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The state-of-the-art of active microwave remote sensors (altimeters, scatterometers and imagers) used in geologic applications is assessed and the ongoing radar geology activities within NASA, government agencies, industry, universities and foreign organizations is summarized. Plans for radar geology research and development and space flight missions are also outlined.
A laboratory model of a 16 channel integrated optical data preprocessor was fabricated and tested in response to a need for a device to evaluate the outputs of a set of remote sensors. It does this by accepting the outputs of these sensors, in parallel, as the components of a multidimensional vector descriptive of the data and comparing this vector to one or more reference vectors which are used to classify the data set. The comparison is performed by taking the difference between the signal and reference vectors. The preprocessor is wholly integrated upon the surface of a LiNbO3 single crystal with the exceptions of the source and the detector. He-Ne laser light is coupled in and out of the waveguide by prism couplers. The integrated optical circuit consists of a titanium infused waveguide pattern, electrode structures and grating beam splitters. The waveguide and electrode patterns, by virtue of their complexity, make the vector subtraction device the most complex integrated optical structure fabricated to date.
One of the most important parameters for accurate snowmelt runoff prediction is snow water equivalent (SWE) which is contentionally monitored using observations made at widely scattered points in or around specific watersheds. Remote sensors which provide data with better spatial and temporal coverage can be used to improve the SWE estimates. Microwave radiation, which can penetrate through a snowpack, may be used to infer the SWE. Calculations made from a microscopic scattering model were used to simulate the effect of varying SWE on the microwave brightness temperature. Data obtained from truck mounted, airborne and spaceborne systems from various test sites were studied. The simulated SWE compares favorable with the measured SWE. In addition, whether the underlying soil is frozen or thawed can be discriminated successfully on the basis of the polarization of the microwave radiation.
A selection of NASA Earth observations programs are reviewed, emphasizing hardware capabilities. Sampling theory, noise and detection considerations, and image evaluation are discussed for remote sensor imagery. Vision and perception are considered, leading to numerical image processing. The use of multispectral scanners and of multispectral data processing systems, including digital image processing, is depicted. Multispectral sensing and analysis in application with land use and geographical data systems are also covered.
The state-of-the-art advancements in remote sensor technology due to the Superflux program are examined. Three major individual sensor technologies benefitted from the program: laser fluorosensors, optical-range scanners, and passive microwave sensors. Under Superflux, convincing evidence was obtained that the airborne oceanographic lidar fluorosensor can map chlorophyll, i.e., is linear, over a wide range from less than 0.5 to 5.0 mg/cu m. The lidar oceanographic probe dual-excitation concept for addressing phytoplankton color group composition was also demonstrated convincingly. Algorithm development, real time capabilities, and multisensor integration are also addressed.
An experiment was conducted by the National Langley Research Center to measure atmospheric optical conditions using a 10-channel solar spectral photometer system. This experiment was part of a larger series of multidisciplinary experiments performed in the area of Nantucket Shoals aimed at studying the dynamics of phytoplankton production processes. Analysis of the collected atmospheric data yield total and aerosol optical depths, transmittances, normalized sky radiance distributions, and total and sky irradiances. Results of this analysis may aid in atmospheric corrections of remote sensor data obtained by several sensors overflying the Nantucket Shoals area. Recommendations are presented concerning future experiments using the described solar photometer system and calibration and operational deficiencies uncovered during the experiment.
The interactions and support functions required between the early warning/crop condition assessment (EW/CCA) project and soil moisture (SM) project are defined. The EW Project aims to develop, test and evaluate techniques and procedures for adapting remote sensing technology to provide early warning of events and the timely assessment of those factors which affect the quality and quantity of production of economically important crops. Those techniques to augment and reinforce the current assessment activities are to be developed to improve the definition of the relationship between the plant(s) and its environment. This assessment and evaluation will certainly include the need for soil moisture measurement and estimation. The SM Project aims to develop, test, and evaluate techniques and procedures to measure or predict soil moisture in the root zone using both contact and remote sensors.
The CTS maps the Earth's surface with a resolution of 0.1 km from an altitude of 18km with 60km side-to-side coverage of the field. It has three spectral channels. The 0.625 micrometer centered visual channel detects reflectance to within 1 percent. The 6.75 micrometer centered water vapor channel detects changes in temperature of less than one degree Kelvin at 175 K. The 11.5 micrometer centered infrared window channel detects changes of less one half degree Kelvin at 175 K. The data can be converted graphically into three display images of the scene. Values for scene temperature and albedo are calculated from calibration equations. The equations were derived from in-situ and laboratory measurements. Intercomparisons of the flight data temperatures with ground based and other remote sensor results established the certainty of the derived temperature values to within 3 K over a wide temperature range (180 to 320 K). The system performance, calibration, and operation is successful and the engineering information describing this system should prove useful to scientists and potential users of the data.
Methods used for interpreting orbital (LANDSAT) data for regional geological mapping in Brazil are examined. Particular attention is given to the levels of analysis used for studying geomorphology, structural geology, lithology, stratigraphy, surface geology, and dynamic processes. Examples of regional mapping described include: (1) rock intrusions in SE Sao Paulo, the southern parts of Minas Gerais, and the states of Rio de Janeiro, and Espiritu Santo; (2) a preliminary survey of Pre-Cambrian geology in the State of Piaui; and (3) the Gondwana Project - surveying Jaguaribe plants. Mineral exploration in Rio Grande do Sul, and the geology of the Alcalino complex of Itatiaia are discussed as well as the use of automatic classifications of rock intrusions and of ilmenite deposits in the Floresta Region. Aerial photography, side looking radar, and thermal infrared scanning are other types of remote sensors also used in prospecting for geothermal anomalies in the city of Caldas Novas-Goias.
