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At least 469 records · Page 26

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NASA NTRS1973

Ionospheric fading effects on the equatorial zone

Microwave fading of space communication channels in the equatorial region is caused by the effects of the disturbed ionosphere. Three dimensional plots of percentage occurence of very high frequency scintillation effects shown as a function of time of day and week of the year prove that, most fading occurs at nighttime and around the weeks of the equinox. The magnitude of fading at the equator violates existing scattering theories and must be taken into account when designing a microwave communication link to space.

Golden, T. S.↗

NASA NTRS1973

Semi-automatic crop inventory from sequential ERTS-1 imagery

The detection of a newly introduced crop into the Imperial (California) Valley by sequential ERTS-1 imagery is proving that individual crop types can be identified by remote sensing techniques. Initial results have provided an extremely useful product for water agencies. A system for the identification of field conditions enables the production of a statistical summary within two to three days of receipt of the ERTS-1 imagery. The summary indicates the total acreage of producing crops and irrigated planted crops currently demanding water and further indicates freshly plowed fields that will be demanding water in the near future. Relating the field conditions to the crop calendar of the region by means of computer techniques will provide specific crop identification for the 8000 plus fields.

Johnson, C. W.↗

NASA NTRS1973

Identification of large masses of citrus fruit and rice fields in eastern Spain

ERTS-1 imagery has been successfully used for the identification of large areas of citrus groves and rice fields in the Valencia region of Eastern Spain. Results are encouraging and will facilitate the elaboration of a land use map with a fair degree of definition once methods prove to be fully operational.

Desagredo, F. L.↗

NASA NTRS1973

Agricultural applications of ERTS-1 data

In an attempt to evaluate the usefulness of ERTS imagery for the production of land use stratifications as a preliminary step in the crop inventory process, all land within San Joaquin County was delineated into broad land use and crop category classes based on their appearance on the ERTS-1 Color composite image. The stratification of the agricultural land use categories proved to be a relatively simple task, taking each of three interpreters approximately 30 minutes to complete. The three interpretations were quite similar requiring only minor revisions to produce a consensus stratification. A total of 13 different agricultural strata were recognized, differing both in general field size and relative proportions of crop types and degree of irrigation. Upon comparing these interpretations, it was concluded that nearly all boundaries were truly representative of differing cropping practices. In a number of cases, the stratifications agreed almost exactly with soil type boundaries as drawn by earlier soils surveys.

Draeger, W. C.↗

NASA NTRS1973

Application of ERTS-1 multispectral imagery to monitoring the present episode of accelerated erosion in southern Arizona

An episode of accelerated arroyo-cutting and sheet erosion commenced about 1890 in southern Arizona, following several thousand years of generally sluggish erosion. For a 17,000-square-mile study area, ERTS-1 images, supplemented by ultrahigh-altitude (U-2 and RB-57) airphotos, are proving effective for producing the first comprehensive maps showing the distribution and seriousness of the post-1890 erosion features, for monitoring new erosion changes, and for assessing the effectiveness of ameliorative measures. Such data are essential for understanding and controlling the accelerated erosion, a key environmental problem in this region.

Morrison, R. B.↗

NASA NTRS1973

Mapping quaternary landforms and deposits in the Midwest and Great Plains by means of ERTS-1 multispectral imagery

ERTS-1 multispectral images are proving effective for differentiating many kinds of Quaternary surficial deposits and landforms units in Illinois, Iowa, Missouri, Kansas, Nebraska, and South Dakota. Examples of features that have been distinguished are: (1) the more prominent end moraines of the last glaciation; (2) certain possible palimpsests of older moraines mantled by younger deposits; (3) various abandoned river valleys, including suspected ones deeply filled by deposits; (4) river terraces; and (5) some known faults and a few previously unmapped lineaments that may be faults. The ERTS images are being used for systematic mapping of Quaternary landforms and deposits in about 20 potential study areas. Some study areas, already well mapped, provide checks on the reliability of mapping from the images. For other study areas, previously mapped only partly or not at all, our maps will be the first comprehensive, synoptic ones, and should be useful for regional land-use planning and ground-water, engineering-geology, and other environmental applications.

