REG NASA-LLIS-0384-1995 Lessons Learned - Cone Angle Anomaly in Canopus Star Tracker.pdf

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1、Lessons Learned Entry: 0384Lesson Info:a71 Lesson Number: 0384a71 Lesson Date: 1995-02-15a71 Submitting Organization: JPLa71 Submitted by: K. FlynnSubject: Cone Angle Anomaly in Canopus Star Tracker Abstract: An anomaly in the cone angle circuitry of the Voyager Canopus Star Tracker was probably due

2、 to a Delrin insulating sleeve decomposing after exposure to Jupiter radiation fields, causing a high resistance path through the Delrin. Ground metal shielding boxes and metal masses on circuit boards, analyze/test materials that could be exposed to ionizing radiation, and maintain spare hardware t

3、o enable failure analysis.Description of Driving Event: Shortly after Voyager I Jupiter encounter, an anomaly occurred in the cone angle circuitry of the Canopus Star Tracker (CST). The cause of the problem was determined to be a base-emitter or collector-emitter leakage in a transistor circuit that

4、 drives the cone angle deflection plates. This problem was duplicated in a spare CST.The most probable cause of the leakage path in the transistor circuitry is believed to be two-fold; 1) a Delrin insulating sleeve decomposed after exposure to Jupiter radiation fields and 2) development of a high re

5、sistance path through the Delrin by electrostatic discharge from an ungrounded tungsten radiation shield box.Additional Keyword(s): GroundingReference(s): Failure Investigation Report EM 343-494Lesson(s) Learned: 1. Charging of internal elements to as high as several hundred volts can occur due to r

6、adiation Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-fields.2. Exposure to ionizing radiation can degrade spacecraft materials.3. Availability of spare hardware is extremely useful in verifying in-flight failure modes.Recommendation(s): 1. All me

7、tal shielding boxes and metal masses on circuit boards should be grounded even though they are inside equipment housings.2. All materials that could be exposed to ionizing radiation should be analyzed/ tested to insure that unacceptable degradation will not occur.3. A set of spare hardware should be

8、 maintained to enable analysis of in-flight failures and validation of proposed corrective actions.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Environmenta71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1988-03-14a71 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-,-,-