Friday, October 14, 2011

ESA BepiColombo: Mercury Planetary Orbiter takes a simulated trip to the innermost planet

Thermal-balance testing of the BepiColombo Mercury Planetary Orbiter Structural and Thermal Model, which has been under way in ESA's Large Space Simulator since 20 September, has been successfully completed.

During these tests the conditions the spacecraft will encounter during the cruise to Mercury and while in orbit have been simulated, and a number of tests to characterise the spacecraft performance under some worst-case scenarios have been carried out.

'Dry run' in the Large Space Simulator
Following the installation of the Mercury Planetary Orbiter (MPO) Structural and Thermal Model (STM) in the Large Space Simulator (LSS) at ESA's Test Centre in Noordwijk, the Netherlands on 31 August.

The completion of all the necessary preparations, a 'dry run' was conducted on 13 September to verify the performance of the spacecraft, its instrumentation, and the gimbal stand / spin box and levelling table that support, orient, rotate and level the spacecraft during testing.

The dry run was performed with the LSS top cover open; the MPO was illuminated with just one of the nineteen 25-kW lamps that make up the solar simulator.

To reach the radiation intensity that the orbiter will experience in orbit around Mercury, the 121 hexagonal mirror segments that produce the beam have been adjusted to produce a converging beam rather than the standard parallel beam.

To allow the wall of the LSS to cope with the increased beam intensity while continuing to simulate the cold of space, an additional shroud has been installed.

Pump down and cold calibration
After the dry run, the LSS top hatch was closed and vacuum pumping commenced on 20 September. Once a vacuum of around 10-5 mbar had been achieved, liquid nitrogen started to be pumped through the shrouds of the chamber walls to cool the interior of the LSS down to less than -173 degrees C (100 K).

Once cool-down was completed, the steady state under cold conditions (referred to as 'cold calibration') was achieved and baseline data were acquired.

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