This PDF file contains the front matter associated with SPIE Proceedings Volume 10748, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Molecular contamination of optical surfaces, thermal control components, or other spacecraft components can lead to end-of-life performance degradation. In particular, exposure to vacuum ultraviolet (VUV) radiation is known to enhance contaminant deposition rates. Known mechanisms for photodeposition and photopolymerization of contaminants are here reviewed to provide insight into the underlying chemistry and reaction mechanisms. Previous works have shown that many variables influence the rate of contaminant uptake, including temperature, VUV energy, and material properties of both the contaminant molecules and the substrate. Additionally, the photochemistries of three common spacecraft outgassing contaminants (DOP, BPA, and DC 704) are discussed to provide insight into future modeling efforts.

Silver coated Teflon (SCT) has been used as a radiator material for spacecraft thermal control. In order to reduce the specular reflection, an attempt was made to roughen the heritage smooth SCT surface via sanding, leading to abraded surfaces. The objective of this study is to gain insight into the relative thermal performance degradation of smooth and abraded SCT radiator materials under identical exposure of concurrent UV irradiation and contaminant deposition. Contaminant molecules outgassed from representative spacecraft materials were deposited onto the smooth and abraded SCT samples with quartz crystal microbalances (QCMs) in close proximity to monitor real-time contaminant deposition. Thermal performance degradation is characterized by measuring solar absorptance () change on the SCT samples before and after contaminant film accumulation. Atomic force microscope (AFM) was used to examine the extent of surface roughness before and after contaminant deposition on smooth SCT samples. The preliminary findings indicate that less contamination accumulation was observed on SCT surfaces in comparison to the gold coated crystal surface of QCMs. In addition, the roughness of SCT surface appears to play a role in contributing a more pronounced  change, suggesting the possibility of faster performance degradation of the abraded SCT materials in comparison to that of smooth SCT surfaces.

The Stratospheric Aerosol and Gas Experiment III (SAGE III) is an external payload on the International Space Station (ISS) that measures vertical profiles of ozone and other atmospheric constituents through the use of a moderate resolution spectrometer with an operating wavelength range of 290 nm to 1550 nm utilizing the method of occultation. Because of the contamination sensitivity [particularly to silicate contamination] of the payload, a suite of eight Thermoelectric Quartz Crystal Microbalances (TQCMs) were included to monitor the operating environment. During the first year of operation, the SAGE III/ISS TQCMs were instrumental in detecting several periods of relatively high contamination and identifying the sources. A transparent window made of quartz crystal covers the instrument assembly's aperture. The contamination window may open during science acquisition under nominal operating conditions. However, if the contamination sensors measure mass adsorption rates significantly elevated above the background level, the window may be commanded to remain closed during science to protect the contamination sensitive scan mirror and telescope. An analysis of the spectral transmission through the window for the wavelength range of 290 nm to 1550 nm has been conducted to determine any possible degradation of the window transmission and potential effects on science data collected to date, and establish a baseline for future analysis.

The Robotic External Leak Locator (RELL) was deployed to the International Space Station (ISS) with the goal of detecting and locating on-orbit leaks around the ISS. Three activities to characterize the background natural and induced environment of ISS were performed with RELL as part of the on-orbit validation and demonstration conducted in November – December 2016. The first demonstration activity pointed RELL directly in the ram (+X) and wake (-X) directions for one orbit each. The ram facing measurements showed high partial pressure for mass-to-charge ratio 16, corresponding to atomic oxygen (AO), as well as the presence of mass-to-charge ratio 17. RELL’s view in the wake-facing direction included more ISS structure and several Environmental Control and Life Support System (ECLSS) on-orbit vents were detected, including the Carbon Dioxide Removal Assembly (CDRA), Russian segment ECLSS, and Sabatier vents. The second demonstration activity pointed RELL at three faces of the P1 Truss segment. Effluents from ECLSS and European Space Agency (ESA) Columbus module on-orbit vents were detected by RELL. The partial pressures of massto- charge ratios 17 and 18 remained consistent with the first on-orbit activity of characterizing the natural environment. The third demonstration activity involved RELL scanning an Active Thermal Control System (ATCS) radiator. Three locations along the radiator were scanned and the angular position of RELL with respect to the radiator was varied. Mass-to-charge ratios 16 and 17 both had upward shifts in partial pressure when pointing toward the Radiator Beam Valve Modules (RBVMs), likely corresponding to a known, small ammonia leak.

