This PDF file contains the front matter associated with SPIE Proceedings Volume 8492, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Chromate Conversion Coating (CCC) BOL and EOL thermal properties (absorptance and emittance) have been unspecified throughout the industry and throughout its use here at GSFC. Being key values essential for thermal engineers to assess thermal space conditions, this study focuses on the current application process, its outputted properties and assess whether these properties can in turn be classified under proper documentation. The results show that wide variations in the process overcome any possibility in thermally classifying this coating. A new set of samples were fabricated (in preparation for space environmental studies) in which a more controlled approach to applying the CCC was made. The resulting thermal values continued to show variations indicating lack of bath agitation existing within the bath. From this study you can conclude that witness samples may not best represent the flight hardware for this coating. The study then turns to space environmental study testing samples to high temperature (80°C), high vacuum, and combination of both, and UV radiation totaling 1625 ESH. The results showed an extremely dynamic coating sensitive to every environmental condition it was exposed to. Though the initial changes to the coating are drastic, post initial changes appear to be minuscule making EOL predictions more attainable. These results show that the worst case alpha/emittance values are likely after ground processing and before space exposure. From the data obtained in this study greater understanding and more informed decisions can be made with respect to this coating.

The effect of on-orbit molecular contamination has the potential to degrade the performance of spaceflight hardware and diminish the lifetime of the spacecraft. For example, sensitive surfaces, such as optical surfaces, electronics, detectors, and thermal control surfaces, are vulnerable to the damaging effects of contamination from outgassed materials. The current solution to protect these surfaces is through the use of zeolite coated ceramic adsorber pucks. However, these pucks and its additional complex mounting hardware requirements result in several disadvantages, such as size, weight, and cost related concerns, that impact the spacecraft design and the integration and test schedule. As a result, a new innovative molecular adsorber coating was developed as a sprayable alternative to mitigate the risk of on-orbit molecular contamination. In this study, the formulation for molecular adsorber coatings was optimized using various binders, pigment treatment methods, binder to pigment ratios, thicknesses, and spray application techniques. The formulas that passed coating adhesion and vacuum thermal cycling were further tested for its adsorptive capacity. Accelerated molecular capacitance tests were performed in an innovatively designed multi-unit system containing idealized contaminant sources. This novel system significantly increased the productivity of the testing phase for the various formulations that were developed. Work performed during the development and testing phases has demonstrated successful application of molecular adsorber coatings onto metallic substrates, as well as, very promising results for the adhesion performance and the molecular capacitance of the coating. Continued testing will assist in the qualification of molecular adsorber coatings for use on future contamination sensitive spaceflight missions.

Pre-launch acceptance testing and evaluation of mirrors coated for use in space are almost never performed on the actual flight mirror. Smaller witness mirrors, coated at the same time as the flight component, are used as test proxies for the spaceflight component. The intent of the acceptance testing is generally aimed at identifying any mirror surface quality problems before the larger mirror experiences qualification testing that usually occurs at the assembled instrument level when recovery from a previously undetected flaw can be costly. Only in rare cases will the testing of a smaller proxy sample reveal a mirror’s substrate structural flaws. This presentation will discuss details associated with pre-launch radiation sensitivity and cryogenic acceptance testing of the commonly used mirror reflector coatings aboard space optical instruments. The sufficiency of reflectance and transmittance measurements as the primary diagnostic tool for evaluating mirror coating quality, and as a predictor of on-orbit performance, will be emphasized with reference to specific space missions.

An experiment was performed to study and measure the deposition of water (H₂O) ice on optical component surfaces under high-vacuum cryogenic conditions. Water was introduced into a cryogenic vacuum chamber via a hydrated molecular sieve zeolite housed in a valved external chamber, through an effusion cell, and impinged upon a quartz-crystal microbalance (QCM) and first-surface gold-plated mirror. A laser and photodiode setup external to the vacuum chamber monitored the multiple-beam interference reflectance of the ice-mirror configuration while the QCM measured the mass deposition. Data acquired and analyzed from this experiment indicate that water ice under these conditions accumulates on optical component surfaces as a thin film up to thicknesses over 45 microns and can be detected and measured by nonintrusive optical methods based upon multiple-beam interference phenomena. The QCM, a well-established measurement technique, was used to validate the interferometer.

