No. 140 - First Pericentre Lowering Manoeuvre
The table below shows a chronology of the main activities in the reporting period:
| MET (Day) | Date | DOY | Main Activity |
| 978 | 13/07/08 | 195 | Routine Operations. Dump of data from first apocentre raising OCM #1 |
| 979 | 14/07/08 | 196 | Routine Operations. Performance of first pericentre lowering OCM #1, to bring pericentre altitude down to 220 km |
| 980 | 15/07/08 | 197 | New Norcia pass, to monitor the spacecraft status after pericentre manoeuvre. Pass was interrupted by an occultation from 04.11z to 04.51z |
| 981 | 16/07/08 | 198 | Routine Operations |
| 982 | 17/07/08 | 199 | Routine Operations. Telemetry bit rate was increased to 76182.5051 bit/sec |
| 983 | 18/07/08 | 200 | Routine Operations |
| 984 | 19/07/08 | 201 | Routine operations |
At the end of the last Cebreros pass in the reporting period (DOY 201) Venus Express was orbiting Venus at 252.5 million km from the Earth. The one-way signal travel time was 841.7 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#1
The purpose of the OCM executed at pericentre on 13 July was to raise the apocentre altitude by 176.3 km. The manoeuvre had a nominal magnitude of 0.9497 ms-1. The calibration within the orbit determination showed a slight under performance of 0.005% (-0.05 mms-1) with a 1-sigma uncertainty of 0.019% (0.18 mms-1). The difference between the planned and actual change in apocentre altitude was insignificant.
Pericentre lowering OCM#1
The purpose of the OCM executed at apocentre on 14 July was to lower the pericentre altitude by 137.1 km to 220 km. The manoeuvre had a nominal magnitude of 8.4117 ms-1. The calibration within the orbit determination showed a slight under performance of 0.280% (-23.5 mms-1) with a 1-sigma uncertainty of 0.003% (0.3 mms-1). The reduction in pericentre altitude was 0.38 km less than planned.
Orbital period change
The combined effect of the two manoeuvres was foreseen to increase the orbital period by only 63.6 seconds. The actual increase in orbital period was 0.63 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
Three occultation passes took place with the New Norcia ground station in S-band on DOY 198, 200 and 201.
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
- Second set of apocentre raising manoeuvre and pericentre lowering manoeuvre to take place on 20 and 21 July, respectively
- High gain antenna (HGA1) S-band carrier power test via New Norcia ground station will be performed before next quadrature entry. Tentative date is 15 December 2008
- Operations preparation for next quadrature phase
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Legal disclaimer
This report is based on the ESOC mission operations report, MOR #140. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.