The Greenhouse Gases Observing SATellite (GOSAT) is a satellite to monitor the carbon dioxide (CO₂) and the methane (CH₄) globally from orbit. Two instruments are accommodated on GOSAT. Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) detects the Short wave infrared (SWIR) reflected on the earth's surface as well as the thermal infrared (TIR) radiated from the ground and the atmosphere. TANSO-FTS is capable of detecting wide spectral coverage, specifically, three narrow bands (0.76, 1.6, and 2 micron) and a wide band (5.5-14.3 micron) with 0.24 wavenumber spectral resolution. TANSO Cloud and Aerosol Imager (TANSO-CAI) is a radiometer of ultraviolet (UV), visible, and SWIR to correct cloud and aerosol interference. The contaminant deposition on the sensors significantly affects the sensing capability. So the spectroscopic contamination control over wide spectral range is required from the process of GOSAT development to on-orbit operation. The paper presents the instrument design of TANSO-FTS and TANSO-CAI, overview of GOSAT contamination control plan, results from spectral analysis of deposited outgas, test result of hydrazine (rocket and satellite thruster propellant) injection to an optical surface, as well as test result from contamination environment monitoring using a vacuum chamber and contamination witness plates.

A 2⁵ full factorial designed experiment was performed in order to investigate the cause of the increase in resistance of various precision resistors used in the MESSENGER spacecraft. Even though the largest increase was less than 5 %, it was troubling because the cause of the resistance change had not been determined other than the usual suspects of ESD, solder tip temperature, environmental stress screening (ESS) or corrosion (disputed by the commercial manufacturer). Because of the need to quickly resolve the root cause of this change, it was decided to study all the variables simultaneously by the use of Design of Experiments (DOE). The five variables studied were the different resistor types, operating voltages, solder tip temperatures, temperature cycling, and the highly accelerated stress test (HAST). The statistically significant findings are: 1) The most probable cause of the increase in resistance is moisture ingress through the old passivation layer inherent with only one chip resistor type. The old passivation coating is not as impervious to moisture as the new passivation coating on the other resistor type. The failure mechanism is therefore a chemical reaction, most probably the oxidation of chromium present in the nichrome resistor element to form a non-conductive chromium sub-oxide. 2) To a much less significant extent, the higher solder tip temperature of 700 F and the higher test voltage (e.g. 40 volts) contribute to a higher resistance change. Materials analyses of the coatings explain the difference in moisture permeation rates.

This paper describes the power of leveraging radiation modeling software to quickly construct direct simulation Monte-Carlo models. The radiation modeling code, GEANT, provides not only the framework to develop models with complicated geometries, but it gives one control over particle kinematics and propagation. An obvious added benefit to this approach is that the same model used for contamination analysis can also be used to perform radiation studies. Results of a simple model are presented followed by a discussion of the full potential of this approach.

Space based laser missions have gained their popularity in areas such as: communication, power beaming, ranging, altimetry, and Light Detection and Ranging. The capabilities of 1.0 micron lasers offer a host of improvements in the knowledge gaps that exist and help promote our understanding of our Earth and lunar environments as well as planetary and space science applications. Some past and present National Aeronautics and Space Administration missions that have been developed for increasing our universal knowledge of such environments and applications include: The Shuttle Laser Altimeter, Mars Orbiter Laser Altimeter, Geoscience Laser Altimeter System, Mercury Laser Altimeter, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, and Lunar Orbiter Laser Altimeter. The effort of contamination control depends on the specific performance goals, instrument designs, and planned operating scenarios of such missions. Trace amounts of contamination have been shown to greatly reduce the performance of 1.0 micron space based laser systems. In addition, the type of contamination plays an important role in the degree of degradation and helps to define the "contamination sensitivity" of the mission. A space based laser mission is considered highly contamination sensitive and therefore requires an unprecedented contamination control effort.

The preliminary investigation of solid phase microextraction (SPME) as a method for conducting contamination analysis in clean nitrogen streams is presented. The basic operation and the potential advantages of SPME technology are presented for readers unfamiliar with the technique. A detailed description of sample collection and analysis is provided. A discussion of sampling theory and quantification is also included. Results of laboratory experiments and some preliminary field tests are discussed, as well as the direction for future development of the technique.

