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  • EARTH RESOURCES AND REMOTE SENSING  (828)
  • ASTROPHYSICS  (578)
  • 2010-2014
  • 1980-1984  (1,406)
  • 1981  (1,406)
Collection
Keywords
Years
  • 2010-2014
  • 1980-1984  (1,406)
Year
  • 101
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    Digital image processing on a small computer system (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A minicomputer-based image processing facility provides a relatively low-cost entry point for education about image analysis applications in remote sensing. While a minicomputer has sufficient processing power to produce results quite rapidly for low volumes of small images, it does not have sufficient power to perform CPU- or 1/0-bound tasks on large images. A system equipped with a display terminal is ideally suited for interactive tasks. Software procurement is a limiting factor for most end users, and software availability may well be the overriding consideration in selecting a particular hardware configuration. The hardware chosen should be selected to be compatible with the software and with concern for future expansion.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 239-242
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  • 102
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    Considerations in developing geographic informations systems based on low-cost digital image processing (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The potential of digital image processing systems costing $20,000 or less for geographic information systems is assessed with the emphasis on the volume of data to be handled, the commercial hardware systems available, and the basic software for: (1) data entry, conversion and digitization; (2) georeferencing and geometric correction; (3) data structuring; (4) editing and updating; (5) analysis and retrieval; (6) output drivers; and (7) data management. Costs must also be considered as tangible and intangible factors.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 243-246
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  • 103
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    Low-cost digital image processing on a university mainframe computer (1981)
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    Publication Date: 2011-08-18
    Description: The advantages and limitations of using university mainframe computers in digital image processing instruction are listed. Aspects to be considered when designing software for this purpose include not only two general audience, but also the capabilities of the system regarding the size of the image/subimage, preprocessing and enhancement functions, geometric correction and registration techniques; classification strategy, classification algorithm, multitemporal analysis, and ancilliary data and geographic information systems. The user/software/hardware interaction as well as acquisition and operating costs must also be considered.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 231-236
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  • 104
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    Remote sensing education for the Earth sciences: The University of Georgia experience (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A prospectus is presented of the following courses offered by the Department of Geography: (1) use and interpretation of aerial photographs; (2) advanced photogrammetry; (3) remote sensing of environment; (4) geographic information systems; and (5) directed problems in the remote sensing of the environment. In addition to the course content and objectives, the various equipments available for student training and use are listed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 222-227
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  • 105
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    Communicating remote sensing concepts in an interdisciplinary environment (1981)
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    Publication Date: 2011-08-18
    Description: Although remote sensing is currently multidisciplinary in its applications, many of its terms come from the engineering sciences, particularly from the field of pattern recognition. Scholars from fields such as the social sciences, botany, and biology, may experience initial difficulty with remote sensing terminology, even though parallel concepts exist in their own fields. Some parallel concepts and terminologies from nonengineering fields, which might enhance the understanding of remote sensing concepts in an interdisciplinary situation are identified. Feedbacks which this analogue strategy might have on remote sensing itself are explored.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 217-220
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  • 106
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    Remote sensing education at the University of British Columbia (1981)
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    Publication Date: 2011-08-18
    Description: The development, current status, and organization of the University of British Columbia's interdisciplinary graduate program in remote sensing are described. Specialized programs are tailored to meet student's needs and interest and can range from the theoretical development of technology (sensor development, modelling, and computer analysis) to specialized application of remote sensing in resource analysis such as the determination of vegetation damage, land classification, and land use. The courses and faculty members are listed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 207-210
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  • 107
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    Toward multidisciplinary use of LANDSAT: Interfacing computerized LANDSAT analysis systems with geographic information systems (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The LANDSAT-geographic information system (GIS) interface must summarize the results of the LANDSAT classification over the same cells that serve as geographic referencing units for the GIS, and output these summaries on a cell-by-cell basis in a form that is readable by the input routines of the GIS. The ZONAL interface for cell-oriented systems consists of two primary programs. The PIXCEL program scans the grid of cells and outputs a channel of pixels. Each pixel contains not the reflectance values but the identifier of the cell in which the center of the pixel is located. This file of pixelized cells along with the results of a pixel-by-pixel classification of the scene produced by the LANDSAT analysis system are input to the CELSUM program which then outputs a cell-by-cell summary formatted according to the requirements of the host GIS. Cross-correlation of the LANDSAT layer with the other layers in the data base is accomplished with the analysis and display facilities of the GIS.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 212-215
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  • 108
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    Methods of training the graduate level and professional geologist in remote sensing technology (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Requirements for a basic course in remote sensing to accommodate the needs of the graduate level and professional geologist are described. The course should stress the general topics of basic remote sensing theory, the theory and data types relating to different remote sensing systems, an introduction to the basic concepts of computer image processing and analysis, the characteristics of different data types, the development of methods for geological interpretations, the integration of all scales and data types of remote sensing in a given study, the integration of other data bases (geophysical and geochemical) into a remote sensing study, and geological remote sensing applications. The laboratories should stress hands on experience to reinforce the concepts and procedures presented in the lecture. The geologist should then be encouraged to pursue a second course in computer image processing and analysis of remotely sensed data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 196-203
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  • 109
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    Using LANDSAT imagery as a basis for the understanding of the physiographic regions of the United States (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An undergraduate level course in regional geology is described in which map exercises using LANDSAT composite images are required. From these exercises, students lean to appreciate LANDSAT imagery, learn elementary skills in imagery reading and interpretation, in addition to making the association of geography, geology, maps, and imagery.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 191-194
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  • 110
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    The first year: Development of a LANDSAT capability at Sam Houston State University (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Problems encountered in initiating a LANDSAT data processing capability at Sam Houston State University are discussed. Computer requirements, financing, and academic and administrative support are addressed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 179-182
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  • 111
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    Developing an undergraduate geography course on digital image processing of remotely sensed data (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Problems relating to the development of a digital image processing course in an undergraduate geography environment is discussed. Computer resource requirements, course prerequisites, and the size of the study area are addressed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 174-182
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  • 112
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    Remote sensing research in geographic education: An alternative view (1981)
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    Publication Date: 2011-08-18
    Description: It is noted that within many geography departments remote sensing is viewed as a mere technique a student should learn in order to carry out true geographic research. This view inhibits both students and faculty from investigation of remotely sensed data as a new source of geographic knowledge that may alter our understanding of the Earth. The tendency is for geographers to accept these new data and analysis techniques from engineers and mathematicians without questioning the accompanying premises. This black-box approach hinders geographic applications of the new remotely sensed data and limits the geographer's contribution to further development of remote sensing observation systems. It is suggested that geographers contribute to the development of remote sensing through pursuit of basic research. This research can be encouraged, particularly among students, by demonstrating the links between geographic theory and remotely sensed observations, encouraging a healthy skepticism concerning the current understanding of these data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 183-188
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  • 113
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    Applications of densitometry in remote sensing learning experiences (1981)
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    Publication Date: 2011-08-18
    Description: Information on the use of densitometry in remote sensing courses is provided. The use of a densitometer provides the student with a type of hands on experience in which direct manipulation of image products is involved, and the procedures are easily and quickly learned facilitating the collection and analysis of quantitative data on the radiometric properties of aerial photographs and satellite images. These data can then be used for examining relationships between image tones or colors and ground conditions. Suggestions regarding the selection of equipment and imagery are made.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 169-173
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  • 114
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    The location and scope of geographic remote sensing training in the United States (1981)
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    Publication Date: 2011-08-18
    Description: Maps displaying the distribution of graduate departments of geography in the United States and enrollments in remote sensing courses in all geography departments during the past two calendar years were compiled. It was anticipated that the two distributions would show a marked similarity since remote sensing is a relatively new geographic tool requiring specialized training to use as well as equipment not normally found in most geography departments. Thus only the larger graduate departments can afford to devote time and resources to this specialty. A broad correspondence does exist between the graduate departments of geography and the courses in remote ensing. However, the correlation is far from complete and the exceptions are frequent and large enough to cast doubt upon the accuracy of the original hypothesis. Whereas many large departments do offer courses in remote sensing, many smaller colleges and universities do also. A number of possible explanations can be offered for the discrepancies: (1) course titles, (2) the liberal arts orientation of geography departments in many universities, (3) job-oriented skills which many smaller departments have emphasized, and (4) in the tight job market many new graduates of even the larger departments have had to accept position in smaller departments and colleges.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 161-166
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  • 115
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    Diazo processing of LANDSAT imagery: A low-cost instructional technique (1981)
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    Publication Date: 2011-08-18
    Description: Diazo processing of LANDSAT imagery is a relatively simple and cost effective method of producing enhanced renditions of the visual LANDSAT products. This technique is capable of producing a variety of image enhancements which have value in a teaching laboratory environment. Additionally, with the appropriate equipment, applications research which relys on accurate and repeatable results is possible. Exposure and development equipment options, diazo materials, and enhancement routines are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 128-136
