LISA orbit selection and stability

The Laser Interferometer Space Antenna (LISA) is a space mission designed to detect gravitational waves in the frequency range from below 0.0001 Hz to 1 Hz by measuring changes in the distance between spacecraft separated by several million kilometres. The spacecraft orbit in a triangular formation forming three (not independent) interferometers with arm lengths determined by the distances between the vertices. The nominal orbit configuration is described and contrasted with an alternative configuration. Changes in the distances between the vertices cause a Doppler shift in the laser signals between spacecraft. The size of the measurement error introduced by this Doppler shift is dependent on the stability of the spacecraft formation.