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NASA NTRS1991

Improving Sparse-Aperture Interferometric Radiometry

Proposed method for designing spatial arrangement of antennas of sparse-aperture interferometric radiometry (SAIR) system increases spatial resolution of images produced by system. Technique involves cross-correlation of signals received by pairs of small antennas at different locations. Includes ring array of "flood-beam" antennas. Signals from all possible pairs of antennas cross-correlated simultaneously. Diameter of ring determines spatial resolution of image, and distribution of antennas around ring determines sampling characteristics. Conceived to improve proposed remote-sensing SAIR system placed in geosynchronous orbit; also applied to other SAIR systems intended to stare at stationary targets for relatively long times.

Ruf, Christopher S.↗

NASA NTRS1991

Acousto-optical Filter Can Rapidly Tune Solid-State Lasers

Incorporation of acousto-optical tunable filter (AOTF) in cavity of solid-state laser, provides means of adjusting wavelength of laser output electronically, according to recent proposal. Output wavelength randomly selected in microseconds. Technique useful in remote-sensing applications, such as in differential-absorption lidar (DIAL) and in communications for wavelength-division multiplexing.

Lambert, James L.↗

NASA NTRS1991

Spaceborne Microwave Imagers

Monograph presents comprehensive overview of science and technology of spaceborne microwave-imaging systems. Microwave images used as versatile orbiting, remote-sensing systems to investigate atmospheres and surfaces of planets. Detect surface objects through canopies of clouds, measure distributions of raindrops in clouds that their views penetrate, find meandering rivers in rain forests and underground water in arid regions, and provide information on ocean currents, wakes, ice/water boundaries, aircraft, ships, buoys, and bridges.

Stacey, J. M.↗

NASA NTRS1990

Cloud and boundary layer structure over San Nicolas Island during FIRE

The temporal evolution of the structure of the marine boundary layer and of the associated low-level clouds observed in the vicinity of the San Nicolas Island (SNI) is defined from data collected during the First ISCCP Regional Experiment (FIRE) Marine Stratocumulus Intense Field Observations (IFO) (July 1 to 19). Surface, radiosonde, and remote-sensing measurements are used for this analysis. Sounding from the Island and from the ship Point Sur, which was located approximately 100 km northwest of SNI, are used to define variations in the thermodynamic structure of the lower-troposphere on time scales of 12 hours and longer. Time-height sections of potential temperature and equivalent potential temperature clearly define large-scale variations in the height and the strength of the inversion and periods where the conditions for cloud-top entrainment instability (CTEI) are met. Well defined variations in the height and the strength of the inversion were associated with a Cataline Eddy that was present at various times during the experiment and with the passage of the remnants of a tropical cyclone on July 18. The large-scale variations in the mean thermodynamic structure at SNI correlate well with those observed from the Point Sur. Cloud characteristics are defined for 19 days of the experiment using data from a microwave radiometer, a cloud ceilometer, a sodar, and longwave and shortwave radiometers. The depth of the cloud layer is estimated by defining inversion heights from the sodar reflectivity and cloud-base heights from a laser ceilometer. The integrated liquid water obtained from NOAA's microwave radiometer is compared with the adiabatic liquid water content that is calculated by lifting a parcel adiabatically from cloud base. In addition, the cloud structure is characterized by the variability in cloud-base height and in the integrated liquid water.

Albrecht, Bruce A.↗

NASA NTRS1990

Rapid calculation of terrain parameters for radiation modeling from digital elevation data

Digital elevation models are now widely used to calculate terrain parameters to determine incoming solar and longwave radiation for use in surface climate models, interpretation of remote-sensing data, and parameters in hydrologic models. Because of the large number of points in an elevation grid, fast algorithms are useful to save computation time. A description is given of rapid methods for calculating slope and azimuth, solar illumination angle, horizons, and view factors for radiation from sky and terrain. Calculation time is reduced by fast algorithms and lookup tables.

Dozier, Jeff↗

NASA NTRS1989

Modelling Rift Valley fever (RVF) disease vector habitats using active and passive remote sensing systems

The NASA Ames Ecosystem Science and Technology Branch and the U.S. Army Medical Research Institute of Infectious Diseases are conducting research to detect Rift Valley fever (RVF) vector habitats in eastern Africa using active and passive remote-sensing. The normalized difference vegetation index (NDVI) calculated from Landsat TM and SPOT data is used to characterize the vegetation common to the Aedes mosquito. Relationships have been found between the highest NDVI and the 'dambo' habitat areas near Riuru, Kenya on both wet and dry data. High NDVI values, when combined with the vegetation classifications, are clearly related to the areas of vector habitats. SAR data have been proposed for use during the rainy season when optical systems are of minimal use and the short frequency and duration of the optimum RVF mosquito habitat conditions necessitate rapid evaluation of the vegetation/moisture conditions; only then can disease potential be stemmed and eradication efforts initiated.