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  • 116
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    University/industry collaboration in remote sensing education (1981)
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    Publication Date: 2011-08-18
    Description: A graduate level course covering the development and structure of geographical information systems and the acquisition and processing of LANDSAT data for input to these systems is described. A portion of the course was devoted to hands-on classification of LANDSAT digital tapes utilizing both university and private industry processing systems. This industry/university collaboration was extremely successful and resulted in a high quality course. It gave the students an excellent experience in working in a real-world client/consultant relationship undertaken to accomplish a specific task. There were two key factors in the success of the collaboration. First, there was a very careful product definition and advance meetings between the University faculty and the company personnel to be involved. Second, the students were not taken into the industrial facility until late in the course, after they had a reasonable knowledge of the physical bases of remote sensing, the concept of spectral signatures, and the fundamentals of pattern analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 141-145
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  • 117
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    Laboratory exercises, remote sensing of the environment (1981)
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    Publication Date: 2011-08-18
    Description: The exercises are designed to convey principles and theory of remote sensing, and methodologies of its application to civil engineering and environmental concerns, including agronomy, geography, geology, wildlife, forestry, hydrology, and other related fields. During the exercises the student is introduced to several types of remote sensing represented by imagery from conventional format: panchromatic, black-and-white infrared, color, and infrared, 35mm aerial photography, thermal infrared, radar, multispectral scanner, and LANDSAT. Upon completion of the exercises the student is expected to know: (1) the electromagnetic spectrum, its various wavelength sub-sections and their uses as sensors, (2) the limitations of each sensor, (3) the interpretation techniques used for extracting data from the various types of imagery, and (4) the cost effectiveness of remote sensing procedures for acquiring and evaluating data of the natural environment.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 120-126
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  • 118
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    Ground photography for improvved image interpretation training (1981)
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    Publication Date: 2011-08-18
    Description: Systematic sets of ground based color and color infrared photography were presented to students in remote sensing classes to enhance their ability to interpret satellite images. Features readily apparent on computer enhanced LANDSAT images were presented simultaneously with ground based photography in the format of slide triplicates. It was hypothesized that this instructional approach would improve the students' abilities to recognize, understand and interpret ground phenomena present on remotely sensed imagery. Tests conducted in undergraduate remote sensing classes substantially upheld this hypothesis. Student image interpretive abilities were tested before and after being exposed to the ground level photography. In general, image interpretive skills of the class improved by 25%. Also, the performance of students having different academic majors varied greatly for differing types of image subjects.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 115-119
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  • 119
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    Performing and updating an inventory of Oregon's expanding irrigated agricultural lands utilizing remote sensing technology (1981)
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    Publication Date: 2011-08-18
    Description: An inventory technique based upon using remote sensing technology, interpreting both high altitude aerial photography and LANDSAT multispectral scanner imagery, is discussed. It is noted that once the final land use inventory maps of irrigated agricultural lands are available and approximately scaled they may be overlaid directly onto either multispectral scanner or return beam vidicon prints, thereby providing an inexpensive updating procedure.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 103-107
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  • 120
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    Customized remote sensing short courses (1981)
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    Publication Date: 2011-08-18
    Description: The advantages of customized courses over general purpose courses are outlined. The development of course objectives and content and the incorporation of hands-on exercises are discussed. Criteria for ensuring the quality of the course are also defined.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 93-101
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  • 121
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    Remote sensing: Present and future (1981)
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    Publication Date: 2011-08-18
    Description: Satellite remote sensing technology is overviewed with particular emphasis on the present and planned LANDSAT satellite systems. Satellite-borne instrumentation and their capabilities are discussed including multispectral scanners, return beam vidicons, the thermal inertia mapper, and STEREOSAT instrumentation.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 87-92
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  • 122
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    The requirements of teaching an interdisciplinary technology from the geographic perspective (1981)
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    Publication Date: 2011-08-18
    Description: The growth of remote sensing course offerings within geography is reviewed and the impact of remote sensing on the discipline is discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 72-76
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  • 123
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    Some characteristics and advantages of LANDSAT 3 return beam vidicon images (1981)
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    Publication Date: 2011-08-18
    Description: One advantage of a LANDSAT 3 return beam vidicon (RBV) scene is the synoptic view it provides. A 1:500,000 paper print of the size 19.4 cm x 19.4 cm encompasses an area of about 3,721 square miles (9,637 sq. km.) and this compares very favorably in coverage to small scale aerial photography. A second important advantage is that the ground resolution is 38 by 38 meters. Compared to the resolution of the MSS which is 79 by 79 meters the RBV provides a wealth of detail useful for many purposes. A great variety of man made structures are visible including bridges, roads, docks, and small airfields. Agricultural field patterns are clear and settlements of various sizes can be identified and delineated. A third advantage is related to the approximate panchromatic spectral response displayed in RBV images. Since many aerial photographic interpreters are accustomed to working with panchromatic photographs, they should have no difficulty understanding and putting RBV images immediately into use.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 84-85
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  • 124
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    Geological applications and training in remote sensing (1981)
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    Publication Date: 2011-08-18
    Description: Some of the experiences, methods, and opinions developed during 15 years of teaching an introductory course in remote sensing at several universities in the Southern California area are related. Although the course is offered in Geology departments, every class includes significant numbers of students from other disciplines including geography, computer science, biology, and environmental science. The instructor or teaching assistant provides a few hours of tutorial lectures (outside of regular class time) on basic geology for these nongeologists. This approach is successful because the grade distribution for nongeologists is similar to that for geologists. The schedule for a typical one-semester course is given.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 77-82
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  • 125
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    Remote sensing training needs in professional forest and range resource management curricula (1981)
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    Publication Date: 2011-08-18
    Description: The status of remote sensing training in accredited U.S. forestry schools is reviewed. It is noted that there is a serious lack of emphasis on aerial photography and aerial photointerpretation in the current curricula. This lack of training at the professional school limits entering employee capability and necessitates expensive on-the-job training.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 68-71
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  • 126
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    The quantitative methodology of remote sensing: An educator's perspective (1981)
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    Publication Date: 2011-08-18
    Description: Strategies for teaching the fundamentals of quantitative remote sensing to students from diverse disciplines and with a broad range of mathematical backgrounds are described. Because the concepts are fairly abstract and complex, the successful educator must take care to motivate and assist the students in mastering the concepts. He/she should strive to communicate intuitive notions of the concepts couched in settings as familiar as possible and use these settings to illustrate each mathematical or statistical formulation which is introduced. The utilization of laboratory-type experiences and lectures from experts is also suggested.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 65-67
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  • 127
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    Equipment and approaches for teaching visual image interpretation (1981)
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    Publication Date: 2011-08-18
    Description: The equipment needs for teaching a visual image interpretation course, and the advantages and limitations of using multimedia and programmed teaching approaches are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 50-55
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  • 128
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    Survey of instructional material for remote sensing (1981)
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    Publication Date: 2011-08-18
    Description: The contents of 17 major textbooks and reference guides on remote sensing technology are listed and compared. As a group, these books concentrate more on principles of the electromagnetic spectrum, sensors and data processing, than on applications. Secondly, it appears that basic photointerpretation receives considerable attention, but that photogrammetry does not. Four texts which provide well-rounded treatments of the systematics of remote sensing are suggested.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 45-49
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  • 129
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    Remote sensing programs and courses in engineering and water resources (1981)
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    Publication Date: 2011-08-18
    Description: The content of typical basic and advanced remote sensing and image interpretation courses are described and typical remote sensing graduate programs of study in civil engineering and in interdisciplinary environmental remote sensing and water resources management programs are outlined. Ideally, graduate programs with an emphasis on remote sensing and image interpretation should be built around a core of five courses: (1) a basic course in fundamentals of remote sensing upon which the more specialized advanced remote sensing courses can build; (2) a course dealing with visual image interpretation; (3) a course dealing with quantitative (computer-based) image interpretation; (4) a basic photogrammetry course; and (5) a basic surveying course. These five courses comprise up to one-half of the course work required for the M.S. degree. The nature of other course work and thesis requirements vary greatly, depending on the department in which the degree is being awarded.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Purdue Univ. CORSE-81: The 1981 Conf. on Remote Sensing Educ.; p 60-64
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  • 130
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    On the formation of protostellar disks (1981)
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    Publication Date: 2011-08-18
    Description: An analysis is presented of the hydrodynamic aspects of the growth of protostellar disks from the accretion of a rotating gas cloud. Streamline equations for the flow onto the disk are derived, including the special case where the disk is very thin. For the radial structure of the disk, detailed equations of conservation of mass, momentum, angular momentum, and energy are given. Exact solutions are found for the case of no internal viscosity. For the more general case where there is viscous stress, hypotheses are formulated with the objective of discovering the main qualitative characteristics of a turbulent system and to estimate the magnitude of the turbulent stress. Solutions are also found for boundary conditions, and the large and small viscosity limits. The relation of energy balance to disk thermal structure is detailed. Finally, trends in the collapse of the dust cloud are discussed in the light of the solutions given.
