This PDF file contains the front matter associated with SPIE Proceedings Volume 12224, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

This video presentation is of the live keynote James Webb Space Telescope (JWST) address.

This paper summarizes a recent numerical analysis of water vapor and volatile condensible material deposition on the James Webb Space Telescope from the initial orbit insertion up to 180 days post launch. The analysis utilized 17 distinct geometry files capturing observatory configuration changes during the deployment. Surface temperature was set from a time-dependent thermal analysis solution. A vapor pressure model was used to calculate the net water ice adsorption. Molecular contamination included a contribution from UV photopolymerization. The analysis predicted levels of ice and molecular accumulation were found to be within the allowable limits specified by the observatory contamination control plan.

The James Webb Space Telescope (JWST) has a primary mirror, made of 18 segments, and a secondary mirror (SM) that are used to direct the light of desired targets. After launch, the secondary mirror assembly (SMA) is stowed for approximately 10 days and is subject to molecular contamination outgassing from the cavity of the secondary mirror support structure (SMSS) in-board hinge (IBH) which contains cables, motors, resolvers, and coatings. The main concern during this period before SMA deployment is the accumulation of ice due to the lack of a heater on the SMA. The temperature differentials between the IBH surfaces and SMA could cause redistribution of water vapor contamination. To address this concern, single layer insulation (SLI) was reconfigured to direct the vent path of IBH outgassing sources away from the SM. Two separate thermal vacuum (TVAC) tests were performed to quantify this contamination: a Z307 ASTM E 1559 materials test of the radiator paint used on the motor of the IBH and a separate test on the hinge motor from the primary mirror backplane assembly (PMBA) qualification engineering test unit (ETU). The PMBA ETU hinge was similar in design to the IBH. These tests approximately followed the predicted SMA predeployment thermal environment. To quantify source rates in case of a leak in the new SLI enclosure or baffle, the motor and resolver sides were separated, and quartz crystal microbalances (QCM) were used to measure the deposition of water. The SLI redesign and implementation and outgassing measurements to understand leak effects from the IBH were essential to mitigate the deposition of contamination on the SMA.

The James Webb Space Telescope (JWST) is a multi-national program with Instruments and hardware supplied by companies all over the world and numerous states in the United States. In order to transport larger assemblies, like the Optical Telescope Element / Integrated Science Instrument Module (OTIS), and ultimately JWST, the Space Telescope Transporter for Air, Road and Sea (STTARS) was designed and constructed. STTARS is a massive mobile cleanroom (longer than 2 semi-trailers) that provides an ISO class 7 payload environment while being transported by road, airborne and marine vehicles. Temperature, humidity and particle counts are controlled and continuously tracked, with fallout and NVR witness samples for confirmation. Instruments or sensitive hardware may be purged continuously during transport. STTARS has 5 main components: the upper tent frame, lower tent frame, pallet, strong back and lid. After transporting OTIS to Northrup Grumman (NG), STTARS was modified to increase its height to house the JWST Observatory on its voyage to French Guiana. This new configuration was designated Observatory STTARS (OSTTARS). OSTTARS was too tall to travel by C5 aircraft, so the trip to the launch site was made by ship. Through JWST’s land, air and sea transports, STTARS and OSTTARS kept JWST hardware exceptionally clean and safe.

The James Webb Space Telescope (JWST) program was supported by a unique team of Contamination Control Technicians (CCTs) who received Webb specific training from Webb Contamination Control Engineers (CCEs) and Lead CCTs. Webb’s design featured exposed optics and thermal control surfaces. These remained susceptible to damage or degraded performance from particulate and molecular contamination if a systematic approach to controlling contamination generating processes was not strictly enforced. Cleanroom maintenance is typically performed by janitorial services throughout the industry. However, Webb’s requirements necessitated a team who safely and effectively performed various tasks including daily facility cleaning to flight hardware handling. The CCT team performed daily cleanings of the processing facilities and effortlessly switched to inspecting and cleaning flight hardware, assisting CCEs with inspections, lab work, and performing on-demand cleaning of all items entering the cleanroom facilities. The versatility of the CCT team was on display as each CCT took on additional responsibilities and maintained ownership of subtasks such as Image Analysis and Ellipsometry, transportation, Self-Contained Atmospheric Protection Ensemble (SCAPE) suit support, inventory, and cleanroom garment laundering, while supporting the demanding launch campaign. The CCTs maintained a constant presence on the integration floor, allowing for quick resolution to CC issues and elevation of more serious problems that required further guidance. These dedicated CCTs broke new ground in efficient collaborative work with the integration and testing team while cultivating positive attitudes towards contamination control.

