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At least 1,027 records · Page 57

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NASA NTRS1993

OLS data system/global survey of lightning

A global lightning climatology is being assembled from the nighttime imagery of the DMSP Optical Linescan Sensor (OLS). Lightning saturates the visible channel of the OLS at nighttime and can be identified as a horizontal streak on the order of 50-100 km in horizontal extent. Lightning streaks apparent in the film strips located at the National Snow and Ice Data Center (NSIDC) prior to 1991 are being digitized. An initial survey was completed for the F7 satellite observation period January 1986 - October 1987 and for the Q satellite for the period June-July 1973. Comparisons between the OLS lightning climatology with the Arkin GPI data set during the 1986-87 El Nino event shows similar regional variations in convective activity. The digital archive of global DMSP data began at the end of February. Software is being developed at both MSFC and NSIDC to extract, navigate, and view the OLS fine and smooth imagery.

Goodman, Steven J.↗

NASA NTRS1993

Interim report on Landsat national archive activities

The Department of the Interior (DOI) has the responsibility to preserve and to distribute most Landsat Thematic Mapper (TM) and Multispectral Scanner (MSS) data that have been acquired by the five Landsat satellites operational since July 1972. Data that are still covered by exclusive marketing rights, which were granted by the U.S. Government to the commercial Landsat operator, cannot be distributed by the DOI. As the designated national archive for Landsat data, the U.S. Geological Survey's EROS Data Center (EDC) has initiated two new programs to protect and make available any of the 625,000 MSS scenes currently archived and the 200,000 TM scenes to be archived at EDC by 1995. A specially configured system has begun converting Landsat MSS data from obsolete high density tapes (HDT's) to more dense digital cassette tapes. After transcription, continuous satellite swaths are (1) divided into standard scenes defined by a world reference system, (2) geographically located by latitude and longitude, and (3) assessed for overall quality. Digital browse images are created by subsampling the full-resolution swaths. Conversion of the TM HDT's will begin in the fourth quarter of 1992 and will be conducted concurrently with MSS conversion. Although the TM archive is three times larger than the entire MSS archive, conversion of data from both sensor systems and consolidation of the entire Landsat archive at EDC will be completed by the end of 1994. Some MSS HDT's have deteriorated, primarily as a result of hydrolysis of the pigment binder. Based on a small sample of the 11 terabytes of post-1978 MSS data and the 41 terabytes of TM data to be converted, it appears that to date, less than 2 percent of the data have been lost. The data loss occurs within small portions of some scenes; few scenes are lost entirely. Approximately 10,000 pre-1979 MSS HDT's have deteriorated to such an extent, as a result of hydrolysis, that the data cannot be recovered without special treatment of the tapes. An independent consulting division of a major tape manufacturer has analyzed affected tapes and is confident that restorative procedures can be applied to the HDT's to permit one pass to reproduce the data on another recording media. A system to distribute minimally processed Landsat data will be procured in 1992 and will be operational by mid-1994. Any TM or MSS data in the national archive that are not restricted by exclusive marketing rights will be reproduced directly from the archive media onto user specified computer-compatible media. TM data will be produced either at a raw level (radiometrically and geometrically uncorrected) or at an intermediate level (radiometrically corrected and geometrically indexed). MSS data will be produced to an intermediate level or to a fully corrected level (radiometrically corrected and geometrically transformed to an Oblique Mercator projection). The system will be capable of providing ordered scenes within 48 hours of receipt of order.

Boyd, John E.↗

NASA NTRS1996

SeaWiFS Technical Report Series: SeaWiFS Calibration Topics - Volume 39

For Earth-observing satellite instruments, it was standard to consider each instrument band to have a spectral response that is infinitely narrow, i.e., to have a response from a single wavelength. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) bands, however, have nominal spectral bandwidths of 20 and 40nm. These bandwidths affect the SeaWiFS measurements on orbit. The effects are also linked to the manner in which the instrument was calibrated and to the spectral shape of the radiance that SeaWiFS views. Currently, SeaWiFS is calibrated such that the digital counts from each instrument band are linked to the Earth-exiting radiance at an individual center wavelength. Before launch, SeaWiFS will be recalibrated so that the digital counts from each band will be linked to the Earth-exiting radiance integrated over the spectral response of that band. In this technical memorandum, the effects of the instrument calibration and the source spectral shape on SeaWiFS measurements, including the in-band and out-of-band responses, and the center wavelengths are discussed.

