Publish Date: 
May 22, 2016



SIM/SIM-Lite was not recommended for development this decade by the Astro2010 Decadal Survey. As a consequence NASA sponsorship of the project was discontinued effective December 31, 2010.

SIM was intended to exploit the classical measuring tool of astrometry with unprecedented precision to make dramatic advances in many areas of astronomy and astrophysics. Of particular importance to NASA's goal of searching for habitable planets was SIM's survey of the closest ~100 stars for planets of a few earth-masses to identify potential Earth analogs and determine their mass and orbital properties.

SIM also planned to survey a few thousand stars of a wide variety of ages, spectral types, and other properties to build up an understanding of the architecture of planetary systems generally, providing data that will guide and test theories of planet formation and evolution. SIM would also improve the understanding of the physical properties of stars, determining mass, including the dark matter component, and its distribution in our Galaxy, observing the motions of the Milky Way's companions in the Local Group of galaxies, and probing the behavior of supermassive black holes in other galaxies.

SIM planned to address:

  • Astrometric search for brown dwarfs, massive planets, and terrestrial planets around nearby stars
  • Search for newly-formed planets around young stars
  • Masses and evolution of stars in close binary systems
  • Accurate masses for low-mass binary stars
  • Astrometric signatures of MACHO microlensing events
  • Internal dynamics and ages of globular clusters
  • Mass distribution of the halo of our Galaxy and its spiral structure
  • Dynamics of our Local Group of galaxies including dwarf spheroidal galaxies and tidal tails
  • Proper motions of nearby active galactic nuclei and the question of binary black holes
  • Calibration of several components of the cosmic distance 'ladder'

The SIM project was in Phase B before NASA sponsorship was discontinued. It completed a series of technology milestones and risk reduction engineering tasks which helped make micro-arcsecond astrometric measurements a possibility.

Last updated: June 3, 2015.

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Full Name: 
Space Interferometry Mission