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NASA NTRS1979

UV blocking filters for polymeric films

The concept of incorporating UV screening agents in silicone resins as a means of protecting underlying solar cell covers and adhesives from UV degradation is presented. A silicone hard-coat resin incorporating a UV screening agent was selected as a suitable coating material for PFA Teflon solar cell covers. Consideration is given to fabrication procedures and techniques for introduction of the UV screening agents into silicone resins and application of these UV-inhibited coatings to the Teflons. Some preliminary environmental tests, such as thermal shock and temperature humidity, were conducted.

Rayl, G. J.↗

NASA NTRS2001

Transmission Properties of Zitex in the Infrared to Submillimeter

The results of measurements of the refractive index and power absorption coefficient of Zitex at 290 K, 77 K, and 4 K in the spectral region from 1 to 1000 microns are presented. Zitex is a porous Teflon sheet with a filling factor of approximately 50%, and is manufactured in several varieties as a filter paper. Zitex is found to be an effective infrared radiation block, with thin (200 micrometer) sheets transmitting less than 1% in the 1-50 micrometer range while absorbing <10% at wavelengths longer than 200 micrometers. Some variation in the cutoff wavelength is seen, tending to be a shorter wavelength cutoff for a smaller pore size. Additionally, the thermal conductivity of Zitex at cryogenic temperatures has been measured, and is found to be roughly one-half that of bulk Teflon.

Benford, D. J.↗

NASA NTRS1980

Large-aperture high-resolution X-ray collimator for the Solar Maximum Mission

A description is presented of a flight-qualified large-aperture 12 x 12-arcsec angular resolution multigrid X-ray collimator developed for the Solar Maximum Mission (SMM) flat crystal spectrometer. This collimator, designed for the 1.4-22.4-A wavelength range, utilizes an optical bench/metering structure to align and support prealigned grid subassemblies. The optical bench is a lightweight, rigid, and stable aluminum honeycomb structure. The grids are of a compound and bimetallic design, having 63.5-micron square holes on an 88.9-micron spacing in 8-micron thick gold, which is in turn supported by a 76-micron thick Invar grid having 600-micron square holes on a 739-micron spacing. The small apertures in the gold provide the 12-arcsec collimation with the Invar grids providing wide angle off-axis blocking out to an approximately 35 arcmin view angle. The collimator has seven individual channels, four of a 5.1- x 10-cm area and three of a 1.3- x 10-cm area. Laboratory measurements gave an average angular resolution of 12.5 arcsec FWHM with 0.259 transmission for the large-area channels and 12.0 arcsec and 0.200 transmission for the small-area channels. A thermal filter composed of two layers of approximately 1000-A thick aluminum prevents solar heating of the front collimator grids by absorbing longer wavelength radiation while passing most of the X radiation in the band of interest.

Nobles, R. A.↗

NASA NTRS2006

Characterization Tests of WFC3 Filters

The WFC3 instrument to be installed on HST during the next servicing mission consists of a UVIS and an IR channel. Each channel is allocated its own complement of filters: 48 elements for the UVIS (42 filters, 5 quads, and 1 UV grism) and 17 slots for the IR (15 filters and 2 grisms). While a majority of the UVIS filters exhibit excellent performance consistent with or exceeding expectations, a subset show significant filter ghosts. Procurement of improved replacement filters is in progress and a summary of the characterization tests being performed on the new filters is presented. In the IR channel, while no filter ghosting was detected in any of the filters during thermal vacuum testing, the grisms were found to be installed incorrectly; they have been removed and will be reinstalled. In addition, due to the significantly improved response blueward of 800nm expected in the new substrate-removed IR detector (see Invited talk by R.A.Kimble, this volume), two IR filters originally constructed on a fused silica substrate are being remade using an IR transmitting color glass to block any visible light transmission. Tests of the new IR filters and preparations for the grism reinstallation are summarized