    Keywords: ASTROPHYSICS
    Type: Icarus; 48; Dec. 198
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  • 131
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    The 1979-1980 eclipse of Zeta Aurigae. II - The emission spectrum (1981)
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    Publication Date: 2011-08-18
    Description: UV observations using the IUE are employed to discuss the strength and changes of Zeta Aur between a second contact and mid-eclipse in 1979, the relative visibility of the supergiant's chromosphere as compared with the circumstellar (CS) nebular scattering of the B star photons, and the origin of the high speed CS components observed at all orbital phases. Agreement has been found for a spectoscopic radius of 200 solar radii and a 400 pc distance, and eclipse emission lines were recorded from 1238.9-2802.7 microns. An asymmetry in the Fe III lines at 46 plus or minus 15 km/sec was seen during eclipse and is taken to indicate downflowing material. The high speed wind flowing from the K supergiant is thought to expand homogeneously until encountering the B type main sequence star, where an accretion bow shock forms, and the smaller star's passage near the K star at periastron may cause local surface heating and subsequent high speed flows.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 251
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    Hard X-ray structure of the Crab Nebula (1981)
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    Publication Date: 2011-08-18
    Description: Two-dimensional maps of the Crab Nebula have been synthesized in 22-64 keV range through the modulation collimator experiment. The effective angular resolution is about 15-arcmin. The result indicates that the Crab morphology is strictly controlled by the pulsar.
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    Cosmic ray antiprotons in the closed galaxy model (1981)
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    Publication Date: 2011-08-18
    Description: A calculation is made of the flux of secondary antiprotons expected for the leaky box model and for the closed galaxy model of Peters and Westergaard (1977). The antiproton/proton ratio observed at several GeV is a factor of 4 higher than the prediction for the leaky box model but is consistent with that predicted for the closed galaxy model. It is found that new low-energy data are not consistent with either model. Attention is given to the possibility of a primary antiproton component.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 251
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  • 134
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    The asymmetric 4.8 hour X-ray modulation of Cygnus X-3 - Model light curves and inferred orbital parameters (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The 4.8 hour X-ray light curve of Cygnus X-3 is quantitatively described by several proposed models under the assumption that the binary orbit of Cyg X-3 is elliptic. The cocoon model implies an apparent size for the X-ray star's companion, which is larger than that of its critical lobe, and it is suggested that the emission of a dense stellar wind by the companion could lead to such a situation. It is shown that a helium star, with or without a hydrogen-rich envelope, seems to be the most likely Cyg X-3 companion, and that some of the observed variations in the 4.8 hour period can be accounted for by the apparent period variations due to apsidal motion.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 251
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  • 135
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    Millimeter-wave experiments for cometary space missions (1981)
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    Publication Date: 2011-08-18
    Description: Predicted brightness temperatures, computed by means of radiative transfer techniques adapted from the modeling of terrestrial ice and snow fields, are given for cometary nucleus models consisting of homogeneous layers of water ice and refractory grain mixtures presented as functions of wavelength. The computed millimeter-wave spectra are sensitive to the values of such physically significant nucleus parameters as (1) crust thickness, (2) subsurface temperature gradient, and (3) sublimating surface boundary temperature. Although antenna beam dilution is a major obstacle for ground-based molecular spectral line radio observations of comets, a millimeter-wave radiometer in the vicinity of the comet would be immune to this effect and able to make observations of several candidate parent molecules in the gas phase.
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  • 136
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    Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Measurements in the 0.1-2.5 micron range are presented for the reflectance spectra of the frosts of several volatiles pertinent to the study of comet nuclei. The frost spectra have distinctive features permitting their identification by spectroscopic reflectance remote sensing, notably in the far UV. It is found that: (1) H2O has a minimum at 0.16 microns and a maximum at 0.13 microns; (2) CO2 has minima near 0.21, 0.18 and 0.125 microns, with maxima at 0.19, 0.135 and 0.120 microns; (3) NH3 is bright at wavelengths longer than 0.21 microns, where reflectance drops to a value of only a few per cent at shorter wavelengths; (4) SO2 has a sharp drop at 0.32 microns, with a minimum at 0.18 microns and a maximum at 0.13 microns. The features in the frost spectra largely correspond to absorption line bands in the gas phase.
