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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

The mixture problem in computer mapping of terrain: Improved techniques for establishing spectral signature, atmospheric path radiance, and transmittance

The results of LANDSAT and Skylab research programs on the effects of the atmosphere on computer mapping of terrain include: (1) the concept of a ground truth map needs to be drastically revised; (2) the concept of training areas and test areas is not as simple as generally thought because of the problem of pixels that represent a mixture of terrain classes; (3) this mixture problem needs to be more widely recognized and dealt with by techniques of calculating spectral signatures of mixed classes, or by other methods; (4) atmospheric effects should be considered in computer mapping of terrain and in monitoring changes; and (5) terrain features may be used as calibration panels on the ground, from which atmospheric conditions can be determined and monitored. Results are presented of a test area in mountainous terrain of south-central Colorado for which an initial classification was made using simulated mixture-class spectral signatures and actual LANDSAT-1-MSS data.

Smedes, H. W.↗
NASA NTRS1976

Ballastic signature identification systems study

The results are described of an attempt to establish a uniform procedure for documenting (recording) expended bullet signatures as effortlessly as possible and to build a comprehensive library of these signatures in a form that will permit the automated comparison of a new suspect bullet with the prestored library. The ultimate objective is to achieve a standardized format that will permit nationwide interaction between police departments, crime laboratories, and other interested law enforcement agencies.

Reich, A.↗
NASA NTRS1976

Ballistic Signature Identification System Study

The first phase of a research project directed toward development of a high speed automatic process to be used to match gun barrel signatures imparted to fired bullets was documented. An optical projection technique has been devised to produce and photograph a planar image of the entire signature, and the phototransparency produced is subjected to analysis using digital Fourier transform techniques. The success of this approach appears to be limited primarily by the accuracy of the photographic step since no significant processing limitations have been encountered.

Source record↗
NASA NTRS1977

Remotely sensed and laboratory spectral signatures of an ocean-dumped acid waste

An ocean-dumped acid waste plume was studied by using a rapid scanning spectrometer to remotely measure ocean radiance from a helicopter. The results of these studies are presented and compared with results from sea truth samples and laboratory experiments. An ocean spectral reflectance signature and a laboratory spectral transmission signature were established for the iron-acid waste pollutant. The spectrally and chemically significant component of the acid waste pollutant was determined to be ferric iron.

Lewis, B. W.↗
NASA NTRS1976

The ground signatures of the expansion phase during multiple onset substorms

The paper examines the signatures of multiple-expansion-phase substorm onsets in night-time magnetograms as well as in recordings of auroral activity and energetic electron precipitation. Individual onsets of Pi2 magnetic pulsations observed at three widely spaced stations are used to define and time each onset accurately in order to distinguish between local variations in bay activity and fully developed substorm onsets; this method is equivalent to defining each new onset in terms of the brightening of an auroral arc and the formation of a westward-travelling surge. It is found that the formation of multiple auroral surges appears to be a fundamental feature of multiple-onset substorms, that each surge seems to be associated with a localized field-aligned current system which moves westward with the surge and perturbs the preexisting current wedge, and that this gives rise to the multiple-onset signatures observed on subauroral and low-latitude magnetograms. Since certain findings contradict existing models of multiple-onset events, an alternative model is proposed which is based on the fundamental role of surge activity and localized current wedges.

Pytte, T.↗
NASA NTRS1977

LANDSAT data from agricultural sites: Crop signature analysis

The LANDSAT multispectral scanner (MSS) data were analyzed with a view toward classification to identify wheat. The notion of spectral signature of a crop, a commonly used basis for classification, was found to be inadequate. Data analysis has revealed that the MSS data from agricultural sites were essentially two dimensional, and that the data from different sites and different acquisition lay on parallel planes in the four dimensional feature space. These results were exploited to gain new insight into the data and to develop alternate models for classification. In particular, it was found that the temporal pattern of change in the spectral response of a crop constitutes its signature and provides a basis for crop classification.

Misra, P. N.↗
NASA NTRS1977

Performance tests of signature extension algorithms

Comparative tests were performed on seven signature extension algorithms to evaluate their effectiveness in correcting for changes in atmospheric haze and sun angle in a LANDSAT scene. Four of the algorithms were cluster matching, and two were maximum likelihood algorithms. The seventh algorithm determined the haze level in both training and recognition segments and used a set of tables calculated from an atmospheric model to determine the affine transformation that corrects the training signatures for changes in sun angle and haze level. Three of the algorithms were tested on a simulated data set, and all of the algorithms were tested on consecutive-day data.

Abotteen, R. A.↗
NASA NTRS1977

Evaluation of the in-flight noise signature of a 32-chute suppressor nozzle: Acoustic data report

Outdoor static and 40 x 80 FT wind tunnel tests of the J79-15 engine/nacelle system with the conic nozzle and 32-chute exhaust suppressor were conducted to acquire the data necessary to evaluate the simulated in-flight signature of an engine-size 32-chute exhaust nozzle suppressor using the 40 x 80 ft wind tunnel and to study possible engine core noise contamination of the jet signature. The tests are described and and a sampling of the data acquired is presented. Included are aero performance summaries, as-measured and composite 1/3 OBSPL spectra for the 70 ft sideline high and low mics from the outdoor static tests, sideline traverse spectra and internal noise measurements from both the outdoor static and the 40 x 80 ft wind tunnel tests.

Moore, M. T.↗
NASA NTRS1977

Landsat data from agricultural sites - Crop signature analysis

The Landsat multispectral scanner (MSS) data have been analyzed with a view toward classification to identify wheat. The notion of spectral signature of a crop, a commonly used basis for classification, has been found to be inadequate. Data analysis has revealed that the MSS data from agricultural sites are essentially two dimensional, and that the data from different sites and different acquisitions lie on parallel planes in the four-dimensional feature space. These results have been exploited to gain new insight into the data and to develop alternate models for classification. In particular, it has been found that the temporal pattern of change in the spectral response of a crop constitutes its signature and provides a basis for crop classification.

