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Landsat-4 Thematic Mapper (TM) For Cold Environments

The TM aboard Landsat-4 launched on July 16, 1982, represents a major advance in Earth resources sensors. Its seven spectral bands record surface radiation in blue, green, red, near infrared, middle infrared and thermal wavelengths. The spatial resolution of approximately 30 meters represents a sevenfold increase over the previous Landsat sensor, the multispectral scanner subsystem (MSS). In addition, TM has greater radiometric sensitivity, distinguishing 256 quantization levels, compared with 64 for the MSS. These potential improvements have significant implications for satellite remote sensing in cold environments. The addition of the middle infrared bands will permit clouds to be distinguished from snow. It may also be possible to relate spectral response in this range to snow condition and hence water content. The thermal band responds to differences in surface temperature, which may be related to variations in soil moisture and drainage. These are important considerations for cold region construction. Water features, which can be related to circulation and quality, can be detected in the thermal and blue bands as well as the previously available green and red. The finer spatial resolution of TM will permit more accurate location, differentiation and monitoring of the extent and movement of ice and snow. Both spectral and spatial characteristics of TM contribute to more accurate land cover classification and geographical location of individual land cover features. These improved capabilities will make the TM considerably more useful for both civilian and military needs in cold environments.