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NASA NTRS1989

Laser light scattering review

Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

Schaetzel, Klaus↗

NASA NTRS1991

Instrumentation for optical ocean remote sensing

Instruments used in ocean color remote sensing algorithm development, validation, and data acquisition which have the potential for further commercial development and marketing are discussed. The Ocean Data Acquisition System (ODAS) is an aircraft-borne radiometer system suitable for light aircraft, which has applications for rapid measurement of chlorophyll pigment concentrations along the flight line. The instrument package includes a three channel radiometer system for upwelling radiance, an infrared temperature sensor, a three-channel downwelling irradiance sensor, and Loran-C navigation. Data are stored on a PC and processed to transects or interpolated 'images' on the ground. The instrument has been in operational use for two and one half years. The accuracy of pigment concentrations from the instrument is quite good, even in complex Chesapeake Bay waters. To help meet the requirement for validation of future satellite missions, a prototype air-deployable drifting buoy for measurement of near-surface upwelled radiance in multiple channnels is undergoing test deployment. The optical drifter burst samples radiance, stores and processes the data, and uses the Argos system as a data link. Studies are underway to explore the limits to useful lifetime with respect to power and fouling.

Esaias, W. E.↗

NASA NTRS1978

An investigation for the development of an integrated optical data preprocessor

The successful fabrication and demonstration of an integrated optical circuit designed to perform a parallel processing operation by utilizing holographic subtraction to simultaneously compare N analog signal voltages with N predetermined reference voltages is summarized. The device alleviates transmission, storage and processing loads of satellite data systems by performing, at the sensor site, some preprocessing of data taken by remote sensors. Major accomplishments in the fabrication of integrated optics components include: (1) fabrication of the first LiNbO3 waveguide geodesic lens; (2) development of techniques for polishing TIR mirrors on LiNbO3 waveguides; (3) fabrication of high efficiency metal-over-photoresist gratings for waveguide beam splitters; (4) demonstration of high S/N holographic subtraction using waveguide holograms; and (5) development of alignment techniques for fabrication of integrated optics circuits. Important developments made in integrated optics are the discovery and suggested use of holographic self-subtraction in LiNbO3, development of a mathematical description of the operating modes of the preprocessor, and the development of theories for diffraction efficiency and beam quality of two dimensional beam defined gratings.

Verber, C. M.↗

NASA NTRS1997

International Ultraviolet Explorer Final Archive

CSC processed IUE images through the Final Archive Data Processing System. Raw images were obtained from both NDADS and the IUEGTC optical disk platters for processing on the Alpha cluster, and from the IUEGTC optical disk platters for DECstation processing. Input parameters were obtained from the IUE database. Backup tapes of data to send to VILSPA were routinely made on the Alpha cluster. IPC handled more than 263 requests for priority NEWSIPS processing during the contract. Staff members also answered various questions and requests for information and sent copies of IUE documents to requesters. CSC implemented new processing capabilities into the NEWSIPS processing systems as they became available. In addition, steps were taken to improve efficiency and throughput whenever possible. The node TORTE was reconfigured as the I/O server for Alpha processing in May. The number of Alpha nodes used for the NEWSIPS processing queue was increased to a maximum of six in measured fashion in order to understand the dependence of throughput on the number of nodes and to be able to recognize when a point of diminishing returns was reached. With Project approval, generation of the VD FITS files was dropped in July. This action not only saved processing time but, even more significantly, also reduced the archive storage media requirements, and the time required to perform the archiving, drastically. The throughput of images verified through CDIVS and processed through NEWSIPS for the contract period is summarized below. The number of images of a given dispersion type and camera that were processed in any given month reflects several factors, including the availability of the required NEWSIPS software system, the availability of the corresponding required calibrations (e.g., the LWR high-dispersion ripple correction and absolute calibration), and the occurrence of reprocessing efforts such as that conducted to incorporate the updated SWP sensitivity-degradation correction in May.

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NASA NTRS1971

Construction and testing of a Scanning Laser Radar (SLR), phase 2

The scanning laser radar overall system is described. Block diagrams and photographs of the hardware are included with the system description. Detailed descriptions of all the subsystems that make up the scanning laser radar system are included. Block diagrams, photographs, and detailed optical and electronic schematics are used to help describe such subsystem hardware as the laser, beam steerer, receiver optics and detector, control and processing electronics, visual data displays, and the equipment used on the target. Tests were performed on the scanning laser radar to determine its acquisition and tracking performance and to determine its range and angle accuracies while tracking a moving target. The tests and test results are described.

