1 Introduction

The first High Energy Transient Experiment satellite was a multiwavelength mission built to detect and localize gamma-ray bursts (GRBs). It was equipped with NaI gamma-ray detectors (the French Gamma Telescope, or Fregate), two crossed one-dimensional X-ray coded-aperture detectors (the Wide-Field X-ray Monitor, or WXM; see [Yoshida et al. 1999]) and four near-UV-sensitive CCD cameras, which doubled as the spacecraft's star trackers. HETE was designed to detect and localize GRBs in real time and to send the coordinates of detected bursts to ground observers within seconds of burst onset for prompt followup observations. The first HETE satellite was launched in November 1996, but was not deployed in orbit due to a failure in the third stage of the Pegasus launcher.

The observations of GRBs by BeppoSAX in the months following the loss of HETE demonstrated the existence of X-ray afterglows in a large fraction of GRBs and also led to the discovery of faint ($m\sim 20-22$) optical afterglows. Analyses of GRBs detected by Ginga ([Strohmayer et al. 1998]) discussed that year show that many GRBs emit a significant fraction of their total energy in photons with E<10 keV. Thus, for the reflight of HETE ([Ricker 1999]), we have replaced two of the UV camera systems with two one-dimensional CCD-based coded aperture systems sensitive to soft X-rays (0.5-12 keV): these are the Soft X-ray Cameras, or SXCs. (The other two UV cameras have been converted to standard CCD cameras sensitive to optical photons). In this paper, we review the details of the SXC instrumentation, flight operation, and sensitivity.