1、Lessons Learned Entry: 0992Lesson Info:a71 Lesson Number: 0992a71 Lesson Date: 2001-08-03a71 Submitting Organization: JPLa71 Submitted by: Thomas C. DuxburySubject: Spaceborne Imaging Camera Contamination (1999) Abstract: Contamination analysis does not always identify contamination sources or compl
2、ex migration paths. Designs should keep camera systems and thermal control surfaces away from vent paths and/or keep sensitive surfaces covered or sealed. Designs should include mitigation measures, (application of heat) for water vapor contamination and when using structural composite materials con
3、sideration should be given to selecting low hygroscopic materials or using non-outgassing coatings.Description of Driving Event: During first use after launch, the optical surfaces of the imaging camera onboard the NASA Discovery STARDUST spacecraft were found to be contaminated, thereby degrading t
4、he image quality. The cold operational temperatures of the camera CCD detector and optics offered a convenient “cold sink“ for contamination molecules. This phenomenon occurs when free molecules migrate to the coldest available surface. This contamination may have originated from spacecraft outgassi
5、ng and/or trapped contaminates within the camera. Such events have happened in the past on U.S. and international cold-biased instruments. Heat from internal heaters (or the sun for inorganic molecules) is commonly used to remove such contaminates, and has been used successfully on this mission to i
6、mprove imaging quality.Following the successful removal of contaminants through the heating process, a recontamination of the camera optical surfaces occurred as the temperature gradient between the spacecraft and the camera optical components returned to its nominal value (warm contamination source
7、s and cold optical surfaces). Using internal heaters again removed the contaminants.Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Theoretical contamination analyses may not always identify all contamination sources and complex mi
8、gration paths. This may require unanticipated decontamination of optical surfaces during mission operations.Recommendation(s): Special attention should be placed on design and operational details when dealing with optical systems that are particularly sensitive to contamination.1. Develop spacecraft
9、 configurations that keep camera system components away from all outgassing sources and vent paths to the greatest extent practical.2. When using composite materials for primary spacecraft structure or instrument elements, consider the use of low hygroscopic materials. Also consider the use of non-o
10、utgassing coatings on composite structures to reduce hygroscopic absorption, which further reduces the possibility of outgassing.3. During periods of possible contamination, keep space-born camera optical components covered or sealed; or keep them warm to avoid cold surfaces that may attract contami
11、nating molecules.4. Use heaters or direct sunlight on optical instrument radiators to raise internal temperatures to drive off contaminants. Do not permit sunlight directly on contaminated optical surfaces. If the contaminants are organic, sunlight ultraviolet may cause them to permanently darken an
12、d adhere to optical surfaces or thermal control surfaces.Additional key words: Subsystem and Instrument DevelopmentEvidence of Recurrence Control Effectiveness: A JPL Corrective Action Notice may be assigned and practices may be modified as appropriate.Documents Related to Lesson: N/AMission Directo
13、rate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Flight Operationsa71 Flight Equipmenta71 Hardwarea71 Parts Materials & Processesa71 P
14、ayloadsa71 Safety & Mission Assurancea71 Spacecrafta71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 2001-10-01a71 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-,-,-