Flom, T.↗

NASA NTRS1973

Two dimensional digital computer

The development of a two dimensional data processing system is reported that extracts data from optical images by performing multiple logical operations simultaneously. A two dimensional logical circuits is described that contains a liquid crystal negation element and an OR-ing element. The negation element performs 20,000 negations simultaneously, and the OR does 20,000 OR operations simultaneously.

Schaefer, D. H.↗

NASA NTRS1982

Application of laser anemometry in turbine engine research

The application of laser anemometry to the study of flow fields in turbine engine components is reviewed. Included are discussions of optical configurations, seeding requirements, electronic signal processing, and data processing. Some typical results are presented along with a discussion of ongoing work.

Seasholtz, R. G.↗

NASA NTRS1983

Application of laser anemometry in turbine engine research

Seasholtz, R. G.↗

NASA NTRS1994

Effects of the Mount Pinatubo eruption on the radiative and chemical processes in the troposphere and stratosphere

The Lawrence Livermore National Laboratory two-dimensional zonally-averaged chemical-radiative-transport model of the global atmosphere was used to study the effects of the 15 June 1991 eruption of the Mt. Pinatubo volcano on stratospheric processes. SAGE 2 time-dependent aerosol surface area density and optical extinction data were used as input into the model. By 22 December 1991, a maximum equatorial change of -1.8 percent in column ozone was derived from heterogeneous chemical processes that convert NO(x) into HNO3 on sulfuric acid aerosols. Radiative feedbacks from increased aerosol optical thickness independently changes column ozone by approximately -3.5 percent for the same period. This occurs from increasing the net heating of the lower stratosphere, which indirectly increases chemical reaction rates via their temperature dependence and from changes in actinic fluxes, which directly modify photodissociation rates. Including both heterogeneous and radiative effects changes column ozone by -5.5 percent. The model-derived change overestimates the decrease in column ozone relative to the TOMS instrument on the Nimbus 7 satellite. Maximum local ozone decreases of 12 percent were derived in the equatorial region, at 25 km. Model-derived column NO2 peaked (-14 percent) at 30 deg S in October 1991. The timing of the NO2 peak is consistent with observation, but the model underestimates the magnitude of the decrease. Local concentrations of NO(x) (NO + NO2), ClO(x) (Cl + ClO), and HO(x) (OH + HO2), in the lower stratosphere between 30 deg S and 30 deg N, were calculated to have changed by -40 percent, +100 to +160 percent, and +120 to +140 percent respectively.

Kinnison, Douglas E.↗

NASA NTRS2004

Reannealed Fiber Bragg Gratings Demonstrated High Repeatability in Temperature Measurements

Fiber Bragg gratings (FBGs) are formed by periodic variations of the refractive index of an optical fiber. These periodic variations allow an FBG to act as an embedded optical filter, passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change the wavelengths that are transmitted and reflected by it. Both thermal and mechanical forces acting on the grating will alter its physical characteristics, allowing the FBG sensor to detect both the temperature variations and the physical stresses and strains placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. To assess the feasibility of using Bragg gratings as temperature sensors for propulsion applications, researchers at the NASA Glenn Research Center evaluated the performance of Bragg gratings at elevated temperatures for up to 300 C. For these purposes, commercially available polyimide-coated high-temperature gratings were used that were annealed by the manufacturer to 300 C. To assure the most thermally stable gratings at the operating temperatures, we reannealed the gratings to 400 C at a very slow rate for 12 to 24 hr until their reflected optical powers were stabilized. The reannealed gratings were then subjected to periodic thermal cycling from room temperature to 300 C, and their peak reflected wavelengths were monitored. The setup shown is used for reannealing and thermal cycling the FBGs. Signals from the photodetectors and the spectrum analyzer were fed into a computer equipped with LabVIEW software. The software synchronously monitored the oven/furnace temperature and the optical spectrum analyzer as well as processed the data. Experimental results presented in the following graph show typical wavelength versus temperature dependence of a reannealed FBG through six thermal cycles (80 hr). The average standard deviation of the temperature-to-wavelength relationship ranged from 1.86 to 2.92 C over the six thermal cycles each grating was subjected to. This is an error of less than 1.0 percent of full scale throughout the entire evaluation temperature range from ambient to 300 C.

