Dolores Beasley
Headquarters, Washington, DC               October 2, 2000 
(Phone: 202/358-1753)

Nancy Neal
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-0039)

RELEASE: 00-160

HETE-2 FLIES IN SEARCH OF GAMMA-RAY BURSTS

     Locating the ever-mystifying phenomena called gamma-ray 
bursts and other short-lived and remarkable cosmic occurrences 
will soon be the job of the High-Energy Transient Explorer 2 
(HETE-2), poised for launch Oct 7.

For a brief, bright moment, gamma-ray bursts outshine the rest of 
the universe, but scientists do not know what causes them. One 
theory is that gamma-ray bursts come from the merger of two black 
holes. Another theory suggests these bursts are from a huge star 
explosion, called a hypernova, which is 1000 times more powerful 
than the already potent supernova. Snapping a photograph of a 
burst while it is exploding is a key goal for astronomers.

"HETE-2 may well revolutionize the field of high-energy astronomy 
by alerting optical and radio observatories when gamma-ray bursts 
are in progress, and precisely where observers should look," said 
Dr. George R. Ricker of the Massachusetts Institute of Technology 
(MIT) in Cambridge, MA, principal investigator of the HETE-2 
mission.

HETE-2 is scheduled for launch at 1:45 a.m. EDT from Kwajalein 
Missile Range, Marshall Islands, aboard a Hybrid Pegasus 
expendable launch vehicle.

HETE-2 will detect hundreds of bursts a year during its four-year 
lifetime. The spacecraft also will provide very detailed 
information about the location and spectra, or light 
characteristics, of many of these bursts. A key feature of HETE-2 
is its superior rapid response. Within seconds, HETE-2 can catch a 
burst and notify observatories both in space and on the ground of 
its approximate location. In less than a minute, HETE-2 will 
obtain a precise location. Previous satellites have taken many 
hours or even days to notify observatories of an accurate burst 
location.

HETE-2 will be placed in a 370-mile-by-400-mile (592-km x 640-km) 
elliptical orbit by a three-stage rocket. The Hybrid Pegasus 
launch vehicle will be carried by an L-1011 aircraft to a point 
approximately 40,000 feet above the Western Pacific, near 
Kwajalein Atoll. From this point, the vehicle will be released and 
free-fall in a horizontal configuration for five seconds before 
the first-stage rocket motor ignites. It will take a little more 
than 10 minutes for HETE-2 to reach its final orbit. 

HETE-2 replaces the original HETE spacecraft that was lost due to 
a rocket malfunction in November 1996. The spacecraft was built by 
MIT and the technology is essentially the same as the previous 
HETE, except for a new detector built by MIT. MIT is responsible 
for development and integration, as well as mission and science 
operations, for the satellite. NASA's Goddard Space Flight Center 
in Greenbelt, MD, has project oversight. The Kennedy Space Center, 
FL, is responsible for all launch operations.

The HETE-2 is a collaboration between NASA; MIT; Los Alamos 
National Laboratory, New Mexico; France's Centre National d'Etudes 
Spatiales (CNES), Centre d'Etude Spatiale des Rayonnements (CESR), 
and Ecole Nationale Superieure de l'Aeronautique et de l'Espace 
(Sup'Aero); and Japan's Institute of Physical and Chemical 
Research (RIKEN). The science team includes members from the 
University of California (Berkley and Santa Cruz) and the 
University of Chicago. 

The spacecraft carries three main instruments and a computer 
network that transmits data to other observatories. The French 
Gamma Telescope (FREGATE), built by CESR, will detect gamma-ray 
bursts and very bright (higher energy) X-ray transients. The Wide-
Field X-ray Monitor (WXM), built by RIKEN and Los Alamos National 
Laboratory, detects light slightly lower in energy than the 
FREGATE does. The WXM therefore will detect fewer gamma-ray bursts 
than FREGATE, but because of its superior resolution, will be able 
to locate the FREGATE-detected bursts to within 10 arc minutes (an 
area of sky about equal to 1/10 the size of the full Moon). The 
Soft X-ray Camera (SXC), built by MIT, replaces the ultraviolet 
cameras on the original HETE. The SXC covers the lowest-energy 
band of the three instruments. It also provides the best angular 
resolution, resulting in a location accuracy of about 10 arc 
seconds, more than an order of magnitude finer that any previous 
gamma-ray burst instrument.

The HETE-2 satellite will continuously broadcast the burst 
information. On the ground, an array of listen-only "burst-alert" 
stations receives the data and transmits it to the MIT Control 
Center. From there, burst information will immediately be relayed 
to the Gamma Ray Burst Coordinate Distribution Network at Goddard 
for distribution to interested ground observers. 

More information on the HETE-2 mission can be found at: 
http://space.mit.edu/HETE

                            - end -