1、Lessons Learned Entry: 0209Lesson Info:a71 Lesson Number: 0209a71 Lesson Date: 1992-11-13a71 Submitting Organization: KSCa71 Submitted by: Lisa L. MusgraveSubject: Time Correlation Between Multiple Telemetry Systems Description of Driving Event: The Space Shuttle Main Engine (SSME) telemetry system
2、does not show absolute Greenwich Mean Time (GMT), but rather, the number of controller cycles since change in mode. Approximate timing had been established (during the STS 51-L launch process) by aligning the first guidance cycle after engine start with the engine start command time determined by an
3、alysis of the General Purpose Computer (GPC) event times. This aligned the SSME event times to the GPC event times to within a few tens of milliseconds, sufficient for normal flight analysis but insufficient for determining event sequencing for a system failure, which involves an interaction between
4、 the SSME and the rest of the vehicle. Without precise correlation between multiple data systems, there may be a delay in subsequent anomaly investigations due to timing uncertainties or a need to correct data timing.Lesson(s) Learned: The SSME telemetry system provides only approximate time correla
5、tion between multiple data systems, resulting in timing uncertainties.Recommendation(s): Install a master timing unit to provide precise time correlation between multiple data systems to determine event sequencing in a system failure.Evidence of Recurrence Control Effectiveness: N/ADocuments Related
6、 to Lesson: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Flight Operationsa71 Flight Equipmenta71 Launch VehicleAdditional Info: Approval Info: a71 Approval Date: 1994-06-08a71 Approval Name: James G. Klinea71 Approval Organization: KSC/HEIa71 Approval Phone Number: 407-867-7614Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