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    Collapse and fragmentation of rotating, adiabatic clouds (1981)
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    Publication Date: 2011-08-18
    Description: A numerical hydrodynamics code has been used to calculate the collapse of rotating, adiabatic clouds. The three-dimensional nature of the calculation allows the clouds to fragment in the dynamic collapse phase. Clouds with adiabatic exponent of 7/5 and initial cos(2 phi) density variations fragment into binary systems if the initial ratio of thermal to gravitational energy is small (about 0.05). Clouds with higher thermal energy, however, damp the density variation and form near-equilibrium ellipsoids, with ratios of rotational to gravitational energy less than the critical value for dynamic growth of nonaxisymmetry in Maclaurin spheroids. Even with an adiabatic pressure law, dynamic fragmentation of a collapsing cloud is possible, implying for star formation theory that the low thermal energy fragments produced in isothermal collapse calculations may undergo a subsequent dynamic fragmentation in the nonisothermal regime.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 250
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  • 138
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    Temporal relationships between spectral response and agronomic variables of a corn canopy (1981)
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    Publication Date: 2011-08-18
    Description: Attention is given to an experiment in which spectral radiance data collected in three spectral regions are related to corn canopy variables. The study extends the work of Tucker et al. (1979) in that more detailed measurements of corn canopy variables were made using quantitative techniques. Wet and dry green leaf biomass is considered along with the green leaf area index, chlorotic leaf biomass, chlorotic leaf area, and leaf water content. In addition, spectral data were collected with a hand-held radiometer having Landsat-D Thematic Mapper (TM) bands TM3 (0.63-0.69 micrometers), TM4 (0.76-0.90 micrometers), and TM5 (1.55-1.75 micrometers). TM3, TM4, and TM5 seem to be well situated spectrally for making remotely sensed measurements related to chlorophyll concentration, leaf density, and leaf water content.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Remote Sensing of Environment; 11; Nov. 198
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  • 139
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    Optically processed Seasat radar mosaic of Florida (1981)
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    Publication Date: 2011-08-18
    Description: An uncontrolled mosaic of optically correlated Seasat radar imagery of Florida is presented to illustrate the data and the large area synoptic coverage made possible by combining multiple data sets. The images were taken from a total of 12 passes over 33 days from July 24, 1978 to August 27, 1978. The mosaic is controlled geometrically and with respect to image tone (representing radar backscatter). The SAR data was obtained at an L-band frequency (1.275 GHz, 23.5 cm) and in a horizontal transmit/receive mode, resulting in a 25 m resolution in 100 km swath widths.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing; 47; Sept
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  • 140
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    Very high resolution observations of SS433 at 10.65 GHz (1981)
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    Publication Date: 2011-08-18
    Description: Observations of SS433 made on June 12, 1979, from West Germany, Massachusetts, and West Virginia are discussed. It is noted that SS433 did not show fringes on any baseline although all the calibration sources were seen at their expected strengths. The measured total flux density of SS433 was found to be approximately 0.5 Jy, consistent with previous observations. The source was observed by on-offs at each telescope, which indicates that they were all pointed properly during the observations. The absence of fringes is not attributed to poor observing conditions or instrumental difficulties. It is concluded that if all the 10.65 GHz radiation emanates from a single component, then that component is at least 0.005 arcsec (approximately 10 to the 14th cm) in size. The measurements made on more sensitive intercontinental baselines indicate that there is no component of SS433 smaller than 0.001 arcsec emitting 10.65 GHz radiation above a level of 50 mJy.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 98; 1, Ma; May 1981
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  • 141
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    de Sitter's model and luminosity - Distance in cosmology (1981)
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    Publication Date: 2011-08-18
    Description: The behavior of luminosity-distance with redshift is analyzed within the framework of homogeneous zero-pressure relativistic cosmology. de Sitter's model is shown to have the most redshift sensitive luminosity-distance function of all cosmologies which have q sub 0 not less than -1. Quasar data which suggest a cut-off in absolute luminosity are reanalyzed and the cut-off disappears if either de Sitter's model or the assumption L(L-alpha) = 3 L(H-beta) is used.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 195
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  • 142
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    Fine-scale characteristics of interplanetary sector boundaries (1981)
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    Publication Date: 2011-08-18
    Description: The study examines the structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions during the time interval from December 1974 to April 1975. The transition regions are found to be complex in character, consisting of intermediate average field orientations in some cases as well as a number of large-angle directional discontinuities (DDs). It is suggested that the observed DDs represent multiple traversals of the global heliospheric current sheet caused by local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05-0.1 AU, superimposed on the large-scale structure.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 86; May 1
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  • 143
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    A companion quasar to 3C345 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The discovery of a new quasistellar object (QSO) which presents the strongest evidence to date for the membership of quasars in rich clusters is reported. During X-ray observations of quasar 3C345, a serendipitous X-ray source located 8 arcmin northeast of the quasar was discovered. The observed flux of the new source is 3.2 x 10 to the -13th erg/sq cm/sec in the 0.5-4.5 keV band. Three separate observations over a six-month period failed to show intensity variability in excess of the statistical uncertainty in the count rate. The spectrum shows a modest signal-to-noise ratio but four strong emission lines. It is suggested that the redshift agreement between the two QSOs indicates a common membership in a cluster of galaxies which may well be a rich cluster.
    Keywords: ASTROPHYSICS
    Type: Nature; 290; Apr. 9
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  • 144
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    A variable mixing-length ratio for convection theory (1981)
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    Publication Date: 2011-08-18
    Description: It is argued that a natural choice for the local mixing length in the mixing-length theory of convection has a value proportional to the local density scale height of the convective bubbles. The resultant variable mixing-length ratio (the ratio between the mixing length and the pressure scale height) of this theory is enhanced in the superadiabatic region and approaches a constant in deeper layers. Numerical tests comparing the new mixing length successfully eliminate most of the density inversion that typically plagues conventional results. The new approach also seems to indicate the existence of granular motion at the top of the convection zone.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 145
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    Remote sensing of temperature profiles in vegetation canopies using multiple view angles and inversion techniques (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A mathematical method is presented which allows the determination of vertical temperature profiles of vegetation canopies from multiple sensor view angles and some knowledge of the vegetation geometric structure. The technique was evaluated with data from several wheat canopies at different stages of development, and shown to be most useful in the separation of vegetation and substrate temperatures with greater accuracy in the case of intermediate and dense vegetation canopies than in sparse ones. The converse is true for substrate temperatures. Root-mean-square prediction accuracies of temperatures for intermediate-density wheat canopies were 1.8 C and 1.4 C for an exact and an overdeterminate system, respectively. The findings have implication for remote sensing research in agriculture, geology or other earth resources disciplines.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing; GE-19; Apr. 198
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  • 146
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    A seismic signal processor suitable for use with the NOAA/GOES satellite data collection system (1981)
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    Publication Date: 2011-08-18
    Description: Because of the high data-rate requirements, a practical system capable of collecting seismic information in the field and relaying it, via satellite, to a central collection point is not yet available. A seismic signal processor has been developed and tested for use with the NOAA/GOES satellite data collection system. Performance tests on recorded, as well as real time, short period signals indicate that the event recognition technique used is nearly perfect in its rejection of environmental noise and other non-seismic signals and that, with the use of solid state buffer memories, data can be acquired in many swarm situations. The design of a complete field data collection platform is discussed based on the prototype evaluation.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing; GE-19; Apr. 198
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  • 147
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    Dipole and quadrupole anisotropy of the 2.7 K radiation (1981)
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    Publication Date: 2011-08-18
    Description: Results of measurements of the dipole and quadrupole anisotropy of the microwave background radiation are reported. Balloon-borne measurements of the temperature difference between two horn antennas pointed 90 deg apart and 45 deg from the zenith were carried out at frequencies of 24.8, 31.4 and 46.0 GHz to determine three dipole and four quadrupole parameters. When combined with data from two previous balloon flights, a dipole anisotropy of 3.78 + or - 0.30 mK in the direction 11.6 + or - 0.2 h RA, -12 + or - 5 deg dec is obtained. The measurements reveal a spectral index of 0.04 + or - 0.28 between 19.0 and 46.0 GHz, indicating that the dipole effect arises from an intrinsic anisotropy in the temperature of the background and/or a first-order Doppler shift due to solar motions. A statistically significant quadrupole effect is also detected which is attributed to the intrinsic anisotropy of the 2.7 K background.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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  • 148
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    Far-ultraviolet spectra and flux distributions of some Orion stars (1981)
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    Publication Date: 2011-08-18
    Description: Far-ultraviolet (950-1800 A) spectra with about 2 A resolution were obtained of a number of stars in Orion during a sounding-rocket flight 1975 December 6. These spectra have been reduced to absolute flux distributions with the aid of preflight calibrations. The derived fluxes are in good agreement with model-atmosphere predictions and previous observations down to about 1200 A. In the 1200-1080 A range, the present results are in good agreement with model predictions but fall above the rocket measurements of Brune, Mount and Feldman. Below 1080 A, our measurements fall below the model predictions, reaching a deviation of a factor of 2 near 1010 A and a factor of 4 near 950 A. The present results are compared with those of Brune et al. via Copernicus U2 observations in this spectral range, and possible sources of discrepancies between the various observations and model-atmosphere predictions are discussed. Other aspects of the spectra, particularly with regard to spectral classification, are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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  • 149
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    The cosmic X-ray background (1981)
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    Publication Date: 2011-08-18
    Description: The cosmic X-ray experiment performed with the A2 instrument on HEAO-1 was especially developed to make systematics-free measurements of the extragalactic X-ray sky and has yielded the broadband spectral characteristics for two extreme aspects of this radiation. For the apparently isotropic radiation of cosmological origin that dominates the extragalactic X-ray flux, the spectrum over the energy band of maximum intensity is remarkably well described by a thermal model with a temperature of a half-billion degrees. At the other extreme, broadband observations of individual extragalactic X-ray sources with HEAO-1 are restricted to objects within the present epoch. These X-ray sources include a large sample of active galaxies studied in some detail over a broad bandwidth for the first time. Details of the cosmic X-ray background at these two extremes are reviewed, and some models describing X-ray emission mechanisms are discussed.
