1、Lessons Learned Entry: 1840Lesson Info:a71 Lesson Number: 1840a71 Lesson Date: 2006-07-30a71 Submitting Organization: LARCa71 Submitted by: Sudha Natarajana71 POC Name: William Lucka71 POC Email: william.s.lucknasa.gova71 POC Phone: 757-864-1857Subject: CALIPSO Avalanche Photodiode (APD) Detector As
2、sembly Electrical Failure Abstract: The APD detector assembly failed during the Satellite Thermal/Vacuum test due to design-drawing error. The design-drawing error indicated reversed installation of a polarized capacitor. The assembly quality assurance (QA) did not detect the error because the assem
3、bly matched the drawing. Make certain that QA is involved at every stage including drawing reviews to aid in systems successfully built, tested, integrated and flown at minimum cost.Description of Driving Event: The APD detector assembly failed during the Satellite Thermal/Vac test. A tantalum polar
4、ized capacitor was installed, improperly, such that it was reverse biased. Cost/schedule impact of more than four months, and increased risk due to the required extensive disassembly and rework: (1) Recovery involved: de-integration of the Payload and Platform for removal of the detector assembly, e
5、xtensive repair rework (the detector assembly was encapsulated in potting compound), full qualification testing of the repaired assembly, reinstallation and optical alignment of the detector, and re-integration of the Payload and Platform. (2) To minimize the cost and schedule impact of the recovery
6、, the risk was accepted of reintegrating the Payload and Platform without repeating all qualification testing (the re-integration was verified through inspection, acoustic test, and functional test). This risk acceptance paid off. Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or ne
7、tworking permitted without license from IHS-,-,-(1) Polarized capacitors will work but will have a drastically reduced lifetime if ever improperly reverse biased. The use of polarized capacitors, especially tantalum capacitors, should have solid justification due to this risk of delayed shorting fai
8、lures. (2) Maintain a list of all polarized components used in a system to make tracking and QA easier. Extra QA precautions should be taken at every stage, including drawing reviews.Recommendation(s): Maintain a list of all polarized components used in a system to make tracking and QA easier. Extra
9、 QA precautions should be taken at every stage, including drawing reviews.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Space OperationsAdditional Key Phrase(s): a71 Systems Engineering and Analysis.a71 Safety and Mission Assurance.Additional Info: a71 Project: CALIPSOApproval Info: a71 Approval Date: 2008-05-29a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