Progress in the application of digital analysis of multispectral scanner data to agro-environmental studies is described. Simulation of LANDSAT D thematic mapper (TM) observations from aircraft multispectral scanner data and field spectrometer data collected over a corn-soybean agricultural region in Webster County, Iowa during the 1979 growing season in support of the NASA/AgRISTARS program is described. The simulations were analyzed to evaluate the potential utility of the TM (1.55-1.75 micron) mid-infrared observations in corn-soybean discrimination. Current LANDSAT data was analyzed to study snow cover in northern New England and wetlands in Nebraska and Vermont. The application of satellite remote sensor data in additional environmental research areas is described.
The Southeastern Virginia Urban Plume Study is intended to provide a testing ground for NASA remote sensors designed for urban and regional scale monitoring of air quality phenomena. The air quality experiments it has conducted have incorporated surface, airborne, sonde and balloon platforms which measured air quality and meteorology parameters, with emphasis on photochemically produced O3 and its primary precursors upwind, above, and downwind of the Hampton Roads area urban complex. The results from three years of experiments have shown that such different meteorological conditions as blue/broken skies, high/moderate temperatures and low/high winds have a direct impact on the degree of downwind aging of the summer urban O3 airmass. In 1979, the urban plume was traced at aging times of 0.5, 1.5, and 5 hr.
Aircraft microwave scatterometer measurements are presented, which were made in 1979 as part of a project to study the response of a number of active and passive microwave and optical remote sensors to an oil-covered sea surface conducted by NASA Langley Research Center. A 13.9-GHz Doppler scatterometer with a fan beam antenna and coherent detection was used to measure radar backscatter as a function of incidence angle. The radar scattering signature of the clear surface and signatures of the surface covered with various crude oil films are compared. Reductions in Ku band microwave backscatter up to 14 dB are observed for both treated and untreated LaRosa and Murban crude oil films deposited on the sea surface. Maximum Ku band sensitivity to the effects of the oil in terms of differential scatter is observed in the 25-35 deg incidence angle region.
An investigation is conducted regarding the feasibility to develop improved methods for the identification and analysis of urban landscapes on the basis of a utilization of longwave infrared observations. Attention is given to landscape thermal behavior, urban thermal properties, modeled thermal behavior of pavements and buildings, and observed urban landscape thermal emissions. The differential thermal behavior of buildings, pavements, and natural areas within urban landscapes is found to suggest that integrated multispectral solar radiant reflectance and terrestrial radiant emissions data will significantly increase potentials for analyzing urban landscapes. In particular, daytime satellite observations of the considered type should permit better identification of urban areas and an analysis of the density of buildings and pavements within urban areas. This capability should enhance the utility of satellite remote sensor data in urban applications.
Liu et al. (1980) suggested that NOx transported from the stratosphere, as opposed to the anthropogenic source of NOx, may be the dominant source that controls the distribution of NOx in the global troposphere. These ideas require a reinvestigation, and, in particular, an assessment of the role of the oxidation of ammonia as a source of NOx. Attention is given to the results of an ammonia measurement program, in which the vertical distribution of ammonia in the troposphere and lower stratosphere could be studied with the aid of the Infrared Heterodyne Radiometer (IHR), a solar-viewing remote sensor. A one-dimensional photochemical model of the troposphere reported by Levine et al. (1980) was employed to study the chemical and physical processes that control the loss of ammonia in the troposphere. The results of the considered investigation suggest that the oxidation of ammonia may indeed be a significant source of NOx in the troposphere.
A portion of the broad domestic non-Federal oceanographic community that represents a potential market for satellite remote sensor derived oceanographic data and/or marine environmental information is presented. The overview consists of listings of individuals and/or organizations who have used, or are likely to use such data or information for scientific research, offshore engineering purposes, marine resources exploration and utilization, marine related operational applications, or coastal zone management.
Images acquired by the Shuttle Imaging Radar (SIR-A) in November 1981, demonstrate the capability of this microwave remote sensor system to perceive and map a wide range of different surface features around the Earth. A selection of 60 scenes displays this capability with respect to Earth resources - geology, hydrology, agriculture, forest cover, ocean surface features, and prominent man-made structures. The combined area covered by the scenes presented amounts to about 3% of the total acquired. Most of the SIR-A images are accompanied by a LANDSAT multispectral scanner (MSS) or SEASAT synthetic-aperture radar (SAR) image of the same scene for comparison. Differences between the SIR-A image and its companion LANDSAT or SEASAT image at each scene are related to the characteristics of the respective imaging systems, and to seasonal or other changes that occurred in the time interval between acquisition of the images.
An atmospheric correction model was extended to account for various atmospheric radiation components in remotely sensed data. Components such as the atmospheric path radiance which results from singly scattered sky radiation specularly reflected by the water surface are considered. A component which is referred to as the virtual Sun path radiance, i.e. the singly scattered path radiance which results from the solar radiation which is specularly reflected by the water surface is also considered. These atmospheric radiation components are coded into a computer program for the analysis of multispectral remote sensor data over the Great Lakes of the United States. The user must know certain parameters, such as the visibility or spectral optical thickness of the atmosphere and the geometry of the sensor with respect to the Sun and the target elements under investigation.
Area estimates of irrigated crops and knowledge of crop type are required for modeling water consumption to assist farmers, rangers, and agricultural consultants in scheduling irrigation for distributed management of crop yields. Information on canopy physiology and soil moisture status on a spatial basis is potentially available from remote sensors, so the questions to be addressed relate to: (1) timing (data frequency, instantaneous and integrated measurement); and scheduling (widely distributed spatial demands); (2) spatial resolution; (3) radiometric and geometric accuracy and geoencoding; and (4) information/data distribution. This latter should be overnight, with no central storage, onsite capture, and low cost.