No. 142 - Third Pericentre Lowering Manoeuvre
The table below shows a chronology of the main activities in the reporting period:
| MET (Day) | Date | DOY | Main Activity |
| 992 | 27/07/08 | 209 | Performance of apocentre raising OCM#3 just before Cebreros communication pass |
| 993 | 28/07/08 | 210 | Performance of pericentre lowering OCM#3 during Cebreros communication pass, to bring pericentre altitude down to 190 km |
| 994 | 29/07/08 | 211 | New Norcia pass, for tracking and to monitor the spacecraft status after pericentre manoeuvre. Routine Operations at Cebreros pass |
| 995 | 30/07/08 | 212 |
Routine Operations. |
| 996 | 31/07/08 | 213 | Routine Operations. Combined atmospheric drag experiment + occultation pass with New Norcia ground station |
| 997 | 01/08/08 | 214 |
Routine Operations. |
| 998 | 02/08/08 | 215 | Routine Operations. Combined atmospheric drag experiment + occultation pass with Deep Space Network ground station |
At the end of the last Cebreros pass in the reporting period (DOY 215) Venus Express was orbiting Venus at 246.8 million km from the Earth. The one-way signal travel time was 823 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#3
The purpose of the OCM executed at pericentre on 27 July was to raise the apocentre altitude by 10 km. The manoeuvre had a nominal magnitude of 53.6 mms-1. The calibration within the orbit determination showed a slight under-performance of 0.65% (-0.35 mms-1) with a 1-sigma uncertainty of 0.99% (0.53 mms-1). The increase in apocentre altitude was about 50 m less than planned.
Pericentre lowering OCM#3
The purpose of the OCM executed at apocentre on 28 July was to lower the pericentre altitude by 11 km to 190 km. The manoeuvre had a nominal magnitude of 705.8 mms-1. The calibration within the orbit determination showed a slight over-performance of 0.36% (+2.5 mms-1) with a 1-sigma uncertainty of 0.08% (0.6 mms-1). The reduction in pericentre altitude was about 40 m more than planned.
Orbital period change
The combined effect of the two manoeuvres was foreseen to decrease the orbital period by about 2 seconds. The actual decrease in orbital period was 0.15 seconds more 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 combined atmospheric drag experiment & occultation measurements were taken with the New Norcia ground station and Deep Space Network ground station on DOY 212, 213, 214 and 215.
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
- 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 on 19 December 2008
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Legal disclaimer
This report is based on the ESOC mission operations report, MOR #142. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.