High Energy Transient Explorer

The High Energy Transient Explorer (abbreviated HETE) is an American astronomical satellite with international participation (mainly Japan and France). The prime objective of HETE is 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 is 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 first HETE was lost during the launch on Nov.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 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).

Among the achievements of the HETE-2 mission are:

1. The discovery of GRB030329, a widely observed, nearby gamma ray burst, firmly connecting GRBs with supernovas.

2. The discovery of GRB050709, which was the first short/hard GRB to be found with an optical counterpart, leading to a firm establishment of the cosmological origin of this subclass of GRBs.

3. Dark bursts, or GRBs previously thought to have no optical counterparts, are not completely optically dark. Some of these dark GRBs fade in the optical very rapidly, others are dimmer but detectable with large (meter class) telescopes.

4. The establishment of another subclass of GRBs, the less energetic X-Ray Flashes (XRF), and its first optical counterpart.

5. The first to send out arcminute positions of GRBs to the observation community within tens of seconds of the onset of GRB (and in a few instances, while the burst was ongoing).