The James Webb Space Telescope (JWST) Optical Telescope Element + Integrated Science Instrument Module (OTIS) went through environmental testing at the Goddard Space Flight Center. The vibration and acoustic tests occurred outside of cleanrooms. These areas are typically around ISO Class 8, far out of specifications for JWST. Through collaboration between the OTIS Mechanical and Contamination Engineering teams, a portable clean enclosure was designed, built, and verified to prevent contamination of the sensitive OTIS assembly. This manuscript describes the process of designing and building this enclosure, including materials selection and High Efficiency Particle Air (HEPA) filtration. This enclosure also provided environmental control with a portable air conditioning unit to control the relative humidity level enabling personnel to work within it. The manuscript emphasizes working in a systematic order to maintain cleanliness and integrity. “Clean as you go” during construction was a top priority to ensure that this critical Ground Support Equipment (GSE) was acceptable. The process of installing the walls and then sealing their internal and external surfaces with approved films was critical to maintaining OTIS integrity. This proved important because OTIS was in the enclosure for months longer than originally planned. This manuscript concludes by reviewing the process used to verify that the OTIS clean enclosure could achieve acceptable contamination level fallout accumulation for use during the vibration and acoustic testing and then verifying that the predicted performance was achieved after testing was complete.

In order to maintain cleanliness during preparations for JWST’s OTIS (Optical Telescope Element-Integrated Science Instrument Module) Cryogenic Thermal Vacuum Test, a cleanroom was built that attached directly to the 60-year-old Chamber A. The cleanroom and chamber were outfitted with independent environmental control systems each providing ISO Class 71 air cleanliness. To maintain balanced, positive pressure in both the cleanroom and chamber volumes, a special control protocol was developed and successfully implemented. Dual back-up environmental control units (one each for the chamber and cleanroom) were installed just outside the building to provide environmental control redundancy due to a single source chilled water supply and weather threats. In addition, lack of a dedicated cleanroom airlock facilitating clean ingress and egress made it necessary to perform additional cleaning and packaging, as well as augment the uncontrolled truck lock space with small clean tents for pre-cleaning. Special procedures were developed to allow ingress of extra-large support equipment required for load testing of the cleanroom crane, installation of optical equipment in Chamber A and accommodation of the OTIS shipping container. A thorough bake-out and cleaning of Chamber A was also necessary to reduce volatiles from the shroud’s black thermal paint and to reduce particle fallout. Acrylic adhesive fracture discovered during early cryo-testing represented a significant challenge that was successfully mitigated prior to OTIS testing. A dedicated team of Contamination Control (CC) Technicians was specifically trained to clean support equipment and screen materials entering the cleanroom and chamber to ensure cleanliness and vacuum compatibility.

A venting equation commonly used to describe the transient evolution of pressure within a volume containing an outgassing or offgassing source and a restrictive vent conductance under conditions of molecular flow has been solved analytically. Solutions are found for sources of finite thickness characterized by classical diffusion-limited behavior (proportional to inverse square root of time), as well as responses for thick material sources often observed in testing that are characterized by a more general form of power-law decay, up to inverse time behavior associated with surface desorption. Solutions involve evaluating integrals where both numerators and denominators of the integrands diverge with time, making wide-ranging transient solutions difficult to directly compute numerically. Usually, one can avoid evaluating these integrals by assuming quasistatic conditions at long time scales. A novel approach is used in this work to analytically produce solutions by generating bespoke mathematical functions, some of which solve integrals that have apparently had no previous analytical solution.

