NASA-LLIS-0479

Abstract

<strong>Description of Driving Event:</strong> <br>The XTE Instrument Development Team experienced monumental problems with the development of the three small proportional counter detectors used in the All Sky Monitor Instrument. This was completely unexpected since the proportional counters were presented by the Instrument Development Team as low-risk heritage detectors that were nearly identical to detectors that had previously flown many times. <br>As it turned out, the heritage vendor was unsuccessful in fabricating a working detector. After an exhaustive search by the Instrument Development Team, a second vendor was located in Finland. It took the new vender over a year to fabricate, test, and deliver the required three flight and one spare detector. Unfortunately, all of the detectors degraded after delivery and they needed multiple rework cycles of several months each to get acceptable flight detectors. The XTE Program Management Team was able to maintain the Mission schedule by installing degraded flight and/or spare detectors on the spacecraft during Observatory integration, testing, and launch site activities. The flight detectors were finally installed at the launch site.