Baggett, S.↗

NASA NTRS2019

NASA Astrophysics Technology Gaps, Prioritization, and Development

Physics of the Cosmos (PCOS) X-ray astrophysics: grazing-angle mirrors, optical blocking filters, fast event ID, gratings, micro-calorimeters, radiation-tolerant detectorsGravitational-wave astrophysics: phase measurement system, micro-Newton thrusters, non-contact charge-management system, stable laser system, low-stray-light telescope Cosmic Microwave Background (CMB): superconducting FPAs and optical elements (cryo filters and coatings)Cosmic Origins (COR)UV/Optical/IR: Next-gen detectors, ultra-stable high-precision telescope systems (including mirrors, thermal control, structures, metrology, etc.), and advanced UV coatingsFar-IR: Heterodyne detectors, advanced cooling systems, ultra-sensitive detectors and large arraysLarge Space Optics: As discussed earlier by Mario Perez, the Program Office supports HQ in monitoring/tracking the Segmented Mirror Technology Program (SMTP) and other technology development projects targeting large space telescopes

Ganel, Opher↗

NASA NTRS2005

Modeling contamination migration on the Chandra X-Ray Observatory

During its first 5 years of operation, the cold (-60 C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), on board the Chandra X-ray Observatory, has accumulated a contaminating layer that attenuates the low-energy x rays. To assist in assessing the likelihood of successfully baking off the contaminant, members of the Chandra Team developed contamination-migration simulation software. The simulation follows deposition onto and (temperature-dependent) vaporization from surfaces comprising a geometrical model of the Observatory. A separate thermal analysis, augmented by on-board temperature monitoring, provides temperatures for each surface of the same geometrical model. This paper describes the physical basis for the simulations, the methodologies, and the predicted migration of the contaminant for various bake-out scenarios and assumptions.

O'Dell, Stephen L.↗

NASA NTRS2013

Modeling Contamination Migration on the Chandra X-ray Observatory - II

During its first 14 years of operation, the cold (about -60C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon temperature data, and a refined model of the molecular transport.

O'Dell, Stephen L.↗

NASA NTRSDate not supplied

Novel Infrared-blocking Aerogel Scattering Filters and Their Applications in Astrophysical and Planetary Science Observations

Infrared-blocking scattering aerogel filters have a broad range of potential applications in astrophysics and planetary science observations in the far-infrared, sub-millimeter, and microwave regimes. Successful dielectric modeling of aerogel filters allowed the fabrication of samples to meet the mechanical and science instrument requirements for several experiments, including the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE), the Cosmology Large Angular Scale Surveyor (CLASS), and the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM). Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4 K with no degradation in mechanical properties.

Kyle R Helson↗

NASA NTRS2026

Diamond-Loaded Polyimide Aerogel Scattering Filters and Their Applications in Astrophysical and Planetary Science Observations

Infrared-blocking, aerogel-based scattering filters have a broad range of potential applications in astrophysics and planetary science instruments in the far-infrared, sub-millimeter, and microwave regimes. This paper demonstrates the ability of conductively-loaded, polyimide aerogel filters to meet the mechanical and science instrument requirements for several experiments, including the Cosmology Large Angular Scale Surveyor (CLASS), the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), and the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE). Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4 K with no degradation in mechanical properties. Measurement of total hemispherical reflectance and transmittance, as well as cryogenic tests of the aerogel filters in a full receiver context, allow estimates of the integrated infrared emissivity of the filters. Knowledge of the emissivity will help instrument designers incorporate the filters into future experiments in planetary science, astrophysics, and cosmology.

Kyle R Helson↗

NASA NTRS2000

ACIS Door Failure Investigation and Mitigation Procedures

NASA's Chandra X-ray Observatory (formerly AXAF) was launched on July 23, 1999 and is currently in orbit performing scientific studies. Chandra is the third of NASA's Great Observatories to be launched, following the Hubble Space Telescope and the Compton Gamma Ray Observatory. One of four primary science instruments on Chandra, and one of only two focal plane instruments, is the Advanced CCD Imaging Spectrometer, or ACIS. The ACIS focal plane and Optical Blocking Filter (OBF) must be launched under vacuum, so a tightly sealed, functioning door and venting subsystem were implemented. The door was opened two and one-half weeks after launch (after most out-gassing of composite materials) and allowed X-rays to be imaged by the ACIS CCD's in the focal plane. A failure of this door to open on-orbit would have eliminated all ACIS capabilities, severely degrading mission science. During the final pre-flight thermal-vacuum test of the fully integrated Chandra Observatory at TRW, the ACIS door failed to open when commanded to do so. This paper describes the efforts, under considerable time pressure, by NASA, its contractors and outside review teams to investigate the failure and to develop modified hardware and procedures which would correct the problem. Of interest is the fact that the root cause of the test failure was never clearly identified despite massive effort. We ultimately focussed on hardware and procedures designed to mitigate the effects of potential, but unproven, failure modes. We describe a frequent real-world engineering situation in which one must proceed on the best basis possible in the absence of the complete set of facts.