The Robotic External Leak Locator (RELL) was deployed to the International Space Station (ISS) with the objective of demonstrating the ability to detect and locate small leaks. On-orbit operations began in late November 2016 and following scanning activities to characterize the natural and induced environment of the ISS, RELL focused on the United States External Active Thermal Control System (EATCS). RELL successfully detected ammonia related to a known small ammonia leak in the port-side EATCS, with the highest pressure values around the inboard Radiator Beam Valve Module 1 (RBVM 1). An additional day of scanning was subsequently performed in December 2017 to focus on RBVM 1. RELL was approved for additional external operations in February 2017 with the goal of fine tuning the location of the leak. Using grid scanning patterns, RELL detected ammonia around RBVM 1 and located the approximate source of the leak. The potential leak site was inspected by a crew member during an Extravehicular Activity (EVA) in March 2017, and the suspected radiator-side lines were isolated from the port-side EATCS coolant loop in April 2017. Subsequent monitoring of the system pressures showed that the leak has stopped, indicating RELL accurately located the source of the EATCS leak. These activities verify that RELL enhances the ISS Program’s ability to not only locate small leaks, but isolate the source with minimal impact to the entire ISS system.

On-orbit Robotic External Leak Locator (RELL) (i.e., mass spectrometer and ion gauge) measurements on the International Space Station (ISS) are presented to show the detection of recurring Environmental Control and Life Support System (ECLSS) vents at multiple ISS locations and RELL pointing directions. The path of ECLSS effluents to the RELL detectors is not entirely obvious at some locations, but the data indicates that diffuse gas-surface reflection or scattering resulting from plume interaction with vehicle surfaces is responsible. RELL was also able to confirm the ISS ECLSS constituents and distinguish them from the ammonia leak based on the ion mass spectra and known venting times during its operation to locate a leak in the ISS port-side External Active Thermal Control System (EATCS) coolant loop.

Contamination modeling in Europe has long been based on physical mechanisms, such as desorption. However other physical mechanisms, such as diffusion, evaporation or mixing effects exist. These alternative mechanisms were experimentally evaluated and modelled. It was yet observed that, without an experimental capability to reliably separate the (re)emitted chemical species, it is very difficult to determine whether the modeling and its underlying physical mechanisms are representative of reality, or simply a mathematical fit of reality. This is the reason why in the last years emphasis was put on the experimental separation of species, mostly through TGA/MS coupling. This paper presents a review of these efforts and promising results on species separation to reach a really physical modeling of outgassing, deposition/reemission and UV synergy.

“NASA’s Mars 2020 mission … rover is being designed to seek signs of past life on Mars, collect and store a set of soil and rock samples that could be returned to Earth in the future.^”1 The Mars 2020 Project has a top-level requirement that soil and rock samples contain less than 10 ppb Total Organic Carbon (TOC) of terrestrial origin ². The approach taken to meet this requirement is to identify and model for each Mars 2020 mission phase the TOC sources, model TOC transport from sources to sample contacting surfaces, and combine them into an end-to-end model that calculates the TOC in each sample during the mission. The calculations show that Mars 2020 can achieve the TOC sample cleanliness requirement because the project has adopted specific TOC mitigations strategies.

A molecular transport model for the Europa UV Spectrograph instrument has been developed to predict optical throughput over the course of the mission lifetime. At beginning of life, internal surfaces will be covered with a thin layer of non-volatile residue (NVR); after launch, contaminants from the electronics components will diffuse out of their parent materials, adding to the overall contaminant environment. The transport of these contaminants, and accumulation onto optical elements, is dependent on geometry, temperature, transport kinetics, and contamination process control during instrument build. Quantitative thermogravimetric analysis (QTGA) was used to estimate the distribution of activation energies for desorption of contaminant from electronics, and that of NVR. An assessment of the effectiveness of different lengths and frequencies of decontamination cycles was performed, and a 12-hour decontamination sequence was effective at removing accumulated contaminant. We found that the combined effects of temperature and view factors resulted in the curious result that whether the telescope aperture door was open or closed had insignificant effect on optics cleanliness. Allowing the door to be closed through much of mission life, in turn, protects the spectrograph from being contaminated by thruster plumes or contaminant from the spacecraft environment. Finally, a parametric analysis of the effect of activation energy distribution was performed. If a lower energy distribution, characteristic of electronics outgassing was used for NVR transport, the throughput margin would be reduced significantly, but the coverage would still be below that at beginning of life.

