Artist's concept of SMART-2 highlighting the 'LISA' side

1- The core of the USA Technology Package is a little cube of gold floating in space whose trajectory must not be affected by any external influence.

SMART-2 satellite acts as a protective shell. A highly sensitive 'inertial sensor' measures the distance between the proof-mass and the satellite.

2- The solar wind and micrometeorite showers, for example, would influence the trajectory of the free-floating cube.

Instead, these phenomena move the 'protective' satellite, but the cube remains unaffected.

3- When the sensor detects changes in the satellite's position the thrusters are activated, to bring the satellite back to its original position.

SMART-2 thrusters control the spacecraft position to a few thousands of a millimetre.

4- The sensor confirms that the satellite is again centred on the free floating cube.