Start of Planck TBTV Test Campaign
26 June 2008Last week saw the start of the thermal balance / thermal vacuum (TBTV) test campaign for the Planck spacecraft. The test campaign is performed at the Centre Spatial de Liège test facilities in Belgium.
During the TBTV test campaign the cold vacuum conditions of space are simulated. The objectives of the thermal balance tests are twofold: one part is to demonstrate the correct performance of the spacecraft when exposed to near flight-like environmental conditions; the second part is a verification that the sophisticated cryogenic cooling system of Planck achieves the correct temperatures (down to a tenth of a degree above absolute zero) and that the scientific detectors demonstrate the required performance. The objective of the thermal vacuum tests is to demonstrate that the spacecraft is working nominally when the temperatures of its units are at lower and upper operational limits.
In the final few days leading up to the actual start of the test campaign, the Planck spacecraft was placed inside the FOCAL-5 vacuum chamber. The thermal tent that surrounds the spacecraft inside the vacuum chamber was then put into place.
On Monday 16 June, the two doors of the test chamber were closed and the green light was given for the start of the TBTV test campaign. The next day (17 June) marked the formal start of testing. The entire TBTV test campaign lasts several months and includes 13 phases, each of them covering different aspects of the thermal test verification of the Planck spacecraft.When the first four phases of the TBTV test campaign are completed, the spacecraft's active cryogenic chain will be started. This includes the sorption cooler, which will reach 18K on the focal plane unit (FPU) stage, the 4K cooler, which will reach 4.5K and finally the dilution cooler, which will reach a temperature lower than 100mK. It will take more than 22 days to reach this lowest temperature level. At that stage, the test phase of the HFI instrument will start.