The kinetics of molecular transport of contaminant species is highly dependent on the distribution of desorption activation energies. Accurate measurements of these kinetics are essential to improving confidence in molecular transport modeling and setting appropriate beginning of life (BOL) cleanliness requirements. We present results that combine laboratory experiments with computer simulations to determine the distribution of effective activation energies for outgassing species from a urethane paint system and non-volatile residue (NVR) collected from an ISO Class 5 cleanroom contamination monitoring plate. Outgassing from samples of primer overcoated with urethane paint were analyzed with the temperature controlled quartz crystal microbalance thermogravimetric analysis (QTGA) technique during the final stages of vacuum baking; cleanroom NVR was also analyzed via QTGA. A computer model was developed to simulate the QTGA results. Data from the experimental QTGA were compared to the simulated QTGA to obtain a distribution of desorption activation energies for contaminant species. The interior of the Ozone Mapping and Profiler Suite (OMPS) science instrument is primed and painted with polyurethane/epoxy material. The distribution of activation energies derived in this study was incorporated in the molecular transport model of the OMPS science instrument, on the Suomi National Polar-Orbiting Partnership Satellite, yielding results that are consistent with the on-orbit optical performance data.

The field of contamination control has evolved to deal with increasingly sophisticated instruments developed in response to increasingly complex missions. Although there have been failures and degraded instrument performance due to contamination, contamination control methods have been largely successful to date. However, due to improvements in technology and the desire for more sensitive science measurements, spacecraft are no longer clean enough to meet more stringent contamination requirements. New contamination control engineering methods will require institutional investments. As a first step toward identifying appropriate areas for these investments, a “brainstorming” exercise is performed addressing some of the more important areas where improvements are needed.

The Molecular Adsorber Coating (MAC) is a sprayable coatings technology that was developed at NASA Goddard Space Flight Center (GSFC). The coating is comprised of highly porous, zeolite materials that help capture outgassed molecular contaminants on spaceflight applications. The adsorptive capabilities of the coating can alleviate molecular contamination concerns on or near sensitive surfaces and instruments within a spacecraft. This paper will discuss the preliminary testing of NASA’s MAC technology for use on future missions to Mars. The study involves evaluating the coating’s molecular adsorption properties in simulated test conditions, which include the vacuum environment of space and the Martian atmosphere. MAC adsorption testing was performed using a commonly used plasticizer called dioctyl phthalate (DOP) as the test contaminant.

The Molecular Adsorber Coating (MAC) is a sprayable coatings technology that was developed at NASA Goddard Space Flight Center (GSFC). The coating was designed to address molecular contamination concerns on or near sensitive surfaces and instruments within the spacecraft for flight or ground-based applications in vacuum conditions. This paper will discuss the use of NASA’s MAC technology to isolate and protect the critical laser flight optics of the Advanced Topographic Laser Altimeter System (ATLAS) instrument on the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2). MAC was strategically used during thermal vacuum (TVAC) testing efforts to reduce the risk of contaminating the laser optical components from non-baked items and other unknown outgassing sources from the chamber environment. This paper summarizes the design and implementation efforts, and the chemical analysis of the MAC samples that were used during two recent TVAC tests for the ICESat-2/ATLAS mission.

During Integration and Testing of large optical systems the exposed optics can become contaminated with many particles from the various test and integration environments that the hardware is exposed to. The particles may cause degradation of mirror performance due to stray light scatter and optical throughput loss due to obscuration. Cleaning the optics can be a challenge depending on what type of particles are found on the optic, how extensive the coverage, how long they have been on the surface, the type (beryllium), size and concave structure of the optics, as well as the optical coating on the surface.

Common ways to clean optics include drag wiping the surface with various cloths and solvents; blowing off the optics with ionized gaseous nitrogen (GN2); blowing off the optics with carbon dioxide (CO2) (snow gun). With these techniques the surface could be damaged if hard particles such as metallic pieces, are pushed along with the gas or wipe. Drag wiping also had the potential to smear acrylic adhesive particles and other molecular contaminates that may be present on the surface. Ionized GN2 at low velocity does not remove enough particles to make it effective at cleaning. At high velocity GN2 can damage thin light-weighted mirror substrate as well as dislodge beryllium dust from the exposed machined surface causing a potential health hazard. It also dislodges particles in a chaotic fashion potentially causing them to be forced into other sensitive regions of the optics or system. CO2 snow similarly causes all dislodged particles to move in an uncontrolled fashion. CO2 snow also significantly changes the temperature of the optic, and in the case of light-weighted space telescope optics with a thin face it can cool the surface enough to cause condensation, which in turn can leave difficult-to-remove evaporation marks on the optical surface.

