High Energy Transient Explorer 2
Description
The High Energy Transient Explorer 2 (HETE-2) was designed to detect cosmic gamma-ray bursts (GRBs) and help determine their origin and nature. The satellite had three instruments: 1) a set of wide-field gamma-ray (6 - 400 keV) spectrometers (FREGATE); 2) a wide-field X-ray (2 - 25 keV) monitor (WXM), and 3) a set of soft X-ray (0.5 - 10 keV) cameras (SXC). These instruments covered a solid angle of 1.5-2 steradians and were used to make simultaneous, broad-band observations in the various listed energy ranges. The goal of the mission was to continuously scan the sky and identify occurrences of GRBs, establish precise locations and transmit coordinates in near real time (< 10 seconds). The instruments were also to be used to establish relative GRB rates and intensities in the soft X-ray, mid X-ray, and gamma-ray bands, perform spectroscopy of gamma-ray bursts in the energy range 1-400 keV, measure the intensities, time histories, and spectra of soft gamma-ray repeater bursts, X-ray bursts, and black hole X-ray transients. The spacecraft was basically a rectangular cube, roughly one meter by half a meter by half a meter, with four solar panel petals protruding from the bottom. The bottom section of the spacecraft held the power, communications, and attitude control and the upper section the science instruments. Power was supplied by the solar panels, which were made of honeycomb aluminum with a silicon substrate, each supplying 42 W. There were 6 battery packs, each containing 24 1.5 V NiCd cells, each with 1.2 A-hr capacity. Communication was via S-band uplink (2.092 GHz) and downlink (2.272 GHz) using 5 dual-patch antennas. A VHF downlink (137.9622 MHz) was to be used for the real-time burst alerts via a whip antenna mounted on one of the solar panels. Attitude control was achieved by a momentum wheel and three orthogonal magnetic torque coils, controlled by inputs from two magnetometers, twelve sun sensors, and an optical camera. HETE-2 was placed in a 592 km x 640 km elliptical Earth orbit. The spacecraft pointed in the anti-solar direction and all bursts were detected at least 120 degrees from the Sun. The field of view was centered roughly on the ecliptic. Over the course of a year approximately 60% of the sky was surveyed. When GRB's were detected, summary burst data were sent immediately to listen-only equatorial ground stations and were forwarded to observers via the GRB coordinates network within less than 10 seconds of burst detection. The planned operating life was 18 months but the mission lasted more than 6 years. (NASA - National Space Science Data Center) |
Facts
Spectrum Studied: Gamma Rays, X-rays Launch Date: 2000-10-09 Termination Date: 2007-06-30 Orbital Location: (590 to 650 km) Launch Vehicle: Pegasus Launch Site: Kwajalein, Republic of the Marshall Islands Mass: 124.0 kg Nominal Power: 168.0 W Funding Agency NASA |