Misra, P. N.↗
NASA NTRS1978

The statistical magnetic signature of magnetospheric substorms

Daily magnetograms from a midlatitude network of geomagnetic observatories were used in the analysis of approximately 1800 substorm events, and the characteristic magnetic signatures of magnetospheric substorms both on the ground and in space were determined. Auroral electrojet (AE) indices and individual magnetograms at different local times in the auroral zone and at midlatitudes were analyzed with reference to onsets, and superposed epoch averages of individual magnetograms and AE indices confirm the local time magnetic substorm signatures. Superposed epoch averages of the interplanetary magnetic field (IMF) associated with the onsets demonstrates both a distinct southward component prior to the onsets and a dependence of the substorm amplitude on the integrated preceding southward IMF flux. Superposed epoch averages of the tail lobe magnetic field magnitude and vector components are discussed.

Caan, M. N.↗
NASA NTRS1978

A comprehensive data processing plan for crop calendar MSS signature development from satellite imagery: Crop identification using vegetation phenology

The author has identified the following significant results. The phenological method of crop identification involves the creation of crop signatures which characterize multispectral observations as phenological growth states. The phenological signature models spectral reflectance explicitly as a function of crop maturity rather than as a function of date. A correspondence of time to growth state is established which minimizes the smallest difference between the given multispectral multitemporal vector and a category mean vector. The application of the method to the identification of winter wheat and corn shows (1) the method is capable of discriminating crop type with about the same degree of accuracy as more traditional classifiers; (2) the use of LANDSAT observations on two or more dates yields better results than the use of a single observation; and (3) some potential is demonstrated for labeling the degree of maturity of the crop, as well as the crop type.

Hlavka, C. A.↗
NASA NTRS1979

Development of partitioning as an aid to spectral signature extension

Lists of spectrally similar LACIE sample segments may be constructed with the use of three basic information types: static, seasonal, and pass-specific variables. All are related directly or indirectly to spectral signature behavior and can be used to define spatial domains over which crop-specific signatures should be extendable. Topics covered include: (1) static spectral stratification; (2) evaluation of static partitions relative to variance control objectives; (3) evaluation of the relative importance of static versus seasonal and pass-specific partitioning variables in spectral variability; and (4) a current perspective on partitioning.

Thomas, R. W.↗
NASA NTRS1979

Methods of extending crop signatures from one area to another

Efforts to develop a technology for signature extension during LACIE phases 1 and 2 are described. A number of haze and Sun angle correction procedures were developed and tested. These included the ROOSTER and OSCAR cluster-matching algorithms and their modifications, the MLEST and UHMLE maximum likelihood estimation procedures, and the ATCOR procedure. All these algorithms were tested on simulated data and consecutive-day LANDSAT imagery. The ATCOR, OSCAR, and MLEST algorithms were also tested for their capability to geographically extend signatures using LANDSAT imagery.

Minter, T. C.↗
NASA NTRS1980

Cell short circuit, preshort signature

Short-circuit events observed in ground test simulations of DSCS-3 battery in-orbit operations are analyzed. Voltage signatures appearing in the data preceding the short-circuit event are evaluated. The ground test simulation is briefly described along with performance during reconditioning discharges. Results suggest that a characteristic signature develops prior to a shorting event.

Lurie, C.↗
NASA NTRS1979

Signature evaluation of natural targets using high spectral resolution techniques

The concept of 'spectral signature' identification has been applied to LANDSAT and other broad-band multi-spectral scanner data to classify various materials on the earth's surface. A large amount of the spectral information available is invisible, however, to the broad-band sensors. Although the natural targets of interest in remote sensing do not exhibit fine line features such as those associated with gaseous media, there is significant information to be extracted from smoothly varying spectral reflection functions of most natural targets. Subtle variations observed recently in the high resolution 'spectral signatures' of vegetation targets, in particular, promise to open new avenues of application using higher spectral and radiometric resolution techniques. This research was accomplished using a 500-band spectroradiometer system specially adapted to rapid airborne operations

Collins, W.↗
NASA NTRS1980

Radiation signatures from a locally energized flaring loop

The radiation signatures from a locally energized solar flare loop based on the physical properties of the energy release mechanisms were consistent with hard X-ray, microwave, and EUV observations for plausible source parameters. It was found that a suprathermal tail of high energy electrons is produced by the primary energy release, and that the number of energetic charged particles ejected into the interplanetary medium in the model is consistent with observations. The radiation signature model predicts that the intrinsic polarization of the hard X-ray burst should increase over the photon energy range of 20 to 100 keV.

Emslie, A. G.↗
NASA NTRS1981

Preserved signatures of ion flux modulations observed by ATS 6

The considered investigation is concerned with a detailed analysis of the event of August 13, 1974. The considered day was a geomagnetically quiet day, and ATS 6 was stationed at 94 deg W longitude. On the basis of the conducted analysis it is found that the observed flux oscillations may be a fossil signature of flux modulations which have occurred in ions at an earlier time and at a region away from the spot of observation. In conclusion, it is pointed out that the August 13, 1974, and the January 23, 1975, events of proton flux oscillations observed by ATS 6 are of great importance. They reveal another unique capability of the drifting particles for preserving small modulation signatures imposed upon them during earlier wave-particle interactions. At the present, no conclusions are drawn as to what kind of the wave-particle interaction process was responsible for the observation.

Su, S.-Y.↗