Considerable flight experience has established that CAT is frequently associated with temperature anomalies in the atmosphere. It is possible, in principle, to sense such anomalies remotely by the infrared radiation emitted by the atmosphere. This paper reviews the results of several years of flight tests conducted cooperatively by Barnes Engineering Company, and three major airlines (PAA, EA and TWA) to evaluate this technique. Initially, the instrumentation was designed to predict the horizontal temperature profile ahead of the aircraft along its flight path. While some success was obtained, much too high a false alarm rate was experienced. A vertical scan mode was then added to provide information on the vertical temperature structure. Flight results made with the vertical scan show that the radiometric signal responds to the vertical temperature structure of the atmosphere in accordance with theoretical expectations. By this additional dimension of temperature information, it is hoped that false alarm situations can be more effectively identified and eliminated.
The detection and recording of atmospheric scattering data has received a tremendous amount of attention since the development of the laser. The work of such men as Myron Ligda and Ron Collis at the Stanford Research Institute and Georgio Fiocco at MIT has shown that the laser radar (or LIDAR) is a valuable tool for obtaining backscatter information on atmospheric phenomena. The General Electric Company has been actively engaged in laser measurements of the atmosphere since 1964. (Ref..1,2) A number of laser equipments were con-structed and used to obtain atmospheric data at various places in the country. Recently a large laser system was built for use in measuring Rayleigh and Raman scattering in two colors from the atmosphere by the Space Sciences Laboratory of the General, Electric Company in King of Prussia, Penn sylvania. The two color capabilities of the of the system are used to obtain data on the differences between Rayleigh and Mie scat tering which exhibit diffijirent scattering func tion at different wavelength.
A tunable-wavelength lidar system has been constructed for remote probing of various species in the lower and upper atmosphere, The system consists of a flashlamp-pumped dye laser, a 16-inch Schmidt receiver, and a high-speed data-handling system, The laser is capable of delivering 0.5-J pulses with a linewidth of 0.02 A at a rate of 0.25 Hz, Pulse rates up to 1 Hz have been achieved with a somewhat larger linewidth. A survey of atmospheric constituents suitable for probing by resonant scattering has revealed that at the current level of technology only the alkaline species Na, Li, and K, and the alkaline-like ion Ca+ present reasonable prospects of successful detection, With foreseeable increases in sensitivity, measurement of other species will be possible, Potential applications of other scattering processes are under investigation, Altitude profiles of the naturally occurring sodium layer obtained during trial runs of the system show short-term variations, and the characteristic sharp fall in density on the top side of the layer.
A number of recent developments in multiband cameras are discussed. In particular, descriptions are given of the 5065 camera used on Apollo 9, an optical multiplexing camera, the S190 camera for Skylab, and the return-beam-vidicon camera for the Earth Resources Technology Satellite. Also described are the use of an intensifier-vidicon storage tube system, a dispersing element and vidicon, an image dissector, and solid state arrays in four novel multiband cameras. The role of film and electro-optical multiband cameras in future space missions is discussed.
An electronic viewer for real-time viewing and processing of multiband camera imagery is described. The Multiband Camera Film Viewer (MCFV) is a high-resolution, 1000-line system scanning three channels of multiband imagery. The MCFV provides a calibrated output from each of the three channels for viewing in composite true color, analog false-color, and digitized, enhanced false color.
I would like to welcome all of you to this afternoon's session on remote sensing and its applications. I believe we have a number of good papers which illustrate the diversity of activity and which are also indicative of the good quality of work which is going on in the remote sensing and remote sensing applications areas. After having spent the last several years with the Earth Observation Program at NASA - which has provided a unique opportunity to view the entire program throughodt government and industry - I would like to emphasize that I am now speaking as a private citizen.
As the acquisition of aerial photographic imagery continues to grow at a rapid rate, automatic data extraction becomes more and more desirable. To this end, an image processing system is being developed to computerize terrain classification. A laser scanner has been used to digitize Apollo 9 imagery of the Salton Sea area. A signature algorithm has been specified allowing the assignment of small image blocks to specific terrain categories. Results of automatic classification and manual photointerpretation are compared. Categories considered are cultivated terrain, uncultivated terrain, cloud covered terrain, and water. Assignment is based on a single black and white transparency in each case. The assignments are displayed as overwritten alphabetic annotation on the original image. Problems are discussed.