Hooker, Stanford B.↗

NASA NTRS1994

The Area Coverage of Geophysical Fields as a Function of Sensor Field-of View

In many remote sensing studies of geophysical fields such as clouds, land cover, or sea ice characteristics, the fractional area coverage of the field in an image is estimated as the proportion of pixels that have the characteristic of interest (i.e., are part of the field) as determined by some thresholding operation. The effect of sensor field-of-view on this estimate is examined by modeling the unknown distribution of subpixel area fraction with the beta distribution, whose two parameters depend upon the true fractional area coverage, the pixel size, and the spatial structure of the geophysical field. Since it is often not possible to relate digital number, reflectance, or temperature to subpixel area fraction, the statistical models described are used to determine the effect of pixel size and thresholding operations on the estimate of area fraction for hypothetical geophysical fields. Examples are given for simulated cumuliform clouds and linear openings in sea ice, whose spatial structures are described by an exponential autocovariance function. It is shown that the rate and direction of change in total area fraction with changing pixel size depends on the true area fraction, the spatial structure, and the thresholding operation used.

Key, Jeffrey R.↗

NASA NTRSDate not supplied

Development of a Compact Lidar Sensor for Terrain Relative Navigation and Terrain Hazard Avoidance

A Lidar sensor utilizing linear-mode flash lidar technology and a novel Super-Resolution technique has been developed for providing Terrain Relative Navigation and Hazard Avoidance capabilities onboard landing vehicles. Processing algorithms for precision navigation and safe landing location identification take advantage of the uniform fixed pixels property of generated high resolution Digital Elevation Maps to achieve high reliability operation in near real-time. This paper describes the results of drone and helicopter flight tests of a breadboard system, explains the design and capabilities of a recently built compact prototype unit, and proposes a concepts of operation for future landing missions.

3-D Imaging↗

NASA NTRS1990

Computer Assembles Mosaics Of Satellite-SAR Imagery

Digital image-processing system assembles maplike mosaic images of large areas of Earth from overlapping images of smaller areas generated by spaceborne synthetic-aperture radar (SAR). Automatically registers and blends smaller images with each other. Eliminates need for time-consuming, tedious manual processing. Modifiable to accept images from spaceborne optical sensors.

Kwok, R.↗

NASA NTRS1982

The SIR-B science plan

The Shuttle Imaging Radar-B (SIR-B) will be the third in a series of spaceborne SAR experiments conducted by NASA which began with the 1978 launch of SEASAT and continued with the 1981 launch of SIR-A. Like SEASAT and SIR-A, SIR-B will operate at L-band and will be horizontally polarized. However, SIR-B will allow digitally processed imagery to be acquired at selectable incidence angles between 15 and 60 deg, thereby permitting, for the first time, parametric studies of the effect of illumination geometry on SAR image information extraction. This document presents a science plan for SIR-B and serves as a reference for the types of geoscientific, sensor, and processing experiments which are possible.

Source record↗

NASA NTRS1984

Pre-launch Absolute Radiometric Calibration of LANDSAT-4 Protoflight Thematic Mapper

From both scientific and applications perspectives, the usefulness of TM digital imagery is significantly determined by its radiometric characteristics. This includes both the accuracy to which the dynamic range is known and its radiometric reproducibility or precision. Results from several pre-launch tests with a 122-cm Integrating Sphere (IS) used as part of the absolute radiometric calibration experiments for the protoflight TM sensor carried on the LANDSAT-4 satellite are summarized and analyzed. Topics covered include TM radiometric calibration and sensitivity; the TM internal calibrator; and the dynamic range after calibration.

Barker, J. L.↗

NASA NTRSDate not supplied

International Satellite Cloud Climatology Project (ISCCP) Ice Snow Product in Native (NAT) Format (ISCCP_ICESNOW_NAT)

Since 1983 an international group of institutions has collected and analyzed satellite radiance measurements from up to five geostationary and two polar orbiting satellites to infer the global distribution of cloud properties and their diurnal, seasonal and interannual variations. The primary focus of the first phase of the project (1983-1995) was the elucidation of the role of clouds in the radiation budget (top of the atmosphere and surface). In the second phase of the project (1995 onwards) the analysis also concerns improving understanding of clouds in the global hydrological cycle. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1983-07-01; Stop_Date=] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=112 Km; Longitude_Resolution=112 Km; Temporal_Resolution=5-day].

