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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

An assessment of LANDSAT data acquisition history on identification and area estimation of corn and soybeans

Multitemporally registered LANDSAT MSS data from four acquisitions during the 1978 growing season were used in classification of eight sample segments in Iowa and Indiana. The results illustrate that use of LANDSAT acquisition when corn has tasseled is critical, as this is the optimum time for separation of corn and soybeans. An early season acquisition when the summer crops appear as bare soil can be beneficial in reducing the confusion between these two crops and other cover types. A subset of one visible and one infrared band from each date was found to produce results not significantly different from the use of all bands. Selection of a subset of these bands may also be feasible for multitemporal analysis.

Hixson, M. M.↗
NASA NTRS1980

Evaluating LANDSAT wildland classification accuracies

Procedures to evaluate the accuracy of LANDSAT derived wildland cover classifications are described. The evaluation procedures include: (1) implementing a stratified random sample for obtaining unbiased verification data; (2) performing area by area comparisons between verification and LANDSAT data for both heterogeneous and homogeneous fields; (3) providing overall and individual classification accuracies with confidence limits; (4) displaying results within contingency tables for analysis of confusion between classes; and (5) quantifying the amount of information (bits/square kilometer) conveyed in the LANDSAT classification.

Toll, D. L.↗
NASA NTRS1981

Rayleigh scattering

The physical phenomena of molecular scattering are examined with the objective of redefining the confusing terminology currently used. The following definitions are proposed: molecular scattering consists of Rayleigh and vibrational Raman scattering; the Rayleigh scattering consists of rotational Raman lines and the central Cabannes line; the Cabannes line is composed of the Brillouin doublet and the central Gross or Landau-Placzek line. The term 'Rayleigh line' should never be used.

Young, A. T.↗
NASA NTRS1980

Planetary observations with the Tidbinbilla interferometer

Radio observations at a wavelength of 13.1 cm of Saturn and Uranus made with the Tidbinbilla interferometer during 1978 and 1979 are summarized. The observations were made with 64-m and 26-m antennas on a 200-m north-south baseline at a bandwidth of 12 MHz with RCP polarization and a primary beamwidth of about 12 arcmin. A flux density of 198 + or - 15 mJy was measured for Saturn, which indicates a surface temperature, corrected for the occulting effect of the rings, of 191 + or - 15 K, in excellent agreement with previous determinations. With the use of a background subtraction technique to remove the local background confusion, Uranus was found to have a flux density of 11.7 + or - 0.8 mJy, indicating a disk-averaged brightness temperature of 255 + or - 18 K. The increase in Uranus brightness temperature over that measured 15 years previously is attributed to variations in temperature or opacity below the cloud tops, or to a reduction in relative ammonia abundance most likely reflecting a change in the aspect of the planet as viewed from earth.

Batty, M. J.↗
NASA NTRS1981

On the Rayleigh-scattering optical depth of the atmosphere

It is pointed out that revised Rayleigh-scattering optical depths published by Hoyt (1977) are not correct, because King's (1923) formula, which was used by Hoyt, requires that the rotational lines be included in the polarization measurement. To exclude them is to exclude the contribution of the Raman-shifted photons to the total molecular extinction. Hoyt's error was repeated by Froehlich and Shaw (1980), who also confused the depolarization for natural light with that for (polarized) laser light. In an effort to clarify basic concepts, attention is given to the origin of the depolarization correction, depolarization ratios, vibrational Raman effects, and extinction measurements.

Young, A. T.↗
NASA NTRS1981

Infrared reflection nebulae in S 106 and NGC 7538 E

Two micron linear polarimetry of the S 106 and NGC 7538 E regions reveal the presence of infrared reflection nebulae, which may confuse the count of luminosity sources in a region of star formation. S 106 and NGC 7538/IRS 9 are considered the only luminosity sources in their respective regions, and the polarization of S 106/Source 3 is probably due to absorption by aligned grains. Moreover, the reflection nebula model for NGC 7538 E is best supported if the polarization of NGC 7538/IRS 9 itself is due to the absorption by aligned grains.