Podgorski, William A.↗

NASA NTRS2009

NASA Tech Briefs, August 2009

Topics covered include: Aligning a Receiving Antenna Array to Reduce Interference; Collecting Ground Samples for Balloon-Borne Instruments; Tethered Pyrotechnic Apparatus for Acquiring a Ground Sample; Enhanced Video-Oculography System; Joint Carrier-Phase Synchronization and LDPC Decoding; Dual-Polarization, Sideband-Separating, Balanced Receiver for 1.5 THz Modular Battery Charge Controller; Efficient Multiplexer FPGA Block Structures Based on G4FETs; VLSI Microsystem for Rapid Bioinformatic Pattern Recognition; Low-Noise Amplifier for 100 to 180 GHz; Improved Fabrication of Ceramic Matrix Composite/Foam Core Integrated Structures; Inert Welding/Brazing Gas Filters and Dryers; Fabricating Copper Nanotubes by Electrodeposition; Reducing Aerodynamic Drag on Empty Open Cargo Vehicles; Rotary Percussive Auto-Gopher for Deep Drilling and Sampling; More About Reconfigurable Exploratory Robotic Vehicles; Thermostatic Valves Containing Silicone-Oil Actuators; Improving Heat Flux Performance of Flat Surface in Spray-Cooling Systems; Treating Fibrous Insulation to Reduce Thermal Conductivity; Silica-Aerogel Composites Opacified with La(sub0.7)Sr(sub0.3)MnO3; Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles; Ceramic Fiber Structures for Cryogenic Load-Bearing Applications; Elastomer Reinforced with Carbon Nanotubes; Biologically Inspired Purification and Dispersion of SWCNTs; A Technique for Adjusting Eigenfrequencies of WGM Resonators; Low-Pressure, Field-Ionizing Mass Spectrometer; Modifying Operating Cycles to Increase Stability in a LITS; Chamber for Simulating Martian and Terrestrial Environments; Algorithm for Detecting a Bright Spot in an Image; Extreme Programming: Maestro Style; Adaptive Behavior for Mobile Robots; Protocol for Communication Networking for Formation Flying; Planning Complex Sequences Using Compressed Representations; and Self-Supervised Learning of Terrain Traversability from Proprioceptive Sensors.

Source record↗

NASA NTRS1976

Solar cell array design handbook, volume 1

Twelve chapters discuss the following: historical developments, the environment and its effects, solar cells, solar cell filters and covers, solar cell and other electrical interconnections, blocking and shunt diodes, substrates and deployment mechanisms, material properties, design synthesis and optimization, design analysis, procurement, production and cost aspects, evaluation and test, orbital performance, and illustrative design examples. A comprehensive index permits rapid locating of desired topics. The handbook consists of two volumes: Volume 1 is of an expository nature while Volume 2 contains detailed design data in an appendix-like fashion. Volume 2 includes solar cell performance data, applicable unit conversion factors and physical constants, and mechanical, electrical, thermal optical, magnetic, and outgassing material properties. Extensive references are provided.

Rauschenbach, H. S.↗

NASA NTRS1982

Charge-coupled device (CCD) television camera for NASA's Galileo mission to Jupiter

The CCD detector under construction for use in the slow-scan television camera for the NASA Galileo Jupiter orbiter to be launched in 1985 is presented. The science objectives and the design constraints imposed by the earth telemetry link, platform residual motion, and the Jovian radiation environment are discussed. Camera optics are inherited from Voyager; filter wavelengths are chosen to enable discrimination of Galilean-satellite surface chemical composition. The CCO design, an 800 by 800-element 'virtual-phase' solid-state silicon image-sensor array with supporting electronics, is described with detailed discussion of the thermally generated dark current, quantum efficiency, signal-to-noise ratio, and resolution. Tests of the effect of ionizing radiation were performed and are analyzed statistically. An imaging mode using a 2-1/3-sec frame time and on-chip summation of the signal in 2 x 2 blocks of adjacent pixels is designed to limit the effects of the most extreme Jovian radiation. Smearing due to spacecraft/target relative velocity and platform instability will be corrected for via an algorithm maximizing spacial resolution at a given signal-to-noise level. The camera is expected to produce 40,000 images of Jupiter and its satellites during the 20-month mission.

