LISA Pathfinder is the revised name for SMART-2, an ESA space probe to be launched in 2009. SMART stands for Small Missions for Advanced Research in Technology. The aim of the LISA Pathfinder is to test technologies needed for the Laser Interferometer Space Antenna, a joint NASA/ESA gravitational wave detector. It will contain one arm of the LISA interferometer, shortened from 5 Gm (5 million km) to 35 cm. In particular, it will verify:
- Drag-free attitude control of a spacecraft with two proof masses,
- The feasibility of laser interferometry in the desired frequency band (which is not possible on the surface of Earth), and
- The reliability and longevity of the various components—capacitive sensors, microthrusters, lasers and optics.
LISA Pathfinder is being built by EADS Astrium Ltd. of Stevenage, UK under contract to the European Space Agency. It will carry a European 'LISA Test Package' comprising inertial sensors, interferometer and associated instrumentation as well as two drag-free control systems: a European one using field emission electric propulsion (FEEP) thrusters, and a US-built 'Disturbance Reduction System' using slightly different sensors and colloid thrusters that use ionised droplets of a colloid accelerated in an electric field.
The LISA Test Package is being integrated by Astrium Germany, but the instruments and components are being supplied to Astrium by contributing institutions across Europe. The noise rejection technical requirements on the interferometer are very stringent, which means that the physical response of the interferometer to changing environmental conditions, such as temperature, must be minimised. The spacecraft will be placed in a halo orbit around the Earth–Sun L1 point using an on-board propulsion stage. If this mission is successful, it is hoped that the LISA mission will be launched a few years later.