Sublimation rates and energies are critical for modeling the transport of water ice in cryogenic systems. A quick test was devised using an ASTM E-1559 [1] device that measures deposition with quartz crystal microbalances (QCMs). Credible results were obtained at temperatures as low as 120K and compared well with published data above 130K. Deposition and the following sublimation were performed with the QCMs held at constant temperature to alleviate variability due to ice morphology.

In the harsh vacuum environment of deep space, surfaces shielded from the Sun may easily develop temperatures low enough to condense water vapor for extended periods of time. The condensed vapor will subsequently desorb at rates consistent with its temperature-sensitive equilibrium vapor pressure, and under certain circumstances it is important to predict this release rate. A review of available scientific literature to confirm model predictions indicated no such measurements had been reported below 131 K. Contamination control personnel at NASA Goddard Space Flight Center recognized the possibility they readily possessed the means to collect such measurements at lower temperatures with an existing apparatus commonly used for making outgassing observations. This paper will describe how the ASTM E-1559 “MOLEKIT” apparatus was used without modification to measure water vapor sublimation down to 120 K and compare this data to existing equilibrium vapor pressure models. In addition, an in-depth analysis of theoretical formulations for vapor pressure gives insight into the physical basis underlying characteristics associated with high-fidelity models.

We attempted to evaluate the effectiveness of bakeout for certain materials by using the “In-Situ Contamination Spectroscopic Analysis Chamber” newly developed by JAXA, in order to measure the optical properties of a surface contaminated by condensed outgas. In the present case, the sample (RTV-S 691; subject to four bakeout conditions) is heated at 125°C and a gold-coated mirror set opposite the sample is cooled at -10°C to collect outgassing from the sample. FT-IR is set to measure the optical properties on the surface of the gold-coated mirror inside the chamber in-situ. A thermoelectric quartz crystal microbalance (TQCM) is installed in the chamber where the view factor to the sample is equivalent to that of the gold-coated mirror used to measure the thickness of deposited contaminants at the same temperature as that of the mirror. The four bakeout conditions are no bakeout, bakeout at 60°C, at 80°C, and at 125°C for 72 hours, respectively. As a result, TQCM data showed an expected curve, revealing a lower deposition rate at higher bakeout temperature. We then plotted the absorbance for obvious FT-IR spectra peaks against the optical path length, as calculated from the deposition thickness measured using the TQCM. The absorption coefficient at certain wavenumbers was found to vary under the four bakeout conditions. This suggests an insufficient deposition thickness on the optical surface. It therefore follows that direct optical measurement should be performed to evaluate bakeout effectiveness as pertaining to the essential purpose of bakeout.

DC-93-500, SCV-2590 and SCV-2590-2 silicone/siloxane based co-polymers serve as adhesive components of satellites and other spacecraft. It is well known that out gassing of these materials is a major source of contamination. For the past several years we have been optically characterizing the condensates and their photofixed films via in-situ ellipsometry and quartz crystal microbalance (QCM) measurements. We have identified several common outgassed components in each of these materials via FTIR, including polydimethylsiloxane (PDMS), and Tetra-n-propylsilicate (NPS). We have studied the optical properties of the photofixed films produced at various wavelengths of incident light , as well as when mixtures of these films are employed as the outgassing source via variable angle spectroscopy ellipsometry. We can relate the photofixed material optical properties to the bulk liquids and to the films produced by the outgassssing of the actual co-polymers mentioned above. This work may lead to the evaluation of the optical properties of the photofixed effluents of actual adhesives by evaluating a few basic components

