|Mission type||High-energy astronomy|
|Launch mass||128 kilograms (282 lb)|
|End of mission|
|Destroyed||November 4, 1996|
|Decay date||April 7, 2002|
|Perigee altitude||487 kilometres (303 mi)|
|Apogee altitude||555 kilometres (345 mi)|
|Epoch||November 4, 1996|
|Mission duration||October 2000 - March 2008|
|Manufacturer||Massachusetts Institute of Technology|
|Launch mass||124 kilograms (273 lb)|
|Power||4 deployable fixed solar arrays|
|Start of mission|
|Launch date||October 9, 2000, 05:38:00UTC|
|End of mission|
|Semi-major axis||6,932 kilometers (4,307 mi)|
|Perigee altitude||534 kilometers (332 mi)|
|Apogee altitude||559 kilometers (347 mi)|
|Argument of perigee||13.7551 degrees|
|Mean anomaly||346.2996 degrees|
|Epoch||May 9, 2016 at 15:49:27 UTC|
The High Energy Transient Explorer (abbreviated HETE; also known as Explorer 79) was an American astronomical satellite with international participation (mainly Japan and France). The prime objective of HETE was to carry out the first multiwavelength study of gamma-ray bursts with UV, X-ray, and gamma-ray instruments mounted on a single, compact spacecraft. A unique feature of the HETE mission was its capability to localize GRBs with ~10 arc second accuracy in near real time aboard the spacecraft, and to transmit these positions directly to a network of receivers at existing ground-based observatories enabling rapid, sensitive follow-up studies in the radio, IR, and optical bands. The satellite bus for the first HETE-1 was designed and built by AeroAstro, Inc. of Herndon, VA; the replacement satellite, HETE-2, was built by MIT based on the original HETE design.
The first HETE was lost during the launch on November 4, 1996. The Pegasus rocket achieved a good orbit, but explosive bolts releasing HETE from another satellite (Argentina's SAC-B) and from its DPAF (Dual Payload Attach Fitting) envelope failed to charge, dooming both satellites. A battery on the third stage of the rocket and responsible for these bolts cracked during the ascent.
A second HETE satellite, HETE-2, was launched on October 9, 2000 in a follow-up mission. It was similar to the first HETE, but replaced the UV camera with an additional X-ray camera (Soft X-ray Camera or SXC) capable of higher localization accuracy than the original X-ray instrument (Wide-Field X-ray Monitor or WXM).
HETE-2 was placed in a 625 km altitude Earth orbit with an inclination of 0-2 degrees.
Among the achievements of the HETE-2 mission are:
The HETE website lists 6 GRBs in 2001, 19 in 2002, 25 in 2003, 19 in 2004, 12 in 2005, and 3 in 2006 - the last reported being in March 2006.
The trigger summaries list 2 GRBs in May 2006 and an XRB in Jan 2007.
As of March 2007, "the operational efficiency of the HETE spacecraft and instruments has decreased due to the advanced age of the NiCd batteries on board."
The mission ended in March 2008.
HETE under test
HETE-2 attached to its Pegasus launcher
Implementation of the launcher fairing