1、Lessons Learned Entry: 1532Lesson Info:a71 Lesson Number: 1532a71 Lesson Date: 2005-04-25a71 Submitting Organization: JPLa71 Submitted by: David OberhettingerSubject: Space vs. Ground Ambient, Which Environment is More Severe? (2002) Abstract: A test error was suspected during ground performance tes
2、ting of the Tropospheric Emission Spectrometer (TES) until it was determined that the Environmental Requirements Document-specified test limit applied to a different mission phase. Environmental requirements analysis should clearly identify and discriminate between the various specified flight proje
3、ct environments.Description of Driving Event: The Tropospheric Emission Spectrometer (TES) is an Earth observing instrument with focal plane arrays that are mechanically cooled to 63 degrees K. to reduce the instrument thermal background. During ambient performance testing of the instrument (Referen
4、ce (1), several major assemblies violated the upper-limit Allowable Flight Temperature (AFT) and Protoflight (PF) operational temperatures specified by the Environmental Requirements Document (ERD). The ERD (Reference (2) is the JPL document that specifies the environments the mission will encounter
5、 it serves as the basis for the environmental design and test of JPL subsystems and systems, including the specification of test levels and durations. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-refer to D descriptionDIt was determined that the
6、ground test had been performed at an appropriate temperature. The hot operating temperature limit imposed by the ERD was found to pertain solely to the extreme low temperature science data collection periods. The ERD did not specify environmental limits for ambient, “non-science” operating condition
7、s such as the ground environment that was the subject of the test. An ERD typically specifies allowable ground conditions as well as characterizing the spaceflight environment. References:1. JPL Problem/Failure Report No. Z77843, October 8, 2002.2. 3. JPL Environmental Assurance Standard (D-14040),
8、Rev. 3, JPL DocID 35491, November 23, 2004.Additional Key Words: Thermal Model; Test Error; Mission Environments; Environmental Assurance Plan; Environment Definitions; Environmental Design Requirements; Environmental Analysis; Environmental Test; Environmental Verification; Environmental Compliance
9、 Environmental Requirements Engineer (ERE); Maximum Expected Flight Level (MEFL); Environmental Margins Lesson(s) Learned: 1. Because the JPL ERD (or other Centers equivalent documentation) is the primary source of flight system environmental parameters, and the derived specifications for test leve
10、ls and durations, there should be no ambiguity between the various project life-cycle environments defined in the ERD.2. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3. Do not assume that all life-cycle environments (including supposedly benign en
11、vironments) are enveloped by the specification for any of the set of flight environmentsRecommendation(s): 1. Definition of environmental requirements should clearly identify and discriminate between the various project life-cycle environments, ground test, bake-out, ground transport, launch, flight
12、 dormant, flight operating, encounter, landed and surface operations, etc.2. 3. Environments that are thought to be relatively benign, such as the ambient ground environment, must be defined with the same care as in-flight environments.4. The cognizant design engineer must determine the extreme rang
13、e of design and test environments based on all life-cycle environments defined in the environmental requirements documentation.Evidence of Recurrence Control Effectiveness: JPL opened Preventive Action Notice (PAN) No. Z87141 on August 2, 2005 to initiate and document appropriate Laboratory-wide act
14、ion on the above recommendations.Documents Related to Lesson: Refer to reference (2)Mission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Environmenta71 Hardwarea71 Payloadsa71 Safety & Mission Assurancea71 Spacecrafta71 T
15、est & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2005-08-29a71 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-,-,-
