LISA orbit selection and stability

The LISA mission involves three spacecraft separated by 5 X 10(6) km. Each spacecraft needs to be able to point at the other spacecraft in order to tr ansmit and receive laser signals to each other. The initial beam acquisitio n process is dependent on the pointing accuracy of the spacecraft, the lase r beam width and the knowledge of the directions to the other spacecraft. T he directions from one spacecraft to another will be determined by tracking radio signals from each spacecraft independently by Earth tracking station s. An analysis of the position determination estimation is described here. Using conventional Doppler and range information, the relative angular posi tions of each spacecraft can be determined to better than 1 mu rad (0.2 are sec), which is less than the laser beamwidth.