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Hofer, R.

Publications and source records attributed to Hofer, R..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Regression techniques for oceanographic parameter retrieval using space-borne microwave radiometry

Variations of conventional multiple regression techniques are applied to the problem of remote sensing of oceanographic parameters from space. The techniques are specifically adapted to the scanning multichannel microwave radiometer (SMRR) launched on the Seasat and Nimbus 7 satellites to determine ocean surface temperature, wind speed, and atmospheric water content. The retrievals are studied primarily from a theoretical viewpoint, to illustrate the retrieval error structure, the relative importances of different radiometer channels, and the tradeoffs between spatial resolution and retrieval accuracy. Comparisons between regressions using simulated and actual SMMR data are discussed; they show similar behavior.

Hofer, R.↗
NASA NTRS1981

Seasat SMMR observations of ocean surface temperature and wind speed in the North Pacific

The Scanning Multichannel Microwave Radiometer (SMMR), aboard both the SEASAT and Nimbus-7 satellites, was designed primarily to determine global sea surface temperatures and wind speeds over an extended range of atmospheric conditions. The Seasat mission lasted approximately three months from July to October 1978, during which time sufficient data was acquired to enable an assessment of SMMR measurement capabilities under a variety of conditions. This paper reports some results of initial Seasat SMMR assessments in the North Pacific area. A brief description is given of retrieval techniques used to derive the geophysical parameters. SMMR-derived sea surface temperatures and winds are compared with surface truth point measurements from XBT's and buoys, and with surface truth fields derived from point measurements. Accuracies of approximately 1.5 C and 2.5 m/s rms are obtained in these comparisons.

Njoku, E. G.↗
NASA NTRS1980

Microwave signatures of the natural snow cover at Weissfluhjoch

The natural snow cover on a high altitude alphine test site was monitored with a multi-frequency radiometer for more than three years. Some measurements were also made with a 10.5 GHz scatterometer. The microwave observations are supported by a large set of ground truth data. From year to year a wide variation in the development of the snowpack above and below average was observed. Typical microwave data are presented for the different snow conditions in view of the applicability as signatures for remote sensing.

Hofer, R.↗
NASA NTRS1980

Comparison of conventionally measured sea surface temperature and wind speed with data retrieved from satellite-borne microwave radiometry

The Scanning Multichannel Microwave Radiometer aboard both the Seasat and Nimbus-7 satellites was designed to estimate sea surface temperature (SST) and wind speed (WS) over an extended range of atmospheric conditions. The retrieval technique is described briefly, and it is demonstrated in a case study that the instrument design goals (SST:1.5 C; WS:2 m/s) appear to be feasible.

Hofer, R.↗
NASA NTRS1977

Microwave multispectral investigations of snow

A long term observational program on microwave emission and scatter behavior under controlled conditions, was started at a high altitude alpine test site. All stages of development of snow cover during the whole season are under investigation. The study was done to achieve required knowledge on microwave radiative properties of snow for optimization of the microwave payloads of air and spaceborne snow sensors and for the interpretation of large scale snow maps obtained by these sensors. Preliminary results of the first month obtained with radiometers at 4.9, 10.5, 21 and 36 GHz are presented.

Schanda, E.↗