This work presents further evaluation of the mechanisms driving the formation of molecular contaminant films and arrays of droplets on silicon and other types of space system optical surfaces. A simple model is presented describing a competition between the self-cohesive forces of a liquid-like droplet and the adhesive forces between the droplet and surface. We show in this work that irradiation of the silicon surface prior to contaminant deposition increases the adhesive forces, enhancing film formation. However, the surface states achieved by the VUV exposure cannot be reproduced by simple approaches such as solvent wiping. Higher intensity VUV exposure produces a silicon surface that allows film formation for even very pure contaminant analogs with high self-cohesion.

As a spacecraft undergoes ascent in a launch vehicle, its ambient pressure environment transitions from one atmosphere to high vacuum in a matter of a few minutes. Venting of internal cavities is necessary to prevent the buildup of pressure differentials across cavity walls. These pressure differentials are often restricted to low levels to prevent violation of container integrity. Such vents usually consist of fixed orifices, ducts, or combinations of both. Duct conductance behavior is fundamentally different from that for orifices in pressure driven flows governing the launch vehicle ascent depressurization environment. Duct conductance is governed by the average pressure across its length, while orifice conductance is dictated by a pressure ratio. Hence, one cannot define a valid “equivalent orifice” for a given duct across a range of pressure levels. The purpose of this paper is to develop expressions for these two types of vent elements in the limit of small pressure differentials, explore conditions for their validity, and to compare features regarding ascent depressurization performance.

Concerns were raised for potential payload contamination inside payload faring (PLF) contributed from the soot particles in the launch vehicle ignition plume. Soot particles, once ingested into PLF through vents, can pose potential payload contamination risks due to their light absorbing characteristics. To gain insights into the extent of soot particle contamination inside the PLF, analytical calculations and laboratory experiments were performed using a PLF simulator to determine the rate of soot particle deposition onto surfaces. The analysis assumed a non-venting setting as the worst case scenario, in which particles were trapped inside the PLF simulator and allowed to deposit onto available surfaces. Soot particles were briefly introduced inside a PLF mockup and after the soot generation source ceased, particle deposition rates were examined by measuring the particle concentration decay as a function of time. Based on the experimentally determined particle deposition rates and other parameters including the venting scenarios, the impact of soot particle deposition for the full scale PLF and payload was evaluated. The effects of soot particles contamination were also studied, and pronounced transmission degradation toward the UV region on a fused silica substrate was observed.

Current particle counting techniques employ common technologies: lasers, detectors, and optics. The theory of light scattering and particles is well known, and is standard in most particle counters. However, the need to detect smaller particles (nanoparticles) challenges the technological limits of traditional light-scattering techniques. Counting nanoparticles in liquids offers unique problems because of the intensity of scattered light from the particles relative to the light scattered by the fluid and flow cell. Consequently, the particle may be lost in the background noise. New technologies employ sophisticated detection elements and high-powered lasers to provide three-dimensional particle signatures and real-time videos as the particle passes through the laser. Aerosol nanoparticle counting offers the challenge of light scatter in an open sample chamber. Simply, the nanoparticles are too small to be effectively illuminated by lasers, so a new technique employs dynamic mobility to classify specific particle sizes. This technique can provide particle counting—and accurate particle size classification—down to 5 nm. Employing traditional optical particle counting technology is not efficient for detecting nanoparticles, but new technologies can meet these challenges. When combined with other support equipment (e.g. WiFi, software, etc.), new technologies provide innovative techniques for monitoring nanoparticles and managing nano-contamination in clean environments.

