MIT-made satellite — first ever devoted to gamma ray bursts — set for Oct. 7 launch

Contact: Deborah Halber, MIT News Office

Phone: 617-258-9276

Email: dhalber@mit.edu

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CAMBRIDGE, Mass. — On October 7, an MIT-built satellite roughly the size
and shape of a dishwasher will be launched into near-Earth orbit to detect
the largest known explosions in the universe. These occurrences, called
gamma-ray bursts (GRBs), signal the extragalactic release of as much power
as a billion trillion suns, but no one is sure what causes them or exactly
where they originate.

The High-Energy Transient Explorer (HETE-2) — the first satellite
dedicated to the study of GRBs — will help scientists understand these
perplexing explosions. HETE-2 is the result of an international
collaboration of scientists and engineers at the Massachusetts Institute of
Technology and other institutions in the US, France and Japan. HETE-2 will
serve the world’s astronomers as the premiere burst spotter until the end
of its extended mission in 2004.

HETE-2 is the replacement mission for the original HETE satellite, lost
during its launch in 1996 because of a rocket malfunction.

A BEACON TO THE PAST

Gamma-ray bursts are one of the hottest topics in astronomy. Like beacons
from the early universe, these bursts are thought to originate billions of
light years away, at the limit of the Hubble Space Telescope’s vision.
Because the speed of light is finite, looking far away is like looking back
in time.

Gamma-ray bursts may be the product of a hypernova — a giant star
explosion up to 1,000 times more powerful than a supernova — or they may
be caused by an orbiting pair of neutron stars coalescing, or even a
neutron star being sucked into a black hole.

“Gamma ray bursts are colossal explosions. They are the most energetic
events since the Big Bang, yet one occurs about once a day in the sky,”
said George R. Ricker, senior research scientist at the Center for Space
Research at MIT and principal investigator for the 20-person international
team. “The magic of HETE-2 is that it not only detects a large sample of
these bursts, but it also will relay the accurate location of each burst in
real time to ground-based optical and radio observatories.”

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray
Observatory, deorbited by NASA in June, detected nearly 3,000 GRBs over its
10-year lifetime, yet no two were ever seen in exactly the same place in
the sky. Astronomers have been able to pinpoint the exact distances of only
a dozen GRBs, mainly with the help of the Italian BeppoSAX mission.

GRBs can last from 10 milliseconds to more than 15 minutes. They are
followed by afterglows that are visible at X-ray and optical wavelengths
for several days. HETE-2 was designed to facilitate observations of these
afterglows.

The HETE-2 satellite is being prepared for launch from Kwajalein Atoll in
the Republic of the Marshall Islands. It will be deployed to an orbit
around 600 kilometers above the Earth by an expendable Pegasus rocket
launched with the aid of an L-1011 aircraft. The chosen orbit allows the
satellite to race above the equator, circling the Earth 15 times per day
along the exact same path.

DATA IN SECONDS

Within seconds of detecting a burst, HETE-2 will calculate the precise
coordinates of the event and transmit its calculations to the nearest of 12
receiving stations girdling the planet, immediately allowing ground-based
observers to gather detailed observations of the initial phases of GRBs.
The satellite uses a low-rate VHF transmitter to continuously broadcast the
burst information; on the ground, an array of listen-only burst alert
stations (BAS) receive the data and transmit them to the MIT Control
Center. Once received at MIT, burst information is immediately relayed to
the GRB Coordinate Distribution Network (GCN) at Goddard Space Flight
Center in Greenbelt, MD, for wide distribution through the Internet.
Ground-based optical and radio observatories, as well as space telescopes
such as Chandra and Hubble, can then follow up with a closer look.

News of a burst will reach the astronomy community in approximately 10-20
seconds, as opposed to hours or days in the past. “Routinely, HETE-2 will
provide astronomers with a good chance of seeing a burst while it is still
going on,” Ricker said. “Using HETE-2’s localizations, observatories
worldwide will be able to rapidly acquire the burst and study its evolution
at all wavelengths.” In addition, HETE-2 will determine the location and
environment of short bursts, a class of bursts about which little is known.

At MIT, the HETE-2 team includes Ricker, Bob Dill, John Doty, Geoffrey
Crew, Roland K. Vanderspek, Joel Villasenor, Glen Monnelly, Francois
Martel, Alan Levine, Tye Brady, Nat Butler, Dave Breslau, Nat Butler,
Janice Crisafulli, Mike Doucette, Arnaud Dupuy, Rick Foster, Jim Francis,
Gene Galton, Greg Huffman, Steve Kissel, Frank LaRosa, Fred Miller, Grigory
Prigozhin, Jerry Roberts, Michael Vezie and Pete Young; at Japan’s
Institute of Physical and Chemical Research, team members are Masaru
Matsuoka, Nobuyuki Kawai and Atsumasa Yoshida; at the Centre D’Etude
Spatiale des Rayonnements in France, team members are Jean-Luc Atteia,
Michel Boer and Gilbert Vedrenne; at the Consiglio Nazionale Delle
Richerche at the Instituto Tecnologie E Studio Delle Radiazioni
Extraterrestri in Italy, the team member is Graziella Pizzichini; at Los
Alamos National Laboratory, team members are Edward E. Fenimore and Mark
Galassi; at the University of California at Berkeley, team members are
Kevin Hurley and J. Garrett Jernigan; at the University of California at
Santa Cruz, Stanford E. Woolsey; at the University of Chicago, team members
are Don Lamb and Carlo Graziani; and NASA project scientist at Goddard
Space Flight Center is Thomas L. Cline.

In the US, the HETE mission is supported by NASA. For more about HETE-2,
see http://space.mit.edu/HETE/.

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