Asset Publisher

No. 151 - Spacecraft ranging and trim burn

No. 151 - Spacecraft ranging and trim burn

Report for the period 25 January to 11 February 2011This report covers 18 days of Rosetta mission operations. The main activities were delta differential one-way ranging (DDOR) to determine the outcome of the burns performed during the previous reporting period as part of the first rendezvous manoeuvre (RDVM#1), and an attempt to perform the TRIM1 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.

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

---
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.

Last Update: 1 September 2019
29-May-2020 10:47 UT

ShortUrl Portlet

Shortcut URL

https://sci.esa.int/s/AMey4yA

Images And Videos

Related Publications

Related Links

See Also

Documentation

Further Readings