2. ELECTROMAGNETIC OBSERVATIONS
2.1 HIGH ENERGY TRANSIENT EXPLORER (HETE-II)
Highlights from the High Energy Transient Experiment (HETE-II) mission have been summarized in (Lamb et al 2004). HETE-II carries three instruments onboard (HETE 2005):
French Gamma Telescope (FREGATE): 60-400 keV
Wide-Field X-ray Monitor (WXM): 2-25 keV, accurate to ≤ 10 degrees
Soft X-ray Camera (SXC): 0.5-10 keV, accurate to ≤ 30'
FREGATE Instrument specifications (Atteia et al. 2002) are given in table 2.1.1 below. The HETE-II satellite is shown in figure 2.1.1 below while the effective area of FREGATE, as a function of off-axis angle, is illustrated in figure 2.1.2.
TABLE 2.1.1: FREGATE Instrument Specifications.
aTaken from Atteia 2002
FIGURE 2.1.1: The High Energy Transient Explorer (HETE-II) shown during a mass properties test at Goddard Space Flight Center (HETE 2005b). In order to simulate the flight state, the solar panels are deployed and the spacecraft is rotated about the z-axis. The moments of inertia about the three spacecraft axes are determined via its reaction to small torques.
FIGURE 2.1.2: Effective area of the FREGATE onboard HETE-II (Atteia et al. 2002). Solid and dotted lines indicate angular responses at 50 and 300 keV, respectively. The dashed-dotted line indicates an estimated distribution of GRBs as a function of off-axis detector angle.
