1、Lessons Learned Entry: 0416Lesson Info:a71 Lesson Number: 0416a71 Lesson Date: 1996-07-01a71 Submitting Organization: JPLa71 Submitted by: J.A. RobertsSubject: Voyager - S/X-Band Antenna Subsystem Intermodulation Products at Cold Temperatures (1976) Abstract: Qualification testing at extreme cold te
2、mperatures found that noise could be generated from the minute differential expansion between semi-rigid aluminum coaxial cables and their attached stainless steel shells. Beware of the intermodulation product phenomenon, and test for it during antenna subsystem pre- and post-environmental tests, af
3、ter antenna installation on the spacecraft, and prelaunch.Description of Driving Event: (Relevant Historical Lesson(s) Learned)During qualification testing of coaxial cables at cold temperature (-200C for TA) it was found that intermodulation product signal levels were generated. These levels only o
4、ccurred at the extreme cold temperature. On Viking it had been found that broadband noise could be generated in the mating surfaces of the aluminum four channel track connector. To eliminate that problem the Voyager connector mating parts were made of stainless steel. It was found in testing that th
5、ere was minute differential expansion between the semi-rigid aluminum coaxial cables and the stainless steel shells that attach to the cables. The problem was eliminated by increasing the fabrication torque from 20 in-lbs to 45 in-lbs to prevent the loosening at extreme temperatures.Additional Keywo
6、rd(s): Connector Fabrication Techniques, RF Intermodulation, Thermal ExpansionReference(s): Voyager PFR 38668Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Maintain a rigorous test program for detecting intermodulation products al
7、l the way up to launch. This would involve the use of a two-signal intermodulation test-set to assure that coaxial connectors or other components with contacting metal surfaces do not generate intermodulation products.Recommendation(s): 1. Testing to verify the absence of such products should be per
8、formed during the pre- and post-environmental tests at the antenna subsystem level, and also after installation of the antenna on the spacecraft in tests at the Spacecraft Assembly Facility (SAF) and as part of prelaunch preparations.2. The Hardware Design Engineer must be continuously cognizant of
9、the intermodulation product phenomenon and implement design practices for its avoidance.3. Install the stainless steel mating shells on the semi-rigid aluminum cables with a torque from at least 45 in-lbs.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Direct
10、orate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1995-10-19a71 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-,-,-
