1. The Broad Band X-Ray Telescope

**Figure 1:** BBXRT in the Space Shuttle's cargo bay (citeKimsPhD).
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BBXRT consisted of two identical, coaligned telescopes (labeled A and B) with cooled Si(Li) detectors. The telescope mirrors were conical approximations to the Wolter Type I geometry (VanSpeybroeck and Chase (1972)). This allowed lightweight X-ray-reflecting foils to be used which could be nested as shown in Figure 1 to maximize the effective area at the expense of position resolution. Each BBXRT telescope had 118 coaxially nested mirrors.

**Figure 2:** Nested X-ray mirrors.
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The calibration of the instruments is discussed in detail by Weaver et al. (1995). Each segmented detector consisted of a central pixel (denoted A0 or B0), with a field of view 4 arcmin in diameter, surrounded by four outer pixels giving the detector a total field of view 17 arcmin in diameter. The point spread function was such that about 62% of the events from a point source fell on the central pixel for an on-axis pointing. The energy resolution was about 150 eV FWHM at 6 keV in the central pixels.

**Figure 3:** Layout of the BBXRT segmented detectors (Serlemitsos et al. (1984)).
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Photon arrival times were recorded with a resolution of 63 $\mu$ s. There were five photon quality flags recorded with each event. These used anticoincidence techniques to reject spurious events which were probably not due to X-ray photons. Events which were detected simultaneously with events in the same or other pixels were labeled with the pulse-pulse and pixel-pixel flags respectively. Events which had a deposited charge greater than about 14 keV were flagged as very large events (VLE). Firings of the opto-feedback circuits caused events to be labeled with the LED flag. The final anticoincidence flag was against triggering of the charged particle guard detector.