International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / During the NASA Ka-band propagation experiment it was discovered that rainwater on the antenna caused significant attenuation. It is necessary to estimate the losses caused by water on the antenna in order to separate these losses from the atmospheric propagation losses. A prediction model is developed for losses caused by rainwater on a satellite dish antenna. The model is based entirely on physical parameters including elevation angle, dish diameter, focal length, properties of present coating layers, feed window properties, frequency, polarization, water temperature and rain rate. The prediction model is implemented using Matlab and has been tested against experimental data.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / The need for increased downlink data rates and bandwidth for Earth Observation (EO) missions is driving mission planners to consider Ka-Band (25.5 to 27.0 GHz) downlinks to replace or augment the existing X-Band (8.025 to 8.400 GHz) services. Future ground stations will be required to support both bands as well as S-Band (2.0-2.3) GHz telemetry and command functions. This paper discusses the inherent tradeoffs in such a design, and proposes an implementation which permits simultaneous data reception in X-Band and Ka-Band, while providing TT&C functionality at S-Band. Analytical and measured data for the implementation are provided.

The Topographic Interferometry Mapping Mission (TIMMi) instrument is a unique millimeter wave interferometric radar system operating at 35 GHz (Ka-band). It was constructed in part to advance the technology readiness level of NASA’s Surface Water and Ocean Topography (SWOT) mission, a spaceborne platform that will globally map the altimetry of Earth’s water to gain insight into surface water interactions and dynamics. Previous ground deployments of TIMMi were successful in demonstrating the abilities of the system from a stationary platform. The next logical step was to move TIMMi closer to space by installing it on an airborne platform prove its capability in mapping wide swaths of land at a higher incidence angle. This thesis outlines the design considerations and challenges in adapting TIMMi to a small airborne platform. Documentation is included from many points throughout the development cycle, including hardware and software development, flight planning, data acquisition, and post-flight data processing.

No description available.

Zugl.: Hamburg, Techn. Univ., Diss., 2008

Wireless communications systems of all types must deliver reliable connections to the end users to be accepted by the public. The reliability of these systems is composed of two aspects. The first aspect is the reliability of the actual hardware and software composing the device and is completely under the control of the designers of the equipment. The second aspect of reliability or availability is the wireless propagation link connecting the users. This link is very difficult to model exactly and is composed of a fixed propagation loss plus random elements of propagation loss.This thesis focuses on the propagation links associated with satellite communications systems (Satcom). The fixed portion of the link loss in this case is the "spreading loss" or free space loss which occurs due to the large distance between the user and the satellite. The random portion of the link loss in these systems is due to many things such as rain, absorption, shadowing, multipath and cross polarization effects. However the major element associated with fades in Satcom systems is rain and the fades associated with rain. Rain becomes an even more dominate term in the situation as higher frequencies are used to obtain the increases in bandwidths required to accommodate the increases in use. Rain fades on the satellite links are modeled as random processes whose parameters are given in RECOMMENDATION ITU-R P.837-5 of the International Telecommunications Union (ITU). Over the years this recommendation has been revised and the current revision is 837-5 as indicated above. However, the data used to develop these models has always come from the European Centre for Medium-range Weather Forecasts based upon data measured at approximately 100 stations around the world. Since 1998 satellite sensory data is available for the tropics which directly measures rain data in this area. The Tropical Rainfall Measuring Mission (TRMM) is a join satellite project involving the USA and Japan. As a result of the availability of TRMM data it is possible to improve the statistical rain rate models for the tropical regions of the world. Recently a number of researchers (T.V, Omotosho, C.O. Oluwafemi, C Prabhakara et all) have begun to use TRMM data to improve the rain rate and rain fade estimates. The ITU has also begun to study using TRMM data in their recommendations. In this thesis the TRMM data is used to construct a rain rate and rain fade models for the Indian sub-continent as well as other parts of the tropics. This model is compared to the predictions based upon the ITU 837-5 models and substantial differences are found in the heavy rain fall areas. India is currently building a satellite (GSAT-4) to measure rain fades at 20/30 GHz and it is hoped that these results can be used to compare with the measured GSAT-4 data when it is available.

