The current method for the prediction of molecular contamination build up in systems such as the James Webb Space Telescope and other large astronomical satellites is based on a monotonic linear model of accumulation. Recent long term observations carried out at Northrop Grumman facilities have shown this model to be extremely conservative and therefore highly misleading. The over prediction of molecular contamination using the traditional model causes excessive expenditure of resources to mitigate overestimated buildup. This paper reviews the long term observations of contaminant film thickness accumulation made at Northrop Grumman facilities. The formulation of a semi-empirical method for the prediction of film thickness evolution consistent with both observation and first principles is discussed in detail. The paper concludes with a validation of the predictions of the semi-empirical model. The increased accuracy of the semi-empirical method holds the promise of improved and effective means of contamination control, thus reducing mission cost and risk.
KEYWORDS: James Webb Space Telescope, Space operations, Contamination, Contamination control, Inspection, Observatories, Manufacturing, Foam, Acoustics, Picture Archiving and Communication System
This paper will continue from Part 1 of JWST contamination control implementation. In addition to optics, instruments, and thermal vacuum testing, JWST also requires contamination control for a spacecraft that must be vented carefully in order to maintain solar array and thermal radiator thermal properties; a tennis court-sized sunshield made with 1-2 mil Kapton™ layers that must be manufactured and maintained clean; an observatory that must be integrated, stowed and transported to South America; and a rocket that typically launches commercial payloads without contamination sensitivity. An overview of plans developed to implement contamination control for the JWST spacecraft, sunshield, observatory and launch vehicle will be presented.
The derivation of contamination control (CC) requirements for the JWST Optical Telescope Element (OTE) was presented at the SPIE conference in 20081. Since then, much work has been done to allocate contamination at each phase of Integration and Test (IandT) and to plan for achieving the allocations. Because JWST is such a large and complicated observatory, plans for meeting the requirements are many and varied. There are primary mirror segments that must be cleaned early and maintained clean; there are four science instruments that each have tight contamination requirements but cannot be cleaned after they are integrated onto the Integrated Science Instrument Module (ISIM) structure; there is the composite ISIM structure that is fragile and must be minimally handled; there are numerous cryo-vacuum tests that must be controlled and monitored in order to minimize molecular contamination during return to ambient; … and more. An overview of plans developed to implement contamination control for JWST optics, instruments, and thermal vacuum testing for JWST will be presented.
KEYWORDS: James Webb Space Telescope, Mirrors, Particles, Contamination, Aluminum, Reflectivity, Aerospace engineering, Telescopes, Stray light, Picture Archiving and Communication System
The James Webb Telescope (JWST) is a large cryo-optical system. Many critical thermal control
or optical surfaces are exposed to ground and flight environments and are expected to be contaminated to
some level. In order to calculate key system performance parameters, such as stray light and radiative
thermal transfer, the emissivity must be known in terms of contamination level and temperature. This
paper will introduce the methods of determining these emissivities, and the discussion will cover the types
of particulate and molecular contamination expected on JWST. The results of the calculations will be
introduced and discussed.
Conference Committee Involvement (6)
Space Systems Contamination: Prediction, Control, and Performance 2025
3 August 2025 | San Diego, California, United States
Space Systems Contamination: Prediction, Control, and Performance 2022
23 August 2022 | San Diego, California, United States
Systems Contamination: Prediction, Control, and Performance 2020
24 August 2020 | Online Only, California, United States
Systems Contamination: Prediction, Control, and Performance 2018
20 August 2018 | San Diego, California, United States
Systems Contamination: Prediction, Control, and Performance 2016
31 August 2016 | San Diego, California, United States
Systems Contamination: Prediction, Control, and Performance
18 August 2014 | San Diego, California, United States
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