Maintaining molecular cleanliness during the JWST’s Optical Telescope/Instrument Module (OTIS) Cryogenic Thermal Vacuum (TV) test campaign was critical to the success of its optical mission on orbit. In the thermal vacuum tests leading up to the final cryogenic test to validate the OTIS flight hardware, NASA Johnson Space Center’s (JSC’s) TV Chamber A was fully characterized for molecular contamination. It was found to contain common volatile condensable materials (VCM), including hydrocarbons, plasticizers, and silicones, all of which absorb in JWST’s infrared wavelength region. Due to the risks involved, cleaning molecular contamination from the OTIS mirrors was not an option and heating the Primary Mirror (PM) segments would have also been a risky and expensive endeavor. As a result, a monitoring process was developed and implemented during four different Pathfinder or risk reduction tests that were scheduled to occur prior to the flight hardware test. The goal was to quantify and assess the risk of molecular contamination depositing on the PM resulting from relatively warm chamber shrouds “leading” colder PM mirrors during warmup, by a margin of 10-50 Kelvin (K). This was accomplished using Cryogenic Quartz Crystal Microbalances (CQCMs), held at temperatures slightly cooler than the segments to signal the onset of contamination events. Per the JWST Contamination Control Plan (CCP), the total Primary Mirror molecular allocation requirement was 50 angstroms. In all tests, the results showed an average accumulated molecular contamination of <10 angstroms.

The James Webb Space Telescope (JWST) launched from the Centre Spatial Guyanais (CSG) in December 2021. JWST’s requirements permitted processing in International Organization for Standardization (ISO) Class 7 or better facilities, but CSG was only equipped with ISO Class 8 facilities. To temporarily upgrade the air cleanliness in the Payload Processing Facility, Fueling Hall, and Final Assembly Building Encapsulation Hall, NASA provided two portable High Efficiency Particulate Air (HEPA) and carbon filter walls that were used in each location. The walls were comprised of stacks of two modules high and arranged in push-push configurations as shown to be most effective via Computational Fluid Dynamics simulations of expected floor layouts in each facility. After delivery to NASA’s Goddard Space Flight Center in 2020, the walls underwent initial verification measurements inside a cleanroom and validation testing in an uncontrolled area to quantify their improvement of air cleanliness and particle and molecular fallout. Validation testing showed improvements of 83-99% for airborne particle counts, 79-91% for particle fallout, and 50- 90% for molecular fallout. The particle improvements were applied to the contamination budget analysis that tracked current and predicted future cleanliness against End-of-Life requirements for JWST’s critical surfaces. At CSG, the walls successfully maintained an ISO Class 7 environment or better within their envelope in each location, despite their presence in ISO Class 8 facilities with dense integration operations.

Over the life of the James Webb Space Telescope (JWST), Integration & Test (I&T) has taken place in areas that needed considerable work to make the facility itself and/or the protocols used while working in the rooms suitable to meet JWST percent area coverage (PAC) and molecular accumulation requirements. In addition to normal particulate matter, JWST had a uniquely significant challenge: fibers! Fibers not only cause much higher PAC levels, but they also risk damaging the angstrom sized Near Infrared Spectrometer (NIRSpec) microshutter array (MSA), which is critical to NIRSpec instrument performance. The primary emphasis of this paper is to address particulate and fiber contamination. The success of the JWST mission required effective cleanrooms, protocols, and mitigations in non-cleanroom areas that were pressed into service to house contamination-sensitive optics and scientific instruments. Some presented profound challenges. These included: NASA’s 60-year-old Johnson Space Center (JSC) Chamber A, which had never been used for anything contamination-sensitive, and the European tropical launch facilities, which were designed to meet International Standard Organization (ISO) Class 8 processing for communication satellites. The final challenge for JWST, as if to stare us in the face and say, “I dare you to try and make me clean enough,” was preparing the 4 areas in the Centre Spatial Guyanais (CSG) Final Assembly Building (BAF) located in French Guiana, a building in which one entire side opens for Ariane 5 rocket ingress and egress. This paper will describe our initial evaluation processes and the actual work undertaken to transform even the most challenging areas into first class cleanrooms that met JWST particulate and fiber requirements.

