1、Lessons Learned Entry: 0378Lesson Info:a71 Lesson Number: 0378a71 Lesson Date: 1995-02-01a71 Submitting Organization: JPLa71 Submitted by: Jim TaylorSubject: Untestable System Mode In Flight Abstract: An essential in-flight test of the Viking Lander transmitter output could not be conducted due to t
2、he antennas proximity to the Orbiter receiver antenna when Lander and Orbiter were mated. During the system design phase, system engineers must be sensitive to the various configurations to be encountered during the system test program.Description of Driving Event: Prior to launch, telecommunication
3、 analysts responsible for the Viking Orbiter and the Lander identified that in-flight checkout of the Lander transmitter could be a potential problem. The transmitter outputs are 1, 10, and 30 watts. When the Orbiter and Lander are mated, there is only a small separation between the Lander relay tra
4、nsmitter antenna and the Orbiter relay receiver antenna. The analysts realized that at the higher relay transmitter output levels, the relay receiver would be subject to an overload condition and could suffer possible damage. Prelaunch tests of the antenna geometry and Orbiter/Lander mated tests wer
5、e insufficient because of limited modeling capability, nonflight conditions, and noisy environments.To verify a working Lander transmitter output before the first descent to Mars surface, an in-flight test was essential. Engineers, working at the bounds of analysis with nonlinear telemetry, deemed a
6、 10-watt test safe. Because of parameter tolerance buildup, they could not guarantee damage-free testing at the 30-watt level. Therefore, the project decided the critical Lander-1 Mars-descent data would be transmitted at 10 watts, thereby accepting the risk of some data loss due to atmospheric fadi
7、ng.Additional Keyword(s): RF System DesignProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Lesson(s) Learned: System engineers cannot rely on the individual subsystem engineers to predict problems of their subsystems interacting with other subsystems
8、during system tests.Recommendation(s): During the system design phase, system engineers must be sensitive to the various configurations to be encountered during the system test program.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditio
9、nal Key Phrase(s): a71 Configuration Managementa71 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-,-,-