A new technique utilizing a fine bristle brush was developed for JWST to safely and effectively remove the majority of the particles. This technique removes particles in a controlled fashion making sure they do not migrate to other parts of the telescope, and uses very light pressure, which avoids damage to the coating from metallic particles. Not all particles are removed but the surface is left in a much cleaner state without loose particles present. Several of the individual types such as adhesive and large fibers can be removed later with a spot cleaning technique.

Potential damage from the brush to the surface was evaluated utilizing several different techniques.

The James Webb Space Telescope (JWST), expected to launch in 2021, will be the next premier observatory for astronomers worldwide. It is optimized for infrared wavelengths and observation 1.5 million kilometers from Earth. JWST includes an Integrated Science Instrument Module (ISIM) that contains the four main instruments used to observe deep space: Near-Infrared Camera (NIRCam), Near-Infrared Spectrograph (NIRSpec), Mid-Infrared Instrument (MIRI), and Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS)¹.

JWST will make ultra-deep near-infrared surveys of the Universe to see back 13.5 billion years to “First Light” which occurred 100 – 250 million years after the Big Bang when the first stars and galaxies formed. Its ability to observe very high redshifts will enable astronomers to study the faintest galaxies, observe stars forming within clouds of dust, determine how galaxies evolved, and search for exoplanets^1,2.

JWST is extremely sensitive to even small amounts of contamination, which can directly cause degradation to performance of the telescope, and impact the mission lifetime. Contamination control has been an essential focus of this mission since conception of the JWST observatory³.

The James Webb Space Telescope Primary Mirror Segment Assemblies (PMSAs) and Secondary Mirror Assembly (SMA) were cleaned at the Johnson Space Center (JSC) in January 2018. In order to quantify the effectiveness of the cleaning, the same cleaning process was performed on the PMSA and SMA traveling witness wafers. These wafers have accompanied their respective mirror segments from their arrival at the Goddard Space Flight Center, through transport to JSC, and ultimately their exposure in Chamber A for cryogenic testing. The traveling wafers were analyzed using an Image Analysis automated microscope both prior to and after the cleaning. The resulting data showed that the PMSA wafers’ Percent Area Coverage (PAC) reduced by 83.5% on average, from 0.1524 PAC to 0.0251 PAC. The SMA wafer’s PAC decreased by 97.2%, from 0.1194 PAC to 0.0034 PAC. Further analysis of the particle size bins was completed in order to calculate their particle distribution slopes. The slope of the PMSA wafers increased by 0.025 on average, and the SMA wafer slope increased by 0.066. This indicates that the ratio of large to small particles slightly increased after the cleaning across all mirror segments. Visual inspections of the wafers and the flight PMSAs and SMA showed considerable and comparable particulate coverage improvements, thus leading to the conclusion that the average PAC on the PMSAs and SMA improved by the same factor as their respective wafers.

National Ignition Facility (NIF) is the world’s most energetic laser system, capable of delivering over 1.8 MJ of energy at UV. After operating for over 10 years and working continuously to improve the damage resistance of the optics, there seems to be a disconnect between the offline measured damage performance of optics and the actual lifetime of an installed optic. Recently, we have discovered a source of laser-induced optic damage that originated from particles ejected from damage of a neighboring disposable optic. We were able to replicate this contamination-driven laser-induced damage experimentally in an offline facility and have developed a phenomenological model based on the results which includes particle generation, particle cleaning, and particle damage as a function of damage size as well as laser fluence. The model was able to accurately predict the multi-shot process of the offline experiment. Since then, we have used this model to predict online damage performance on NIF on a series of very high energy shots to test the validity of model with surprising results that shows the success of the model along with new features that will need to be address. This work was performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. (LLNL-ABS-745711)

The air present in every spacecraft will vent during launch, so spacecraft hardware must be designed sufficiently to withstand the resulting pressure differences that develop as the external pressure decreases from that at sea level to negligible levels in about 2 minutes. Pressure differentials can be significant, especially for honeycomb panels within which air must travel through many small perforations in honeycomb cell walls to reach vent ports, and cases have been reported of honeycomb panels exploding during launch. Thus, work has been conducted at Ball Aerospace to not only model air venting from honeycomb panels, but also develop techniques to simplify the simulations. Predictions have compared well with pressure differences measured in a test panel during depressurization tests. The results provide confidence in the ability to predict pressure differences in honeycomb panels of any shape and cell size.