Ways are described to minimize errors when the Planck law is used for single- and two-color temperature measurements. Various approximations useful in remote sensing are discussed, as well as a suggested method for measuring temperature and emissivity simultaneously with active and passive systems at each of two wave-lengths. Measurements at multiple wavelengths are also presented in this mathematical discussion.
One of the most important hydrologic variables is the total precipitation over a finite area during a specified period of time. The area of interest frequently is located within rugged terrain that offers a difficult background for observation by remote sensing, including weather radar. Surface observations at widely scattered points within the region often fail to provide sufficiently representative data for inferring the spatially-integrated precipitation. On the other hand, it is believed that useful information on precipitation can be deduced from data collected routinely by meteorological satellites.
A study of the statistics of selected aerial photographs was made to determine the usefulness of these quantities for the control of an Automatic Exposure system. The photos typify cloud-free, heavy haze conditions; cloud-free, clear conditions; and scattered-cloud, haze-free conditions. The photographs were converted to digital tape records, using the FAIRSCAN image analyzer, a system for scanning and digitizing imagery. The tapes were then fed to an appropriately programmed computer and five statistics were derived for each photo. The first two statistics, the "mean" and the "standard deviation", proved to contain the necessary information. Higher order moments and the statistics derived from them appeared inconsistent and uninformative, at least for the small sample of three photos. In addition, it was determined that about one thousand elements per picture was adequate to determine the statistics and that the values obtained were insensitive to the elemental aspect ratio for ratios up to about 4:1.
The Earth Resources Program relies on the fundamental premise that remote sensing can provide knowledge of ground conditions over large areas, and possibly all, of the earth's surface. The collection of this information, by means of radiant energy sensors in aircraft or satellites, depends on two important factors:(1) that all objects on the earth's surface continuously radiate or reflect electromagnetic energy; and (2) that spectrally-selective emission and reflection can uniquely identify objects of interest, with "spectral signatures" serving as the leading means of identification. A major facet of the problem of translating this basic concept to practice is that of data correlation. In the most general case, large quantities of data are collected from a variety of sensors, over a broad range of wavelengths, and from different gyrating vehicle platforms at different altitudes and times. Automatic correlation of the data from one collection to another, with other reference data, and with the ground is necessary if the acquired information is to be useful in providing a basis for subsequent corrective action. This paper discusses a pilot system design for an Automatic Data Correlation System which was the subject of a year long study performed for NASA. The Pilot version, although intended to be primarily a research and development tool, provides all the essential functional capabilities of the ultimate, advanced system. It was designed as an inexpensive, easily assembled, configuration of required equipments that allows thorough experimentation with all stages of the needed film and magnetic tape data handling while accomodating all presently identified Earth Resources remote sensors.
The ultraviolet fluorescence property of oil suggests the possibility of a more sensitive technique for the detection of oil pollution on water than either UV or visible photography alone. To demonstrate the advantages of this technique, several photographic methods of oil detection were compared in a feasibility experiment in the laboratory. Ultraviolet reflectance photography at 3600 A also gave good results. Theoretically, the fluorescence of oil by the 2537 A mercury line is stronger than fluorescence at 3600 A and therefore should be even more sensitive in detecting oil pollution. Methods of discriminating against ambient light are discussed.
Use of the Barringer Dual-Gas COSPEC II Correlation Spectrometer permits the measurement of total burden or ground-level concentrations of SO2 and NO2 simultaneously. The instrumentation utilizes separate analysis systems to measure the absorption spectra of the two target molecules developed on a single input beam of light. The source of the energy may be either Rayleigh-scattered light from the sky or an artificial source located up to three km distant. Total burdens of NO2 and SO2 measured in traverses over a number of areas demonstrate the horizontal variations in contaminant level. Effluent plume analysis indicates the rate of production of specific stationary sources. The long-line artificial light configuration is sensitive to spatially integrated variations in gas concentration as low as one ppb.