Computer models that predict the rate at which molecular contamination will deposit on optical surfaces typically use outgassing source terms, measured with quartz crystal microbalances, as a basis for the prediction. The American Society of Testing and Materials, Standard Test Method for Contamination Outgassing Characteristics of Spacecraft Materials (Method E-1559), is probably the best know technique used by the aerospace community to measure the outgassing rates or source terms of materials. A simple method for the insitu calibration of quartz crystal microbalances, based on the heat of enthalphy of Adipic Acid, has been developed and demonstrated by the Marshall Space Flight Center, Environmental Effects Branch. The calibration has been demonstrated over a sample temperature range of 25 to 66 degrees Celsius and deposition rates of 2 x 10^-11 grams/cm2-s and greater, for several measurement system configurations. This calibration technique is fully compatible with the American Society for Testing and Materials, Method E-1559, as well as other methodology. The calibration requires no modification of outgassing facilities employing an effusion cell and does not degrade the performance or function of typical vacuum systems.

A mirror cleaning study was conducted to assess the effectiveness of three cleaning methods in their ability to remove particulate contamination from reflective mirror surfaces. Presently, the detergent bath, solvent rinse, and CO₂ snow cleaning methods are the most commonly used optical cleaning techniques within the optics industry. These techniques are also commonly used by the Optics Branch/Code 551 at Goddard Space Flight Center (GSFC) to remove particulate contamination from optical surfaces. In this experimental study, the above-mentioned cleaning methods were used to clean twelve uncoated silicon wafers, twelve gold coated silicon wafers, and twelve gold coated silicon wafers with a silicon oxide protective coating. CO₂ snow cleaning had an average removal percentage of 84%, followed by the solvent rinse at 74%, and the detergent bath at 61%. In addition to the average removal percentage, this comparative study was designed to: (1) determine the cleaning ability of each method based on the number and size of removed particles; (2) assess the risk of surface damage for each cleaning procedure; (3) evaluate each cleaning method as a function of its initial "qualitative" contamination level ("fairly clean", "dirty", and "very dirty"). The particulate cleanliness of all wafers was characterized using Image Analysis and Image-Pro Plus 5.0 software. In addition, the experimental design and experimental results were analyzed using JMP/Statistical Analytical Software Version 6.0.

The efficacy of five particulate verification techniques on four types of materials was studied. Statistical Analysis Software/JMP 6.0 was used to create a statistically valid design of experiments. In doing so, 35 witness coupons consisting of the four types of materials being studied, were intentionally contaminated with particulate fallout. Image Analysis was used to characterize the extent of particulate fallout on the coupons and was used to establish a baseline, or basis of comparison, against the five techniques that were studied. The five particulate verification techniques were the Tapelift, the Particulate Solvent Rinse, the GelPak lift, an in-line vacuum filtration probe, and the Infinity Focusing Microscope (IFM). The four types of materials consisted of magnesium flouride (MgF₂) coated mirrors, composite coated silver aluminum (CCAg), Z93 and NS43G coated aluminum, and silicon (si) wafers. The vacuum probe was determined to be most effective for Z93, the tapelift or vacuum probe for MgF2, and the GelPak Lift for CCAg and si substrates. A margin of error for each technique, based on experimental data from two experiments, for si wafer substrates, yielded the following: Tapelift - 67%, Solvent Rinse - 58%, GelPak- 26%, Vacuum Probe - 93%, IFM-to be determined.

The New Horizons (NH) Pluto probe was launched on an Atlas V-551 equipped with a five-meter payload fairing (PLF). In-situ Gel-Pak witness plates were used to monitor fall-out at spacecraft level and at Centaur level within the PLF. Based upon the composition of particles captured on a Gel-Pak that witnessed encapsulation and transport to the launch facility significant particle fall-out is associated with fairing materials of construction. The weekly variation of particle fall-out onto subsequent Gel-Pak surfaces over the course of launch preparation indicates that upward transport of particles occurred. Based upon the sum of all Gel-Pak particle counts combined with visual detection of dust on the top deck of New Horizons during installation of the radioisotope thermoelectric generator (RTG) our goal of level 450 beginning of life (BOL) was probably exceeded. A big contributor to this excedance was removal of the isolation diaphragm that normally separates the spacecraft form activity below due to mission unique requirements. The launch service provider confirmed detection of upward air movement in previous ground testing of an Atlas V fairing. Future contamination sensitive missions using the Atlas V may want to consider the following: 1) reduced PLF airflow (NH used 280 Lbm/min.), 2) ultraviolet inspection of the PLF, 3) use of isolation diaphragm, 4) in-situ particle counting. Sodium chloride was evident on many particles examined by SEM/EDS, indicating intrusion of the sea coast atmosphere into KSC cleanrooms.

