Thomas G. Campbell

Computational Electromagnetics and Its Applications

This publication documents the proceedings of the first Workshop on Computational Electromagnetics (CEM) and Applications, hosted by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center, Hampton, Virginia, 29-31 May, 1996, and attended by approximately 70 people from academia, government laboratories, and industry. ICASEs charter mission in 1972 remains today - to explore novel computer environments (vector in the 1970s; parallel in the 1990s) for scientific computing. These proceedings provide a necessary foundation for symposia in computational electromagnetics for future aerospace applications. The objectives of this CEM Workshop were to provide a forum for many of the leaders of the community to assess the state of CEM technology and to discuss areas of research for future programmatic planning activities. Workshop sessions included topics on optimization, industrial applications, algorithms, and a special panel session was provided during which issues were discussed and future research areas were identified. Hopefully, this publication will stimulate and improve communication among multidisciplinary researchers as well as highlighting several CEM areas that need improvement - especially for highly challenging problems. The two most important criteria in the selection of speakers for the workshop were their substantial contribution to large-scale CEM problems and their ability to articulate the issues confronting the CEM research community. Based on the results obtained, it is anticipated that this publication will be useful to government, industry, and university researchers to plan future research tasks in CEM analytical methods and applications.

Radiometric characterization of mesh reflector material for deployable real aperture remote sensing applications

The simultaneous requirement for long wavelength and high spatial resolution for important geophysical remote sensing application, such as soil moisture and salinity, suggest the use of large to moderate sized deployable reflectors as a possible solution. Many studies have recognized the potential advantages of mesh reflectors. However, the emissivity of the reflector and its stability are major concerns and must the carefully considered to enable the advantages of deployable reflector technology for remote sensing applications. This paper will describe an advanced measurement system to evaluate the emissivity of reflector materials for these applications.

Microwave radiometer sensor technology research for Earth science measurements

A research program has been initiated at NASA Langley Research Center to investigate the critical technologies for developing advanced microwave radiometers suitable for Earth science observations. A significant objective of this research is to enable microwave measurements with adequate spatial resolutions for a number of Earth science parameters, such as sea ice, precipitation, soil moisture, sea surface temperature, and wind speed over oceans. High spatial resolution microwave sensing from space with reasonable swath widths and revisit times favor large real aperture radiometer systems. However, the size requirements for such systems are in conflict with the need to emphasize small launch vehicles. This paper describes a tradeoff between the science requirements, basic operational parameters, test configurations, and expected sensor performance for a satellite radiometer concept. The preliminary designs of real aperture systems utilizing novel light-weight compact-packaging techniques are used as a means of demonstrating this technology.

Development Of Microwave Wiometer Sensor Technology For Geostationary Earth Science Platforms

A new research and technology program has been initiated at the Langley Research Center of the National Aeronautics and Space Administration (NASA) for developing advanced, High Resolution Microwave Radiometer (HI-RES) sensors suitable for Mission to Planet Earth (MPE) remote sensing applications. This research program is sponsored by the NASA Office of Aeronautics, Exploration, and Technology (OAET) with a goal to provide the technology needed to enable and enhance the long-term observations, documentation, and understanding of the Earth as a system. In order for the technology to be relevant and useful, the program objectives and scheduled milestones are in support of the science and technology needs advocated by the Office of Space Science and Applications (OSSA). BACKGROUND

Panel Discussion Summary and Recommendations

The objectives of the CEM Workshop Panel Session were to provide a forum for many of the leaders of the CEM community to discuss the state of the technology and, more importantly, to describe new areas of research that should be considered for future applications. This information should be extremely valuable to all organizations involved in EM analytical research and especially to NASA as research activities are being evaluated for future funding possibilities.

Surface control adjustment experiments on a mesh reflector antenna

The authors present results of experiments performed for the purpose of determining the practicality of utilizing active surface control as a means of correcting for distortions in a mesh reflector antenna. A 15-m diameter hoop/column reflector antenna was reconfigured with surface-adjustment capability by installation of control motors on 28 surface shaping tension cords. Only one quadrant of the surface was configured with control motors; all other surface cords had preset tensions. After the motors were installed, the antenna was deployed and the surface distortion measured. The initial deployed surface had a root-mean-square (RMS) distortion of 0.164 in. determined by measuring 239 photogrametric targets over the surface of the controllable quadrant. A finite-element structural model was used to determine the amount of adjustment required for each surface shaping cord to minimize the deviation from a paraboloid.<<ETX>>