Flite: Free Flyer Laser Interferometer Technology Experiment

Abstract

Ambitious future space missions require extreme pointing accuracy and internal length stability, because they are based on optical/infrared interferometry. A technology precursor experiment is proposed, involving the German built ASTRO-SPAS, a space shuttle retrievable subsatellite. The objective of this experiment is the verification of key technologies and functions for an optical free-flyer interferometer, a laser gravitational wave detector (LISA) -both potential Horizon 2000plus cornerstone missions- and coherent inter-satellite laser communications (SOLACOS).

The experiment shall focus on a laser link between ASTRO-SPAS and a small, slowly departing subsatellite. Procedures common or similar in function and performance requirements for the application missions are laser-based pointing, initial acquisition and tracking (PAT), interferometric distance monitoring and control, laser optical phase locking and coherent laser communications (PSK homodyne). The free-flyer laser metrology mode for accurate internal sub-nm OPD-control and positioning of fiducial points for an optical interferometer will be verified in close distance range below 1 km. For LISA -essentially a gigant Michelson laser interferometer in space- one arm can be simulated in the range up to few km, depending on laser coherence. After increasing the distance to beyond 100 km, the laser communication mode can be tested in far-field geometry. Crucial functions and technologies (laser assembly) are verified in a realistic environment before taking the leap from laboratory to costly large science missions.

Similar configurations -to our knowledge- have not been flown in space up to now. The experiment can be performed also in a pure small satellites mission and can be expanded to include stare fringe tracking e.g. in a subsequent flight.