Publications

The variance and spectra of angle-of-arrival and Doppler fluctuations were estimated by using 150- and 400-MHz transmissions from the low-orbiting U.S. Navy navigation satellites observed at the Millstone Hill radar facility. A theoretical model for the variance and spectra was also constructed by using the Rytov approximation and a power...

Available observations of ionospheric scintillation are analyzed to evaluate the adequacy of existing models used for the interpretation of scintillation data. The theoretical models are reviewed and the frequency and propagation geometry dependences predicted by the models are compared with the observations. The models were used to construct scintillation occurrence...

A procedure was developed to detect hazardous regions within thunderstorms using weather radar data. The procedure is based upon the hypothesis that convective turbulence occurs within 2-3 km of relative radar reflectivity maxima (cells). The hypothesis was tested using a limited set of simultaneous aircraft and radar data. Good agreement...

Tropospheric angle-of-arrival and amplitude scintillation measurements were made at X-band (7.3 GHz) and at UHF (0.4 GHz). The measurements were made using sources on satellites with 12-day orbits. The angle of arrival of the ray path to a satellite changed slowly allowing observations of fluctuations caused by atmospheric irregularities as...

Observation of amplitude and phase scintillation were made at the Millstone Hill radar facility by using phase coherent sources at 150 and 400 MHz on the U.S. Navy navigation system satellites. These observations have been processed to yield power spectra of the fluctuations in the logarithm of the received power...

This report is directed toward providing information to communication systems designers first about scintillation as observed in a single experiment, second about the adequacy of the existing models used to interpret scintillation data, and finally about the variation of scintillation with geophysical parameters.

An experimental investigation of bistatic scatter from rain was conducted using a 143 km scatter path at frequencies of 4.5 and 7.7 GHz. The ratio of transmitted to received power (transmission loss) was measured for scattering angles ranging from6\degto130\deg. Simultaneous weather radar observations were made at a frequency of 1.3...

The rain range experiment was conducted to test the adequacy of the assumptions usually made in the analysis of attenuation or phase shift due to rain: spherical drop shape, Mie scattering for a single drop, and single scattering theory for the coherent summation of the effects of each drop. A...

Small scale ionospheric irregularities in the F-region can cause fluctuations in the amplitude, phase, and angle of arrival of VHF. UHF, and SHF signals traversing the ionosphere. Under some conditions, the power level fluctuations or scintillations at VHF and UHF may become severe with 12 dB signal level increases and...

The theories describing the effects of the troposphere on satellite communication systems operating in the microwave region are reviewed. The results of computations based upon the theories and atmospheric models are presented and compared with available experimental data. From the model computations it is seen that rain causes the major...