The James Webb Space Telescope (JWST) is a large, infrared space telescope operating at Lagrange point 2. JWST is a joint effort between NASA, ESA, and CSA and was launched from the Centre Spatial Guyanais (CSG) on an Ariane 5 rocket in December 2021. The three-month launch campaign utilized enhanced contamination controls to meet JWST’s strict cleanliness requirements. Prior to launch, JWST was permitted to only be exposed to ISO Class 7 cleanrooms, whereas the processing facilities at CSG are ISO Class 8. NASA, ESA, Arianespace, and CNES implemented temporary upgrades to the nominal contamination control operations for the launch campaign unique to JWST, including the use of vetted, portable High Efficiency Particulate Air (HEPA) filter walls, pre-entrance cleanliness acceptance surveys of each facility and the intra-plant transporter, tightened cleanroom protocols, upgraded garmenting and laundering techniques, cleaning of Self-Contained Atmospheric Protection Ensemble (SCAPE) suits, increased maintenance, staffed precleaning stations, adaptation of the house purge network, and a contamination control enclosure atop the Ariane 5 launcher prior to fairing encapsulation. The Ariane 5 fairing interior and Vehicle Equipment Bay membrane also received multiple cleanings, detailed inspections, and verification sampling to achieve necessary cleanliness levels. The fairing itself was specially sealed to protect the inner environment with just a small, doored porthole accessible via diving board for final closeout of the purge interface. All these enhancements together allowed JWST to meet its contamination requirements for launch, ensuring successful post-separation deployments and mission science.

In preparation for the James Webb Space Telescope (JWST) launch at the Centre Spatial Guyanias (CSG) in French Guiana, particulate contamination accumulation predictions were necessary for each facility in which the hardware would be exposed because the Telescope would be uncovered in each of the facilities and had strict particulate requirements. These included facilities for final integration and testing, fueling, transportation and encapsulation. Minimal heritage data existed from CSG and previous launch campaigns to use as a basis for contamination predictions. Data from the Automatic Transfer Vehicle and Herschel-Planck launch campaigns were used in conjunction with facility monitoring data provided by the European Space Agency (ESA) and data collected during a JWST working group visit to CSG. These campaigns were conducted at varying cleanliness levels that were typically less stringent than JWST requirements. Each facility was evaluated using the data provided and likely performance improvement with the addition of High Efficiency Particulate Air filter (HEPA) banks operating when possible. Once the launch campaign was completed, the predicted fallout was compared with actual data collected throughout the campaign. Based on the actual measurements, JWST’s primary and secondary mirrors turned out to be much cleaner than what was predicted.

A general, lumped-parameter, control volume equation is developed to describe the rapid loss of pressure associated with a launch vehicle fairing jettison event in its initial phase. Beginning with a general mass conservation statement, a sonic constraint is applied to the expanding gap between receding fairing halves to produce a statement for transient density. This is related to fairing pressure by assuming the expansion may be described by a polytropic process. A generic, singlestep, lateral fairing half separation case is created and explored for illustrative purposes.

The James Webb Space Telescope (JWST) spent considerable time in multiple clean facilities during its launch campaign at the Centre Spatial Guyanais (CSG) in French Guiana. Throughout this time, it was imperative that personnel wear approved cleanroom or safety suits when working in proximity to the JWST observatory. This proved to be challenging for two reasons: 1) A large quantity of NASA cleanroom suits needed to be shipped to CSG to account for the heavy volume of NASA and ESA personnel requiring access to the clean facilities. It became evident that shipping clean suits from the US to CSG in a timely fashion during the launch campaign would be challenging. Consequently, a backup plan needed to be established to avoid running out. 2) For safety purposes, Self-Contained Atmospheric Protection Ensemble (SCAPE) and Splash suits were required for hazardous operations. Neither type of suit was cleanroom compatible; therefore, a viable cleaning process needed to be developed to ensure both types of suits met JWST’s approved cleanliness standards. The NASA Contamination Control (CC) team partnered with CSG’s S5E cleanroom and suit processing team. The teams were able to make modifications to the S5E facility to create a NASA approved makeshift clean environment where NASA cleanroom suits and CSG Splash suits were inspected, folded, and bagged for cleanroom use once they were washed and dried. Since SCAPE suits could not be cleaned using conventional methods, a procedure was developed to clean and inspect the suits by the CC team in a temporary clean environment prior to fueling.

