High Energy Transient Explorer 1 (HETE-1) was a

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astronomical satellite with international participation (mainly

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and

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History

The concept of a satellite capable of multi-wavelength observations of gamma-ray bursts (GRB) was discussed at the

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meeting on GRBs in 1981. In 1986, the first realistic implementation of the HETE concept by a

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

MIT-led International Team was proposed. This concept, which was adopted, emphasized accurate locations and multi-wavelength coverage as the primary scientific goals for a sharply-focused small satellite mission which would ultimately solve the gamma-ray burst mystery. In 1989, NASA approved funding for a low-cost "University Class" explorer satellite to search for GRBs. In 1992, the HETE-1 program was funded, and the design and construction of HETE-1 began. The original spacecraft contractor for HETE-1 was AeroAstro, Inc., of

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. AeroAstro was responsible for the spacecraft bus, including power, communications, attitude control, and computers. The instrument complement for HETE-1 consisted of four wide-field gamma-ray detectors, supplied by the CESR of

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. A wide-field coded-aperture X-ray imager, supplied by a collaboration of

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(LANL) and the Institute of Chemistry and Physics ( RIKEN) of

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. Four wide-field near-UV CCD cameras, supplied by the Center for Space Research at the Massachusetts Institute of Techology. Due to the tragic fate of HETE-1 and the continuing timeliness of GRB science, NASA agreed to a reflight of the HETE-1 satellite, using flight spare hardware from the first satellite. In July 1997, funding for a second HETE satellite was granted, with a target launch date early 2000.

Mission

The prime objective of HETE-1 was to carry out the first multi-wavelength study of GRBs with

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

(UV),

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

, and gamma-ray instruments mounted on a single, compact spacecraft. A unique feature of the HETE-1 mission was its capability to localize GRBs with ~10

arcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

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 Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

(IR), and

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

bands.

Spacecraft

The satellite bus for the HETE-1 satellite was designed and built by AeroAstro, Inc. (USA) of

. The HETE-1 spacecraft was Sun-pointing with four

solar panels A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a phot ...

connected to the bottom of the spacecraft bus. Spacecraft attitude was to be controlled by magnetic torque coils and a momentum wheel.

Experiments

Omnidirectional Gamma-Ray Spectrometer

The Omnidirectional Gamma-Ray Spectrometer was designed to operate from 6

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to greater than 1 MeV. The instrument consisted of four wide-field gamma-ray detectors with a total effective area of . The HETE satellite remained within the launch vehicle due to battery failure. The experiment was unable to operate.

Ultraviolet Transient Camera Array

The Ultraviolet Transient Camera Array was designed to provide accurate directional information on transient events, and to assist with spacecraft attitude determination. The instrument consisted of four ultraviolet Charge-coupled device (CCD) cameras operating in the 5 to 7 eV range.

Wide Field X-ray Monitor

The Widefield X-ray Monitor was designed to perform X-ray studies of gamma-ray bursts. The instrument consisted of coded aperture cameras, sensitive in the 2-25 keV energy range, and with location accuracy to ~ 10 arcminutes or better.

Launch

The HETE-1 satellite was launched with the

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satellite SAC-B. HETE-1 was lost during the launch on 4 November 1996, at 17:08:56 UTC, from

Wallops Flight Facility Wallops Flight Facility (WFF) is a rocket launch site on Wallops Island on the Eastern Shore of Virginia, United States, just east of the Delmarva Peninsula and approximately north-northeast of Norfolk. The facility is operated by the Goddard ...

(WFF), launch area-3. The

Pegasus XL Pegasus is an air-launched launch vehicle developed by Orbital Sciences Corporation (OSC) and now built and launched by Northrop Grumman. Capable of carrying small payloads of up to into low Earth orbit, Pegasus first flew in 1990 and remai ...

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...

achieved a good orbit, but

explosive bolts A pyrotechnic fastener (also called an explosive bolt, or pyro, within context) is a fastener, usually a nut or bolt, that incorporates a Explosive material, pyrotechnic charge that can be initiated remotely. One or more explosive charges embedde ...

releasing HETE-1 from another satellite, SAC-B, and from its Dual Payload Attach Fitting (DPAF) envelope failed to charge, dooming both satellites. A battery on the third stage of the launch vehicle and responsible for these bolts cracked during the ascent. Due to its inability to deploy the solar panels, HETE lost power several days after launch.

Atmospheric entry

HETE-1 re-entered on 7 April 2002.

References

{{Orbital launches in 1996 Gamma-ray telescopes X-ray telescopes Space telescopes Satellites orbiting Earth Spacecraft launched in 1996 Spacecraft launched in 2000 Spacecraft launched by Pegasus rockets Explorers Program