NEUTRAL EXTERNAL CONTAMINATION

B.D. Green, Satellite Contamination and Materials Outgassing Knowledgebase - An Interactive Database Reference, NASA/CR-2001-210909, George C. Marshall Space Flight Center Marshall Space Flight Center, AL 35812, Physical Sciences, Inc.,  Andover, MA 01810-1077, Prepared for NASA's Space Environments and Effects (SEE) Program Technical Monitor: Dewitt Burns, March 2001, pp. 131. 

Keywords: contamination testing, spacecraft contamination, materials outgassing

Abstract: The goal of this program is to collect at one site much of the knowledge accumulated about the outgassing properties of aerospace materials based on ground testing, the effects of this outgassing observed on spacecraft in flight, and the broader contamination environment measured by instruments in orbit. We believe that this web site will help move contamination a step forward, away from anecdotal folklore toward engineering discipline. Our hope is that once operational, this site will form a nucleus for information exchange, that users will not only take information from our knowledgebase, but also provide new information from ground testing and space missions, expanding and increasing the value of this site to all. We urge the Government and industry users to endorse this approach that will reduce redundant testing, reduce unnecessary delays, permit uniform comparisons, and permit informed decisions. 

J. Tveekrem, Contamination Effects on EUV Optics, NASA/TP -1999-209264, NASA's Space Environments and Effects (SEE) Program, NASA Marshall Space Flight Center, AL 35812 , June 1999 , pp. 34 .

Keywords: contamination on optics, EUV effects on optics, contamination, optics

Abstract: During ground-based assembly and upon exposure to the space environment, optical surfaces accumulate both particles and molecular condensibles, inevitably resulting in degradation of optical instrument performance. Currently, this performance degradation (and the resulting end-of-life instrument performance) cannot be predicted with sufficient accuracy using existing software tools. Optical design codes exist to calculate instrument performance, but these codes generally assume uncontaminated optical urfaces. Contamination models exist which predict approximate end-of-life contamination levels, but the optical effects of these contamination levels can not be quantified without detailed information about the optical constants and scattering properties of the contaminant. The problem is particularly pronounced in the extreme ultraviolet (EUV, 300-1,200 Å) and far (FUV, 1,200-2,000 Å) regimes due to a lack of data and a lack of knowledge of the detailed physical and chemical processes involved. Yet it is in recisely these wavelength regimes that accurate predictions are most important, because EUV/FUV instruments are extremely sensitive to contamination.

Dr. G.H. Pippin, Comparison of Spacecraft Contamination Models with Well-Defined Flight Experiment, NASA/CR-1998-208800 , NASA's Space Environments and Effects (SEE), NASA Marshall Space Flight Center, AL 35812, September 1998, pp. 287.

Abstractt: "Comparison of Spacecraft Contamination Models with Well-Defined Flight Experiment" report presents analyzed surface areas on particular experiment trays from the Long Duration Exposure Facility (LDEF) for silicone based molecular contamination.  The trays for examination were part of the Ultra-Heavy Cosmic Ray Experiment (UHCRE).  These particular trays were chosen because each tray was identical to the others in construction, and the materials on each tray were well known, documented, and characterized.  In particular, a known specific source of silicone contamination was present on each tray.  Only the exposure conditions varied from tray to tray.

The results of post-flight analyses of surfaces of 3 trays were compared with the predictions of the three different spacecraft molecular contamination models.  Phase one tasks included (1) documenting the detailed geometry of the hardware, (2) determining essential properties of the anodized aluminum, velcro (trademark), silverized teflon (trademark), silicone gaskets, and DC6-1104 (trademark) silicone adhesive materials used to make the trays, tray covers, and thermal control blankets, (3) selecting and removing areas from each tray, (4) and beginning surface analysis of the selected tray walls.   Phase two tasks included (1) completion of surface analysis measurements of the selected tray surfaces, (2) obtaining auger depth profiles at selected locations, (3) running versions of the ISEM, MOFLUX, and PLIMP (Plume Impingement) contamination prediction models and making comparisons with experimental results.

SPIFEX Contamination Studies

A. C. Tribble, B. Boyadjian, J. Davis, J. Haffner and E. McCullough, Contamination Control Engineering Design Guidelines for the Aerospace Communityy NASA CR-4740 , Prepared for the NASA Goddard Space Flight Center as one of the technology development contracts sponsored by the Space Environments & Effects Program managed at the NASA Marshall Space Flight Center, AL., NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, Contract NAS5-32876, by Rockwell International Corporation, Downey, CA. 90241-7009, May 1996, pp. 130. 

Keywords:: Contamination, Contamination Guidelines

Abstract: Thermal control surfaces, solar arrays, and optical devices may be adversely affected by a small quanitity of molecular and/or particulate contamination. What is rarely discussed is how one: a) quantifies the level of contamination that must be maintained in order for the system to function properly, and b) enforces contamination control to ensure compliance with requirements. This document is designed to address these specific issues and is intended to serve as a handbook on contamination control for the reader, illustrating process and methodology while providing direction to more detailed references when needed. The effects of molecular contamination on reflecting and transmitting surfaces are examined and quantified in accordance with MIL STD 1246C. The generation, transportation, and deposition of molecular contamination is reviewed and specific examples are worked to illustrate the process a design engineer can use to estimate end of life cleanliness levels required by solar arrays, thermal control surfaces, and optical surfaces. A similar process is used to describe the effect of particulate contamination as related to percent area coverage (PAC) and bi-directional reflectance distribution function (BRDF).  Relationships between PAC and surface cleanliness, which include the effects of submicron sized particles, are developed and BRDF is related to specific sensor design parameters such as Point Source Transmittance (PST). The pros and cons of various methods of preventing, monitoring, and cleaning surfaces are examined and discussed. 
 

EM2/Dr. Steve Koontz, Quick Look Report: DTO-829(STS-74) Plume Impingement Contamination

    
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