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Title: TIMS OBSERVATION OF SURFACE EMISSIVITY IN HAPEX-SAHEL

Author
item Schmugge, Thomas
item HOOK, SIMON - JET PROPULSION LAB., CA
item KAHLE, ANNE - JET PROPULSION LAB., CA

Submitted to: International Geoscience and Remote Sensing Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/18/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Knowledge of the surface temperature is important for many applications, such as the surface energy balance and asessing crop water status. Measurements of the thermal emission from the ground at infrared wavelengths by sensors on aircraft or spacecraft platforms can provide this information over large areas. This paper presents some first results of a process for extracting the surface temperature from measurements made on an aircraft during a large scale field experiment conducted in West Africa in 1992. The results are encouraging for the use of remote sensing techniques for the determination of surface temperature.

Technical Abstract: The Thermal Infrared Multispectral Scanner (TIMS) was flown on the NASA C-130 aircraft for a series of 12 flights HAPEX-Sahel at altitudes ranging from 0.25 to 6 km (0.6 to 15 m resolution). TIMS provides coverage of the 8 to 12 micrometer thermal infrared band in 6 contiguous channels. Thus, it is possible to observe the spectral behavior of the surface emissivity over this wavelength interval. A high resolution image, 1.5m, of the west central site on 2 September was processed and the spectral behaviors of the millet and fallow grasslands sites were determined. There was a 4 to 5 K difference in the brightness temperature over the 6 channels when significant bare soil was visible. Channels 1 to 3 (8.2 to 9.4 um) were 4-5 K cooler than the longer wavelength channels which is characteristic of soils rich in quartz. These differences in brightness were converted to emissivity differences using the emissivity normalization and alpha residuals methods. Both methods yielded about the same difference in emissivity over the 6 channels, i.e., 0.09. However, the alpha residuals methods yielded higher values. As expected for a group of vegetated pixel, there was little difference in emissivity, less than 0.02, and the average amplitude was 0.99. The extracted vegetation temperature was close to the air temperature.