This artist's impression shows the interior layout of LISA Pathfinder's science module. The central circle is a cylindrical capsule that contains many of the spacecraft's key payload components — a vacuum enclosure that houses two test masses in their electrode casings, and the optical bench interferometer between them. Scientists will use this interferometer to monitor and measure the masses as they move in a near-perfect gravitational free-fall.

The solar array, which covers the entire top of the science module and is shown here as partly transparent for illustrative purposes, will shield the payload from the Sun, and provide power for the payload and support systems.

click here for high resolution image.