Historical experience and previously published papers have shown that contamination sampling techniques influence the cleanliness results of spaceflight hardware. Programs rely on this data to show that derived or contractual requirements are met at delivery. Particle sampling using tape lifts and rinses was performed on the James Webb Space Telescope (JWST) Primary Mirror Segment Assemblies (PMSAs) hardware. Sampling was performed on identical hardware with both sampling techniques. The hardware was sampled at comparable stages of assembly which provided hardware with similar levels of particulate contamination. Results from the two sampling techniques are compared. In one technique, sampling was performed by rinsing (with a hand-squeeze bottle with low pressure) followed by a tape lift; the other technique used a tape lift only. The relationship of particle size distribution, types of particles, level of particle contamination, and particle removal rate by sampling technique are examined. Comparison of the particle sampling results provides a basis for interpreting results depending on sampling techniques. Improving the contamination engineer’s ability to interpret results is particularly useful when hardware configuration or surface finish dictate which sampling technique can be used. When one can choose the sampling technique, the results of this study can provide guidance on which technique is more appropriate depending on the circumstances. Results show that tape lifts remove more particles than low pressure rinses; furthermore that tape lift only is better than the combined operation of a rinse closely followed by a tape lift. Results also indicate that further work should be performed on different surface finishes, rinsing techniques, and particulate contamination levels.

Three micromachined reference sample prototypes for particle counting have been fabricated by using dark ceramic spots in a transparent glass wafer to simulate particles on a surface. The direct write approach permits the spots to be positioned at random locations within an indicated area of the sample with sizes and numbers that are consistent with a distribution of particles. The goal of this work is to provide a path to creating a set of particle counting and sizing samples that can be used to establish the accuracy and precision of different measurements.

The donning of gloves is an essential handling requirement for minimizing aerospace hardware contamination. . Glove manufacturers frequently tout particle cleanliness, aqueous extractables, and pin holes in their literature. However, t comfort, dexterity, the level of non-volatile residue, and other characteristics are also important characteristics to consider when dealing with contamination sensitive, high-value hardware. In this paper, Ball Aerospace and Technologies (BATC) reports on its s investigation of several readily available gloves for use in the aerospace manufacturing environment and has developed a method of selection, testing, and analysis to ensure that gloves donned are ready for service. The testing method used do not necessarily comply any with any industry standards. The original tests fell into several categories. One of these was a non-volatile residue (NVR) test which examined contamination on the surface of the glove. A number of lots from several manufacturers were evaluated which provided insights into the cleanliness levels of gloves from potential. This has allowed us to track the lot to lot variability of the cleanliness level of gloves we receive from approved vendors.

Contamination-sensitive space flight hardware is typically built in cleanroom facilities in order to protect the hardware from particle contamination. Forest wildfires near the facilities greatly increase the number of particles and amount of vapors in the ambient outside air. Reasonable questions arise as to whether typical cleanroom facilities can adequately protect the hardware from these adverse environmental conditions. On Monday September 6, 2010 (Labor Day Holiday), a large wildfire ignited near the Boulder, Colorado Campus of Ball Aerospace. The fire was approximately 6 miles from the Boulder City limits. Smoke levels from the fire stayed very high in Boulder for the majority of the week after the fire began. Cleanroom operations were halted temporarily on contamination sensitive hardware, until particulate and non-volatile residue (NVR) sampling could be performed. Immediate monitoring showed little, if any effect on the cleanroom facilities, so programs were allowed to resume work while monitoring continued for several days and beyond in some cases. Little, if any, effect was ever noticed in the monitoring performed.

ITT Exelis builds electro optical telescopes and uses an optical throughput model in spreadsheet form to determine the transmission degradation due to contamination. The model can also be used to determine allowable contamination given a transmission requirement. Molecular contamination affects the transmission due to the absorbance of the optical contaminant while the particulate contamination affects the optical transmission due to obstruction and absorption of light, the model does not currently consider diffraction effects. The optical throughput model uses wavelength dependant absorption coefficients to determine the impact of the molecular contaminant. Optical transmission due to particles is analyzed by using the obscuration of the particle distribution. All optical elements in the telescope are analyzed by using the maximum angle of incidence for each optic. An expression was developed for non normal light assuming spherical particles and included light that was blocked by reflected incident light.