No. 206 - Orbit control manoeuvres
Orbit control manoeuvres
The orbit of Venus Express slowly evolves due to natural perturbations. The pericentre altitude is kept within the allowed range by orbit control manoeuvres (OCM) performed at specific times. At the end of the previous reporting period the Venus Express spacecraft reached the currently set lower limit of 175 km for the altitude of the pericentre passage. Two OCMs were therefore performed at the beginning of this reporting period.
On 18 October an OCM was first performed to lower the orbit's apocentre altitude. This was followed by an OCM on 19 October to raise again the pericentre altitude. Both the OCMs were successful and performed nominally.
DDOR
On 20 October delta differential one-way ranging (DDOR) was performed using the New Norcia and Cebreros ground stations to track the spacecraft. These measurements are performed monthly to support the accurate determination of the ephemeris for the planet Venus that is maintained by NASA's Solar System Dynamics Group.
The DDOR measurement principle uses a technique to highly accurately determine the position of a transmitter in space and relies on observing the time delay between reception of the signal from the transmitter by two ground stations at different positions on Earth. In this case the Venus Express spacecraft is the transmitter and the two ground stations are New Norcia in western Australia and Cebreros in Avila, Spain.
The table below shows a chronology of the main activities:
| MET (Day) |
Date | DOY | Main Activity |
| 1440 | 18/10/09 | 291 |
Communications pass over Cebreros. |
| 1441 | 19/10/09 | 292 |
Communications pass over Cebreros. |
| 1442 | 20/10/09 | 293 |
Communications pass over Cebreros. |
| 1443 | 21/10/09 | 294 |
Communications pass over Cebreros |
| 1444 | 22/10/09 | 295 |
Communications pass over Cebreros |
| 1445 | 23/10/09 | 296 |
Communications pass over Cebreros |
| 1446 | 24/10/09 | 297 |
Communications pass over Cebreros |
At the end of the last Cebreros pass in the reporting period (DOY 297) Venus Express was orbiting Venus at 236 million km from the Earth. The one-way signal travel time was 787 seconds.
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
No radio science observations were made during the reporting period.
VIRTIS
VIRTIS-M was operated in the visual channels only.
VMC
The instrument was regularly operated as part of the routine plan.
Future Milestones
- Superior conjunction: 29 December 2009 to 22 January 2010
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Legal disclaimer
This report is based on the ESOC mission operations report, MOR #206. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.