No. 155 - Eclipse Season
DDOR
On 27 October 2008, DOY 301, 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.
VIRTIS coolers temporarily not used
On DOY 301 anomalous behaviour was detected on the VIRTIS M-PEM cooler motor during a calibration cycle at the end of an otherwise routine observation.
As a temporary measure, until the anomaly is fully understood, it was decided to only operate the VIRTIS visual channel.
The table below shows a chronology of the main activities:
| MET (Day) | Date | DOY | Main Activity |
| 1083 | 26/10/08 | 300 | Routine Operations |
| 1084 | 27/10/08 | 301 | Routine Operations. DDOR with Cebreros and New Norcia |
| 1085 | 28/10/08 | 302 | Routine Operations |
| 1086 | 29/10/08 | 303 |
Routine Operations |
| 1087 | 30/10/08 | 304 | Routine Operations. New Norcia Occultation RSI observations |
| 1088 | 31/10/08 | 305 |
Routine Operations |
| 1089 | 01/11/08 | 306 | Routine Operations. New Norcia Occultation RSI observations. Bitrate change to 152 kbit/s |
At the end of the last Cebreros pass in the reporting period (DOY 306) Venus Express was orbiting Venus at 180.0 million km from the Earth. The one-way signal travel time was 600.6 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
Occultation measurements were taken during the reporting period on DOY 304 and 306 with the New Norcia ground station.
VIRTIS
The instrument was regularly operated as part of the routine plan.
An anomaly with the M-PEM cooler occurred on DOY301 and for now VIRTIS is operated in the visual channel only.
VMC
The instrument was regularly operated as part of the routine plan.
Future Milestones
- 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 #155. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.