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    Algol - A further study of the optical polarization (1981)
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    Publication Date: 2011-08-18
    Description: Results of a study of the phase-locked optical polarization of the Algol triple star system are presented. Polarimetry was obtained in the B filter during 75 nights from 1979 to 1980, and results were folded on the AB orbital period for the equatorial Stokes parameters Q and U. As expected for a nearly edge-on system, the polarization variations are predominantly in one direction of the Stokes-vector plane, and are mainly second-harmonic in character. The variable polarization indicates an eigendirection for the AB system at an angle of 137 + or - 4 deg, and a projected major axis of the third star at 133 + or - 3 deg with respect to the AB system. Considerations of the lowest-order theories of polarizing mechanisms, including limb polarization and reflection, indicate that the AB and AB-C orbital planes are almost normal to each other, rather than coplanar. An angular splitting in the Q-U curve between the two quadrature phases 0.25 and 0.75 is also found which can be explained by centrifugal flattening of the secondary's Roche lobe, or reflection from an optically thick, flattened gas cloud near the L1 point.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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    Interstellar C2 molecules toward Omicron Persei (1981)
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    Publication Date: 2011-08-18
    Description: Seven weak interstellar absorption lines of the (2-0) Phillips band of C2 near the wavelength 8760 are detected in the spectrum of Omicron Persei. All of the lines have equivalent widths less than 2 mA and originate from the five lowest rotational levels of C2. The resulting total column density is N(C2) = 1.5 x 10 to the 13th/sq cm, and the excitation temperature is T = 116 plus or minus 16 K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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    Infrared and optical observations of the hydrogen lines in quasars (1981)
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    Publication Date: 2011-08-18
    Description: Infrared and optical spectrophotometric observations of the hydrogen lines in a sample of 16 quasars are discussed. The addition of these observations to previously published observations of hydrogen lines in quasars brings to 12 the number of quasars for which the P-alpha/H-alpha/H-beta line ratios have been measured and to nine the number of quasars for which the L-alpha/H-alpha line ratio has been measured. It is noted that the P-alpha/H-alpha ratios in low-redshift quasars are distributed around the case B value with a tendency toward values lower than that predicted by case B. The H-alpha/H-beta values in these same quasars are for the most part greater than the case B value. The tendency in the P-alpha/H-alpha/H-beta ratios is for the P-alpha/H-alpha ratio to decrease as the H-alpha/H-beta ratio increases. The decrease of the P-alpha/H-alpha ratio with increasing H-alpha/H-beta ratio is the most significant correlation obtained from the present data that any valid model of the line-emitting regions must explain. The low values of the L-alpha/H-alpha in comparison with the case B value are confirmed for a large sample of high-redshift quasars. L-alpha is seemingly destroyed rather than H-alpha being enhanced. It is concluded that reddening external to the emission-line regions cannot satisfactorily explain all the observed hydrogen line ratios.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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  • 153
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    Nonthermal hard X-ray emission from the nucleus of NGC 1275 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations confirming the HEAO 1 discovery of a hard X-ray component in the X-ray spectrum of the Perseus cluster are reported. A comparison of the results with 1978 HEAO 1 observations and 1974 balloon limits shows that this component is variable on a time scale of one year. Synchrotron self-Compton models of the compact radio source centered on the nucleus of NGC 1275 predict a substantial secondary X-ray flux based on the observed radio data. While the observed X-ray flux is one-fourth the predicted value, uncertainties in the radio data are sufficient to account for the discrepancy. It is concluded that the hard X-ray flux originates in the active nucleus of the Seyfert galaxy NGC 1275 through the synchrotron self-Compton process.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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  • 154
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    Very dusty galaxies (1981)
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    Publication Date: 2011-08-18
    Description: The existence of a significant population of dust shrouded galaxies that do not emit much optical light but instead are primarily infrared sources is considered. It is noted that if very dusty galaxies are assumed to have a luminosity function similar to that of normal galaxies, then current observations seem to show that there are not more dusty galaxies than normal objects. Until more extensive infrared observations are obtained, however, it seems at least possible, though perhaps unlikely, that there are in fact a significant number of dusty galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
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    A study of the Mg II k line in Beta Persei (1981)
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    Publication Date: 2011-08-18
    Description: Spectral scans of the Mg II k line in Beta Per were obtained with Copernicus during two primary eclipses. A brief description of observation in a short frame mode is given. The observed data are compared with computed line profiles based on the eclipse geometry of spherical stars. It is shown that a nonuniform circumstellar envelope, or cloud, probably is present. In one scan, a red-shifted line of P Cygni-type profile appeared, indicating the occurrence of an unusual event in the close binary system.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 86; Feb. 198
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  • 156
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    The close multiple system mu Orionis - Masses and the mass-luminosity relation (1981)
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    Publication Date: 2011-08-18
    Description: The observations made of the secondary component B of the close visual binary mu Ori are described. The Reticon observations made at red wavelengths showed the secondary to be a double-lined spectroscopic binary with a period of 4.78 days and nearly identical components having minimum masses of 1.1 solar mass each. Previous estimates are corroborated by the large spectroscopic mass ratio of B to A and B. The discovery that B is a pair of late-F dwarfs solves the apparent mass-luminosity relation discrepancy noted in previous studies.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 92
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  • 157
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    On the angular variation of solar reflectance of snow (1981)
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    Publication Date: 2011-08-18
    Description: Spectral and integrated solar reflectance of nonhomogeneous snowpacks are derived assuming surface reflection of direct radiation and subsurface multiple scattering. For surface reflection, a bidirectional reflectance distribution function derived for an isotropic Gaussian faceted surface is considered, and for subsurface multiple scattering an approximate solution of the radiative transfer equation is studied. Solar radiation incident on the snowpack is decomposed into direct and atmospherically scattered radiation. Spectral attenuation coefficients of ozone, carbon dioxide, water vapor, aerosol, and molecular scattering are included in the calculation of incident solar radiation. Illustrative numerical results are given for a case of North American winter atmospheric condition. The calculated dependence of spectrally integrated directional reflectance (or albedo) on solar elevation is in qualitative agreement with available observations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Journal of Geophysical Research; 86; Jan. 20
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  • 158
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    Spectral characteristics of wetland habitats (1981)
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    Publication Date: 2011-08-18
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing; 47; Feb. 198
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  • 159
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    Pulsations and oscillations (1981)
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    Publication Date: 2011-08-18
    Description: The observations of the oscillations of the solar atmosphere are a powerful diagnostic tool for research into the structure of the atmosphere from inside the convection zone to the upper chromosphere. Interpretations of the global pulsations or oscillations are presented with emphasis on using these observations to study the structure of the interior of the Sun.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 65-84
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  • 160
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    Magnetic flux tubes (1981)
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    Publication Date: 2011-08-18
    Description: The magnetohydrodynamics of flux tubes are considered. The sections on equilibrium of flux tubes, and stability and waves deal with sunspots, the largest members of the general class of photospheric flux tubes.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 385-413
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  • 161
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    The energy balance of the solar wind (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The effects of modifying some of the 'classical' assumptions underlying many of the solar wind models constructed over the past 20 years are examined in an effort to obtain both a better fit with the observations and a deeper understanding of the relevant physical processes.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 355-372
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  • 162
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    Mechanical heating in the transition region (1981)
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    Publication Date: 2011-08-18
    Description: Attention is focused on the energy balance in the transition region and the role that mechanical heating plays in determining the temperature density structure of this region in a stellar atmosphere. Because of its role as the interface layer through which mass and energy flow between the chromospheres and corona, direct deposition of mechanical energy is a relatively unimportant factor in the overall energy balance in the transition region, except in the uppermost layers where the temperature approaches coronal values.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 321-329
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  • 163
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    Chromospheric heating (1981)
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    Publication Date: 2011-08-18
    Description: General features of the solar chromospheric heating problem, which also apply to many stellar chromospheres, are reviewed. Current theories are discussed, including: heating by short period sound waves; the weak shock theory; and the time-dependent approach.
