Space Interferometry Mission (SIM)


The SIM Lite Astrometric Observatory (formerly known as the Space Interferometry Mission) will be the first spacecraft whose primary mission is to perform precision astrometry by long-baseline interferometry. Above the distortion of Earth's atmosphere, SIM Lite will enable astronomers to measure the positions and motions of stars with microarcsecond precision for the first time -- enabling the detection of the reflex motion (or "wobble") of stars induced by orbiting planets a few times the mass of Earth. SIM Lite will conduct a detailed survey for planetary companions to stars in the solar neighborhood, and will give us a more complete picture of the architecture of planetary systems around a representative sample of different stellar types.


Astrometric displacement of the Sun due to
Jupiter as seen from 10 parsecs.

SIM Lite will further use astrometry to determine the distances and motions of stars throughout the Milky Way hundreds of times more accurately than any previous program, and create a stellar reference grid, providing a visible light astronomical reference frame with unprecedented precision. Against this reference frame SIM Lite will measure the internal dynamics of our galaxy and the dynamics in our local group of galaxies, measure the photometric and astrometric effects of condensed dark matter in our galactic halo, and calibrate the brightness of several classes of astronomical "standard candles."

SIM Lite is designed to operate for minimum five year baseline mission. The NExScI is responsible for developing and operating the Science Operations System (SOS) for SIM Lite - including program solicitation, user interface and consultation, data infrastructure, and (jointly with JPL) science operations for SIM Lite.

In August 2008, NExScI selected 19 SIM Science Study Teams in response to a call for proposals. These teams are conducting concept studies that will lead to the most scientifically productive observations using SIM Lite. The final reports from these science teams are summarized here.

For more information on NExScI SIM Lite support and planning tools, click here.

For more information on the SIM Lite Observatory, click here.