1、Lessons Learned Entry: 0281Lesson Info:a71 Lesson Number: 0281a71 Lesson Date: 1993-07-12a71 Submitting Organization: JPLa71 Submitted by: R. F. CollinsSubject: Galileo Attitude Control Power on Reset Problem Abstract: A potentially catastrophic Power On Reset (POR) was discovered during testing of
2、the Galileo orbiter. The problem was traced to noise from a capacitive coupling path between flight subsystem ground and support equipment ground. AC ground paths should be testable and should be verified in system interface verification tests. Interface circuits should be analyzed to identify any A
3、C coupling paths between independent ground trees.Description of Driving Event: During testing of the Galileo orbiter, an anomaly occurred at infrequent intervals: an unexpected Power On Reset (POR) event would reinitialize the attitude control subsystem. The POR was recognized as a serious, potenti
4、ally catastrophic problem, and high priority was given to isolating a cause and verifying a fix. Despite exhaustive investigations and significant design changes to improve noise immunity, the problem continued to occur, infrequently but persistently.Ultimately, a cause and cure were identified. Alt
5、hough exhaustive test and analysis of ground paths had been carried out, the noise source was identified as a capacitive coupling path between flight subsystem ground and support equipment ground. When spacecraft power surges such as turning on the Travelling Wave Tube Amplifier (TWTA) occurred, the
6、 two grounds would experience a transient oscillatory voltage difference of over seven (7) volts. The “AC Ground Loop“ fed the transient into the POR sensing circuit and occasionally triggered it. Eliminating the capacitor in the support equipment solved the problem.Additional Keyword(s): GroundingL
7、esson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AC as well as DC ground paths can be significant in noise coupling between circuits.Recommendation(s): 1. AC ground paths should be testable and should be verified in system interface
8、verification tests.2. Interface circuits should be analyzed to identify any AC coupling paths between independent ground trees.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Energya71 Flight Equipmenta71 Ground EquipmentAdditional Info: Approval Info: a71 Approval Date: 1988-08-11a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
