1、Lessons Learned Entry: 1336Lesson Info:a71 Lesson Number: 1336a71 Lesson Date: 2003-05-05a71 Submitting Organization: JPLa71 Submitted by: Bob Axsom/David OberhettingerSubject: Verify Flight & GSE Cables Against Unit & System Schematics Prior to Test (1998) Description of Driving Event: During integ
2、ration of the Genesis spacecraft, many flight and ground support equipment (GSE) cables were found to be electrically incompatible with spacecraft systems although they matched the cable wiring diagrams. Several times, testing had to be halted and the system analyzed for possible electrical overstre
3、ss caused by power having been applied to the wrong pins. Eventually, spacecraft testing was stopped long enough to perform a pin-by-pin comparison of the cable wiring diagrams to the latest unit and system schematics. Once this was completed, errors were identified, the cables were reworked, and th
4、e problems were resolved. The accuracy of cable wiring diagrams was a continuing problem on Genesis. Typically, cables are built by cable harness shops to the specifications provided by cable drawings and cable wiring diagrams. Cable design and fabrication may take place concurrently with the design
5、 of spacecraft black boxes. As a system design evolves and pin-out requirements change, there is a time lag before the interface control drawing (ICD) is updated and the changes flow back to the cable design and documentation. Should the cables be built to an outdated document, the first powering of
6、 a given spacecraft may cause major damage. Since the connectors still mate with their assigned receptacles, the electrical mismatches may not be apparent. Validating the cable harness configuration against unit and system schematics is a very time-consuming activity. If it is delayed until integrat
7、ion and test has already commenced, the task can impact the project schedule. References:1. JPL Lesson Learned No. 1201, “Flight Hardware Damage Due to Inadequate Planning and Insufficient QA Involvement,” April 25, 2002.2. JPL Lesson Learned No. 0573, “Power Bus/GSE Sneak Paths May Energize Spacecr
8、aft in the Ground Test Environment,” October 22, 1997.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Lesson(s) Learned: 1. As the system design evolves, emerging interface incompatibilities between the cabling and the spacecraft may not be captured
9、in the cable design documentation that drives cable fabrication.2. Updating of cable wiring diagrams and drawings tends to lag the updating of circuit schematics, although maintaining accurate ICD and cable documentation is just as important.Recommendation(s): 1. Perform regular updates of cable wir
10、ing diagrams to reflect changes in the electrical configuration of units, the spacecraft bus, and GSE.2. Check unit and system cable wiring diagrams for interface incompatibilities with the current spacecraft configuration immediately prior to the first combined use of flight and GSE cables. If the
11、as-built cables cannot be clearly traced back to the current spacecraft and GSE interface requirements, it may also be necessary to perform continuity checks on the cables.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phras
12、e(s): a71 Configuration Managementa71 Flight Equipmenta71 Ground Equipmenta71 Hardwarea71 Payloadsa71 Spacecrafta71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2003-05-14a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