SNOW COVER↗

NASA NTRS1993

An Application of a New Electromagnetic Sensor to Real-Time Monitoring of Fatigue Crack Growth in Thin Metal Plates

A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles which necessitates automation of the whole process. If the rate of crack growth can be determined the experimenter can vary externally controlled parameters such as load level, load cycle frequency and so on. Hence, knowledge of the precise location of the crack tip at any given time is very valuable. One technique currently available for measuring fatigue crack length is the DC potential drop method. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another approach is to digitize an optical image of the test specimen surface and then apply a pattern recognition technique to locate the crack tip, but this method is still under development. The present work is an initial study on applying eddy current-type probes to monitoring fatigue crack growth. The performance of two types of electromagnetic probes, a conventional eddy current probe and a newly developed self-nulling probe, was evaluated for the detection characteristics at and near the tips of fatigue cracks. The scan results show that the latter probe provides a very well defined local maximum in its output in the crack tip region suggesting the definite possibility of precisely locating the tip, while the former provides a somewhat ambiguous distribution of the sensor output in the same region. The paper is organized as follows: We start by reviewing the design and performance characteristics of the self-nulling probe and then describe the scan results which demonstrate the basic properties of the self-nulling probe. Next, we provide a brief description of the software developed for tracing a simulated crack and give a brief discussion of the main results of the test. The final section summarizes the major accomplishments of the present work and the elements of the future R&D needs.

Namkung, M.↗

NASA NTRS1974

Michigan experimental multispectral mapping system: A description of the M7 airborne sensor and its performance

The development and characteristics of a multispectral band scanner for an airborne mapping system are discussed. The sensor operates in the ultraviolet, visual, and infrared frequencies. Any twelve of the bands may be selected for simultaneous, optically registered recording on a 14-track analog tape recorder. Multispectral imagery recorded on magnetic tape in the aircraft can be laboratory reproduced on film strips for visual analysis or optionally machine processed in analog and/or digital computers before display. The airborne system performance is analyzed.

Hasell, P. G., Jr.↗

NASA NTRS1988

Digital and optical shape representation and pattern recognition; Proceedings of the Meeting, Orlando, FL, Apr. 4-6, 1988

The present conference discusses topics in pattern-recognition correlator architectures, digital stereo systems, geometric image transformations and their applications, topics in pattern recognition, filter algorithms, object detection and classification, shape representation techniques, and model-based object recognition methods. Attention is given to edge-enhancement preprocessing using liquid crystal TVs, massively-parallel optical data base management, three-dimensional sensing with polar exponential sensor arrays, the optical processing of imaging spectrometer data, hybrid associative memories and metric data models, the representation of shape primitives in neural networks, and the Monte Carlo estimation of moment invariants for pattern recognition.

Juday, Richard D.↗

NASA NTRS2012

Simulation of Image Performance Characteristics of the Landsat Data Continuity Mission (LDCM) Thermal Infrared Sensor (TIRS)

The next Landsat satellite, which is scheduled for launch in early 2013, will carry two instruments: the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). Significant design changes over previous Landsat instruments have been made to these sensors to potentially enhance the quality of Landsat image data. TIRS, which is the focus of this study, is a dual-band instrument that uses a push-broom style architecture to collect data. To help understand the impact of design trades during instrument build, an effort was initiated to model TIRS imagery. The Digital Imaging and Remote Sensing Image Generation (DIRSIG) tool was used to produce synthetic "on-orbit" TIRS data with detailed radiometric, geometric, and digital image characteristics. This work presents several studies that used DIRSIG simulated TIRS data to test the impact of engineering performance data on image quality in an effort to determine if the image data meet specifications or, in the event that they do not, to determine if the resulting image data are still acceptable.

Landsat↗

NASA NTRSDate not supplied

Development and Airborne Demonstration of the Concurrent Artificially-Intelligent Spectrometry and Adaptive Lidar System: Advancing Lidar Capabilities for the STV Observing System