Ambrosia, Vincent G.↗

NASA NTRS1989

Radiometric sensitivity comparisons of multispectral imaging systems

Multispectral imaging systems provide much of the basic data used by the land and ocean civilian remote-sensing community. There are numerous multispectral imaging systems which have been and are being developed. A common way to compare the radiometric performance of these systems is to examine their noise-equivalent change in reflectance, NE Delta-rho. The NE Delta-rho of a system is the reflectance difference that is equal to the noise in the recorded signal. A comparison is made of the noise equivalent change in reflectance of seven different multispectral imaging systems (AVHRR, AVIRIS, ETM, HIRIS, MODIS-N, SPOT-1, HRV, and TM) for a set of three atmospheric conditions (continental aerosol with 23-km visibility, continental aerosol with 5-km visibility, and a Rayleigh atmosphere), five values of ground reflectance (0.01, 0.10, 0.25, 0.50, and 1.00), a nadir viewing angle, and a solar zenith angle of 45 deg.

Lu, Nadine C.↗

NASA NTRS1990

Thematic Conference on Remote Sensing for Exploration Geology - Methods, Integration, Solutions, 7th, Calgary, Canada, Oct. 2-6, 1989, Proceedings. Volumes 1 & 2

Recent advances in airborne and satellite remote-sensing technology for application to geological exploration are discussed in reviews and reports. Sections are devoted to basement tectonics and their surface expressions, spectral geology, hydrocarbon exploration applications, radar applications and future systems, engineering and environment issues, geobotanical remote sensing, advanced image processing, data integration and mapping, and mineral exploration. Extensive diagrams, graphs, and sample images are provided.

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NASA NTRS1989

Spectral mineralogy of terrestrial planets - Scanning their surfaces remotely

Information on the surface mineralogy, chemical composition, and lithology of terrestrial planets, as well as on their atmospheres, that can be obtained by earth-based from visible and NIR spectra of light reflected from planetary surfaces is discussed. Such reflectance spectra may have absorption bands in the 1- and 2-micron wavelength regions which originate from crystal field transitions within Fe(2+) ions. Since pyroxenes with Fe(2+) in M2 positions usually dominate the spectra, the resulting 1-micron vs 2-micron spectral determinative curves can be used to identify compositions and structural types of pyroxenes on the surface of a planet or an asteroid. Future spececraft missions to solar system objects will concentrate on remote-sensing experiments using visible and NIR reflectance spectra. These include the Galileo mission to Jupiter; the Mars Orbiter mission to Phoebus; the Comet Rendezvous Asteroid Flyby mission; the Cassini mission to Saturn; the Lunar Geoscience Observer; and the Mars Rover/Sample Return mission.

Burns, Roger G.↗

NASA NTRS1991

Calculations of H2O microwave line broadening in collisions with He atoms - Sensitivity to potential energy surfaces

Theoretical computations of broadening parameters are reported for three microwave lines of H2O in a bath of He atoms. The potential-energy surfaces employed are corrected for basis-set superposition error, and their reliability is checked by repeating the calculations with a different basis set for orbital expansion. The results are presented in extensive tables and discussed in detail. The corrections applied are shown to have a significant impact on the accuracy of the room-temperature broadenings determined: 8.9 sq A for the 22.2-GHz line, 11.8 sq A for the 183,3-GHz line, and 10.0 sq A for the 380.2-GHz line, in good agreement with published experimental data. The importance of collisional broadening for the atmospheric transmission of radiation and for remote-sensing applications is indicated.

Green, Sheldon↗

NASA NTRS1991

Mapping the composition of planetary surfaces by Auger electron spectroscopy

The feasibility of AES as a remote-sensing technique to map the composition of the sunlit surfaces of planetary bodies without atmospheres is studied. Solar X-rays eject photoelectrons from the planetary surface. The resulting ions relax by emission of fluorescence X-rays or Auger electrons, with energies characteristic of the element which is ionized. The spectrum of Auger electrons and photoelectrons is computed for a variety of elements and for representative lunar rock types illuminated by soft-X-ray line and continuum emission typical of solar long-lived coronal active regions. The Auger electron lines for O, Si, Mg, Al, Fe, and Ca in lunar rocks stand well above the continuum background from photoelectrons and backscattered interplanetary electrons, with typical line-to-continuum ratios from about 20 to over 1000.

