Heart of ESA vacuum testing

These four crucial hardware units are built to endure spaceflight conditions but never leave the ground. Together they form the thermal data acquisition system of the largest thermal vacuum chamber in Europe, the Large Space Simulator.

Featuring a Sun simulator that reproduces unfiltered sunshine, the mammoth LSS chamber allows entire satellites to be operated in the equivalent illumination, vacuum and temperature conditions of space for weeks on end.

Known as NgDCUs, New Generation Data Collection Units, these rarely glimpsed boxes are normally fitted into the equipment bay of the motion simulator within the LSS. This is used to rotate a satellite being tested within the cylindrical test chamber, which at 15 m high and 10 m wide is big enough to accommodate an upended London double decker bus.

Currently undergoing their biennial calibration process to make sure their accuracy remains well within specification, the NgDCUs are used to gather thermal data from within a satellite during each test campaign.

The cables that extend from each unit are connected to thermocouples and other sensors embedded within the test satellite. Each unit fits seven data cards within up acquiring test data across a maximum 54 channels, adding up to more than 1500 channels overall. These internal thermal measurements are supplemented by optical and thermal cameras mounted within the LSS.

“For typical test chambers, this kind of acquisition system would be operated outside vacuum,” explains electronics engineer Koen Debeule of ESA’s ESTEC Test Centre. “But because these units need to rotate along with the test satellite they have to be built to withstand sustained hard vacuum and temperature swings. Being built to flight quality in this way really makes them unique.”

Hardware for the NgDCUs came from Syderal in Switzerland with software supplied by Terma in the Netherlands.

Based at the ESTEC Test Centre in Noordwijk, the Netherlands, the LSS has performed pre-flight testing for many of ESA’s biggest missions, including Rosetta, Juice and Plato. The chamber incorporates a Sun simulator with up to 19 IMAX cinema-class Xenon light bulbs and liquid or gaseous nitrogen shrouds lining its walls to reproduce the chill of space.

The Test Centre is operated for ESA by European Test Services. It is the largest facility of its kind in Europe, providing a complete suite of equipment for all aspects of satellite testing under a single roof.