Space Interferometry Mission

Abstract

The Space Interferometry Mission (SIM) will be a 10-m optical interferometer in Earth orbit. SIM will enable a wide variety of science programs in Galactic and extra-galactic astronomy, including the calibration of cosmic distance indicators, and will address questions related to the origins and prevalence of planetary systems. SIM is designed primarily as an astrometric mission, providing high-throughput wide-angle astrometry, with an expected noise floor of about 4 μas for bright targets, and about 1 μas over small angles. Accurate parallaxes and proper motions will be available for a large number of stars of various types, providing data for fundamental programs in the stellar dynamics of star clusters and our Galaxy as a whole. SIM will have seven light-collecting siderostats (effective diameters 0.3m) spaced along the main boom, to allow synthesis imaging with a resolution of 10 mas, by rotating the spacecraft about the line of sight. It is NASA’s first space science interferometer, and in addition to enabling a strong astronomical science program, it is designed to demonstrate several key technologies needed for future missions in NASA’s Origins Program, such as the Next Generation Space Telescope (NGST) and Terrestrial Planet Finder (TPF). Interferometric nulling will be used by TPF to provide coronagraphic-type extinction of a bright star, allowing detection of faint companions. SIM will implement an achromatic null to a level of 10⁻⁴ and will study dust disks around main-sequence stars, and image the disks around young stellar objects.