    Keywords: ASTROPHYSICS
    Type: The Sun as a Star; p 301-319
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  • 164
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    Penetrative convection (1981)
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    Publication Date: 2011-08-18
    Description: The current state of understanding of the most directly observable solar convection, the granulation and supergranulation is summarized. The body of work in which the complete time dependent Navier-Stokes equations and entropy transport equation are solved for a fully compressible atmosphere is considered. Relevant anelastic and incompressible calculations in two dimensions are also discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 253-262
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  • 165
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    Solar flare observations and their interpretations (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A solar flare has a characteristic spatial extent of 10,000 to 100,000 km. It develops rapidly, with a characteristic time scale of 100 to 1000 s but its manifestations can be observed for hours after onset. A solar flare is the source of highly energetic particles with energies that extend into the GeV range; it produces copious amounts of electromagnetic radiation from gamma-rays to wavelengths of 10 km; and it produces violent magnetohydrodynamic phenomena such as shocks and fast mass ejections. The three basic phases of a flare are described and are: the precursor (preflare) phase, lasting for minutes to hours; the flash phase, lasting for 1 to 5 minutes; and the main (gradual) phase, lasting, on occasion, for hours.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 181-227
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  • 166
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    Solar magnetic structure and the solar activity cycle review of observational data (1981)
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    Publication Date: 2011-08-18
    Description: Data on solar magnetism that may offer clues for understanding stellar magnetism in general were reviewed. Magnetic phenomena in the photosphere and low chromosphere, where the magnetic structure can be studied in detail, are discussed. Properties of the discrete magnetic elements and their extensions through the chromosphere and transition zone up to the corona are described. The structure and evolution of active regions and other structured aggregates of magnetic elements are considered.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 163-179
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  • 167
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    The chromosphere and transition region (1981)
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    Publication Date: 2011-08-18
    Description: An empirical definition of the chromosphere and chromosphere-corona transition region is presented. Various general characteristics of the chromosphere are described and include: radiative equilibrium; spatial and temporal fluctuations; spectral characteristics; and thermodynamic structure.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Sun as a Star; p 85-133
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  • 168
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    Remote sensing of soil moisture content over bare field at 1.4 GHz frequency (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An algorithm for estimating moisture content of a bare soil from the observed brightness temperature at 1.4 GHz is discussed and applied to a limited data base. The method is based on a radiative transfer model calculation, which has been successfully used in the past to account for many observational results, with some modifications to take into account the effect of surface roughness. Besides the measured brightness temperatures, the three additional inputs required by the method are the effective soil thermodynamic temperature, the precise relation between moisture content and the smooth field brightness temperatures and a pair of parameters related to surface roughness. The procedures of estimating surface roughness parameters and of obtaining moisture content from observed brightness temperature are discussed. The algorithm is applied to observations from truck mounted and airborne radiometers. The estimated moisture contents compare favorably with the observations in the top 2 cm layer.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Journal of Geophysical Research; 86; June 20
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  • 169
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    X-ray spectra of the Crab pulsar and Nebula (1981)
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    Publication Date: 2011-08-18
    Description: The X-ray spectra of the Crab pulsar and Crab Nebula are analyzed. Observations were made with OSO 8 on March 17-18, 1978, with all spacecraft telemetry assigned to one detector during seven dwell mode experiments. A resolution of 1.25 ms was obtained for pulse-height-analyzed counts in 64 channels. Progressive hardening and subsequent softening of the spectrum across the pulse was found. The fraction of the pulsed flux, exhibiting a spectral variability of about 0.14 was concentrated solely in the region between the two peaks. A model is suggested in which the pulsed X-ray emission from the Crab pulsar consists of two components: one is physically related to the double-peaked gamma-ray pulse and possibly to radio and optical pulses, but has no spectral dependence on the pulse phase, while the other exhibits spectral variability with the pulse phase but is confined to the interpeak emission seen with X-ray energies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 170
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    Identification of new infrared bands in a carbon-rich Mira variable (1981)
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    Publication Date: 2011-08-18
    Description: Complete 0.75-13 micron spectrometry of a carbon-rich, Mira-class variable star is presented for the first time. It is noted that although the near-infrared is dominated by photospheric absorption bands of the CN red system, the infrared becomes progressively dominated by the bands of the polyatomic molecules HCN and C2H2. Since the band at 3.1 microns is known to be due to HCN and C2H2, it is possible to associate bands at 1.04, 1.53, 1.85, 2.5, 2.7, 3.56, 3.85, 4.8, and 7.1 microns with HCN and C2H2. The spectrum suggests that radiative transfer in the carbon Mira class cannot be discussed quantitatively without the inclusion of HCN and C2H2 opacity. On the basis of the carbon star models of Querci and Querci (1974), it is deduced that the abundance ratio of HCN to C2H2 can be used to indicate whether 3-alpha-processed or CNO-processed material is in the outer atmosphere. An 11.3 micron SiC dust-emission feature is present, although it differs significantly from the 11.7 micron SiC feature in Y CVn. A featureless emission is present from 4 to 13 microns and can be ascribed to optically thin graphite grains having a temperature of 450 K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 171
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    Cyg X-1 - A massive neutron star (1981)
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    Publication Date: 2011-08-18
    Description: The expected X-ray emission from Cyg X-1, considered a massive neutron star (8-15 solar masses) according to some gravity theories, is studied within the framework of Rosen's bimetric gravity theory (1973, 1974). It is shown that in such massive neutron stars, the innermost stable orbit lies far outside the star surface, and therefore the X-ray spectrum consists of two components: a soft one emitted from a cold accretion disk and a hard one emitted by the matter striking the neutron star surface after spiraling down freely from the disk. The proposed model is shown to be in good agreement with the observed luminosities. The model predicts a surface gravitational redshift of 3.16 which could be tested by the future X- and gamma-ray detectors.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 97; 2, Ap; Apr. 198
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  • 172
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    Interplanetary gas. XXVI - On the reconnection of magnetic fields in cometary ionospheres at interplanetary sector boundary crossings (1981)
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    Publication Date: 2011-08-18
    Description: The reconnection process in the cometary ionosphere believed responsible for the disconnecting plasma tails phenomenon is studied through the basic equations of reconnection theory and current sheet instability criteria. It is proposed that reconnection occurs when the interplanetary magnetic fields incident on a comet that has gone just past a sector boundary are pressed into the fields captured from the previous sector. The fields are of opposite polarity, and the previously captured fields constitute the 'roots' of the plasma tail. An estimated duration of reconnection during a disconnection event (DE) of 0.75 days is used along with estimates of other cometary parameters to construct fusion region dimensions and resistivity with the adopted time scale.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 245
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  • 173
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    Modeling the effects of various radiant transfers in mountainous terrain on sensor response (1981)
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    Publication Date: 2011-08-18
    Description: A model is developed for the study of remote sensing spectral data problems encountered in mountainous terrain, where slope orientation with respect to sources of incident radiation must be considered for accurate classification of multispectral data. The model simulates the effects of solar, sky and adjacent slope irradiance fluxes and the bidirectional reflectance properties of the target surface on sensor response for various slope orientations. The errors associated with two practical techniques used to account for topographic effects on sensor response were evaluated in light of the model, and it was found that the simple cosine correction of the direct solar source showed reflectance errors greater than 11% while the technique considering both direct solar and diffuse sky sources was 50% more accurate.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing; GE-19; Apr. 198
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  • 174
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    On stellar wind accretion in widely separated X-ray binaries, and the nature of 4U0115+63 (1981)
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    Publication Date: 2011-08-18
    Description: Widely separated, eccentric pulsating X-ray binaries are shown to be appropriate systems for studying the basic properties of stellar wind accretion. They are free from the complications encountered in closed binaries, where the optical star nearly fills its critical lobe (Avni, 1977). A framework of four observational tests was set up to study the characteristics of wind accretion, and to distinguish between different models of wind acceleration. The tests are applied to the source 4U0115+63, and the accretion process is discussed in both its quiescent states, and during its transient high luminosity outbursts. For the quiescent steady state, two wind profiles, determined from observational data, are compared (Barlow-Lohen, 1977; Castor et al., 1975). The difficulties encountered during the transient high states with respect to the possibility of stellar wind accretion are discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 102; 1, Se; Sept
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  • 175