Contamination modeling provides important insights into the transport mechanisms among sources, sinks, and sensitive surfaces. It is an indispensable tool in the discipline of contamination control and is often used to predict the outcome of a contamination event. As problems in contamination control can span multiple flow regimes and types of contaminants, it is important to develop such capability using a versatile tool. The Open source Field Operation and Manipulation (OpenFOAM) open source software is a customizable numerical solver that provides a solid foundation for the development of contamination modeling capability. It is a computational fluid dynamics tool that over the years has added particle tracing capabilities rendering it extremely versatile for transport modeling. In this paper, we show how OpenFOAM can be modified for modeling particulates settling under a flow field and molecular flow under the space vacuum environment. We show how new boundaries are created to simulate sources and vents and the accumulation of contaminants on surfaces over time. Finally, we discuss performance of OpenFOAM using our load-balanced Atlas Cluster on a computational intensive simulation.

Contamination control engineers are constantly challenged by time-consuming processes during the system assembly, integration and test phase for spacecraft. Hardware components, subassemblies, and integrated systems must be visually inspected throughout the process, and any signs of contamination found are usually analyzed by processes that can take days to complete. Portable Raman spectroscopy is a promising technology for spacecraft integration, where it may be possible to probe hardware or witness surfaces and identify contaminants throughout the assembly, integration and test phase. This study explored detection of five common spacecraft contaminants with portable Raman spectroscopy: silicone, hydrocarbon, fluorocarbon, ester, and a glycol polymer. It was found portable Raman spectroscopy can provide a quick-look capability which can be followed by more detailed contaminant quantification analysis techniques. In this way, portable Raman spectroscopy can aid contamination control engineers in providing actionable information to projects earlier in the assembly, integration and test phase of the project lifecycle.

The ExoMars 2020 MOMA (Mars Organic Molecule Analyzer) Gas Chromatograph Mass Spectrometer instrument is a key component of the Pasteur life detection payload on the ExoMars 2020 rover mission. As such it is subject to Planetary Protection requirements which include being sufficiently contamination controlled to preclude false positive or false negative results due to contamination. Detailed evaluation of the interaction instrument background and the other performance attributes of the Gas Chromatograph Mass Spectrometer during testing under Mars like conditions of temperature and pressure was carried out. This was the first test of the fully integrated test of the Gas Chromatograph Mass Spectrometer. The data from the testing was evaluated in four different modes of data analysis commonly used for processing gas chromatograph mass spectrometer data. This analysis showed that the instrument was capable of meeting its detection limit requirements. The analysis of the data also showed that the probability of false positives and false negatives within the specified instrument performance capabilities was minimal as evaluated at this time.

Contamination control engineers provide critical plans to monitor, mitigate, and reduce the impact of molecular and particulate contamination on spacecraft systems. Witness monitoring programs are dependable methods that utilize strategically placed witness samples on space flight hardware to monitor particulate and molecular contaminants during the assembly, integration, and test (AI&T) phases. Traditionally, optical characterization of these witness plates is the tool to determine the presence of molecular films on space flight hardware in the AI&T environment. Once a visual inspection or optical measurement identifies the presence of a contaminant, analysts collect tape lifts and wipe samples from the witness plate for analysis in an analytical lab with a potential contaminant identified within 24 hours. To speed up this process and reduce the impact to project schedule and cost the use of a non-invasive and in situ method for optical witness plate program with portable Raman spectroscopy to detect molecular contamination on spacecraft was explored.