The launch of the James Webb Space Telescope (JWST) was successfully performed by Ariane 5 from French Guiana on December 25th 2021. The unique nature of the JWST mission led to various adaptations of the Ariane 5 launch system to fulfill stringent cleanliness and hygrometry requirements all along the launch preparation. JWST integration and test activities in the Final Assembly Building (BAF) had to be performed in ISO Class 7 equivalent conditions under Volatile Organic Compounds (VOC) protection and monitoring. For this purpose, a dedicated air supply system equipped with Airborne Molecular Contamination (AMC) filters was installed in the umbilical mast. The fairing itself was specially sealed to protect the inner environment, and to, guarantee ISO Class 7, the BAF Composite Hall (BAF-HC) facilities were upgraded with a removable “Air Shower Curtain” (AShC) containment enclosure between the mobile platforms around JWST. The preparation of these Ariane 5 launch system adaptations started several years before the launch campaign with close cooperation and coordination between Arianespace, ArianeGroup, the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). This paper describes their specificities and addresses the challenges experienced to achieve the successful mission preparation.

The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) is a Jet Propulsion Laboratory (JPL) and Caltech led mission which will perform the first near-infrared all-sky survey to address the goals of NASA’s astrophysics division. SPHEREx accomplishes these surveys of the entire celestial sphere with an infrared telescope cooled to cryogenic temperatures by a passive thermal system. Because the SPHEREx payload has both an optical telescope and a passive thermal system, it is highly sensitive to particulate contamination. In this work the JPL Contamination Control (CC) group develops a computational physics framework to model particulate transport contamination from the fairing environment during launch, which is the largest particulate contamination source for most missions. Even with strict contamination control during ground processing, the launch environment can induce enough particulate contamination to exceed the scientific requirements of sensitive missions. For SPHEREx, particulate contamination in the telescope has a direct impact on the quality of the scientific data gathered during the surveys. Additionally, particulate contamination of the thermal system has a detrimental effect on its ability to cool the instrument to its cryogenic operating temperatures and maintain temperature stability. Due to these sensitivities it is imperative for SPHEREx that the particulate contamination from launch be comprehensively understood and mitigated wherever possible. The computational physics framework developed in this work is used to obtain precise estimates of particulate contamination on the SPHEREx payload and provides mitigations to ensure the mission meets its scientific requirements.

Psyche is a NASA Discovery-class mission that is designed to visit the metallic asteroid (16) Psyche to determine its origin and conditions of formation and to understand whether parallels between the asteroid and the cores of terrestrial planets can be drawn. [1] The Psyche instrument suite consists of a magnetometer, a gamma ray and neutron spectrometer (GRNS), the Psyche Multispectral Imagers (PMI) and the Deep Space Optical Communications (DSOC) technology demonstration payload. PMI and DSOC drive the overall contamination sensitivity of the Psyche mission. Unique contamination analysis challenges for the Psyche mission included: developing a novel molecular contamination transport model for parametric assessments of outgassing risk [2]; implementing a contamination-induced optical throughput degradation model; justifying the need for a T-0 purge and deployable aperture cover for DSOC; and modelling the sputtering and transport of contaminants due to electric propulsion system plume impingement. Contamination control implementation challenges on Psyche included: using a commercial telecommunications satellite bus to host scientific instruments; interfacing with a new spacecraft contractor; and creating a “chamber inside a chamber” for spacecraft TVAC to protect JPL’s 25ft Space Simulator. [3] This work describes JPL’s Contamination Control program for the Psyche mission, including the planning and execution of strategies to resolve those mission-unique challenges in preparation for launch.

NASA’s Europa Clipper mission will conduct a detailed reconnaissance of Jupiter’s moon Europa and investigate whether the icy moon could host conditions suitable for life. To perform these tasks, the spacecraft will carry several scientific instruments, including cameras, mass spectrometers, radars, magnetometers, plasma sensors and dust analyzer. These state-of-the-art instruments are very sensitive to molecular contamination; hence it is important to properly design preferential venting paths that minimize the transport of contaminants to the instruments sensitive surfaces. The JPL Contamination Control Group developed a physics-based approach to quantify the amount of contaminants escaping from the thermal blankets vents. This approach includes a thorough design of the thermal blankets and vents in the Europa Clipper geometrical model and a detailed analysis of the transport of contaminants from outgassing components underneath the thermal blankets to the vents. The physics-based thermal blankets venting model enhances the ability to assess and control outgassing contamination on Europa Clipper, and subsequently to properly design venting locations that provide a preferential escape path for outgassed molecules. The model also provides more accurate results compared to the historic approach (area ratio) widely used in literature to estimate outgassing from thermal blankets vents.