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    Temporal changes of the global reflectance of a wheat field as a function of daily solar irradiance (1981)
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    Publication Date: 2011-08-18
    Description: Based on in situ measurements of incident and reflected solar irradiation over a wheat field, daily values of the surface reflectance, a scene signature, were determined for a crop year. Diagnoses of these data reveal the character of the signature, and its changes with time, crop stage, and the magnitude of incident irradiance. The latter varies inversely with cloud cover.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 1; 21 p
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    Cosmology (1981)
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    Publication Date: 2011-08-18
    Description: The current view of the universe is summarized. The equations used to described it and the means of interpreting the diffuse gamma radiation which might result from phenomena which occurred in the distant past are described. The Friedmann model is described in detail.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 187-201
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    Diffuse radiation (1981)
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    Publication Date: 2011-08-18
    Description: A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 203-228
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  • 178
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    The interstellar medium and galactic structure (1981)
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    Publication Date: 2011-08-18
    Description: High energy gamma rays are produced by the interaction of cosmic rays with the interstellar matter in the galaxy. By combining the gamma ray information with radio data, a picture of the galaxy is presented with regard to the general structure and the effects of cosmic ray pressure. The interaction processes and galactic matter distribution are discussed. Galactic cosmic ray distribution and current gamma ray results are reported.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 99-130
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    Gamma ray astronomy in perspective (1981)
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    Description: A brief overview of the development of gamma ray astronomy is presented. Gamma ray telescopes and other optical measuring instruments are highlighted. Emphasis is placed on findings that were unobtainable before gamma ray astronomy. Information on evolution of the solar system, the relationship of the solar system to the galaxy, and the composition of interstellar matter is discussed.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 1-14
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    Relativistic astrophysics - The view from Texas in Baltimore /Review/ (1981)
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    Publication Date: 2011-08-18
    Description: Recent observational and theoretical work presented at the Tenth Texas Symposium on Relativistic Astrophysics held in Baltimore, Maryland from December 15-19, 1980, is outlined. Areas covered include the theoretical foundations of relativistic astrophysics in general relativity, quantum gravitational theory and the association of grand unification with astronomical and cosmological issues, the cosmic microwave, X-ray, gamma-ray, UV, cosmic ray and gravitational wave backgrounds, the current expansion rate and average mass-energy density of the universe, and mechanisms of galaxy formation. Also discussed are the characteristics of active galaxies and clusters emitting in the gamma-ray and X-ray regions, and compact objects formed from supernova explosions, including pulsars, X-ray-emitting neutron stars, Sco X-1 and SS 433, gamma-ray sources, and X-ray and gamma-ray bursters.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 22; 1, 19; 1981
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    One millimeter continuum observations of high redshift quasars (1981)
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    Publication Date: 2011-08-18
    Description: Upper limits to the one-millimeter continuum flux densities of the high redshift quasars B2 1225 + 31, Ton 490, and PHL 957 are presented. The upper limit to the power observed from these quasars at 1 mm is, on the average, one half of the observed power in the continuum at L-alpha. These observations are used to constrain the temperature of a hypothetical dust shell which reddens the quasar line and continuum emission by an extinction optical depth sufficient to account for the anomalously low L-alpha/H-alpha emission line ratio observed in each of these quasars. For the quasars studied, dust shell temperatures between 25 K and 50 to 95 K are prohibited by the present data. A dust shell at a temperature within this span reradiating all the power absorbed from the quasar ultraviolet continuum would produce a one-millimeter flux density greater than the measured upper limit. The average radius of the model dust shell cannot be between 70 kpc and 1 Mpc.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Letters; 22; 1, 19; 1981
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  • 182
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    Mantle convection and subcrustal stresses under Australia - A reply (1981)
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    Publication Date: 2011-08-18
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Modern Geology; 7; 4, 19; 1981
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  • 183
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    A comparison of radiative transfer models for predicting the microwave emission from soils (1981)
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    Publication Date: 2011-08-18
    Description: Noncoherent and coherent numerical models for predicting emission from soils are compared. Coherent models use the boundary conditions on the electric fields across the layer boundaries to calculate the radiation intensity, and noncoherent models consider radiation intensities directly. Interference may cause different results in the two approaches when coupling between soil layers in coherent models causes greater soil moisture sampling depths. Calculations performed at frequencies of 1.4 and 19.4 GHz show little difference between the models at 19.4 GHz, although differences are apparent at the lower frequency. A definition for an effective emissivity is also given for when a nonuniform temperature profile is present, and measurements made from a tower show good agreement with calculations from the coherent model.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Radio Science; 16; Sept
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    GPS application to mapping, charting and geodesy (1981)
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    Publication Date: 2011-08-18
    Description: GPSPAC, a receiver being developed for space applications by the Defense Mapping Agency and NASA, will use signals from GPS constellations to generate real-time values of host vehicle position and velocity. The GPSPAC has an L-band antenna and preamp capable of receiving the 1575 MHz and 1227 MHz spread spectrum signals; its stable oscillator at 5.115 MHz provides the basic frequency reference, resulting in a long term drift of less than one part in 10 to the -10th day. The GPSPAC performs many functions on board the spacecraft which were previously relegated to large-scale ground-based computer/receiver systems. A positional accuracy of better than 8 can be achieved for those periods when four or more NAVSTAR satellites are visible to the host satellite. The GPS geodetic receiver development, which will provide prototype receivers for utilization in terrestrial surveying operations, has the potential to significantly enhance the accuracy of point geodetic surveys over the current user hardware capability.
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    The interstellar medium and the highly ionized species observed in the spectrum of the nearby white dwarf G191-B2B (1981)
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    Publication Date: 2011-08-18
    Description: High-resolution spectra of the nearby (48 pc) white dwarf G191-B2B, obtained with the International Ultraviolet Explorer, reveal sharp resonance lines of N V, C IV, and Si IV. The origin of these features is most likely linked to the white dwarf, possibly being formed in an expanding halo around the star. Interstellar lines of C II, N I, Mg II, Si II, and Fe II are also seen in the spectrum. Analysis of these features indicates an average neutral hydrogen number density of 0.064 for this line of sight. In combination with the recent EUV and soft X-ray results, this is interpreted to mean that the interstellar medium in the most immediate solar vicinity is of the normal density n approximately equal to 0.1/cu cm of lower ionization, while just beyond it, at least in some directions, is a hot lower density plasma. These results are apparently in conflict with the model of the interstellar medium by McKee and Ostriker (1977) in its present form.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
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    The 1979-1980 eclipse of Zeta Aurigae. I - The circumstellar envelope (1981)
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    Publication Date: 2011-08-18
    Description: A model of the K-star wind far from the K star, and its interaction with the B star, has been derived from a study of Mg(+) and C(+++) resonance lines in the spectrum of Zeta Aurigae during 1979 and 1980. A mass loss rate from the K star of 2 x 10 to the -8th solar masses/year is suggested by the data; the rate of accretion of the K supergiant's material by the B star then being such that the matter accreted over a period of ten years is of the order of the total mass of the photosphere of the B star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
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    The chemical composition, gravity, and temperature of Sirius (1981)
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    Publication Date: 2011-08-18
    Description: Observational data available for Sirius are of poorer quality than those for Vega, with both the angular diameter and absolute fluxes at different wavelengths being less accurately known. While these data yield an effective temperature of 10,000 + or - 250 K, the 13-color photometry of Johnson and Mitchell (1975) suggests that Sirius is about 450 K hotter than Vega's effective temperature of 9650 + or - 200 K. The c(1) color of the uvby system, the 33-52 and 35-52 colors of the 13-color photometry, and the H-alpha, H-beta and H-gamma line profiles all give log g values of about 4.3, which is in agreement with the value deduced from the mass and the radius, the latter being deduced from the angular diameter and the parallax.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
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    The nearby interstellar medium (1981)
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    Publication Date: 2011-08-18
    Description: The high dispersion spectrometer on board the International Ultraviolet Explorer (IUE) satellite was used to observe interstellar absorption lines in Rasalhague (Alpha Oph). This star is located 18 pc from the sun in the direction of the North Polar Spur, a prominent radio continuum feature in the Ophiuchus region of the sky. The satellite results, combined with previous interstellar line data and observations of the 'local interstellar wind' and soft X-ray emission, support earlier suggestions that the sun is immersed in a supernova remnant which may be an extension of the 'Loop I' or 'North Polar Spur' supernova remnant seen in the Scorpius-Ophiuchus region of the sky.
