No. 179 - Mission Operations Update
DDOR
On 16 April 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.
Mosaic images with star tracker
On 16 April and again on 17 April, star tracker B was commanded into CCD Health Check mode and images of the star field in its field of view were taken. Due to restrictions on the size of the CCD sub-window that can be commanded, mosaics of 3-by-3 sub-windows, each of them 15 pixels wide were used to build a 45-by-45 pixel view of the STR B boresight. The acquired data will be processed to assess its applicability in future scientific studies.
VeRa gravity observation campaign
The 70m NASA DSN ground station at Canberra, Australia, was not available for the VeRa gravity observation campaign on 15 and 17 April during the two originally planned passes on these dates. The first pass of the gravity observation campaign now is scheduled for 20 April.
The table below shows a chronology of the main activities:
| MET (Day) |
Date | DOY | Main Activity |
| 1251 | 12/04/09 | 102 |
Communications pass over Cebreros |
| 1252 | 13/04/09 | 103 |
Communications pass over Cebreros |
| 1253 | 14/04/09 | 104 |
Communications pass over Cebreros. |
| 1254 | 15/04/09 | 105 |
Communications pass over Cebreros. |
| 1255 | 16/04/09 | 106 |
Communications pass over Cebreros. |
| 1256 | 17/04/09 | 107 |
Communications pass over Cebreros. |
| 1257 | 18/04/09 | 108 |
Communications pass over Cebreros |
At the end of the last Cebreros pass in the reporting period (DOY 108) Venus Express was orbiting Venus at 51.9 million km from the Earth. The one-way signal travel time was 173 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 measurements were taken 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
- Battery Deep Discharge Test is planned for 22 April 2009.
- Start of next (outbound) quadrature phase on 29 May 2009.
- Swap of high gain antenna (HGA) from HGA2 to HGA1 on 8 June 2009.
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This report is based on the ESOC mission operations report, MOR #179. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.