Entry 18: A busy week

Activating the ion propulsion valves

3 March 2009 – With less than two weeks to go before ESA's gravity mission launches, activities at the Plesetsk Cosmodrome are in full swing.

Last week was particularly intense with a number of important tests being carried out.

Firstly, the satellite's ion propulsion valves were successfully checked. Although some of the valves had been dormant for almost two years, all went well. By counteracting drag along GOCE's exceptionally low orbit above the Earth, the specialised ion propulsion system is integral to keeping the satellite stable.

Secondly, a two-part 'Integrated System Check' took place. The first part went well but the second part, on the redundant part of the system, took longer than expected as there were a few minor intermittent problems with the ground electronics used for in the second test. The tests were eventually successfully completed and the data transmitted to Thales Alenia Space in Italy for analysis.

Checking star tracker baffles for alignment
Checking star tracker baffles for alignment

After the Integrated System Check, the valves on the cold-gas thruster were activated to check they were in working order. This was done very simply by sensing with a finger if the nitrogen released by the valve was flowing properly. All of the valves were fine.

In addition, one of the star tracker baffles was checked for alignment as it has been removed in November before the satellite went into storage. The star trackers measure the orientation of the spacecraft relative to the stars to enable angular control. The test was achieved with a laser gun and a steady hand. Another check on the star tracker was done in the dark – which meant turning off all the lights in the clean room.

Cleanroom gets busier
Cleanroom gets busier

Lastly, some mechanical work was completed in preparation for the start of this week's activities when the spacecraft will be mated to launcher adapter and then placed onto the Breeze Upper Stage. The Upper Stage was tested on the launch pad last week and returned to the integration facility.

The weather was particularly cold last week with temperatures falling to -17°C but the skies were clear.

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