The HETE-II satellite

The High Energy Transient Explorer (HETE-II) satellite has been launched on October 9, 2000. This mission is devoted to the detection and localization of GRBs. Differently from BeppoSAX, HETE-II takes advantage of a full coverage by ground-based observers: when the GRB is automatically located on board, the calculated coordinates are immediately transmitted to ground, without waiting, like in the case of BeppoSAX, a new passage over the same point on ground.

Figure: Schematic view of HETE-II.

All instruments point in the anti-solar direction and share a common field of view of $\sim 1.5$ steradians; they consist of two X-ray detectors and a gamma-ray instrument (fig. ). The Soft X-ray Camera (SXC, 0.5-14 keV) consists of two CCD-based one-dimensional coded-aperture X-ray imagers, one along spacecraft X-direction, the other parallel to Y-direction, and with a 7.4 cm$^2$ effective area. The SXC has a $0.9$ sr field of view and a spatial resolution less than $30\mbox{$^{\prime\prime}$}$; the spectral resolution is 46 eV at 525 eV and 129 eV at 5.9 keV. The Wide Field X-ray Monitor (WXM, 2-25 keV) consists of two coded-mask one-dimensional position sensitive X-ray detectors oriented perpendicularly to each other for measuring X and Y positions independently, with a 275 cm$^2$ effective area. The WXM has a $\sim 3$ sr field of view and a spatial resolution less than $10\mbox{$^\prime$}$, with a spectral resolution of $\sim 22$% at 8 keV. Finally, the French Gamma-ray Telescope (FREGATE, 6-400 keV), consists of four NaI(Tl) gamma-ray detectors, with an effective area of 120 cm$^2$; the spectral resolution is $\sim 25$% at 20 keV, and $\sim9$% at 662 keV.