Meteor shower

Starburst galaxies -- vast clouds of molecular gas cradling the sites of newborn stars -- will be the target of a new Jet Propulsion Laboratory satellite selected for flight in 1998 as part of NASA's Small Explorer program.

The new satellite, called the Wide Field Infrared Explorer, will be a cryogenically cooled, small infrared telescope designed to study the evolution of starburst galaxies billions of light-years away, and luminous protogalaxies -- or infant galaxies -- at much greater distances.

"Starburst galaxies are galaxies that appear to be undergoing a burst of star formation," said Dr. Perry Hacking, principal investigator at JPL and co-inventor of the telescope along with Dr. Paul Graf of Ball Aerospace in Boulder, Colo.

"These galaxies represent about 10 percent of the local galaxy population and account for about 30 percent of the local energy budget," he said. "If starburst galaxies have continued to evolve since they first formed, they may represent the main source of stars in the universe today."

Most of the luminosity from young, hot stars is blocked at optical wavelengths by dust and molecular material enveloping their nurseries. But their luminosity escapes and can be detected at infrared wavelengths.

For instance, M82 is a typical starburst galaxy in the constellation Ursa Major, which lies at a distance of about 10 million light-years away. WIRE will be able to detect galaxies like M82 at 5 billion to 10 billion light-years away, revealing their evolutionary past. The infrared explorer will also search for protogalaxies even farther back in time that are undergoing extremely luminous starbursts.

JPL has teamed with Space Dynamics Laboratory of Utah State University in Logan, Utah, to build the infrared telescope. As envisioned, WIRE will be a simple, 30centimeter-diameter (12-inch) telescope with no moving parts and a field of view about the size of Earth's full moon. The instrument will require only 35 watts of power and a low data rate of 9,000 bits per second.

Recent major advances in infrared detector technology will allow the satellite to detect distant galaxies in the 12- to 25-micrometer wavelength range (12 to 25 millionths of a meter). The infrared detectors will be supplied by the Rockwell International Science Center in Anaheim, Calif., and the solid hydrogen cryogenic container will be provided by Lockheed Palo Alto Research Laboratories, Calif.

"The telescope is contained in a lightweight cryostat -- that's essentially a super high-performance thermos bottle -- and the optics are surrounded by a jacket of solid hydrogen," said Dr. Helene Schember, WIRE project manager at JPL. "As it melts, the cryostat cools the optics, ensuring that the telescope feels the heat from distant galaxies."

Using this state-of-the-art technology, WIRE will survey about 100 square degrees of sky during its four-month lifetime and amass a catalog exceeding the size of the existing Infrared Astronomical Satellite (IRAS) Point Source Catalog. The satellite will be able to observe starburst galaxies 500 times fainter at these wavelengths than those observed by the 1983 IRAS mission.

The telescope will be carried on a three-axis spacecraft bus designed and built by the Small Explorer project team at NASA's Goddard Space Flight Center in Greenbelt, Md. and launched in October 1998 by a Pegasus XL launch vehicle.

WIRE will be placed in a nearly polar orbit 400 kilometers (248 miles) above the Earth's surface, following a sun-synchronous path in which the sun will be at the same point in the sky at the same time each day. That orbit will simplify other spacecraft requirements, such as being able to use a relatively small, fixed solar array and a small battery to operate the telescope.

The WIRE science team will be composed of astronomers from Cornell University in Ithaca, N.Y., the California Institute of Technology and JPL in Pasadena, Calif., the Goddard Space Flight Center in Greenbelt, Md. and Ball Aerospace in Boulder, Colorado. Data processing and analysis will be performed at the Infrared Processing and Analysis Laboratory at Caltech.

NASA's Small Explorer Program provides frequent flight opportunities for highly focused and relatively inexpensive science missions. WIRE was one of two missions selected by NASA in September for development as a Small Explorer mission.

Design, development and operations of WIRE through the first 30 days of orbit will cost no more than $50 million.

The mission will be managed jointly by the Jet Propulsion Laboratory in collaboration with the Goddard Space Flight Center in Greenbelt, Md., for NASA's Office of Space Science, Washington, D.C.

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