ESA Science & Technology - LISA Pathfinder Inertial Sensor Head test setup

This picture shows the vacuum chamber in which the engineering qualification model of the LISA Pathfinder Inertial Sensor Head (ISH) was placed during thermal vacuum tests.

The ISH is designed to keep a cubic (46 mm × 46 mm × 46 mm) gold:platinum test mass, located at the centre, free from all external forces except gravity.

Packed in a titanium vacuum enclosure (which cannot be seen in this photograph), roughly 43 cm tall and 18 cm wide, are the support structure, capacitors and mechanisms to hold, position and release the test mass once the spacecraft is on orbit. Feedback loops and micro-propulsion thrusters are used to keep the spacecraft centred on the test mass. A charge management system comprising fibre-coupled UV lamps will counteract the build up of electrostatic forces from cosmic rays and solar particles by discharging the test mass at regular intervals.