Engineering topics

Walton, W. T.

Publications and source records attributed to Walton, W. T..

6 records

NASA NTRS1992

Sea surface mean square slope from Ku-band backscatter data

A surface mean-square-slope parameter analysis is conducted for 14-GHz airborne radar altimeter near-nadir, quasi-specular backscatter data, which in raw form obtained by least-squares fitting of an optical scattering model to the return waveform show an approximately linear dependence over the 7-15 m/sec wind speed range. Slope data are used to draw inferences on the structure of the high-wavenumber portion of the spectrum. A directionally-integrated model height spectrum that encompasses wind speed-dependent k exp -5/2 and classical Phillips k exp -3 power laws subranges in the range of gravity waves is supported by the data.

Jackson, F. C.↗

NASA NTRS1985

Aircraft and satellite measurement of ocean wave directional spectra using scanning-beam microwave radars

A microwave radar technique for remotely measuring the vector wave number spectrum of the ocean surface is described. The technique which employs short-pulse, noncoherent radars in a conical scan mode near vertical incidence, is shown to be suitable for both aircraft and satellite application, the technique was validated at 10 km aircraft altitude, where we have found excellent agreement between buoy and radar-inferred absolute wave height spectra.

Jackson, F. C.↗

NASA NTRS1985

A comparison of in situ and airborne radar observations of ocean wave directionality

The directional spectrum of a fully arisen, about 3 m sea as measured by an experimental airborne radar, the NASA K(u)-band radar ocean wave spectrometer (ROWS), is compared to reference pitch-roll buoy data and to the classical SWOP (stereo wave observations project) spectrum for fully developed conditions. The ROWS spectrum, inferred indirectly from backscattered power measurements at 5-km altitude, is shown to be in excellent agreement with the buoy spectrum. Specifically, excellent agreement is found between the two nondirectional height spectra, and mean wave directions and directional spreads as functions of frequency. A comparison of the ROWS and SWOP spectra shows the two spectra to be very similar, in detailed shape as well as in terms of the gross spreading characteristics. Both spectra are seen to exhibit bimodal structures which accord with the Phillips' (1958) resonance mechanism. This observation is thus seen to support Phillips' contention that the SWOP modes were indeed resonance modes, not statistical artifacts.

Jackson, F. C.↗

NASA NTRS1982

Aircraft and satellite measurement of ocean wave directional spectra using scanning-beam microwave radars

A microwave radar technique for remotely measuring the vector wave number spectrum of the ocean surface is described. The technique, which employs short-pulse, noncoherent radars in a conical scan mode near vertical incidence, is shown to be suitable for both aircraft and satellite application, the technique was validated at 10 km aircraft altitude, where we have found excellent agreement between buoy and radar-inferred absolute wave height spectra.

Jackson, F. C.↗

NASA NTRS1981

LAMMR: A new generation satellite microwave radiometer - Its concepts and capabilities

Definition studies and baseline design are summarized for the proposed, and now discontinued, LAMMR. The instrument is an offset parabolic reflector with Cassegrain feeds. The three-meter aperture reflector, to be constructed using graphite-epoxy technology, rotates continuously at 0.833 rps. The scan drive subsystem includes momentum compensation for the rotating mass which includes the reflector, the support arm and Cassegrain subreflector, feed horns and radiometer. Two total power radiometers are recommended for each frequency, one each for horizontal and vertical polarizations. The selection plan, definition study specifications, LAMMR performance specifications, and predicted accuracies and resolutions after processing are shown.

Walton, W. T.↗

NASA NTRS1977

GSFC short pulse radar, JONSWAP-75

In September 1975, the Goddard Space Flight Center operated a short pulse radar during ocean wave measuring experiments off the coast of West Germany in the North Sea. The experiment was part of JONSWAP-75. The radar system and operations during the experiment are described along with examples of data.

Levine, D. M.↗