The GOES-12 spacecraft exhibits a loss of heat rejection capabilities over the long term. It also presents a unique opportunity to evaluate this change at more than one temperature. The Imager and Sounder instruments use passive radiant coolers to reject heat from their sensors, and operate near 200 Kelvin. The Solar X-ray Imager (SXI) instrument mirror operates at or above 273 Kelvin. The mass deposition for SXI is substantially less than that of the Imager and Sounder. The phenomenon is evaluated and reasons for it discussed. This paper follows other descriptions by the author of the electrostatic return and introduces photolytic interactions at different temperatures.

The Solar Occultation for Ice Experiment (SOFIE) instrument is one of three science instruments for the Aeronomy of Ice in the Mesosphere (AIM) mission. SOFIE is used to measure solar attenuation by mesospheric ice aerosols during each observatory sunrise and sunset using an 8-channel (16-detector) differential absorption radiometer. It directly views the sun and compares the near UV to the mid-IR spectral response during exo-atmospheric and endo-atmospheric measurements. Deposition of molecular films can degrade the reflectance and transmittance of SOFIE's optics. During on-orbit performance, it may be possible for the extended solar exposure to promote photochemical deposition and darkening effects in the UV. This paper will review the methods used to derive and verify contamination control budgets for particulate and molecular contamination during the fabrication and testing of the SOFIE instrument. Reported results include the molecular surface cleanliness throughout integration and test as well as outgassing measurements using internal and external quartz crystal microbalances. This information provides important baseline data for future correlation of instrument outgassing and potential photo-deposited contamination effects should they occur during on-orbit solar exposure

The effects of molecular film contamination on optical systems depend strongly on the film uniformity and thickness. Molecular films of uniform thickness are responsible for light transmission losses through absorption. For example, a partially darkened film of dioctyl phthalate 100 Å thick may cause losses of about 2% in the visible spectrum. However, Ternet, et al, Villahermosa, et al, and others, have shown that scattering from droplets or "puddles" can cause transmission losses of 30%. In this paper, we examine properties of the contaminant and surface that drive the formation of smooth films and droplets. It is shown that surfaces play a strong, and sometimes dominant role in controlling film or droplet formation. DC 704, a high purity, siloxane liquid, is shown to assume both droplet and smooth film character depending on the surface.

Recent quartz crystal microbalance measurements made in the Marshall Space Flight Center, Photo-deposition Facility, for several materials, recorded a significant loss of deposited contaminants when the deposition surface of the microbalance was illuminated by a deuterium lamp. Theses measurements differ from observations made by other investigators in which the rate of deposition increased significantly when the deposition surface was illuminated with vacuum ultraviolet radiation, generated by a variety of sources. These observations suggest that the accelerated deposition of molecular contaminants on optically sensitive surfaces is dependant upon the contaminant being deposited and the VUV source and that both must be addressed during the materials screening process.

In contamination control technology relatively dirty surfaces cannot be specified with the same defining equations as those for "clean" surfaces. The current practices in the aerospace community disregard this inaccuracy in defining and specifying gradations of surface cleanliness. Using a 0.926 slope with an IEST-STD-CC1246D particle distribution to describe cleanliness on dirty surfaces, or surfaces subjected to fallout, is inaccurate, unrealistic, misleading, and often impossible to verify. Most importantly, using this model provides incorrect information to experts who calculate sensor performance: a slope of 0.926 is appropriate only for cleaned surfaces. However, the industry continues to use the same slope to describe all surfaces, clean or dirty. Current measurements taken from Raytheon labs have shown that particle distributions dominated by fallout typically have a slope between 0.3 and 0.5, in concurrence with previous studies. Based on the accumulated data, the authors propose that particle distributions for dirty surfaces be described by a second model, which should be incorporated into the next revision of IEST-STD-CC1246.

The use of digital cameras and digital imaging software for the measurement of particle obscuration is discussed. Novel calibration standards are used to evaluate the sensitivity and accuracy of commercially available digital cameras for detecting microscopic dust particles and other contaminant features on surfaces. Lighting and illumination effects are also illustrated and discussed. The digital image histogram of particles on a surface is shown to give good results for the percent area coverage.

This paper describes a numerical model developed recently using MATLAB^® for performing surface particle coverage calculations. The model uses a multi-bin particle size distribution model with incorporation of Barengoltz's areal density integration method and Raab's particle shape factor, a similar approach employed previously by Ma, Fong and Lee at Lockheed Martin Space Systems Company (Sunnyvale). The developed model is a versatile and quick turnaround tool and can easily account for variable particle size bins, variable shape factors or aspect ratios for various size bins, and variable slopes (w.r.t. the IEST-STD-CC1246 slope) for different size bins. Model predictions compare well with image analysis measurements of particle fallout data from various spacecraft cleanrooms and test environments. Moreover, this study recommends using a standard equation to correlate particle area coverage with IEST-STD-CC1246 levels (particles modeled as a cylinder with hemispherical ends) and applying a wide range of conversion factors for accurately calculating particle area coverage for variable slopes for different particle size bins.

