Surface emittance, temperature, and thermal inertia derived from Thermal Infrared Multispectral Scanner (TIMS) data for Death Valley, California

Abstract

The NASA airborne Thermal Infrared Multispectral Scanner (TIMS) was flown over Death Valley, California, on both a daytime flight and a nighttime flight within a two‐day period in July 1983. This Daedulus scanner has six channels in the thermal infrared, between 8 and 12 μm. Calibrated digital spectral radiance data from these flights, along with Landsat Thematic Mapper (TM) reflectance data, permit the calculation of both spectral emittance and thermal inertia. Spectral emittance images were derived for the test area for data sets from both the day and night tests, and they show good qualitative agreement. Comparison of the numerical values of emittance derived from these day and night images shows a decrease in spectral contrast at night. This is probably due primarily to an increased atmospheric contribution to the radiance reaching the sensor at night when the ground is cold, rather than to a change in spectral characteristics of the surface at night. These spectral emittance data contribute to an understanding of the physical basis for the discrimination of differences in surface materials afforded by TIMS data. These emittance data show good qualitative agreement with field emittance data taken in the same areas and with laboratory spectral reflectance data for samples from the Death Valley area. The strongest spectral feature commonly seen lies between 8 and 10 μm and is ascribed to the fundamental silicon‐oxygen stretching vibration of quartz and other silicate minerals. This feature allows identification of quartzite and discrimination of other silicate rocks in images produced from the TIMS data. Spectral features of other minerals, such as the ≈ 11.3 μm band of carbonates, are also detectable in laboratory spectra and field spectra. Using the day and night surface temperature data and Landsat TM reflectance data, an apparent thermal inertia image has been produced. This image allows separation of some bedrock units and separation of bedrock from alluvium. The temperature images allow inferences about the soil moisture and/or soil conditions on some of the alluvial fans.