Tokunaga, A. T.↗
NASA NTRS1981

Using Landsat MSS data with soils information to identify wetland habitats

A previous study showed that certain fresh water wetland vegetation types can be spectrally separated when a maximum likelihood classification procedure is applied to Landsat spectral data. However, wetland and upland types which have similar vegetative life forms (e.g., upland hardwoods and hardwood swamps) are often confused because of spectral similarity. Therefore, the current investigation attempts to differentiate similar wetland and upland types by combining Landsat multispectral scanner (MSS) data with soils information. The Pigeon River area in northern Indiana used in the earlier study was also employed in this investigation. A layered classification algorithm which combined soils and spectral data was used to generate a wetland classification. The results of the spectral/soils wetland classification are compared to the previous classification that had been based on spectral data alone. The results indicate wetland habitat mapping can be improved by combining soils and other ancillary data with Landsat spectral data.

Ernst, C. L.↗
NASA NTRS1981

Spherical harmonic representation of the main geomagnetic field for world charting and investigations of some fundamental problems of physics and geophysics

Quiet-day data from MAGSAT were examined for effects which might test the validity of Maxwell's equations. Both external and toroidal fields which might represent a violation of the equations appear to exist, well within the associated errors. The external field might be associated with the ring current, and varies of a time-scale of one day or less. Its orientation is parallel to the geomagnetic dipole. The toriodal field can be confused with an orientation in error (in yaw). It the toroidal field really exists, its can be related to either ionospheric currents, or to toroidal fields in the Earth's core in accordance with Einstein's unified field theory, or to both.

Barraclough, D. R.↗
NASA NTRS1981

An evaluation of ISOCLS and CLASSY clustering algorithms for forest classification in northern Idaho

Both the iterative self-organizing clustering system (ISOCLS) and the CLASSY algorithms were applied to forest and nonforest classes for one 1:24,000 quadrangle map of northern Idaho and the classification and mapping accuracies were evaluated with 1:30,000 color infrared aerial photography. Confusion matrices for the two clustering algorithms were generated and studied to determine which is most applicable to forest and rangeland inventories in future projects. In an unsupervised mode, ISOCLS requires many trial-and-error runs to find the proper parameters to separate desired information classes. CLASSY tells more in a single run concerning the classes that can be separated, shows more promise for forest stratification than ISOCLS, and shows more promise for consistency. One major drawback to CLASSY is that important forest and range classes that are smaller than a minimum cluster size will be combined with other classes. The algorithm requires so much computer storage that only data sets as small as a quadrangle can be used at one time.

Werth, L. F.↗
NASA NTRS1980

Analysis of urban area land cover using SEASAT Synthetic Aperture Radar data

Digitally processed SEASAT synthetic aperture raar (SAR) imagery of the Denver, Colorado urban area was examined to explore the potential of SAR data for mapping urban land cover and the compatability of SAR derived land cover classes with the United States Geological Survey classification system. The imagery is examined at three different scales to determine the effect of image enlargement on accuracy and level of detail extractable. At each scale the value of employing a simplistic preprocessing smoothing algorithm to improve image interpretation is addressed. A visual interpretation approach and an automated machine/visual approach are employed to evaluate the feasibility of producing a semiautomated land cover classification from SAR data. Confusion matrices of omission and commission errors are employed to define classification accuracies for each interpretation approach and image scale.

Henderson, F. M.↗
NASA NTRS1981

A Wolter type I LAMAR

Observational objectives for the LAMAR and their influence on the instrument design are discussed. It is concluded that the most important design parameter is the angular resolution of the LAMAR modules since it so strongly influences sensitivity, optical identifications, source confusion, spectral resolution for objective gratings and the ability to resolve small extended sources. A high resolution Wolter Type I LAMAR module is described, its hardware status discussed, and the performance of a LAMAR observatory presented. A promising technique for enhancing the reflectivity of Wolter Type I X-ray optics in a selected bandpass at high energy has been investigated and the performance of the LAMAR module, utilizing this method, has been calculated.

Catura, R. C.↗
NASA NTRS1982

Mapping of wildlife habitat in Farmington Bay, Utah

Mapping was accomplished through the interpretation of high-altitude color infrared photography. The feasibility of utilizing LANDSAT digital data to augment the analysis was explored; complex patterns of wildlife habitat and confusion of spectral classes resulted in the decision to make limited use of LANDSAT data in the analysis. The final product is a map which delineates wildlife habitat at a scale of 1:24,000. The map is registered to and printed on a screened U.S.G.S. quadrangle base map. Screened delineations of shoreline contours, mapped from a previous study, are also shown on the map. Intensive field checking of the map was accomplished for the Farmington Bay Waterfowl Management Area in August 1981; other areas on the map received only spot field checking.

