1、Lessons Learned Entry: 0379Lesson Info:a71 Lesson Number: 0379a71 Lesson Date: 1995-02-01a71 Submitting Organization: JPLa71 Submitted by: J.C. MarrSubject: Violation of Magellan Electrical and Grounding Specification Abstract: A violation of electrical interfacing and grounding requirements for Mag
2、ellan resulted in substantial damage to the CDS analog telemetry circuitry. Care must be taken to ensure that design changes are properly reviewed. A formal project waiver of requirements should be obtained.Description of Driving Event: In an effort to take advantage of spare telemetry channels in t
3、he Command and Data System (CDS) hardware, the Attitude Reference Unit (ARU) motor current telemetry was added to the CDS analog telemetry channels of the Magellan (MGN) Spacecraft. This addition was made late in the design of the spacecraft and utilized the spacecraft chassis for the ARU motor curr
4、ent telemetry signal return path which was in direct violation of VRM 2-260, “Electrical Grounding and Interfacing“ specification. A waiver of the VRM 2-260 requirements for this design was not initiated.Subsequent failure of the chassis ground path, caused by a poor mechanical connection at the att
5、itude and articulation control subsystem single point ground, resulted in substantial damage to the MGN CDS analog telemetry circuitry. This required rework of the CDS, resulting in a late delivery to the spacecraft at Kennedy Space Center.Reference(s):1. Martin Marrieta Aerospace Group MARS #B16065
6、2. JPL IOM 5211-89-305, “Removal of Red Flag Rating from MGN Mars #B16065,“ dated 25 April 1989, by M. Boyles, J. Quinn.Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Violations of electrical interfacing and grounding requirement
7、s can have serious consequences and should not be undertaken lightly or without a formal project waiver.Recommendation(s): Care must be taken to ensure that design changes are properly reviewed.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N
8、/AAdditional Key Phrase(s): a71 Configuration Managementa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1989-11-16a71 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-,-,-