Klaasen, K. P.↗

NASA NTRS1990

Development of multiple source data processing for structural analysis at a regional scale

Various image processing techniques developed for enhancement and extraction of linear features, of interest to the structural geologist, from digital remote sensing, geologic, and gravity data, are presented. These techniques include: (1) automatic detection of linear features and construction of rose diagrams from Landsat MSS data; (2) enhancement of principal structural directions using selective filters on Landsat MSS, Spacelab panchromatic, and HCMM NIR data; (3) directional filtering of Spacelab panchromatic data using Fast Fourier Transform; (4) detection of linear/elongated zones of high thermal gradient from thermal infrared data; and (5) extraction of strong gravimetric gradients from digitized Bouguer anomaly maps. Processing results can be compared to each other through the use of a geocoded database to evaluate the structural importance of each lineament according to its depth: superficial structures in the sedimentary cover, or deeper ones affecting the basement. These image processing techniques were successfully applied to achieve a better understanding of the transition between Provence and the Pyrenees structural blocks, in southeastern France, for an improved structural interpretation of the Mediterranean region.

Carrere, Veronique↗

NASA NTRS1995

An X-Band Mixer Engineered for 77 K Operation

An X-band Si-diode singly balanced mixer developed specifically for cryogenic operation is presented. In order to reduce thermal demands on a mechanical cooler, the mixer was designed to operate with a minimum of local oscillator (LO) power. That is, since the LO had to be cooled to reduce phase noise, it was desirable to minimize the LO drive. Novel embedding circuit strategy was responsible for nearly theoretical performance. The signal-matching circuit simultaneously provided a reactive termination to the image, sum, and first, second, and third LO harmonic frequencies. A conversion loss of 3.2 dB at 77 K with an LO drive of +1 dBm was measured. This loss included IF filter, dc block, and hybrid coupler losses. Mixer conversion loss is shown to be consistent with the theoretical performance limit expected from the intrinsic diode. The relationship among junction capacitance, flat-band potential, and conversion loss is examined.

Romanofsky, Robert R.↗

NASA NTRS2013

Modeling Contamination Migration on the Chandra X-ray Observatory II

During its first 14 years of operation, the cold (about ‐60degC) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X‐ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low‐energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition may have changed, perhaps partially related to changes in the operating temperature of the ACIS housing. This evolution of the accumulation of the molecular contamination has motivated further analysis of contamination migration on the Chandra X‐ray Observatory, particularly within and near the ACIS cavity. To this end, the current study employs a higher‐fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon monitored temperature data, and an accordingly refined model of the molecular transport.

O'Dell, Stephen L.↗

NASA NTRS2013

Modeling Contamination Migration on the Chandra X-ray Observatory II

O'Dell, Steve↗

NASA NTRS1992

One Year of Rayleigh Lidar Measurements at Toronto

The Rayleigh lidar technique is being used at York University to study middle atmospheric thermal structure with particular emphasis on the properties and influence of internal gravity waves. These measurements are now carried out on a routine basis (every clear night) in order to determine seasonal variability and, eventually, long term trends. The transmitter consists of a doubled Nd:YAG laser with an output of 0.4 Joules per pulse at 20Hz (8 Watts) which is expanded to obtain a divergence of 0.4 milliradians. Backscattered photons are collected by a half meter cassegrain telescope, filtered to a bandwidth of 1nm, detected by a PMT, and counted with a multi-channel scaling averager. Strong backscatter from lower altitudes is blocked using a rotating chopper (25000rpm) which triggers the laser. The range gate and hardware averaging interval are variable but typically 300m and 5 minutes. Relative density profiles are obtained by simply normalizing to a model (eg. CIRA) at some altitude. Absolute temperature is derived using the hydrostatic equation, ideal gas law, and a model pressure value at the altitude where the photocount statistical uncertainty is about 15 percent - typically 90km for the entire night's average. The lower limit is currently about 30-35km due the presence aerosol from the volcanic eruption of Mt. Pinatubo.

Whiteway, James A.↗