This video presentation is for the development and results of APL box-level effusion cell for outgassing verification of Europa Clipper hardware.

Well-established procedures for the characterization of contamination during outgassing usually involve total mass measurements through quartz crystal microbalance (QCM). Recently, the addition of mass spectrometry (MS) measurements to these data has become more common. The combination of both high sensitivity QCM and MS data may lead to a better understanding of the physics taking place during outgassing contamination processes. The way to do so is to complement the basic measurements of total mass loss on QCMs by the identification of each species and the quantitative determination of each species contribution. In a first characterization step, the thermogravimetric analysis of contaminants deposited on QCMs allows a partial species separation that helps exploiting mass spectrometry data. In return, these data permit a finer species separation. The key to these measurements is to obtain sufficient signal to noise ratio in the mass spectrometer. Though outgassing of space materials is not done the same way in Europe (multi-temperature steps, ECSS-Q-TM-70-52A) and in the US (isothermal, ASTM E-1559-09), both tests could be used to perform a first species separation, as reported here. Most species outgassed by a few common materials were identified (and quantified) through TGA and MS coupling. As reported in a companion paper, the knowledge of these species’ spectra then allows the analysis of the MS data during the initial outgassing phase, determining the quantitative outgassing of each species and leading to the improved comprehension of the physical laws ruling outgassing.

Progress was performed recently on the separation and characterization of the chemical species outgassed by space materials, relying on the assessment of thermogravimetric analysis (TGA) peaks by mass spectrometry (MS). A companion communication reports on this experimental technique and the first level processing of these MS data, which often allows determining which are the outgassed species, and their MS spectra. This communication focusses more on the second analysis step, i.e. the study of the MS data acquired during the initial outgassing phase. Ancient simpler outgassing analyses based on total mass measurements only, most of the time on quartz crystal microbalances (QCMs), cannot realistically determine the separate contribution of different species, even though some models consider the contribution of several species, which are indeed more “mathematical species” than physical ones. In contrast, this new approach, also taking into account the MS measurements during the outgassing, and known species spectra (from the TGA/MS analysis done previously), allows a more realistic determination of the contribution of each real chemical species to the total outgassing. Even though results are not yet final and perfect, measured outgassing fluxes from several species and materials are presented. Their physical analysis, through comparison and fit by diffusion or other possible outgassing laws are also presented. At this level, they clearly point to diffusion laws, rather than to any other outgassing law, although not necessarily always Fickian diffusion. This method was applied to typical US or European outgassing approaches, with either isothermal ASTM-1559 outgassing tests or multi-temperature VBQC-type tests.

This paper presents data from an experimental characterization of molecular transport in vacuum chambers. Specifically, our goal was to determine the applicability of a Quartz Crystal Microbalance (QCM)-derived sticking coefficients for modeling gray-body view factors. The testing was performed at Blue Origin and at USC, and consisted of performing a QCM thermogravimetric analysis (QTGA) to derive the sticking coefficient from a QCM with a direct line of sight to an outgassing sample. This sticking coefficient was then used in a numerical simulation of the chamber, which was used to compute deposition on a secondary QCM with no direct line of sight to the sample. The simulations were found to greatly under-predict the collection on the second QCM. This under-prediction is attributed to the sticking-coefficient based adhesion model reducing flux on each wall impact. In reality, the contaminant population is composed of a heterogeneous mixture of multiple chemical species. Lower vapor pressure gases collect on the first wall impact, while the remaining molecules continue to bounce around without additional sticking. A temperature-based sticking coefficient applies the reduction on each impacting, leading to an artificially low prediction for gray body deposition onto the final cold surface. For the two considered configurations, we found the model to underestimate the experimental measurements by a factor ranging from 7.2 to 1764.3.