Morrison, R. B.↗

NASA NTRS1973

Relation of ERTS-1 detected geologic structure to known economic ore deposits

A preliminary analysis of ERTS-1 imagery of the Northern Coast Ranges and Sacramento Valley, California, has disclosed a potentially important fracture system which may be one of the controlling factors in the location of known mercury deposits in the Coast Ranges and which appears to be associated with some of the oil and gas fields within the Sacramento Valley. Recognition of this fracture system may prove to be an extremely useful exploration tool, hence careful analysis of subsequent ERTS imagery might delineate areas for field evaluation.

Rich, E. I.↗

NASA NTRS1973

Some aspects of active tectonism in Alaska as seen on ERTS-1

ERTS-1 imagery is proving to be exceptionally useful in delineating structural features in Alaska which have never been recognized on the ground. Previously unmapped features such as seismically active faults and major structural lineaments are especially evident. Among the more significant results of this investigation is the discovery of an active strand of the Denali fault. The new fault has a history of scattered seismicity and was the scene of a magnitude 4.8 earthquake on October 1, 1972. Perhaps of greater significance is the disclosure of a large scale conjugate fracture system north of the Alaska Range. This fracture system appears to result from compressive stress radiating outward from around the outside of the great bend of the Alaska Range at Mt. McKinley.

Gedney, L. D.↗

NASA NTRS1973

Water turbidity detection using ERTS-1 imagery

ERTS-1 images of two federal reservoirs in Kansas exhibit good correlation with suspended load. The major reservoirs in Kansas, as well as in other Great Plains states, are playing increasingly important roles in flood control, recreation, agriculture, and urban water supply. Satellite imagery may prove useful for acquiring timely low cost water quality data required for optimum management of these fresh water resources.

Yarger, H. L.↗

NASA NTRS1973

Detection of major river bed changes in the River Ebro (north-eastern Spain)

The application or ERTS-1 data to determine the major river bed changes of the Ebro River in northeastern Spain is discussed. Image quality was good enough to permit a clear identification of the river course and bands MSS 5 and 7 proved to be the most useful for this purpose. Reflectance for band 5 was high due to the high sediment content of the water and sufficed to identify the river. Features like bodies of water related to old channels and depressions were only apparent in band 7.

Espejo, R.↗

NASA NTRS1973

Land use in the northern Coachella Valley

Satellite imagery has proved to have great utility for monitoring land use change and as a data source for regional planning. In California, open space desert resources are under severe pressure to serve as a source for recreational gratification to individuals living in the heavily populated southern coastal plain. Concern for these sensitive arid environments has been expressed by both federal and state agencies. The northern half of the Coachella Valley has historically served as a focal point for weekend recreational activity and second homes. Since demand in this area has remained high, land use change from rural to urban residential has been occurring continuously since 1968. This area of rapid change is an ideal site to illustrate the utility of satellite imagery as a data source for planning information, and has served as the areal focus of this investigation.

Bale, J. B.↗

NASA NTRS1973

ERTS-1 image enhancement by optically combining density slices

The technique of density slicing using a photographic film and its application to enhancement of ERTS-1 imagery has proved to be useful for mapping varigated areal phenomena and provides a useful supplement ot the I2S MiniAddcol viewing system. The intial experiments conducted with this film were encouraging, and indicated that this technique of density slicing using readily accessible darkroom facilities and simple darkroom procedures allows rapid, accurate, and facile interpretation of certain areal phenomena to be made from the imagery. The distribution of the tree yucca, Yucca brevifolia Jaegeriana, in the eastern Mojave Desert of Southern California and southern Nevada was used as an example to test the accuracy of the technique for mapping purposes. The distribution was mapped at a relatively high level of accuracy.

Tapper, G. O.↗

NASA NTRS1973

Resource management implications of ERTS-1 data to Ohio

Initial experimental analysis of ERTS-1 imagery has demonstrated that remote sensing from space is a means of delineating and inventorying Ohio's strip-mined areas, detecting power plant smoke plumes, and proving the data necessary for periodically compiling land use maps for the entire state. The nature and extent of these problems throughout Ohio, how ERTS data can contribute to their solution, and estimates of the long term significance of these initial findings to overall resource management interests in Ohio are summarized.

