Engineering topics

Gogineni, Sivaprasad

Publications and source records attributed to Gogineni, Sivaprasad.

3 records

NASA NTRS1999

Program for Arctic Regional Climate Assessment (PARCA)

The Program for Arctic Regional Climate Assessment (PARCA) is a NASA-sponsored initiative with the prime objective of understanding the mass balance of the Greenland ice sheet. In October 1998, PARCA investigators met to review activities of the previous year, assess the program's progress, and plan future investigations directed at accomplishing that objective. Some exciting results were presented and discussed, including evidence of dramatic thinning of the ice sheet near the southeastern coast. Details of the investigations and many of the accomplishments are given in this report, but major highlights are given in the Executive Summary of the report.

Gogineni, Sivaprasad↗

NASA NTRS1991

A numerical procedure for recovering scattering coefficients from measurements with wide-beam antennas

A numerical procedure for estimating true scattering coefficients, sigma0, from measurements made using wide-beam antennas is discussed. The use of wide-beam antennas results in an inaccurate estimate of sigma0. To reduce this error, the authors propose a correction procedure that estimates the error resulting from the use of narrow-beam approximation and utilizes the error to obtain a more accurate estimate of sigma0. An exponential model is assumed to take into account the variation of sigma0 with incidence angles, and the model parameters are estimated from measured data. Based on the model and knowledge of the antenna pattern, the procedure calculates the error due to the narrow-beam approximation. The procedure is shown to provide a significant improvement in the estimation of sigma0 obtained in wide-beam antennas. The proposed procedure is also shown to be insensitive to the assumed sigma0 model.

Wang, Qinglin↗

NASA NTRS1990

Comparison of measurements and theory for backscatter from bare and snow-covered saline ice

C-band radar backscatter measurements were made on artificially grown sea ice during the winters of 1987-1988 and 1988-1989. These measurements were made on smooth, rough, and snow-covered saline ice. The measured sigma-deg(theta) of smooth saline ice (rms height less than 0.05 cm) disagreed with small perturbation method (SPM) surface scattering predictions. Using physical parameters of the ice in a simple layer model, it us shown that this discrepancy can be explained by scattering from beneath the surface. A thin (7-cm) dry snow cover had a significant influence on backscatter from the smooth ice sheet. This influence was due to scattering from particles within the snow, and can be predicted by a commonly used empirical layer model for snow. The results of backscatter measurements of a moderately rough saline ice sheet were found to agree with SPM predictions.

Bredow, Jonathan W.↗