REG NASA-LLIS-0365-1994 Lessons Learned - Antenna Performance Specifications Not Met.pdf

1、Lessons Learned Entry: 0365Lesson Info:a71 Lesson Number: 0365a71 Lesson Date: 1994-12-22a71 Submitting Organization: JPLa71 Submitted by: Jim TaylorSubject: Antenna Performance Specifications Not Met Abstract: The system and end-to-end testing programs for the SEASAT synthetic aperture radar were i

2、mpacted by schedule and cost constraints that contributed to failure to meet the primary mission objective. The development organization and the project should understand the consequences of an inadequate test program. The risks associated with any reduction of testing should be clearly documented a

3、nd communicated to the project.Description of Driving Event: For an end-to-end system test of the SEASAT synthetic aperture radar, the development organization assembled a large radar antenna system, made of eight microstrip panels, each about 4 x 7 feet. The system also required a support structure

4、 for pointing and rigidity. The tight project schedule did not permit full-scale gain and pattern measurement before shipment of the antenna system to the SEASAT system contractor.The system test failed to meet its primary objective, to image the earth-orbiting Skylab satellite. It did accomplish th

5、e backup objective, to image a Learjet plane at 26,000 feet. The antenna was not designed for the heavy rain and severe wind occurring during the test program. Antenna phasing errors and cabling losses may have contributed to post-test antenna gain 6 dB lower and sidelobes 7 dB higher than expected.

6、 Without pre-test measurements, it was impossible to ascribe the test degradation either to the antenna or to other factors (such as uncertainties in the Skylab radar cross-section).Additional Keyword(s): Prototype System Development, Cost vs. Risk TradeoffLesson(s) Learned: Provided by IHSNot for R

7、esaleNo reproduction or networking permitted without license from IHS-,-,-The testing phases of a project, both system and end-to-end, are usually impacted by both schedule and cost constraints, which may affect system performance or reliability.Recommendation(s): The development organization and th

8、e project should understand the consequences of an inadequate test program. This understanding is best accomplished by the development organization defining a comprehensive test program, which will verify all design parameters prior to launch. This test program should have sharp justification and be

9、 based on a good technical analysis and previous experience. The risks associated with any reduction of testing or the deletion of any test should be clearly documented and communicated to the project. The project in turn should carefully consider the risks to performance and reliability if any subs

10、equent changes are made to the test program due to schedule or budget constraints.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Risk Management/Assessmenta71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1985-12-19a71 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-,-,-