1、Lessons Learned Entry: 0366Lesson Info:a71 Lesson Number: 0366a71 Lesson Date: 1995-01-13a71 Submitting Organization: JPLa71 Submitted by: R.F. CollinsSubject: Infrared Astronomical Satellite (IRAS) Contamination Control Challenges Abstract: IRAS posed new challenges to contamination control due to
2、the extremely low temperatures (3 degrees Kelvin) required to achieve successful low noise infrared signal detector operation in the focal plane assembly. The elaborate contamination control precautions listed in the lesson were believed critical to mission success.Description of Driving Event: IRAS
3、 was a cooperative Dutch Space Agency/NASA undertaking in which the spacecraft bus was built in Europe, then integrated with the NASA Infrared Telescope. The new challenges to contamination control were related to the extremely low temperatures (3 degrees Kelvin) required to achieve successful low n
4、oise infrared signal detector operation in the focal plane assembly. At these low temperatures, all gases except helium are solid.There are two separate contamination problems. The first is caused by air leakage into the plumbing when the system is cold and sub-atmospheric, resulting in plugged vent
5、s, tubes and valves, creating major safety problems or system malfunction. The solution includes care in the selection of transfer line and flight plumbing hardware, control of procedures, and use of purge covers to maintain a helium atmosphere on the high pressure side of any valve which may allow
6、air leakage into the cold plumbing.The second problem is that exposed surfaces this cold can readily condense vapors from normal outgasing even in the vacuum of space, causing performance degradation by contamination of the optical surfaces or affecting temperature control surfaces. This complicated
7、 the development, assembly and test program for IRAS by the need to avoid contamination by any materials that could later evaporate and condense on the cold surfaces. Facility air environments had to be monitored and Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
8、e from IHS-,-,-controlled to avoid contaminants, and handling and shipping equipment required the same extreme precautions. The contamination control situation was further complicated by the air shipments to Europe for integration, back to JPL for space simulator testing, and transportation to Vande
9、nberg Air Force Base for launch.The successful completion of the IRAS mission attests to the success of the design and control measures accomplished. No apparent performance degradation occurred during the mission.Additional Keyword(s): CryogenicsReference(s): JPL D-842, IRAS Telescope Development:
10、Technical Lessons Learned.Lesson(s) Learned: When spacecraft design requires extremely low temperatures to achieve successful operation, elaborate contamination control precautions are critical to mission success.Recommendation(s): Required contamination control precautions include:1. Design for avo
11、idance and control of contaminants.2. Measure contaminants in test environments and facilities.3. Identify and control contamination sources.4. Provide for protection during the transportation and launch environments.5. Design to minimize contaminant migration.6. Plan to clean contaminants off.7. De
12、sign for in-mission contaminant removal (heaters, wipers and covers).Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Key Phrase(s): a71 Cryogenic SystemsAdditional Info: Approval Info: a71 Approval Date: 1988-08-04a71 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-,-,-
