A Scheme for On‐Orbit Calibration of theSpace Interferometry MissionBased on Spacecraft Maneuvering

Abstract

ABSTRACT. The Space Interferometry Mission (SIM), part of NASA's Origins Program, aims at the detection of planetary systems around distant stars. The astrometric observations of the SIM instrument are performed via high-accuracy path-length measurements with a system of three Michelson-type white-light stellar interferometers. A procedure for on-orbit calibration of the instrument error function is described, along with a proof of the concept's viability. On a given grid of stars, the procedure generates approximations of the gradient of the instrument error function at a discrete set of field points corresponding to the star locations via a specialized set of maneuvers of the spacecraft. These gradient approximations are then used to estimate the error function via a least-squares procedure in a manner that is analogous to the wave-front reconstruction problem in adaptiveoptics systems. An error analysis of the procedure is presented that provides further insights into the connections between instrument errors and the grid reduction solution. Finally, numerical results are presented on a randomly generated grid of stars that demonstrate the feasibility of the method.