system, there appears to be a real commitment to this form of remote sensing as well. 
The commitment to a long term data archive have been encouraging. Most nations which have been receiving 
Landsat data report their historical data as available through an archive. However, degradation of tapes and 
changes in equipment are known to have resulted in some loss of archival data. The actual amount of loss is 
not well known. Benefiting from the lessons of the Landsat program, historical SPOT data generally seem well 
archived and available. 
Interest in atmospheric corrections waned after a flurry of effort associated with Landsat 1, and only Canada 
continued research and development which led to operational use of atmospheric corrections for Landsat data. 
Correction of georadiometric effects is gaining prominence as a research topic, but the complexity of the 
problem and the need for on-line digital terrain models for correction are serious impediments to operational 
corrections in the near future. 
In summary, there appears reason for optimism regarding data stability and continuity related to global 
environmental monitoring programs. 
However, the ability to monitor continuing deterioration of the terrestrial environment is not much of an 
accomplishment by itself. Only when global monitoring is clearly a means for global protection does it really 
make any sense. 
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