No. 141 - Second Pericentre Lowering Manoeuvre
29 Jul 2008 15:59
Report for Period 20 July to 26 July 2008
All operations have been nominal during the reporting period. During this period the second pair of Orbit Control Manoeuvres (OCM) to reduce the pericentre altitude and to raise the apocentre altitude was executed. Planning of the third pair was performed and commands were uploaded to the spacecraft for execution during the next reporting period.
The table below shows a chronology of the main activities in the reporting period:
| MET (Day) |
Date |
DOY |
Main Activity |
| 985 |
20/07/08 |
202 |
Performance of apocentre raising OCM#2 just before Cebreros communication pass |
| 986 |
21/07/08 |
203 |
Performance of pericentre lowering OCM#2 during Cebreros communication pass, to bring pericentre altitude down to 200 km |
| 987 |
22/07/08 |
204 |
New Norcia pass, for tracking and to monitor the spacecraft status after pericentre manoeuvre.
Routine Operations at Cebreros pass |
| 988 |
23/07/08 |
205 |
Routine Operations |
| 989 |
24/07/08 |
206 |
Routine Operations |
| 990 |
25/07/08 |
207 |
Routine Operations.
Upload of telecommands for the drag experiments next week.
Upload of apocentre raising OCM#3 |
| 991 |
26/07/08 |
208 |
Routine Operations.
Upload of pericentre lowering OCM#3 |
At the end of the last Cebreros pass in the reporting period (DOY 208) Venus Express was orbiting Venus at 249.6 million km from the Earth. The one-way signal travel time was 832 seconds.
Pericentre Lowering Campaign
Between 13 July and 5 August 2008 a series of OCMs is performed to lower the pericentre altitude of Venus Express (see also the link on the right hand side for more details).
Apocentre raising OCM#2
The purpose of the OCM executed at pericentre on 20 July was to raise the apocentre altitude by 18.1 km. The manoeuvre had a nominal magnitude of 96.6 mms-1. The calibration within the orbit determination showed a slight over performance of 0.52% (+0.51 mms-1) with a 1-sigma uncertainty of 0.53% (0.51 mms-1). The increase in apocentre altitude was about 100 m more than planned.
Pericentre lowering OCM#2
The purpose of the OCM executed at apocentre on 21 July was to lower the pericentre altitude by 22.7 km to 200 km. The manoeuvre had a nominal magnitude of 1.4136 ms-1. The calibration within the orbit determination showed a slight under performance of 0.13% (-1.9 mms-1) with a 1-sigma uncertainty of 0.09% (1.2 mms-1). The reduction in pericentre altitude was about 20 m less than planned.
Orbital period change
The combined effect of the two manoeuvres was foreseen to decrease the orbital period by about 8 seconds. The actual decrease in orbital period was 0.20 seconds less than planned.
Payload Activities
ASPERA
The instrument was regularly operated as part of the routine plan.
MAG
The instrument was regularly operated as part of the routine plan.
PFS
The instrument was not operated during the reporting period.
SPICAV
The instrument was regularly operated as part of the routine plan.
VeRA
Four RSI occultation measurements were taken with the New Norcia ground station on DOY 205, 206, 207 and 208.
VIRTIS
The instrument was regularly operated as part of the routine plan.
VMC
The instrument was regularly operated as part of the routine plan.
Future Milestones
- Start of drag experiment on DOY 212 (30 July 2008)
- Pericenter lowering operations to be completed on DOY 217 (4 August 2008)
- High gain antenna (HGA1) S-band carrier power test is planned for 15 December 2008
- Next quadrature phase will start in December 2008
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Legal disclaimer
This report is based on the ESOC mission operations report, MOR #141. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.
Last Update: 11 Sep 2008