Sweet, D. C.↗

NASA NTRS1973

Thermal surveillance of Cascade Range volcanoes using ERTS-1 multispectral scanner, aircraft imaging systems, and ground-based data communication platforms

A combination of infrared images depicting areas of thermal emission and ground calibration points have proved to be particularly useful in plotting time-dependent changes in surface temperatures and radiance and in delimiting areas of predominantly convective heat flow to the earth's surface in the Cascade Range and on Surtsey Volcano, Iceland. In an integrated experiment group using ERTS-1 multispectral scanner (MSS) and aircraft infrared imaging systems in conjunction with multiple thermistor arrays, volcano surface temperatures are relayed daily to Washington via data communication platform (DCP) transmitters and ERTS-1. ERTS-1 MSS imagery has revealed curvilinear structures at Lassen, the full extent of which have not been previously mapped. Interestingly, the major surface thermal manifestations at Lassen are aligned along these structures, particularly in the Warner Valley.

Friedman, J. D.↗

NASA NTRS1973

Development of isothermal rigs

The results of the Resonant Infrasonic Gauging System (RIGS) development program are reported. The RIGS is a gauging system that is capable of measuring propellant quantity under zero-G as well as under accelerated (one-G) conditions. With the exception of liquid hydrogen, it can be used to gauge virtually any propellant in liquid form including cryogenics. The gauge consists of a sensor unit which is attached to the propellant tank and electronic control unit which may be positioned separately from the sensor. The control unit receives the signals from the sensor as well as the ullage gas pressure and propellant temperature measurements, and computes the propellant quantity remaining in the tank. During the course of this program two prototype RIGS sensors were designed and constructed. The sensors were tested first in the laboratory using water as the simulated propellant and, later, using LN2 in a 100-gallon tank. The system tests proved that the gauge operates virtually as predicted by theory and yielded an accuracy better than 1%.

Kaminskas, R. A.↗

NASA NTRS1973

Antimatter in the Universe?

The use of gamma rays, cosmic rays, annihilation reactions, and interstellar gas reactions to prove antimatter is present in the universe is discussed.

Steigman, G.↗

NASA NTRS1973

Composite propulsion feedlines for cryogenic space vehicles, volume 1

Thin metallic liners that provide leak-free service in cryogenic propulsion systems are overwrapped with a glass-fiber composite that provides strength and protection from handling damage. The resultant tube is lightweight, strong and has a very low thermal flux. Several styles of tubing ranging from 5 to 38 cm in diameter and up to 305 cm long were fabricated and tested at operating temperatures from 294 to 21 K and operating pressures up to 259 N/sq cm. The primary objective for the smaller sizes was thermal performance optimization of the propulsion system while the primary objective of the larger sizes was weight optimization and to prove fabricability. All major program objectives were met resulting in a design concept that is adaptable to a wide range of aerospace vehicle requirements. Major items of development included: bonding large diameter aluminum end fittings to the thin Inconel liner; fabrication of a 38 cm diameter tube from 0.008 cm thick Inconel; and evaluation of tubing which provides essentially zero quality propellant in a very short period of time resulting in a lower mass of propellant expended in chilldown.

Hall, C. A.↗

NASA NTRS1973

Evaluation of ERTS data for certain hydrological uses

The author has identified the following significant results. Mapping of snow cover using ERTS-1 data proved to be six times faster than that done from U-2 photography. However, NOAA-2 VHRR snow cover mapping was almost as fast as ERTS-1, and it is available more frequently. Ice conditions in the Great Lakes can be readily determined by ERTS-1. Ice features characteristic of thawing conditions such as rotten ice, lack of pressure ridges, brash belts, and compacted ice edges can be identified. A great decrease in apparent reflectivity in band 7 as compared to band 4 also indicated melting conditions. Using sidelap from two successive ERTS-1 images of Lake Erie (February 17 and 18, 1973) a measure of ice movement was made, agreeing closely with the estimate from conventional methods. The same imagery permitted tentative identification of the following features: shuga, light and dark nilas, fast ice, icefoot, ice breccia, brash ice, fracturing, ridging, rafting, sastrugi, thaw holes, rotten ice, ice islands, dried ice puddles, hummocked ice, and leads.

Wiesnet, D. R.↗