The correlation of surface cleanliness defined by MIL-STD-1246B and the resulting geometric obscuration, or percent area coverage (PAC), was rigorously calculated by Ma, Fong, and Lee in 1989. This correlation is effective for surfaces that follow a distribution of particle sizes defined by a slope of -0.926. This evaluation extends the correlation of surface cleanliness level and PAC to a more generalized format, compatible with alternative distribution slopes. In addition, an attempt at determining the distribution slope from a defined slope and cleanliness level is presented.

This paper considers the case of "free" (unattached) particles confined within non-hermetic electronics components, assemblies or units on spacecraft. A methodology is developed for predicting the probability of particle deposition events, especially in areas where the risk for degradation or failure of the spacecraft is high. The effects of high vacuum and microgravity on particle transport processes and particle-wall interactions are discussed. The focus is on solid particles larger than about 1 mil (25 μm), as these particles pose the greatest threat to electronics reliability.

Deionized (DI) water, with a density close to hydrazine, is used to fill spacecraft propellant tanks for mechanical testing during ground operations, after which is it removed and the tanks dried for use with anhydrous hydrazine. Pure nitrogen is used as a pressurant during storage and during water fill and drain operations. Since DI water systems are notorious for contamination by slime-forming bacteria, DI water intended for use in New Horizons and STEREO hydrazine tanks at APL was assessed for microorganism content using the heterotrophic plate count (HPC) method. Results show that some growth occurred during storage of DI water in propellant tanks, however not at the logarithmic rate associated with well-nourished bacteria. Ralstonia and Burkholderia were present in DI water on-loaded however only Ralstonia was present in off-loaded water. One possible source of nutrients during water storage in propellant tanks is organic material originating from the EPDM (EPR per AF-E-332) expulsion diaphragm. This paper will demonstrate potential for bio-fouling of spacecraft propulsion systems due to growth of slime-forming bacteria and will suggest that specifications controlling microorganism content should be imposed on water used for spacecraft ground testing.

Light scatter is a bothersome source of noise in many optical systems. As one example, this is particularly true for telescopes and weapons systems where imaging, tracking and identifying relatively weak signals in the presence of much stronger light sources is critical. As a general rule optical components are not specified for scatter. Instead, almost across the optics industry roughness specifications are routinely (and inadequately) substituted. Issues include: misuse (or ignoring) spatial frequency bandwidths for roughness specifications, using one dimensional roughness statistics for two dimensional applications, ignoring profilometer high frequency roll off (where a lot of scatter is generated) and ignoring the effects surface coatings have on scatter. As an example most roughness measurements extend only to spatial frequencies of about 0.1 μm^-1, which corresponds to visible scatter only about five degrees from the reflected specular beam. Scatter into the rest of the hemisphere is ignored. The problems are not easy. Measuring every optic for scatter at the wavelengths of use, for example, is not a reasonable solution. This paper reviews the relevant technical issues and indicates a cost effective solution that will drop optical noise floors if implemented by both government contractors and their vendors.

The standard use of the parameter σ for the rms surface roughness of optics has obscured the fact that the effective surface roughness is a function of both the measurement wavelength and bandwidth. A more appropriate method for the flowdown of surface specifications from stray light requirements is presented. Acceptance test methods for validating surface properties of optics using a Zygo NewView Profilometer are also discussed.

Particulate contamination scatter is often modeled using Bidirectional Scatter Distribution Functions (BSDFs) based upon Mie scattering by a distribution of spherical particles. Starting with the basic model described in P. R. Spyak and W. L. Wolfe [1,2,3,4], we improve upon it by adding multiplicative geometrical form factors. These factors prevent the Total Integrated Scatter (TIS) from exceeding unity and ensure that reciprocity is always obeyed. Preventing the TIS from exceeding unity is necessary for energy to be conserved in the raytrace, and obeying reciprocity is necessary to obtain consistent results between forward and backwards raytraces. As will be shown, this improved model fits measured data better than the previous model.

