1、Lessons Learned Entry: 0272Lesson Info:a71 Lesson Number: 0272a71 Lesson Date: 1993-07-08a71 Submitting Organization: JPLa71 Submitted by: P. W. SchaperSubject: Flight Anomaly of Atmospheric Trace Molecule Spectroscopy (ATMOS) Instrument, Risk Assessment Abstract: The ATMOS instrument experienced a
2、randomly occurring failure on the ground that was fixed each time by resetting the instrument. After an extended investigation that failed to identify the failure mechanism, the workaround was employed successfully on repeated Shuttle flights.For low-cost, reflyable experiments, generate preplanned
3、in-flight workaround procedures for random performance anomalies to enable successful repeated flights, consider cost tradeoffs in risk assessments, and view the testing and qualification rules established for single flight projects as guidelines only.Description of Driving Event: On March 24, 1992
4、the ATMOS instrument, a fourier transform spectrometer, flew on the Atmospheric Laboratory for Applications and Science (ATLAS 1) payload aboard the shuttle (STS) Atlantis with an open problem/failure report (PFR). The events leading to this state of readiness can be briefly summarized as follows: s
5、ince the experiment for which this instrument was built was proposed as a low cost effort at a very early time in the STS program, the proposal did not plan for a breadboard or prototype model. The instrument had its maiden flight on the SPACELAB 3 mission in 1985 and was expected to be reflown seve
6、ral more times at 12 month intervals on STS missions. During the hiatus of reflights, caused by the Challenger accident, ATMOS was extensively used for making significant ground based observations. During these operations an infrequent, and apparently randomly occurring failure was observed in the s
7、tartup sequence, in that the moving slides stopped. The failure could always be overcome by resetting the instrument. In spite of concerted efforts to isolate the cause of this anomaly, the failure mechanism was not identified even though certain suspect parts were exchanged. An in-flight workaround
8、 was devised for the ATLAS 1 mission and Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the instrument was committed to flight, knowing that a non-catastrophic failure might be experienced. In fact, during the course of the ATLAS mission, the slide
9、failure did occur and the workaround was employed successfully. No data was lost and the mission was concluded without further reoccurrences of slide motion problems. The decision to take this risk was reached taking into account the consideration that in a low cost, reflyable instrument the acquisi
10、tion of a large quantity of quality data was worth the loss of small quantities of specific runs.Reference(s): PFR #52055Lesson(s) Learned: 1. Low-cost experiments with plans for repeated flights can yield a large volume science return in spite of random performance anomalies.2. Low cost STS-borne e
11、xperiments with plans for repeated flights, exemplified by the ATMOS spectrometer, require risk assessments different from those used for single launch experiments.3. The lack of second instruments (breadboard or prototype) for low budget projects makes thorough testing of flight instruments difficu
12、lt when flight schedules need to be met.Recommendation(s): 1. Generate preplanned in-flight workaround procedures for random performance anomalies to enable successful repeated flights of low-cost experiments.2. Base risk assessments for reflyable experiments on considerations involving data quality
13、 versus cost tradeoffs.3. In the case of low cost reflyable instruments, view the rules controlling testing and qualification established for single flight projects as guidelines only. Less than perfect performance can be accepted during any given mission.Evidence of Recurrence Control Effectiveness
14、 N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Hardwarea71 Risk Management/Assessmenta71 SoftwareAdditional Info: Approval Info: a71 Approval Date: 1992-06-11a71 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-,-,-
