INTEGRAL thermal vacuum tests - 24 April 2002
24 April 2002
The thermal vacuum test is now well on its way. The INTEGRAL spacecraft is now fully submitted to the conditions of deep space right here on Earth in ESTEC's Large Space Simulator (LSS), with exposure to:
- Vacuum - various types of powerful pumps maintain the pressure level inside LSS, down to around 2 x 10-6 mbar, to simulate the void of deep space
- Cold deep space exposure - the shrouds lining LSS walls are cooled with liquid nitrogen circulation, down to a temperature of about -170º C
- Sun exposure - during various periods of the test, the Sun simulator is turned on and illuminates the spacecraft, as in orbit
In this 6th day of tests, power dissipation inside the satellite is reduced to a minimum to check that the thermal control system actively switches on heaters to keep all units in a safe mode.
As in space, the spacecraft is closely monitored around the clock from a checkout room close to the LSS. Spacecraft operators and specialists gather around clusters of computers to check the behaviour of the satellite as it cools down or heats up.
To cool the Large Space Simulator (LSS) walls to simulate the cold of deep space, LSS consumes large amounts of liquid nitrogen. Every morning and evening, a truck delivers about 25 000 litres of liquid nitrogen to keep a constant cold temperature of about -170º C. During the transfer from the truck to the facility storage tanks, all the transfer lines cool down, creating a dense mist. |
Graphic interface software allows rapid evaluation of the temperature profiles of more than 400 sensors inside the satellite. Automatic thermostats switch on or off on-board heaters, depending on the thermal environment, to maintain all the equipments to safe temperature ranges. This leads to the cycling effect shown by this monitor. |
