SIM PlanetQuest

A revolutionary spacecraft housing a high-precision optical interferometer will give astronomers the ability to precisely map the location and motion of stellar objects, and search for signs of earth-sized planets around stars close to the sun.

NASA’s SIM PlanetQuest will record star positions several hundred times more accurately than currently possible. With this highly detailed view of the heavens, astronomers will be able to answer questions about the size and age of the universe, measure distances to other galaxies and determine the masses of planets in nearby solar systems.

Interferometry is a technique that measures directions by determining the angle between two rays of light collected from a single source. A basic interferometer consists of two telescopes separated by a common baseline. Interferometers can also be used to produce images with finer resolution than is currently possible with a single telescope. The long baseline optical interferometer aboard SIM PlanetQuest will demonstrate this technology in space for the first time.

The SIM PlanetQuest spacecraft will fly up to four interferometers with two telescopes each, mounted on a Precision Structure Subsystem (PSS). The maximum separation between telescope pairs, which determines the basic resolution of the interferometer, is planned to be 10 meters. With interferometers of this size, SIM PlanetQuest will be able to detect the motion of stars in our galaxy over less than a day’s observing time. Rotating the spacecraft while looking at a single target allows its interferometers to act as a single 10-meter telescope, much larger than the 2.4-meter instrument aboard the Hubble Space Telescope.

The precision demanded by SIM PlanetQuest's mission requires that the difference in the two incoming light beams be determined to an accuracy of less than 1/100th of the wavelength of light. To work, the PSS must be stabilized against minute vibrations of the spacecraft and very small changes in temperature.

Northrop Grumman Space Technology is designing and developing the SIM PlanetQuest spacecraft and PSS in partnership with NASA’s Jet Propulsion Laboratory (JPL). Northrop Grumman’s special expertise in thermal control, vibration isolation, damping, and high precision structures is matched with JPL’s expertise in interferometry. The satellite is scheduled to fly in 2009.

SIM PlanetQuest is also a scientific and technological pathfinder for future missions, including NASA’s Terrestrial Planet Finder (TPF), which will search for earth-like planets in our galactic neighborhood. Both SIM PlanetQuest and TPF are part of NASA’s Origins program, a multi-mission endeavor that will examine stars, galaxies and planets, seeking answers to the fundamental questions of how the universe – and life – began.

Quick Facts

Launch Date:	2011
Launch Vehicle:	Expandable Launch Vehicle (Atlas 551 or Delta IV Heavy)
Interferometry baseline:	10 m
Orbit:	Heliocentric, earth-trailing
Mission Life:	Five years