Lin, R. P.↗

NASA NTRS1990

Cloud microphysical properties from multispectral reflectance measurements

Images as well as statistical properties of the cloud optical thickness and effective particle radius derived from reflected solar radiation measurements at 0.75, 1.65, and 2.16 micron are presented. The remote-sensing-derived cloud optical thickness and effective radius are compared with the values inferred from nearly simultaneous in situ microphysical measurements obtained from an aircraft. A good spatial correlation is observed for both the optical thickness and effective radius, it is noted that the remote sensing has a tendency to overestimate the effective radius; the optical thickness is overestimated for small optical thicknesses and underestimated for large optical thicknesses. The marginal probability density functions of optical thickness and effective radius are derived from the remote-sensing results and discussed.

King, Michael D.↗

NASA NTRS1990

Remote sensing of the biosphere; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

The global context and monitoring of the biological aspects relevant to the EOS program are addressed, the large-scale regional field experiments required to understand ecosystem functioning in more detail and to calibrate the application of remote-sensing techniques for extracting flux and state information are covered, and sensors of the proposed EOS platform are discussed. Attention is given to terrestrial productivity, both tropical-forest and semiarid environments, coastal environments, and global oceanic productivity. Focus is placed on the First International Field Experiment (FIFE) in Kansas, the HAPEX field experiment in France, the ABLE-2 experiment in the Amazon, and the Forest Ecosystem Study in Maine. The proposed electro-optical instruments for EOS including both MODIS-N and MODIS-T, the AIRS and MISR instruments, the ITIR, and ERBE calibration issues are considered.

Smith, James A.↗

NASA NTRS1990

The Galileo mission earth encounters - An earth remote sensing perspective

After its Venus-Earth-Earth Gravity Assist trajectory, the Galileo spacecraft will arrive at Jupiter in 1995. The gravity-assist portion of the mission, however, will allow the spacecraft, which is equipped with a unique set of remote-sensing instruments, to observe earth from 970 km during its December 1990 approach, and from as little as 304 km in its second and last approach of December, 1992. An evaluation is presented of the role that the Galileo instrument suite can play in these earth encounters in virtue of their outstanding spectral and spatial resolutions.

Ocampo, Adriana↗

NASA NTRS1991

Reflectance model for quantifying chlorophyll a in the presence of productivity degradation products

A reflectance model developed to estimate chlorophyll a concentrations in the presence of marine colored dissolved organic matter, pheopigments, detritus, and bacteria is presented. Nomograms and lookup tables are generated to describe the effects of different mixtures of chlorophyll a and these degradation products on the R(412):R(443) and R(443):R(565) remote-sensing reflectance or irradiance reflectance ratios. These are used to simulate the accuracy of potential ocean color satellite algorithms, assuming that atmospheric effects have been removed. For the California Current upwelling and offshore regions, with chlorophyll a not greater than 1.3 mg/cu m, the average error for chlorophyll a retrievals derived from irradiance reflectance data for degradation product-rich areas was reduced from +/-61 percent to +/-23 percent by application of an algorithm using two reflectance ratios rather than the commonly used algorithm applying a single reflectance ratio.

Carder, K. L.↗

NASA NTRS1991

A consensual neural network

A neural network architecture called a consensual neural network (CNN) is proposed for the classification of data from multiple sources. Its relation to hierarchical and ensemble neural networks is discussed. CNN is based on the statistical consensus theory and uses nonlinearly transformed input data. The input data are transformed several times, and the different transformed data are applied as if they were independent inputs. The independent inputs are classified using stage neural networks and outputs from the stage networks are then weighted and combined to make a decision. Experimental results based on remote-sensing data and geographic data are given.

Benediktsson, J. A.↗

NASA NTRS1991

Project Copernicus: An Earth observing system

Hunsaker Aerospace Corporation is presenting this proposal for Project Copernicus to fulfill the need for space-based remote sensing of Earth. Concentration is on data acquisition. Copernicus is designed to be a flexible system of spacecraft in a low near-polar orbit. The goal is to acquire data so that the scientists may begin to understand many Earth processes and interactions. The mission objective of Copernicus is to provide a space-based, remote-sensing measurement data acquisition and transfer system for 15 years. A description of the design project is presented.

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NASA NTRS1988

The Lunar Orbital Prospector

The Moon is a body rich in natural resources and full of intriguing scientific questions, and it will most certainly play a central role in the growth of near-Earth and deep space ventures of the twenty-first century. The LOP mission is an example of one way to catalog the Moon's natural resources and to answer lunar science questions in parallel. In a realistic planetary exploration program, this mission must compete with other interesting planetary missions and therefore the LOP must be as low cost and adaptable as possible. This flexibility is reflected in the LOP's heavy design emphasis on modularity. The LOP mission can easily be expanded to include new technologies, and additional orbiters could be launched into lunar orbit to provide a constellation of remote-sensing platforms. This design thus projects a broad range of possibilities for continued lunar exploration in the next century.

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