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No. 217 - End of Solar Conjunction Operations

No. 217 - End of Solar Conjunction Operations

Report for Period 3 January to 30 January 2010 (week 1 - week 4)The Venus Express spacecraft and instruments performed nominally during the reporting period. The solar conjunction operations phase that had started on 29 December 2009 in the previous reporting period was concluded on 22 January 2010. During this phase all instruments were off. Following the solar conjunction exit, the instruments have again nominally resumed routine science operations.

In the middle of the solar conjunction phase, on 11 January 2010, Venus was at superior conjunction. No communication passes were conducted between 9 and 13 January while the Sun-Earth-spacecraft angle was below 1°. The +X side of the spacecraft was off-pointed from the Sun during this period to avoid long direct Sun exposure on the high-gain antenna 1 (HGA1).

The spacecraft telecommand bit rate remained at 250 bps and the telemetry bit rate at 297 bps, until 22 January 2010, when they were increased to 1000 bps and 57 kbps respectively.

Like during previous solar conjunctions phases of the mission, daily telecommand tests have been conducted up to the solar conjunction exit. These were to characterise the radio link budget in the presence of the scintillation caused by the Sun. During these tests the spacecraft telecommand bit rate was increased to 2000 bps.

Solar conjunction exit activities were carried out on 22 January 2010. MAG was the first instrument to be activated that same day, after the Cebreros communication pass. After the end of the following Cebreros communication pass on 23 January, all instruments resumed science operations nominally.

During the reporting period mission operations have been conducted with support of the ESA Cebreros ground station. Communication passes were performed daily from 3 to 30 January, except between 9 and 13 January.

The table below shows a chronology of the main activities:

MET
(Day)
Date DOY Main Activity
1517 03/01/10 003 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1518 04/01/10 004 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1519 05/01/10 005 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1520 06/01/10 006 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1521 07/01/10 007 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1522 08/01/10 008 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1523 09/01/10 009 No Cebreros communication pass.
1524 10/01/10 010 No Cebreros communication pass.
1525 11/01/10 011 No Cebreros communication pass.
Venus at superior conjunction
1526 12/01/10 012 No Cebreros communication pass.
1527 13/01/10 013 No Cebreros communication pass.
1528 14/01/10 014 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1529 15/01/10 015 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1530 16/01/10 016 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1531 17/01/10 017 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1532 18/01/10 018 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1533 19/01/10 019 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1534 20/01/10 020 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1535 21/01/10 021 Shortened Cebreros pass of 3 hours. Conjunction activities. Telecommand test
1536 22/01/10 022

Cebreros communications pass dedicated to conjunction exit activities.
Telemetry bit rate increased to 57kbps and telecommand bit rate changed to 1kbps.
Upload of first master timeline detailed agenda files (MDAF).
End of solar conjunction operations.

1537 23/01/10 023 Science operations resumed after the Cebreros communication pass concluded.

MET = Mission elapsed time; DOY = Day of year

At the end of the last Cebreros pass in the reporting period (DOY 030) Venus Express was orbiting Venus at 255.13 million km from the Earth. The one-way signal travel time was 850 seconds.

Spacecraft

During solar conjunction only limited telemetry was available. No data dumps were executed because of the very low downlink bandwidth and short duration passes. Throughout solar conjunction all telemetry was recorded and stored on board in the solid state mass memory. It was retrieved on ground after the conjunction exit on 22 January.

Attitude and Orbit Control System (AOCS)
The AOCS is in its nominal configuration and performing nominally. Operations continue with all four reaction wheels (RWs). Wheel off loadings were performed on a daily basis.

The spacecraft's off-Sun pointing between 9 and 13 January, resulted in a drop of the bearing temperature and friction levels on the reaction wheels. Outside this period the reaction wheels friction levels stayed stable at expected levels.

The friction on RW2 continued showing spikes, predominantly during the Earth pointing periods. This behaviour has already been correlated to higher bearing temperatures and has no negative impact on operations. The spikes seemed to disappear during the off-Sun pointing period, coinciding with the lowering of the RW2 bearing temperature.

Payload Activities

No science operations were performed during the conjunction phase between 28 December 2009 and 22 January 2010.

ASPERA
Starting after the end of the Cebreros pass on DOY 023, the instrument was again regularly operated as part of the routine plan.

MAG
Starting after the end of the Cebreros pass on DOY 022, the instrument was again regularly operated as part of the routine plan.

PFS
The instrument was not operated during the reporting period.

SPICAV
Starting after the end of the Cebreros pass on DOY 023, the instrument was again regularly operated as part of the routine plan.

VeRa
No radio science observations were made during the reporting period.

VIRTIS
Starting after the end of the Cebreros pass on DOY 023, the instrument was again regularly operated as part of the routine plan.

VMC
Starting after the end of the Cebreros pass on DOY 023, the instrument was again regularly operated as part of the routine plan.


Future Milestones

  • 22-28 February 2010: atmospheric drag campaign #3a


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Legal disclaimer
This report is based on four ESOC mission operations reports, MOR #217 through #220. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.

Last Update: 1 September 2019
29-Oct-2020 17:03 UT

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