The ExoMars 2020 Rover is a life detection mission, and is classified as Planetary Protection (PP) Mission Category IVb, the first IVb mission since the Viking missions. Mars Organic Molecule Analyzer – Mass Spectrometer (MOMA-MS) is a life detection instrument for the rover. To meet the stringent bioburden requirement of 0.03 spore/m2, the MS is subjected to Dry Heat Microbial Reduction (DHMR) to decrease the bioburden from a measured 88 spores/m2 to 0.009 spores/m2. After DHMR, exposure of the sample path must be kept to an absolute minimum and requires aseptic operations. Aseptic operations include determining the safe exposure time based on the surface area of exposure and particle fallout expected in the aseptic ISO class 5 workspace, preparing an aseptic ISO class 5 workspace, and using sterile garments and tools. During the exposure activity the environment is monitored with active and passive fallout for bioburden and real time airborne particle counts. Sterile tools are handled by a two person team so the operator touches only the tool and not the exterior surfaces of the sterilization pouch, and a sterile operating field is established as a safe place to organize tools or parts during the aseptic operations. In cases where aseptic operations are not feasible, localized DHMR is used after exposure. Any breach in the PP cleanliness can necessitate repeating instrument level DHMR, which not only has significant cost and schedule implications, but also is a risk to hardware that is not rated for repeated long exposures to high temperatures.

Spacecraft design relies upon contamination control plans that specify proper material handling and material choices. Typical manufacturing areas employ control plans that monitor air quality for particulate contamination. All individual materials of construction are controlled for outgassing and purity and are required to comply with ASTM E595 vacuum outgassing requirements. Recently, ASTM E1559 test methods are being used to characterize outgassing of entire systems. However, there is still a significant gap in testing for interactions of multiple materials that may cause a variety of problems, including contamination. Requirements for assemblies such as electronics, circuit cards, and sensors are passed on to subcontractors, often without details beyond meeting ASTM outgassing requirements and particulate standards and neglecting information on design compatibility. Guidance typically is not provided on how to execute assemblies, manage material interactions, or restrict materials that should not be used in manufacturing. Significant contamination can occur during manufacturing from manufacturing tooling aids, fixtures and fixturing designs, accidental or incidental contact, instability of in-use materials (e.g., adhesives), or incompatible material choices in the system design. This contamination may not be detected until failures occur at final assembly or vacuum bake-out because typically limited sampling is specified for cleanliness verification during assembly operations. As innovations to system designs continue, designing and controlling the manufacturing of components and assemblies will require improvements and detailed guidance to minimize material compatibility issues and contamination. Examples of manufacturing tooling aids or material interactions that can lead to contamination will be provided along with recommendations to mitigate the contamination.

Realizing the main amplification system without window glasses is important for high-power laser devices. Not only optical components and B-integration of the system are reduced, but also the output capability and beam quality of the system are improved. While the primary problem is how to maintain the cleanliness after the window glasses being removed. In response to this problem, this paper proposes a cleanness control scheme suitable for realizing the windowless operation of the main amplification system.Take one main amplification system of a high-power laser device for example, some work are conducted: integrated design of optical pipelines, introduction of air knives, and simulation analysis of airflow field and related parameters. The integrated design of the beam tubes makes the entire main amplification system to maintain a closed environment.The air knife which can generate a high-speed air curtain and block the exchange of airflow, divides the entire system into three parts: main amplifiers, beam tubes, other optical components. For each part, we use in-situ control to achieve cleanliness. To beam tubes and main amplifiers, theoretical analysis and verification of gas flow field characteristics for different process parameters are conducted. For other components, the effectiveness of air knife air curtain protection has also been experimentally studied and analyzed. Finally, it provides important guidance for realizing the remove of the window glasses of the main amplification system.

Cleanliness management is essential for the safe operation of high power laser systems. In order to maintain the transmittance and minimize the optics damage, we should protect the optics surface with coatings from contamination. Large aperture optics in the vacuum is easily contaminated by airborne molecular from material outgas. In this paper, we introduce the techniques of cleanliness management in SG-II-UP laser facility. The online monitoring of surface airborne molecular contaminant is carried out with quartz crystal microbalance. We investigated the influence of the airborne molecular contaminant on the 351nm transmittance of fused silica optics with sol-gel coatings.

Contamination outgassed from spacecraft's materials can degrade optical devices in orbit. Therefore, solving the contamination problem is important because it in uences the success of spacecraft missions. In this study, methyl red (MR) and oleamide were decomposed in vacuum by TiO₂ photocatalyst. Absorbance spectra, mass decrease and GC/MS were measured after and before decomposition. In vacuum, TiO₂ could decompose MR to intermediate products, whereas it could not decompose the intermediate products to volatile substances because TiO₂ cannot open benzene rings of the intermediate products. On the other hand, TiO₂ could decompose oleamide to volatile substances even in vacuum. However, decomposition by TiO₂ stopped after a certain period of time in vacuum. The decrease in mass for oleamide by photocatalytic reaction in vacuum was enough compared to standard molecular contamination levels.