REG NASA-LLIS-0419-1996 Lessons Learned SEASAT-A Synthetic Aperture Radar Coherent Leakage (1978).pdf

1、Lessons Learned Entry: 0419Lesson Info:a71 Lesson Number: 0419a71 Lesson Date: 1996-07-08a71 Submitting Organization: JPLa71 Submitted by: J.A. RobertsSubject: SEASAT-A Synthetic Aperture Radar Coherent Leakage (1978) Abstract: The SEASAT-A Synthetic Aperture Radar system end-to-end gain was instabl

2、e due RF leakage that varied with the sensor gain state and with temperature. Use of prototype models and diagnostic RF system analysis and modeling are effective in identifying microwave design susceptibilities to RF leakage.Description of Driving Event: (Relevant Historical Lesson(s) Learned)The S

3、EASAT-A Synthetic Aperture Radar (SAR) system end-to-end gain varied anomalously during measurements made just prior to SAR shipment to the SEASAT system contractor.Tests to resolve the anomaly traced the cause to the presence of leakage in the sensor signal output which was coherent with the Data L

4、ink carrier. (The Data Link in the SAR system is, in effect, an Intermediate Frequency (IF) strip, which converts the radar signal to offset video after transferring the radar signal, with reference signals, through an S-band link.)Phasing and amplitude of the leakage varied with the sensor gain sta

5、te and with temperature, thereby causing variations in the Data Link resultant carrier level. These variations perturbed the unity gain level required of the system. The system was designed for a fixed known relationship between signal and carrier levels.To alleviate the problem, the sensor was remo

6、ved from the satellite, and the leakage as attenuated by application of conducting tape. This did not eliminate the effect, but reduced it to acceptable levels. The leakage subsequently remained within these acceptable levels.Provided by IHSNot for ResaleNo reproduction or networking permitted witho

7、ut license from IHS-,-,-Additional Keyword(s): Communication Link, Design Verification, Spacecraft RadarReference(s):1. SEASAT P/FR 12872. R. L. Horttor/B. L. Huneycutt, et al, “SAR Engineering Assessment Report.“Lesson(s) Learned: Test programs must be designed to uncover operating problems.Recomme

8、ndation(s): Diagnostic Radio Frequency system analysis and modeling are effective in identifying microwave design susceptabilities to RF leakage. They need to be scheduled early enough to allow the necessary design modifications to be accomplished. In addition, use of prototype models offers the opp

9、ortunity to uncover problems without subjecting flight hardware to jeopardy.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Hardwarea71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reprod

10、uction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1996-02-29a71 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-,-,-