ESA Science & Technology - No. 3 - End of LEOP Activities

A pinnacle in the reporting period was the first command send to Venus Express in X-Band via the new ESA 35m Deep Space Ground Station at Cebreros (Avila, Spain). Furthermore, the Trajectory Correction Manoeuvre (TCM-1) was successfully performed, which now brings Venus Express on the exact trajectory required for Venus Orbit Insertion.

Pass 4 Activities
LEOP operations included successful switching from the Low Gain Antenna (LGA) to the High Gain Antenna (HGA2), a test with the second S-Band transponder (S-Tx2), change in radio frequency band from S-Band to X-Band, and increase of the telemetry downlink bit rate to 91.4 kbps.

At 17:10 UTC the uplink carrier was established at Cebreros and the first command was transmitted from Cebreros to the Venus Express spacecraft at 17:21 UTC in X-Band. This marked the successful achievement of a major milestone for the new ESA 35m ground station.

The first dump of the Solid State Mass Memory (SSMM) data was done at 19:47 UTC, the first On-Board Control Procedure (OBCP) executed at 19:52 UTC, and the first Reaction Wheel off-loading was performed from 18:25 to 00:19 UTC.

Bonus activities in pass 4 encompassed Thermal Control System (TCS) heater switching, and successful commissioning of the Data Management System (DMS). It is to be noted that both the power and the thermal behaviour of the spacecraft are very close to pre-launch flight predictions.

Pass 5 Activities
Activities started with the preparation for the Trajectory Correction Manoeuvre (TCM-1). The manoeuvre was again performed in the direction of Earth in order to be fuel optimal. The slew was started 05:39 UTC and was completed 06:09 UTC. Subsequently, TCM-1 started at 06:14:33 UTC, had a manoeuvre duration of 209 seconds and a magnitude of 3.43 metres per second.

Post manoeuvre assessment based on Doppler data indicated that manoeuvre accuracy was within 0.034%. At 07:29 UTC the spacecraft had been slewed back to the starting attitude.

Thereafter, the Solid State Mass Memory (SSMM) data were dumped, the Ultra Stable Oscillator (USO) was switched-on and the Telemetry mode was changed. This completed the foreseen activities for pass 5. As a bonus, the Star Tracker commissioning was done.

With the end of the LEOP, the ground station support has now been significantly reduced and stations have been released. The mission will now be supported primarily by one pass per day from Cebreros. The support given by the ESA stations in Kourou, New Norcia/Perth and Cebreros, and by the NASA DSN stations of Canberra and Goldstone has been excellent.

The LEOP activities were completed on 11 November 2005 (DOY 315) at 08:48 UTC and Mission Elapse Time (MET) 53:15 hrs with Venus Express spacecraft already 634 000 km from Earth.

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