Jaynes, R. A.↗
NASA NTRS1982

Coordinated observations of Markarian 180 at ultraviolet, X-ray, optical and radio wavelengths

The results of multifrequency observations of MrK 180 = 1133+704, a BL Lac object embedded in a giant elliptical galaxy are presented. The importance of MrK 180 derives mostly from its association of a quasar-like object with a galaxy whose absorption line redshift (z = 0.046) unambiguously determines its distance. This implies that physical conditions within this local quasar can be discussed without the confusion introduced by distance uncertainties.

Mufson, S. L.↗
NASA NTRS1982

Coordinated observations of Markarian 501 at ultraviolet, X-ray, optical, and radio wavelengths

The results of multifrequency observations of MrK 501 = B2 1652+39 are presented here. It is a BL Lac object embedded in a giant elliptical galaxy obtained during the period August 1980 - March 1981. It is argued that MrK 501 varies sufficiently slowly at ultraviolet, optical and radio wavelengths on time scales of months that the data are representative of a spectrum obtained at a single epoch. The importance of MrK 501 derives mostly from its association of a quasar-like object with a galaxy whose absorption-line redshift (z = 0.034) unambiguously determines its distance. This implies that physical conditions within this local quasar can be discussed without the confusion introduced by distance uncertainties.

Hutter, D. J.↗
NASA NTRS1980

Preliminary results of mapping urban land cover with Seasat SAR imagery

The detectability of urban land cover types is explored using digitally processed Seasat SAR imagery of the Denver, Colorado area. Test sites within the metropolitan area were selected to include a cross section of Anderson, et. al. Level II land cover classes and cover types representative of the urban area growth stages. Using the Image 100 interactive processing system each test site was level sliced in an attempt to define specific reflectance boundaries for each cover type and to determine the spectral and spatial characteristics of homogeneous response regions. The rural-urban fringe boundary was readily definable, but a precise Level I and Level II land cover classification was not possible. High density housing could be separated from low density housing and from parks, but reflectance values were often look angle dependent. Confusion between some water and vegetation responses also posed problems.

Henderson, F. M.↗
NASA NTRS1981

The planetary nebula NGC 6826

Monochromatic photographs have established the NGC 6826 nebula as the third member of a group of very rare triple-shell planetaries (Feibelman, 1971, 1974). Kaler (1974) also characterized NGC 6826 as a giant halo planetary. Numerous errors and confusing statements regarding its size, structure and stratification are discussed, and the correct dimensions of the nebula are reported: the inner ring is 12.7 arcsec x 8.7 arcsec (Feibelman, 1971); the outer ring is 27 arcsec x 24 arcsec according to Curtis (1918), 25.7 arcsec x 24.4 arcsec according to Feibelman (1971), and 36 arcsec x 36 arcsec according to Coleman et al. (1975). The halo measurements range in diameter from 110 arcsec (Duncan, 1937) to 130 arcsec (Kaler, 1974) to 142 arcsec (Millikan, 1974). Values for the distance of NGC 6826 range from 0.75-1.16 kpc (Cahn and Kaler, 1971) to 2.265 kpc (Cudworth, 1974).

Feibelman, W. A.↗
NASA NTRS1982

Tidbinbilla two-element interferometer

A phase-stable two-element interferometer has been formed by linking the 64- and 34-m antennas of the Deep Space Network at Tidbinbilla, Australia. Utilizing the existing first-stage maser receivers at 2.3 GHz to yield a system temperature of approximately 20 K, the system has a 5 sigma detection sensitivity of 50 mJy in 1 s, with a rms confusion of approximately 6 mJy. The 195-m north-south baseline permits positional measurements to approximately 2 arcsec of sources stronger than approximately 100 mJy over the declination range -80 to +30 deg. Such measurements are ideally suited for the optical identification of weak radio sources. It is planned to extend the frequency of operation of the instrument to 8.4 GHz in the near future.

Batty, M. J.↗
NASA NTRS1984

A File Archival System

ARCH, file archival system for DEC VAX, provides for easy offline storage and retrieval of arbitrary files on DEC VAX system. System designed to eliminate situations that tie up disk space and lead to confusion when different programers develop different versions of same programs and associated files.

Fanselow, J. L.↗