1、Lessons Learned Entry: 0395Lesson Info:a71 Lesson Number: 0395a71 Lesson Date: 1995-06-06a71 Submitting Organization: JPLa71 Submitted by: Jim TaylorSubject: In-Flight Spacecraft Antenna Gain and Polarization Changes Abstract: Before the first Mercury encounter, the MVM73 high gain antenna suddenly
2、lost 3 dB in gain and changed from circular to linear in polarization. It was suspected that either particles or chips left in the S-band feed cavity after antenna assembly caused a short circuit, or a combination of tolerance build-up and thermal effects caused a dimensional change. Worst case anal
3、ysis should be preformed on any equipment suspected to be sensitive to assembly practices or tolerance build-up.Description of Driving Event: Before the first Mercury encounter, the MVM73 high gain antenna suddenly lost 3 dB in gain and changed from circular to linear in polarization. Ground testing
4、 on a similar antenna determined that a short circuit within the S-band feed cavity reproduced these effects as well as the observed changes in internal antenna temperature and standing wave ratio.Successful anomaly resolution during the flight included an induced temperature change by solar illumin
5、ation to “heal“ the antenna, permitting the planned mission. The development organization was very instrumental in the correction of the problem. They theorize that either a short circuit occurred as the result of particles or chips left in the cavity after antenna assembly or a combination of toler
6、ance build-up and thermal effects caused a dimensional change.Additional Keyword(s): OperationsLesson(s) Learned: 1. A worst case analysis could have predicted potential performance anomalies of equipment susceptible to tolerance build-up.Provided by IHSNot for ResaleNo reproduction or networking pe
7、rmitted without license from IHS-,-,-2. During critical spaceflight events it proved to be extremely valuable to have the original development engineers committed and available to assist in any in-flight anomaly analysis and correction.Recommendation(s): 1. Any equipment suspected to be sensitive to
8、 assembly practices of tolerance build-up should have a worst case analysis to reveal any potential performance anomalies.2. Consideration should be given to planning for original development engineers to participate as members of the in-flight anomaly recovery team.Evidence of Recurrence Control Ef
9、fectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Administration/Organizationa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1985-12-19a71 Approval Name: Carol Dumaina71 Approval Organization: 25-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
