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Rangaswamy, S.

Publications and source records attributed to Rangaswamy, S..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Determination of sea surface temperatures from microwave and IR data

Microwave measurements from the Nimbus 7 SMMR were used to derive the atmospheric precipitable water, which was then used to obtain the atmospheric correction for use with AVHRR thermal IR measurements to obtain sea surface temperature (SST). The resulting SST's were compared with the NOAA operational sea surface temperature measurements, and the two sets of measurements were found to be in reasonable agreement. The average residuals between the two sets of measurements was 0.15 K with the NOAA operational SST's being slightly greater.

Rangaswamy, S.↗
NASA NTRS1976

Simulation of radiometer data from a spin stabilized satellite

The effect of misregistration on cloud brightness threshold is investigated by simulating radiometric data as observed from a spin stabilized synchronous satellite such as the SMS. Clouds were introduced randomly and a bidirectional reflectance model was used to create radiance data from clouds and ocean. A theoretical and an empirical reflectance model were compared.

Rangaswamy, S.↗
NASA NTRS1976

Recovery of atmospheric parameters from the Apollo/Soyuz-ATS-F radio occultation data

As part of the Apollo-Soyuz Test Project, Apollo was tracked in the satellite-to-satellite tracking mode by ATS-F. The tracking data obtained at occultation of Apollo by the earth has been used in this study to compute atmospheric parameters like pressure and temperature. The results of the numerical inversion have been compared with data from a radiosonde station near the occultation site. Near the surface of the earth, the refractivity computed from occultation data agreed with the radiosonde-derived values to within 3%. A pressure profile deduced from the refractivity profile by using a simplified model of the atmosphere showed good agreement with radiosonde measurements.

Rangaswamy, S.↗
NASA NTRS1975

Recovery of atmospheric refractivity profiles from simulated satellite-to-satellite tracking data

Techniques for recovering atmospheric refractivity profiles from simulated satellite-to-satellite tracking data are documented. Examples are given using the geometric configuration of the ATS-6/NIMBUS-6 Tracking Experiment. The underlying refractivity model for the lower atmosphere has the spherically symmetric form N = exp P(s) where P(s) is a polynomial in the normalized height s. For the simulation used, the Herglotz-Wiechert technique recovered values which were 0.4% and 40% different from the input values at the surface and at a height of 33 kilometers, respectively. Using the same input data, the model fitting technique recovered refractivity values 0.05% and 1% different from the input values at the surface and at a height of 50 kilometers, respectively. It is also shown that if ionospheric and water vapor effects can be properly modelled or effectively removed from the data, pressure and temperature distributions can be obtained.

Murray, C. W., Jr.↗
NASA NTRS1972

Ionosphere total electron measurements as extracted from satellite tracking data

The Goddard Range and Range Rate System (GRARR) determines the range of a spacecraft by measuring the group delay of a modulated wave and the range rate by measuring the Doppler phase shift of the carrier. An analytical technique is presented for obtaining corrections and equivalent total electron content along the vertical, using VHF GRARR data and a radial model of the ionosphere. The results of computation for a representative pass are given, and estimated accuracy is discussed from a statistical view point. Using VHF GRARR data and a radial model of the ionosphere. The results of computation for a representative pass are given, and estimated accuracy is discussed from a statistical view point. Using GRARR range, range rate, and angle tracking data from Explorer 41, values of total electron content on the order of 10 to the 17th to 10 to the 18th power (electrons/sq m) were obtained. These values agree with estimates of the total electron content from ionospheric profiles using f sub o F sub 2 predict data.

Murray, C. W., Jr.↗
NASA NTRS1971

Measurement of total electron content with a geostationary satellite during the solar eclipse of March 7, 1970.

This note deals with the measurement of the total electron content of the ionosphere at the Goddard Space Flight Center, looking towards the geostationary satellite ATS 3 during the solar eclipse of Mar. 7, 1970. Obscuration at this site was nearly total. Faraday rotation was measured with a stationary circularly polarized antenna and a dual-channel phase-lock receiver tuned to 137.350 MHz. By comparing the electrical phase of the two opposite circularly polarized components, a continuous chart recording was made of Faraday rotation vs local time. A depletion of about 25% in electron content was observed from first contact to the time of minimum electron content. The time variations of the electron content during the eclipse are briefly examined in the light of current theories of ionospheric processes.

Rangaswamy, S.↗
NASA NTRS1971

NASA-GSFC ionospheric corrections to satellite tracking data

An overview is presented of the development, verification, and recent implementation of the NASA-GSFC ionospheric model for satellite tracking data corrections. This model was incorporated into the Goddard Trajectory Determination System which is providing continuous trajectory computation support for the lunar orbiting Radio Astronomy Explorer-B launched on 10 June 1973.

Schmid, P. E.↗