A NASA spacecraft scheduled for launch in 2011 to measure the positions and distances of stars throughout the Galaxy, and to observe nearby stars for Earth-sized planets. SIM (formerly known as the Space Interferometry Mission) will be able to determine these measurements several hundred times more accurately than previous missions by using optical interferometry that combines light from two or more telescopes as if they were one gigantic telescope mirror. It will also pioneer a technique of blocking out light from a bright star in order to take images of areas near it. The spacecraft will reach a distance from Earth of about 95 million km after 5.5 years, and its interferometer will take observations of the complete celestial sphere during that time.
Subjects: Astronomy and Astrophysics.