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No. 152 - Solar array test at four AU and rendezvous trim burn

No. 152 - Solar array test at four AU and rendezvous trim burn

Report for the period 12 to 18 February 2011This report covers seven days of Rosetta mission operations. The main activities were a download performance test of the S-band high-gain antenna, a test of solar array performance at four AU from the Sun, delta differential one-way ranging (DDOR) and a trim burn performed as part of the first rendezvous manoeuvre (RDVM#1).

The trim manoeuvre (ΔV 17.29 ms-1) of RDVM#1, aborted due to a spacecraft attitude error on 10 February, was performed on 17 February. Detailed orbit determination is being carried out to assess the possible need for a further correction. Shortly before the trim manoeuvre, the performance of the solar arrays at four AU was tested; results were very close to the most recent predictions. These data will now be used to perform a detailed assessment of the operations timeline for the deep space phase.

During the reporting period, mission operations were conducted using the ESA New Norcia (NNO) ground station and the DSS-24 (Goldstone, 34 metres), DSS-25 (Goldstone, 34 metres), DSS-26 (Goldstone, 34 metres) and DSS-55 (Madrid, 34 metres) NASA Deep Space Network (DSN) antennas.

Main activities during reporting period

DoY Date Pass Activity
043 12-Feb-2011 DSS-25 2545
NNO 2545
Monitor
044 13-Feb-2011 DSS-26 2546 Monitor
045 14-Feb-2011 DSS-255 2547
NNO 2547
S-band high-gain antenna download performance test
046 15-Feb-2011 DSS-26 2548 Monitor
047 16-Feb-2011 NNO 2548
CEB 2549
DSS-26 2549
NNO 2549
DDOR
DDOR
Monitor
Solar arrays test at 4 AU
048 17-Feb-2011 DSS-24 2550
NNO 2550
Trim manoeuvre 1B (ΔV 17.29 ms-1)
049 18-Feb-2011 DSS-54 2551 Monitor

DoY = Day of year

At the end of the reporting period on 18 February, Rosetta was at 556 million kilometres from the Earth (3.71 AU); one-way signal travel time was 1855 seconds (30 minutes 55 seconds). The distance to Sun was 600.86 million kilometres (4.01 AU).

Spacecraft

Attitude and orbit control system
The Reaction Control Subsystem (RCS) is configured with thruster set A as nominal, set B as redundant. The TRIM 1B burn was performed using RCS A and confirmed that no permanent failure is present in this branch. As reported in the previous period, performance of the RCS during reaction wheel offloading (that is, short, sporadic pulses) is not as expected and the problem seems to be with the cold-start thruster model at low pressures. This will be further investigated in view of the need to employ the thrusters during the spin-up manoeuvre required before entry into deep-space hibernation. Performance during ΔV manoeuvres is consistent with the available model. The manoeuvre, which lasted about 29 minutes, was completed around 30 seconds earlier than predicted, indicating a slight over-performance of the thrusters with respect to the model.

The inconsistent attitude and orbit control system behaviour observed during the safe mode on 10 February has been understood and traced to a non-ideal setting of a filter within the attitude controller.

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 remaining payload activities to be completed before hibernation entry are now being planned and will be executed before mid-March to have the spacecraft ready for the opposition phase in April and May.

Summary of upcoming events:

  • 3 Mar 2011: TRIM 2 burn (if needed)
  • 12 April 2011: Start of opposition phase
  • 20 May 2011: End of opposition phase
  • 8 June 2011: Hibernation entry

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Legal disclaimer
This report is based on the ESOC mission operations report, WOR #152. 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
28-Nov-2020 15:22 UT

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