The Neil Gehrels Swift Observatory

NASA Selects Mission to Search For Planetary Systems and Observe Cosmic Explosions

Donald Savage
Headquarters, Washington, DC
Oct. 14, 1999
(Phone: 202/358-1547)

RELEASE: 99-120

Spacecraft that will search for planetary systems around 40 million stars and observe the largest explosions in the universe have been chosen as the next two missions in NASA's medium-class Explorer (MIDEX) program.

"In my 21 years at NASA, this is the most difficult selection that I have had to make," said Dr. Edward Weiler, Associate Administrator for Space Science, NASA Headquarters. "The number of first-class concepts being submitted to NASA by the space science community for these smaller missions just keeps on climbing."

The first mission, to be launched in 2003, is the Swift Gamma Ray Burst Explorer, a three-telescope space observatory for studying gamma ray bursts. Although gamma ray bursts are the largest known explosions in the universe, outshining the rest of the universe when they explode unpredictably in distant galaxies, the underlying cause of the explosion is a true mystery of astrophysics. Swift will have the unique ability to rotate in orbit and point its gamma ray telescope, X-ray telescope, and ultraviolet/optical telescope at gamma ray bursts within minutes of the burst's first appearance. Since gamma ray bursts are believed to originate billions of light years away, Swift will use these sources as beacons to probe distant regions of the universe.

During its three-year mission, Swift will also survey the sky for new black holes and other sources of cosmic gamma rays. Swift will be led by Dr. Neil Gehrels of NASA's Goddard Space Flight Center, Greenbelt, MD, at a total mission cost to NASA of $163 million.

The second mission, to be launched in 2004, is the Full-sky Astrometric Mapping Explorer (FAME), a space telescope designed to obtain highly precise position and brightness measurements of 40 million stars. This rich database will allow astronomers to accurately determine the distance to all of the stars on this side of the Milky Way galaxy, detect large planets and planetary systems around stars within 1,000 light years of the Sun, and measure the amount of dark matter in the galaxy from its influence on stellar motions.

This 30-fold improvement in accuracy over previous position-measuring spacecraft will establish a new standard for measuring distances in astronomy and help resolve questions about the size and age of the universe. FAME's five-year mission will be led by Dr. Kenneth J. Johnston of the U.S. Naval Observatory, Washington, DC, at a total mission cost to NASA of $162 million.

"MIDEX missions not only return first-class science results, they continue NASA's trend toward greatly lowered mission costs via innovative mission planning and operations," Weiler added. "For example, FAME utilizes a solar sail instead of thrusters to provide the propulsive force needed to re-orient itself to scan the entire sky, and Swift uses its own on-board artificial intelligence software to point itself at new targets faster than human controllers ever could."

The selection of these missions is the second step of a two-step process. In the first step, NASA selected five proposals in January 1999 for detailed four-month feasibility studies. Funded by NASA at $350,000 each, these studies focused on cost, management, and technical plans, including small business involvement and educational outreach.

The first two MIDEX missions, selected in 1996, are the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) and the Microwave Anisotropy Probe (MAP). IMAGE will be launched in the winter of 2000 to study the global response of the Earth's magnetosphere to changes in the solar wind. MAP will be launched in November 2000 to probe conditions in the early universe by measuring the properties of the cosmic microwave background radiation over the full sky.

The selected proposals were among 31 full proposals originally submitted to NASA in August 1998 in response to an Explorer Program Announcement of Opportunity issued in March 1998. The Explorer Program is designed to provide frequent, low-cost access to space for physics and astronomy missions with small to mid-sized spacecraft. The Explorer Program is managed by NASA's Goddard Space Flight Center, Greenbelt, MD, for the Office of Space Science, Washington, DC.

Information and artist's concepts of these missions are available at: and