1、Lessons Learned Entry: 0286Lesson Info:a71 Lesson Number: 0286a71 Lesson Date: 1993-07-13a71 Submitting Organization: JPLa71 Submitted by: P. W. SchaperSubject: Galileo NIMS Cooler Cover Ejection Anomaly Abstract: Contrary to design assumptions and the original flight plan, a decision was made to en
2、ergize the Galileo Near Infrared Mapping Spectrometer (NIMS) cover heater prior to ejecting the covers. The cover failed to deploy until the heater was switched off.The lesson offers recommendations that would deter untested flight sequences and incomplete reviews of mission operations flight rules.
3、 Description of Driving Event: At launch, the Near Infrared Mapping Spectrometer (NIMS) on the Galileo spacecraft had two covers in place to protect the instrument from contamination. Two and a half months after launch, when contamination was deemed to be negligible, an attempt was made to eject the
4、 covers. The “cooler cover“ failed to eject, as determined by not receiving expected temperature changes. Analysis of the data revealed that the temperature of the cooler shield was 38 degrees C., due to the shield heater being energized. This resulted in a temperature differential between the cover
5、 and the shield that caused a mechanical distortion sufficient to prevent the cover from ejecting. All ejection tests before launch were conducted with the shield heater unenergized, which was the original in-flight plan. Because of a concern for contamination caused by spacecraft outgassing, a flig
6、ht rule was modified prior to launch requiring the shield heater to be energized before cover deployment. The flight rule was in error by not requiring the shield heater to be off sometime prior to cover deployment. The shield heater was commanded off and twenty-two minutes later the “cooler cover“
7、ejected properly, as shown by the instrument temperature telemetry. Had the “cooler cover“ not ejected, the NIMS experiment would have been considered a failure.Additional Keyword(s): Testing, Mechanical DevicesProvided by IHSNot for ResaleNo reproduction or networking permitted without license from
8、 IHS-,-,-Reference(s):PFR #52603Review Board Report, IOM 340-90-030-JLSLesson(s) Learned: 1. Untested flight sequences frequently result in unexpected events.2. Incomplete reviews of mission operations flight rules can cause problems.3. Problems are created due to the loss of information in the tran
9、sfer of responsibility from design to operations.Recommendation(s): 1. All primary and backup spacecraft flight configurations should be tested or analyzed before launch, including the most probable failure-mode configurations.2. Subsystem constraints that impose system constraints should be evaluat
10、ed at system design reviews for their system impacts and their possible elimination.3. The flight rules generation cycle should be initiated early in the mission operations design, and emphasis should be placed on their review, including additions or revisions thereto, by all essential personnel (su
11、ch as design cognizant engineers).4. Reviews of critical spacecraft operations should be initiated early in the design cycle and should include design specialists. For long duration missions, re-review before initiation of critical operations is highly desirable.Evidence of Recurrence Control Effect
12、iveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Flight Equipmenta71 Test & VerificationProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Approval Info: a71 Approval Date: 1990-11-08a71 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-,-,-