    Keywords: ASTROPHYSICS
    Type: Nature; 293; Oct. 1
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    Detectors for energies less than 10 MeV (1981)
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    Publication Date: 2011-08-18
    Description: In the energy domain 100 keV to 10 MeV, both crystal scintillations and semiconductors are widely used for gamma ray detectors in spectrometer systems. These detectors' operation depend on the fact that gamma rays lose energy by ionization in these materials and electrons and holes are produced. In the case of semiconductors, these electrons and holes are collected by an electric field, and they provide an electric signal that is a direct measure of the energy lost by the gamma ray in the material. Scintillation detectors depend on a further conversion of the energy lost in electron hole pair production to the production of photons. A photomultiplier tube measures the intensity of the photon flux, and an electrical pulse proportional to the photon intensity is produced at the photomultiplier output.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 247-303
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    Gamma ray interaction processes (1981)
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    Publication Date: 2011-08-18
    Description: Gamma ray detection in the energy region above 1 keV involves measurements of the energy exchange or energy loss between the gamma ray and the mass of the detector. In most cases of interest, it is the kinetic energy imparted to charged particles by the gamma ray which is lost in the detector and measured in order to obtain spectral knowledge between the incident gamma ray photon and the direction of the secondary particles contains important energy information. The interaction gamma ray removal processes in matter are considered. This interaction removal process is characterized by the fact that each gamma ray is removed individually from the incident beam. The number of photons removed in this manner is proportional to the thickness of matter traversed.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 229-246
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    Solar observations (1981)
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    Publication Date: 2011-08-18
    Description: High energy processes that take place in the Sun's atmosphere and the relationship of these phenomena to the basic problems of solar activity are discussed. Gamma ray emission exhibits characteristics of the conditions in regions where accelerated high energy particles interact. A number of gamma ray production mechanisms are considered. These include: the Compton effect, magnetobremsstrahlung, pi meson production by proton-proton interaction or by proton-antiproton annihilation, fission and neutral of charged particle radiative capture on inelastic scatter.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 67-94
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    Gamma ray observations of the solar system (1981)
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    Publication Date: 2011-08-18
    Description: Two general categories are discussed concerning the evolution of the solar system: the dualistic view, the planetesimal approach; and the monistic view, the nebular hypothesis. The major points of each view are given and the models that are developed from these views are described. Possible applications of gamma ray astronomical observations to the question of the dynamic evolution of the solar system are discussed.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 19-24
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  • 193
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    The Seasat commercial demonstration program (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The background and development of the Seasat commercial demonstration program are reviewed and the Seasat spacecraft and its sensors (altimeter, wind field scatterometer, synthetic aperture radar, and scanning multichannel microwave radiometer) are described. The satellite data distribution system allows for selected sets of data, reformatted or tailored to specific needs and geographical regions, to be available to commercial users. Products include sea level and upper atmospheric pressure, sea surface temperature, marine winds, significant wave heights, primary wave direction and period, and spectral wave data. The results of a set of retrospective case studies performed for the commercial demonstration program are described. These are in areas of application such as marine weather and ocean condition forecasting, offshore resource exploration and development, commercial fishing, and marine transportation.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: ESA Appl. of Remote Sensing Data on the Continental Shelf; p 59-72
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  • 194
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    Use of LANDSAT data to define soil boundaries in Carroll County, Missouri (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Bands 4, 5 and 7 false color composite photographs were prepared using data from LANDSAT scenes acquired during April 1977 and April 1981 on computer compatible tapes, and these color composites were compared with band 7 black and white photographs prepared for the entire county. Delineations of soil boundaries at the soil association level were achieved using LANDSAT spectral reflectance data and slope maps for a portion of Carroll County, Missouri. Forty two spectral reflectance classes from April 1977 LANDSAT data were overlaid on digitized slope maps of nine USGS 7.5 minute series topographic quadrangle slope maps to achieve boundary delineations of the soil associations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 1; 12 p
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  • 195
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    Analysis of observational spectra (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The first step in the analysis of gamma ray energy loss spectra is their conversion to differential energy and differential angular photon spectra. This conversion can be carried out if the detector response and the background are both known. Once these parameters are known, there are many techniques that can be used to convert pulse height spectra to photon spectra. These techniques are discussed and background problems are considered. Emphasis is placed on the analysis of energy loss spectra in the lower gamma ray energy domain. Problems of transportations from pulse height to photon space are most complex in this domain and the methods shown illustrate many of the problems which arise in the general analysis of energy loss spectra.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 337-382
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  • 196
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    Detectors for energies greater than 10 MeV (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The detector telescopes used in gamma ray astronomy in general are more similar to particle detectors than to optical devices, since the high frequency of the radiation precludes the use of reflection or diffraction techniques, but the high energy content of each photon does enable them to be detected with scintillators, track imaging chambers, and solid state detectors. Within the gamma ray range, the basic design of the instrument changes as the energy of the gamma ray exceeds 10 to 20 MeV, and therefore, moves from the region where the Compton effect predominates in the absorption of the gamma ray to that where electron pair production is most important. In the energy range from 10 to 20 MeV to several times 10,000 MeV, gamma ray telescopes are usually built so that the electron pair may be seen and the properties of the electrons measured.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 305-336
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  • 197
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    Galaxies (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.
    Keywords: ASTROPHYSICS
    Type: Gamma Ray Astrophys.; p 165-185
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  • 198
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    Freshwater ice thickness observations using passive microwave sensors (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Walden Reservoir, a freshwater lake in north-central Colorado, was overflown six times by a NASA C-130 aircraft between January 1977 and April 1980. The aircraft was equipped with four microwave radiometers operating between 0.81 and 6.0 cm in wavelength (37.0 to 5.0 GHz). The 6.0-cm radiometer data showed a good relationship with ice thickness based on a sample of four ice thickness values. The 1.67- and 1.35-cm radiometer data showed weaker relationships with ice thickness. The 0.81-cm sensor data showed no positive relationship with ice thickness. None of the relationships was statistically significant because of the small sample size. The 6.0-cm sensor data in the nadir-viewing mode was found to have the most potential of all the wavelengths studied, for use in remotely determining ice thickness. The 6.0-cm radiometer probably sensed the entire thickness of the ice on the reservoir (ranging from 25.4 to 67.3 cm in thickness) and was apparently not significantly affected by the snow overlying the ice. The shorter wavelengths are scattered by the snow overlying the ice and are more suitable for snow studies than for ice thickness studies.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing; GE-19; Oct. 198
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  • 199
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    ICAP - An Interactive Cluster Analysis Procedure for analyzing remotely sensed data (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An Interactive Cluster Analysis Procedure (ICAP) was developed to derive classifier training statistics from remotely sensed data. ICAP differs from conventional clustering algorithms by allowing the analyst to optimize the cluster configuration by inspection, rather than by manipulating process parameters. Control of the clustering process alternates between the algorithm, which creates new centroids and forms clusters, and the analyst, who can evaluate and elect to modify the cluster structure. Clusters can be deleted, or lumped together pairwise, or new centroids can be added. A summary of the cluster statistics can be requested to facilitate cluster manipulation. The principal advantage of this approach is that it allows prior information (when available) to be used directly in the analysis, since the analyst interacts with ICAP in a straightforward manner, using basic terms with which he is more likely to be familiar. Results from testing ICAP showed that an informed use of ICAP can improve classification, as compared to an existing cluster analysis procedure.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Remote Sensing of Environment; 11; Sept
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  • 200
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    Rotation of dwarf star chromospheres in the ultraviolet (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Periodic variations in the ultraviolet fluxes of chromospheric emission line multiplets are investigated for F, G and K stars as evidence of rotational modulation. Vacuum ultraviolet spectra were obtained with the IUE spacecraft for six stars as many as 11 times over the period April 23 to December 3, 1980. Variations in the emission fluxes of the hydrogen Lyman-alpha, Si II and Mg II lines are observed with periods up to 47 days. The periodicity, which is identified with rotational modulation, is found to persist over many rotational cycles, although the periods and time dependences of the fluxes from the different ionic species are not identical, probably due to differential rotation and global distributions. The spread of the UV periods is observed to be within 10%, with one or two peaks per cycle and a ratio of modulated to umodulated flux ranging from 1.1 to 3.0, analogous to solar behavior.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
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