Adamovsky, Grigory↗

NASA NTRS2012

Optical Measurements at the Combustor Exit of the HIFiRE 2 Ground Test Engine

The development of optical techniques capable of measuring in-stream flow properties of air breathing hypersonic engines is a goal of the Aerospace Propulsion Division at AFRL. Of particular interest are techniques such as tunable diode laser absorption spectroscopy that can be implemented in both ground and flight test efforts. We recently executed a measurement campaign at the exit of the combustor of the HIFiRE 2 ground test engine during Phase II operation of the engine. Data was collected in anticipation of similar data sets to be collected during the flight experiment. The ground test optical data provides a means to evaluate signal processing algorithms particularly those associated with limited line of sight tomography. Equally important, this in-stream data was collected to compliment data acquired with surface-mounted instrumentation and the accompanying flowpath modeling efforts-both CFD and lower order modeling. Here we discuss the specifics of hardware and data collection along with a coarse-grained look at the acquired data and our approach to processing and analyzing it.

Brown, Michael S.↗

NASA NTRS2016

Extending "Deep Blue" Aerosol Retrieval Coverage to Cases of Absorbing Aerosols Above Clouds: Sensitivity Analysis and First Case Studies

Cases of absorbing aerosols above clouds (AACs), such as smoke or mineral dust, are omitted from most routinely processed space-based aerosol optical depth (AOD) data products, including those from the Moderate Resolution Imaging Spectroradiometer (MODIS). This study presents a sensitivity analysis and preliminary algorithm to retrieve above-cloud AOD and liquid cloud optical depth (COD) for AAC cases from MODIS or similar sensors, for incorporation into a future version of the "Deep Blue" AOD data product. Detailed retrieval simulations suggest that these sensors should be able to determine AAC AOD with a typical level of uncertainty approximately 25-50 percent (with lower uncertainties for more strongly absorbing aerosol types) and COD with an uncertainty approximately10-20 percent, if an appropriate aerosol optical model is known beforehand. Errors are larger, particularly if the aerosols are only weakly absorbing, if the aerosol optical properties are not known, and the appropriate model to use must also be retrieved. Actual retrieval errors are also compared to uncertainty envelopes obtained through the optimal estimation (OE) technique; OE-based uncertainties are found to be generally reasonable for COD but larger than actual retrieval errors for AOD, due in part to difficulties in quantifying the degree of spectral correlation of forward model error. The algorithm is also applied to two MODIS scenes (one smoke and one dust) for which near-coincident NASA Ames Airborne Tracking Sun photometer (AATS) data were available to use as a ground truth AOD data source, and found to be in good agreement, demonstrating the validity of the technique with real observations.

aerosols above clouds↗

NASA NTRSDate not supplied

Revolutionizing Earth Science with Generalized AI Models

Foundation Models (FM) are generalized Artificial Intelligence (AI) models that are designed to replace a task or an application-specific model and can be used for many downstream applications. These FM can be built on any sequence data and are trained utilizing self-supervised approaches. The obstacle of creating a sizable labeled dataset for training is removed by using self-supervised learning. Most FM employ transformer design that takes advantage of the idea of self-attention, allowing the network to represent the impact of distant data points on one another in space and time. The FM models show emergent qualities that are induced from the data. FM can become a valuable tool for Earth science researchers. Due to the size of these models, downstream applications built fine-tuning these FM perform better and exhibit greater accuracy than models created from scratch. FM significantly lowers the entry barrier in terms of both the time and effort required to develop various downstream applications. For some scientific datasets, such as optical remote sensing data, FM can speed up processes like classification, object detection and prediction. By eliminating the training data bottleneck and maximizing the usage of science data, FM can make it simpler to integrate AI into scientific research. Initial results for three different FMs will be presented.

Rahul Ramachandran↗

NASA NTRS2002

Vexcel Spells Excellence for Earth and Space

With assistance from Stennis Space Center, Vexcel was able to strengthen the properties of its Apex Ground Station(TM), an affordable, end-to-end system that comes complete with a tracking antenna that permits coverage within an approximate 2,000-kilometer radius of its location, a high speed direct-to-disk data acquisition system that can download information from virtually any satellite, and data processing software for virtually all synthetic aperture radar and optical satellite sensors. Vexcel is using an Apex system linked to the Terra satellite to help scientists and NASA personnel measure land and ocean surface temperatures, detect fires, monitor ocean color and currents, produce global vegetation maps and data, and assess cloud characteristics and aerosol concentrations. In addition, Vexcel is providing NASA with close-range photogrammetry software for the International Space Station. The technology, commercially available as FotoG(TM), was developed with SBIR funding and support from NASA's Jet Propulsion Laboratory. Commercially, FotoG is used for demanding projects taken on by engineering firms, nuclear power plants, oil refineries, and process facilities. A version of Vexcel's close-range photo measurement system was also used to create virtual 3-D backdrops for a high-tech science fiction film.