The pattern of dancing highlights caused by the reflection of the sun from a roughened water surface, called the sun glitter pattern, has long been of interest to the romantically and esthetically inclined. It has also received scientific attention because of the evident relationship between the size of the glitter pattern and the roughness of the surface, leading to a number of suggestions for the exploitation of this phenomenon for remote sensing of sea state. The investigations to date have established the relationships among glitter pattern characteristics, surface roughness, and near-surface wind speeds, and have demonstrated the feasibility of making useful measurements from a spacecraft. This paper discusses the requirements for a glitter pattern sensor to be used on a sun-synchronous satellite and estimates its potential, both as to the range of applicability and the accuracy of deduced values of sea states and wind speeds.
In the future, spacecraft dedicated to earth resources will carry an ocean color sensor as part of their payloads. It will be used to measure the spectral nature of upwelling scattered sunlight from beneath the sea surface at many spatial points across a swath. The spectral signatures of many oceanographic phenomena (e.g. chlorophyll content) are well known, allowing the data user to map their types and concentrations over the global ocean. Recent studies have been conducted which suggest that there may be advantages in placing the spacecraft in a near polar orbit such that the earth-sun line lies in the orbit plane (i. e. , a "noon" orbit) as opposed to a morning or afternoon orbit in which the sun is to one side of the orbit plane. For example, employing a noon orbit increases the coverage by a factor of two (i.e. a specific geographical location will be overflown twice as often). This paper discusses the noon orbit and its ramifications, including scene contrast, and glitter interference.
One of the most effective ways of remotely sensing the characteristics of a body of ocean water is to measure its spectral radiance in the visible region of the spectrum. The visible region is the only part of the electro-magnetic spectrum in which light is transmitted by water to a substantial degree, and as such is the only spectral region in which remotely sensed information can be obtained directly about subsurface conditions. These conditions can include the distribution, concentration, and type, of plankton, sediments and some pollutants.
The design for a scanning imaging spectroradiometer (Ref. 1) to be utilized for earth resources applications is discussed. This work was perforthed under NASA/MSC Contract Number 9-11146. This f/1.4 optical system consists of two interchangeable objectives that work into a common, unity magnification relay in whose aperture stop has been placed a diffraction grating. Spectral and spatial information is gathered over the 4000 to 8500 angstrom region.
One of the requirements for the Earth Observations Program is a multispectral imaging system for remote sensing in an earth orbiting satellite. This system should be capable of very broad spectral coverage so that a sufficient portion of the electromagnetic spectrum is available for examination to ensure that unique signatures of earth based details may be derived. Experimental evidence gathered during the past 5 years indicates that the region from 0.35 to 14 microns is particularly useful, with a spatial resolution of 25-100 feet desirable. Timeliness of data return and ease of subsequent data reduction are also important, particularly for such disciplines as Meteorology, Agriculture, pollution monitoring, etc.
Experimental and theoretical results concerning the microwave brightness temperature of both natural sea ice and salt water ice grown under controlled laboratory conditions will be considered. Excellent correlation between the theoretical results and laboratory measurements have been achieved for ice thermal temperatures below -8°C, but quantitative discrepancies between theory and experiment exist at higher temperatures. These appear to be connected with a failure of presently available equations to describe the dielectric behavior of salt water ice when the brine volume is high.
A comparison of measured multi-frequency (1.42, 4.99, 13.4 and 37 GHz) microwave brightness temperatures of a relatively homogeneous soil (United States Water Conservation Laboratory, Phoenix, Arizona) over a variety of moisture conditions and antenna view angles with those computed from presently available theory reveals that a partial understanding of the microwave emission properties of specular soils has been achieved. An empirical model is presented which allows relatively good agreement between measured and computed soil moisture profiles over appropriate skin depths for moderately moist to saturated moisture concentrations. Complications arising from non-specular surface and volume scattering due, for example, to vegetal cover or terrain irregularities have been minimized in the measurements and ignored in the calculations.
This paper will cover, in general terms, some important features of the Ka-band airborne mapping system designed for microwave radiometric measurements of the terrain. The unusual aspects of the system, its operational capability and results of some interesting flights are shown.