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Mcintosh, R. E.

Publications and source records attributed to Mcintosh, R. E..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

C-band measurement of radar backscatter from the ocean surface during SWADE

A preliminary analysis of backscatter measurements collected during the joint NASA/ONR Surface Wave Dynamics Experiment (SWADE) by a C-band scatterometer (C-SCAT) is presented. Data were collected during a total of ten flights on board the NASA/Ames C-130B off the coast of Virginia. These backscatter measurements are vertically polarized, and were obtained over a full 360* in azimuth, at incidence angles ranging from 20 to 50 . The data set is now in a state where it can provide a unique test bed for normalized radar cross section (NRCS) model functions because of the variety of phenomena encountered, and the quantity and quality of the measurements.

Carson, S. C.↗
NASA NTRS1991

Frequency dependence of electromagnetic bias in radar altimeter sea surface range measurements

Range measurements made by satellite radar altimeters experience a bias toward the troughs of ocean waves. A series of aircraft flights during February-April 1989 measured this electromagnetic (EM) bias at three radar frequencies and the UV under a variety of wind and wave conditions, and provided the first airborne open-ocean measurements at the 13.6-GHz and 5.3-GHz operating frequencies of the NASA altimeter on the TOPEX/Poseidon satellite. The data suggest that the mean EM bias decreases linearly with increasing radar frequency between 5.3 and 36 GHz, according to the expression: EM bias (percent of significant wave height) = (3.0-0.0617 F)(1 +/-0.5), where F is in gigahertz. EM bias is fairly constant over a mesoscale region on a given day but can fluctuate significantly from one day to another. It shows a strong increase at all radar frequencies with increasing wind speed, although other sea state conditions, such as the wind direction relative to the wave direction, are also factors.

Walsh, E. J.↗
NASA NTRS1989

Coherent radar measurement of ocean currents from geostationary orbit

A coherent HF radar system developed by Barrick has successfully measured ocean surface currents near shore. This innovative system, called CODAR, can map the current vector for coastal areas as large as 10,000 sq km. CODAR's range is limited owing to the strong attenuation suffered by HF ground waves. An alternate technique was proposed by Schuler, in which the cross-product power spectrum of two (different frequency) microwave signals is processed. The frequency of the resonant peak corresponds close by to the Doppler shift of an ocean gravity wave traveling toward the radar at the phase velocity, v(sub p). The slight difference between the frequency of the measured resonant delta K peak and the Doppler frequency shift caused by the motion of the gravity wave is attributed to be the current velocity in the pointing direction of the radar. The Microwave Remote Sensing Laboratory (MIRSL) has considered the feasibility of using this technique to measure ocean surface currents from geostationary satellite platforms. Problems are discussed that must be overcome if a satellite current measurement system is to be realized. MIRSL research activities that address some of these problem areas are discussed. Current measurements are presented that were made using a specially-designed C-Band, step-frequency delta K radar. These measurements suggest that progress is being achieved in detecting ocean surface current motion for a wide variety of ocean surface conditions.

Mcintosh, R. E.↗
NASA NTRS1989

An airborne C-band scatterometer for remote sensing the air-sea interface

An airborne C-band scatterometer system (C-Scat) has been developed for remote sensing of the air-sea interface. The sensor has been designed to fly on a number of research aircraft, beginning with the NASA Ames Research Center's C-130B, on which test flights were conducted in August of 1988. The scatterometer utilizes a 10-W solid-state power amplifier and a frequency-steered microstrip array antenna which is installed beneath the fuselage of the airplane. The antenna is electrically scanned in elevation from 20 to 50 deg off nadir, and it is mechanically rotated 360 deg in azimuth. The system is fully computer controlled and is capable of accurately measuring ocean-surface normalized radar cross section (NRCS) from altitudes as high as 25,000 feet. It has been developed to study the relationship between NRCS and ocean-surface roughness influences such as wind speed and direction, wave height and slope, and air-sea temperature difference.

Mclaughlin, D. J.↗