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NASA NTRS2012

Method to Enhance the Operation of an Optical Inspection Instrument Using Spatial Light Modulators

For many aspheric and freeform optical components, existing interferometric solutions require a custom computer-generated hologram (CGH) to characterize the part. The overall objective of this research is to develop hardware and a procedure to produce a combined, dynamic, Hartmann/ Digital Holographic interferometry inspection system for a wide range of advanced optical components, including aspheric and freeform optics. This new instrument would have greater versatility and dynamic range than currently available measurement systems. The method uses a spatial light modulator to pre-condition wavefronts for imaging, interferometry, and data processing to improve the resolution and versatility of an optical inspection instrument. Existing interferometers and Hartmann inspection systems have either too small a dynamic range or insufficient resolution to characterize conveniently unusual optical surfaces like aspherical and freeform optics. For interferometers, a specially produced, computer-generated holographic optical element is needed to transform the wavefront to within the range of the interferometer. A new hybrid wavefront sensor employs newly available spatial light modulators (SLMs) as programmable holographic optical elements (HOEs). The HOE is programmed to enable the same instrument to inspect an optical element in stages, first by a Hartmann measurement, which has a very large dynamic range but less resolution. The first measurement provides the information required to precondition a reference wave that avails the measurement process to the more precise phase shifting interferometry. The SLM preconditions a wavefront before it is used to inspect an optical component. This adds important features to an optical inspection system, enabling not just wavefront conditioning for null testing and dynamic range extension, but also the creation of hybrid measurement procedures. This, for example, allows the combination of dynamic digital holography and Hartmann sensing procedures to cover a virtually unlimited dynamic range with high resolution. Digital holography technology brings all of the power and benefits of digital holographic interferometry to the requirement, while Hartmann-type wavefront sensors bring deflectometry technologies to the solution. The SLM can be used to generate arbitrary wavefronts in one leg of the interferometer, thereby greatly simplifying its use and extending its range. The SLM can also be used to modify the system into a dynamic Shack-Hartmann system, which is useful for optical components with large amounts of slope. By integrating these capabilities into a single instrument, the system will have tremendous flexibility to measure a variety of optical shapes accurately.

Trolinger, James↗

NASA NTRS1994

Influence of technology on magnetic tape storage device characteristics

There are available today many data storage devices that serve the diverse application requirements of the consumer, professional entertainment, and computer data processing industries. Storage technologies include semiconductors, several varieties of optical disk, optical tape, magnetic disk, and many varieties of magnetic tape. In some cases, devices are developed with specific characteristics to meet specification requirements. In other cases, an existing storage device is modified and adapted to a different application. For magnetic tape storage devices, examples of the former case are 3480/3490 and QIC device types developed for the high end and low end segments of the data processing industry respectively, VHS, Beta, and 8 mm formats developed for consumer video applications, and D-1, D-2, D-3 formats developed for professional video applications. Examples of modified and adapted devices include 4 mm, 8 mm, 12.7 mm and 19 mm computer data storage devices derived from consumer and professional audio and video applications. With the conversion of the consumer and professional entertainment industries from analog to digital storage and signal processing, there have been increasing references to the 'convergence' of the computer data processing and entertainment industry technologies. There has yet to be seen, however, any evidence of convergence of data storage device types. There are several reasons for this. The diversity of application requirements results in varying degrees of importance for each of the tape storage characteristics.

Gniewek, John J.↗

NASA NTRS2016

Wavelet-Based Processing for Fiber Optic Sensing Systems

The present invention is an improved method of processing conglomerate data. The method employs a Triband Wavelet Transform that decomposes and decimates the conglomerate signal to obtain a final result. The invention may be employed to improve performance of Optical Frequency Domain Reflectometry systems.

Hamory, Philip J.↗

NASA NTRS1992

The Airborne Ocean Color Imager - System description and image processing

The Airborne Ocean Color Imager was developed as an aircraft instrument to simulate the spectral and radiometric characteristics of the next generation of satellite ocean color instrumentation. Data processing programs have been developed as extensions of the Coastal Zone Color Scanner algorithms for atmospheric correction and bio-optical output products. The latter include several bio-optical algorithms for estimating phytoplankton pigment concentration, as well as one for the diffuse attenuation coefficient of the water. Additional programs have been developed to geolocate these products and remap them into a georeferenced data base, using data from the aircraft's inertial navigation system. Examples illustrate the sequential data products generated by the processing system, using data from flightlines near the mouth of the Mississippi River: from raw data to atmospherically corrected data, to bio-optical data, to geolocated data, and, finally, to georeferenced data.

Wrigley, Robert C.↗