Jan-2011 | DSS-25 2531 NNO 2531 |
Monitor |
| 030 | 30-Jan-2011 | DSS-26 2532 NNO 2532 |
Monitor |
| 031 | 31-Jan-2011 | DSS-55 2533 NNO 2533 CEB 2534 DSS-24 2534 DSS-34 2534 |
Monitor Monitor + DDOR DDOR DDOR - failed, recovered 3 February (DoY 034) DDOR - failed, recovered 3 February (DoY 034) |
| 032 | 1-Feb-2011 | DSS-25 2534 NNO 2534 |
Monitor |
| 033 | 2-Feb-2011 | DSS-55 2535 NNO 2535 |
Monitor |
| 034 | 3-Feb-2011 | DSS-54 2536 NNO 2536 DSS-25 2536 DSS-34 2536 |
Monitor Monitor DDOR DDOR |
| 035 | 4-Feb-2011 | DSS-54 2537 NNO 2537 |
Monitor |
| 036 | 5-Feb-2011 | DSS-24 2538 NNO 2538 |
Monitor |
| 037 | 6-Feb-2011 | DSS-24 2539 NNO 2539 |
Monitor |
| 038 | 7-Feb-2011 | DSS-24 2540 NNO 2540 |
Monitor |
| 039 | 8-Feb-2011 | DSS-14 | Monitor |
| 040 | 9-Feb-2011 | DSS-55 2542 NNO 2542 |
Monitor |
| 041 | 10-Feb-2011 | DSS-24 2543 NNO 2543 |
TRIM 1 failure and safe mode recovery |
| 042 | 11-Feb-2011 | DSS-24 2544 NNO 2544 |
Post safe mode reconfigurations |
|
DoY = Day of year | |||
At the end of the reporting period on 11 February, Rosetta was 568 million km from Earth (3.79 AU); the one-way signal travel time was 31 min 34 sec (1894 sec). The spacecraft's distance from the Sun was 596 million km (3.98 AU).
Spacecraft
Attitude and orbit control system
RCS branch A was reconfigured to be nominal on 7 February in preparation for the RDVM#1-TRIM 1 burn. Three reaction wheel offloading manoeuvres were performed after burn RDVM#1-2C, two with RCS B and one with RCS A. In all cases, the RCS performance was lower than expected (thrust levels ranging from 80 to 95 per cent); this seems to indicate that the cold-start models are not fully representative of the thruster performance. Further characterisations will have to be done in preparation for hibernation mode. The TRIM1 burn was planned to be executed with RCS A in order to verify the performance of this branch after the failure on 18 January; during the few seconds of the aborted burn, the RCS behaviour was fully as expected. However, due to the operational error that caused a command to adjust the spacecraft attitude before the burn not to be uplinked, thruster 9A - the one suspected of causing the failure of 18 January - was never fired.
| Payload Status | |
| ALICE | The instrument is currently OFF. |
| CONSERT | The instrument is currently OFF. |
| COSIMA | The instrument is currently OFF. |
| GIADA | The instrument is currently OFF. |
| MIDAS | The instrument is currently OFF. |
| MIRO | The instrument is currently OFF. |
| OSIRIS | The instrument is currently OFF. |
| ROSINA | The instrument is currently OFF. |
| RPC | The instrument is currently OFF. |
| RSI | The USO is ON/muted since 3 February 2010 (DoY 032/2010). |
| VIRTIS | The instrument is currently OFF. |
| Lander (Philae) | The instrument is currently OFF. |
| SREM | The instrument is ON with standard settings since 3 February 2010 (DoY 032/2010). |
Future milestones
The trim manoeuvre is now being re-planned with a tentative date of DoY 048, pending further verifications of the Attitude and Orbit Control System (AOCS) software behaviour. Eventual residuals will be cleared with a second trim manoeuvre in March.
Summary of upcoming events:
- 16 February 2011: Solar arrays performance test at 4 AU
- 17 February 2011: TBC – TRIM 1 burn (nominal ΔV 17.6 ms-1)
- 03 March 2011: TRIM 2 burn
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Legal disclaimer
This report is based on the ESOC mission operations report, WOR #151. Please see the copyright section of the legal disclaimer (linked from the home page http://sci.esa.int) for terms of use.