REG NASA-LLIS-0479-1996 Lessons Learned - XTE Instrument Problems.pdf

1、Lessons Learned Entry: 0479Lesson Info:a71 Lesson Number: 0479a71 Lesson Date: 1996-11-06a71 Submitting Organization: GSFCa71 Submitted by: Bill DavisSubject: XTE Instrument Problems Description of Driving Event: The XTE Instrument Development Team experienced monumental problems with the developmen

2、t 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 flow

3、n many times.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 a

4、nd 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 de

5、tectors on the spacecraft during Observatory integration, testing, and launch site activities. The flight detectors were finally installed at the launch site.Lesson(s) Learned: There is no such thing as a low risk heritage detector. Each detector is one-of-a-kind and should be treated as a high risk

6、 item with an appropriate amount of contingency and a good risk mitigation plan. In addition, the XTE detector problem clearly showed the value of flight spare detectors (even if degraded) which can remain on the Observatory to maintain the Mission schedule while other detectors are reworked and qua

7、lified in parallel.Recommendation(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-When developing Mission schedules plan enough schedule and cost contingencies to allow for multiple iterations in the integration of flight detectors with the space

8、craft.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Logisticsa71 Policy & Planninga71 Risk Management/AssessmentAdditional Info: Approval Info: a71 Approval Date: 1996-11-07a71 Approval Name: John W. Remeza71 Approval Organization: 302a71 Approval Phone Number: 301-286-7113Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-