The K-Correlation or ABC model for surface power spectral density (PSD) and BRDF has been around for years. Eugene Church and John Stover, in particular, have published descriptions of its use in describing smooth surfaces. The model has, however, remained underused in the optical analysis community partially due to the lack of a clear summary tailored toward that application. This paper provides the K-Correlation PSD normalized to σ(λ) and BRDF normalized to TIS(σ,λ) in a format intended to be used by stray light analysts. It is hoped that this paper will promote use of the model by analysts and its incorporation as a standard tool into stray light modeling software.

Scattering effects from rough surfaces are non-paraxial diffraction phenomena resulting from random phase variations in the reflected wavefront. Rayleigh-Rice (1951) or Beckmann-Kirchhoff (1963) theories are commonly used to predict surface scatter effects. Also, Harvey and Shack (1976) developed a linear systems formulation of surface scatter phenomena in which the scattering behavior is characterized by a surface transfer function. This treatment provided insight and understanding not readily gleaned from the two previous theories. However, smooth surface and/or paraxial approximations have severely limited the range of applicability of each of the above theoretical treatments. A new linear systems formulation of non-paraxial scalar diffraction theory applied to surface scatter phenomena resulted first in a modified Beckmann-Kirchhoff surface scattering model, then a generalized Harvey-Shack theory that produces accurate results for rougher surfaces than the Rayleigh-Rice theory and for larger incident angles than the classical Beckmann-Kirchhoff theory. These new developments simplify the analysis and understanding of stray light resulting from non-intuitive scattering behavior from rough surfaces illuminated with large incident angles.

There has been a general awareness for several years that the IEST-STD-CC1246 standard particle distribution with a slope of -0.926 does not reasonably represent the contamination on optics that have not been recently cleaned. As a result, the CL (Cleanliness Level) nomenclature actually counters effective communication and modeling of particulate contamination scatter. An analysis method and communication standard centered on Percent Areal Coverage (PAC) and particle distribution slope is presented that improves the ability of Contamination Engineering and Stray Light Engineering to tackle ever more difficult instrument stray light requirements in the most cost-effective manner. Modeling the expected particle distributions for multiple contamination species improves accuracy and reduces costly overdesign.

Ghosting between detector and window surfaces is a common source of stray light in packaged detectors. Simple formulas are presented for predicting window ghost characteristics. Stray light paths in silicon detectors, which are semi-transparent to near-infrared light, can involve non-optical structures deep within the device. Methods for identifying subsurface stray light paths are presented.

The James Webb Space Telescope (JWST) is an infrared, space-based telescope scheduled for launch in 2013. JWST will hold four scientific instruments, including the Near Infrared Spectrograph (NIRSpec). NIRSpec operates in the wavelength range from 0.6 to 5 microns, and will be assembled by the European Space Agency. NASA/Goddard Space Flight Center (GSFC) is responsible for two NIRSpec subsystems: the detector subsystem, with the focal plane array (FPA), and the micro-shutter subsystem, with the micro-shutter assembly (MSA). The FPA consists of two side-by-side Rockwell Scientific HgCdTe 2Kx2K detectors, with the detectors and readout electronics optimized for low noise. The MSA is a GSFC developed micro-electro-mechanical system (MEMS) that serves as a programmable slit mask, allowing NIRSpec to obtain simultaneous spectra of >100 objects in a single field of view. We present the optical characterization test plan of the FPA. The test plan is driven by many requirements: cryogenic operating temperature, a flight-like beam shape, and multi-wavelength flux from 1 to 10,000 photons per second, thus low stray light is critical. We use commercial optical modeling software to predict stray light effects at the FPA. We also present the optical contrast test plan of the MSA. Each individual shutter element operates in an on/off state, and the most important optical metric is contrast. The MSA is designed to minimize stray and scattered light, and the test setup reduces stray light such that the optical contrast is measurable.

Stray light in an imaging system can be unpredictable and may not originate directly from the field of view of the imaged pixel. Depending on the severity of the stray light, this can adversely affect the quality of remote sensing imagery and be difficult to correct. A significant amount of stray light can be visually noticeable and even distracting to the image analyst. Complicating the matter, stray light that originates from outside the field of view can be highly unpredictable and variable across the image, adversely affecting the results of image processing algorithms developed for automated processing. A new algorithm has been developed in an attempt to estimate the amount of stray light in each remote sensing image. The stray light algorithm estimates an average and maximum amount of stray light for each image, and can output an estimated stray light map. The algorithm can be run in an automated batch processing mode for operational monitoring where the results are placed into a database along with other image quality trending factors. This paper presents results of testing the algorithm on simulated and commercial panchromatic and multispectral imagery.