In space applications, more and more organic polymers (adhesives, resins, paints and packaging of electronic devices) are used for their performance, their cost and their flexibility for the design of future satellites. This is especially true in the New Space era, using Off-The-Shelf devices with rarely well-known materials. Outgassed products of these materials under vacuum is a major cause of dramatic flux losses for contaminated optical devices, especially in the UV range. Thus, material outgassing must be studied and better controlled, during all the phases of satellite integration. Fluorescence hyperspectral imaging is a powerful technique for both locating and analyzing materials: their fluorescence spectra can be interpreted as a signature of their physicochemical composition. However, common commercial hyperspectral instruments do not meet the specifications required for such applications: very high sensitivity (SNR < 10000), wide spectral band (ideally 250-1000 nm), integrated multi-wavelength UV excitation and spectral range resolution of about 3 nm. In addition, classical optical design with diopters has to be avoided to prevent chromaticism, which is not compatible with wide spectral bandwidth, especially in UV range. These constraints led us to develop a new dedicated optical design, with the specificity of being catoptric on axis. Therefore, we built a first transportable instrument. In this paper, we present the evaluation of the characteristics of this instrument, its real performance and examples of measurements on flight models. A new version has been designed, using laser sources to limit exposure time of examined materials as much as possible, as they may be degraded under UV light.

Contamination control is required for products and processes that are sensitive to particulate contamination. A cleanroom will be used to create an environment with low particle concentration. In contamination control traditionally the focus is on air cleanliness. This works fine for particles smaller than 5 micrometer. However in many cases particles larger than 5 micrometer are the major threat for products like optical systems. Contamination control of macroparticles (< 5μm) especially visible particles (< 25μm) should focus more on surface cleanliness. Surface contamination can become airborne locally and subsequently deposit on critical surfaces or can be transferred during direct and indirect contact. Many years of collecting particle deposition rate data in various industries has demonstrated the presence of macroparticles and visible particles. Next to limiting the generation of particles and removing airborne particles by ventilation, frequent and effective removal of surface particles by cleaning will reduce the likelihood of contamination significantly. Therefore monitoring surface cleanliness of floors, work surfaces, equipment and tools surfaces in the entire cleanroom will demonstrate the quality of cleanroom use and operational procedure, especially the cleaning program. New instrumentation makes this possible. The role of surface contamination in clean controlled environments and monitoring methods is as important as air cleanliness.

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.

Molecular contamination and space radiation are known to degrade spacecraft performance, but the synergistic effects of the two are less understood. Optical systems are particularly vulnerable to degradation from exposure to contamination and/or space radiation. While traditional contamination assessments throughout the industry generally neglect radiation effects, our study demonstrate the importance of accounting for the space radiation environment when implementing contamination control. In this study, we investigate the impact of these complex degradation mechanisms on optical coatings. Our methodology consists of exposing optical coating coupons to flight-representative contamination and simulated space radiation environments, and we quantify the level of degradation by measuring the transmittance loss after each exposure. Our results show that the cumulative effects of molecular contamination and space radiation degrades optical performance more than either effect alone. In this report, we also discuss the effects of substrate and radiation exposure on the vacuum stability and morphology of the contaminant films.

The tape lift method using 3M 480 tape per ASTM E1216 is commonly used to determine surface cleanliness in the aerospace industry. However, the ease and accuracy of this methodology can be limited due to challenges with the tape adhesive, and sample processing is often manually intensive and subject to human error. As a result, alternative methods such as Gel-Pak® are evaluated against the current 3M 480 tape standard in terms of sampling efficiency, ease of image processing and analysis, and potential for adhesive cross-contamination. We show that alternative surface sampling methodologies can improve efficiency and accuracy of sampling efforts.

Planetary protection requirements help protect other planets and moons from Earth’s biological matter, but restrictions on spacecraft design, compatibility with heat and chemical treatments, and the need for lengthy verification protocols drive cost and schedule. In this work we present an alternative methodology both for detecting surface microbes and for sterilizing them using a low power, pulsed UV laser-based scanning technique that can generate spectral maps of a surface. At sufficient powers, cells can also be eradicated, thus providing both detection and sterilization capabilities. We show how this tool can be practically applied to spacecraft materials to transform current practices.