This thesis describes a possible integrated terrestrial-satellite network system for disaster recovery and response. The motivation of this thesis was based on the adjacent spectrum allocations between the Virginia Tech terrestrial Local Multiple Distribution Service (LMDS) system and a Ka-band satellite system, and potentially being able to provide as an additional Ka-band satellite network backbone to the Virginia Tech terrestrial LMDS system for better and faster communications deployments. The Spaceway satellite system's design parameters were adopted typically for a Ka-band satellite system. The LMDS system was assumed to use IEEE 802.16 standard protocols although it currently uses its own proprietary protocols. Four possible topologies integrating both terrestrial and satellite network were investigated. The study showed that the task was more problematic and complicated than anticipated due to incompatible network protocols, limitations of available hardware components, the high path loss at Ka-band, and the high cost of the equipment, although the adjacent frequency bands do suggest a possible integrated network. In this thesis, the final selected topology was proposed and designed. The technical characteristics of the earth station used for coupling both terrestrial and satellite networks were determined by a link budget analysis and a consideration of network implementations. The reflector antenna used by the earth station was designed. In addition, other system design concerns and engineering tradeoffs, including adjacent satellite interference, rain attenuation, antenna pointing error, noise temperature, and modulation and multiple access selection, were addressed. / Master of Science

No description available.

Array antennas are used extensively in remote sensing applications, where a highly directive beam is needed to scan a particular area of interest on the surface of the earth. The research presented here focuses on the design of different microstrip patch antenna arrays to be used in environmental sensing applications in the X and Ka frequency bands, such as measurements in Snow and Cold Land Processes (SCLP) to detect snow accumulation, snow melt, etc. The goal of this research is to produce highly integrated, low loss, and compact size antenna arrays, while maintaining low power consumption. Multilayer organic (MLO) System-on-a-Package (SOP) technology, using laminates such as Liquid Crystal Polymer (LCP) and RT/Duroid®, provides a lightweight and low cost 3D solution for the fabrication of the antenna arrays. The elements of the antenna arrays are rectangular patches. Two feeding mechanisms, aperture coupling and via feed, were implemented and compared. For the RF distribution network and interconnects, a corporate feed approach was used with reactive T-junctions, Wilkinson dividers, or both, for power division. The feed networks were designed using microstrip. The basic multilayer antenna array design consists of 3 layers of cladded laminate material. The metal layers are as follows: 1) patch antennas, 2) ground plane, 3) feed network, and 4) surface-mount components. The surface mount components would include LNA, PA, TR switch and phase shifter.

Aquarius/SAC-D is a joint NASA/CONAE (Argentine Space Agency) Earth Sciences satellite mission to measure global sea surface salinity (SSS), using an L-band radiometer that measures ocean brightness temperature (Tb). The application of L-band radiometry to retrieve SSS is a difficult task, and therefore, precise Tb corrections are necessary to obtain accurate measurements. One of the major error sources is the effect of ocean roughness that "warms" the ocean Tb. The Aquarius (AQ) instrument (L-band radiometer/scatterometer) baseline approach uses the radar scatterometer to provide this ocean roughness correction, through the correlation of radar backscatter with the excess ocean emissivity. In contrast, this dissertation develops an ocean roughness correction for AQ measurements using the MicroWave Radiometer (MWR) instrument Tb measurements at Ka-band to remove the errors that are caused by ocean wind speed and direction. The new ocean emissivity radiative transfer model was tuned using one year (2012) of on-orbit combined data from the MWR and the AQ instruments that are collocated in space and time. The roughness correction in this paper is a theoretical Radiative Transfer Model (RTM) driven by numerical weather forecast model surface winds, combined with ancillary satellite data from WindSat and SSMIS, and environmental parameters from NCEP. This RTM provides an alternative approach for estimating the scatterometer-derived roughness correction, which is independent. The theoretical basis of the algorithm is described and results are compared with the AQ baseline scatterometer method. Also results are presented for a comparison of AQ SSS retrievals using both roughness corrections.