We report on the design, build and planned airborne demonstration of a spaceflight-prototype Concurrent Artificially-intelligent Spectrometry and Adaptive Lidar System (CASALS). The CASALS lidar is an Adaptive Wavelength Scanning Lidar (AWSL) operating in push broom mode. The demonstration has three major goals: advance the Technical Readiness Level of the AWSL hardware, validate its measurement performance and mature algorithms and methods needed for the Surface Topography and Vegetation (STV) observing system. AWSL acquires parallel tracks of surface heights by rapidly steering a laser beam across a swath. A 1040nm-centered laser is tuned across 30nm and carved into 2-ns pulses, the pulse energy is fiber amplified and the pulses are dispersed cross-track using a non-mechanical wavelength-to-angle grating. For the spaceflight system the beam will be pointable to 1200 10m footprints across a 7km swath. For the airborne demonstration there will be 256 0.7m footprints across a 110m swath. In both cases the footprints overlap across- and along-track for uniform target illumination. For the airborne demonstration a steering mirror will increase the accessible swath width to 4km. At the receiver, solar radiation is filtered with a narrow-slit grating-spectrometer and the footprints are imaged onto a linear-mode, photon-sensitive HgCdTe APD-array. The received pulses are time-division-multiplexed to a few high-speed analog-to-digital converters to record waveforms. Spaceflight and airborne CASALS are designed to nominally detect 20 photons per pulse and, by averaging 27 overlapping footprints, achieve 2cm flat target range precision and high-quality vegetation structure waveforms The AWSL will be flown in the summer of 2024, along with a Headwall VNIR-SWIR hyperspectral sensor imaging a 4km wide swath, at NEON eddy covariance flux towers in the U.S. mid-Atlantic where high resolution hyperspectral and lidar data, acquired annually, are available for validation.

Guangning Yang↗

NASA NTRS2000

Design and Analysis of Precise Pointing Systems

The mathematical models of Glovebox Integrated Microgravity Isolation Technology (g- LIMIT) dynamics/control system, which include six degrees of freedom (DOF) equations of motion, mathematical models of position sensors, accelerometers and actuators, and acceleration and position controller, were developed using MATLAB and TREETOPS simulations. Optimal control parameters of G-LIMIT control system were determined through sensitivity studies and its performance were evaluated with the TREETOPS model of G-LIMIT dynamics and control system. The functional operation and performance of the Tektronix DTM920 digital thermometer were studied and the inputs to the crew procedures and training of the DTM920 were documented.

Kim, Young K.↗

NASA NTRS1992

Terrain Simulation

A highlight of the IMAX film, Blue Planet, is a 100-second computer- generated animation of a flight and earthquake simulation along California's San Andreas Fault. Created by the VESA group at the Jet Propulsion Laboratory, the sequence required the development of a technique to make possible terrain rendering of very large digital images. An image mosaic of California constructed from Landsat data made this possible. An advanced pyramidal terrain rendering technique was developed, significantly reducing the necessary time involved in transferring the Landsat data to film. The new technique has also enabled NASA to develop new perspective rendering technologies in order to cope with anticipated increased remote sensor data.

Source record↗

NASA NTRS1988

Sports Training

Practitioners of martial arts have long seen a need for a precise method of measuring the power of a karate kick or a boxer's punch in training and competition. Impax sensor is a piezoelectric film less than one thousandth of an inch thick, yet extremely durable. They give out a voltage impulse when struck, the greater the force of impact, the higher the voltage. The impulse is transmitted to a compact electronics package where voltage is translated into a force-pounds reading shown on a digital display. Impax, manufactured by Impulse Technology, Inc. is used by martial arts instructors, practitioners, U.S. Olympic Committee Training Center, football blocking sleds, and boxers as well as police defensive tactics, providing a means of evaluating the performance of recruits.

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NASA NTRS1978

Solar Energy Reporting

Last year the people of Cleveland, Ohio were troubled by natural gas shortages during one of the coldest winters on record. The severe winter generated a great deal of interest in solar energy as an alternative source of heat. Home owners, home builders and civic officials wanted to know just how much solar energy is available in Cleveland. Now they get a daily report through the city's news media, from information supplied as a community service by NASA's Lewis Research Center. Lewis routinely makes daily measurements of solar energy as part of its continuing research in behalf of the Department of Energy. The measuring device is a sun sensor called a pyranometer (upper photo) located atop a building at the NASA Center. To make the information conveniently available to news media, Lewis developed a Voice Output Integrating Insolometer, an automated system that acquires information from the sun sensor and translates it into a recorded telephone message. The Lewis pyranometer collects sun data for 15 hours daily and measures the total solar energy yield. For reporting to the public, the information is electronically converted to a specific reading. A media representative calling in gets a voice-synthesized announcement of a two or three digit number; the number corresponds to the kilowatt-hours of solar energy that would be available to a typical 500-square-foot solar collector system. Response in Cleveland has been favorable and interest is developing in other parts of the country.

Source record↗