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monitoring will be possible until the answer to this question is found and implemented. In 
this Section we note several examples relating to data policy that are pertinent to the 
question. 
AVHRR 
In recent years, increasing use has been made of the normalized global vegetation 
index, a parameter derived from the Advanced Very High Resolution Radiometer 
(AVHRR) carried on NOAA weather satellites [Justice 1986]. This index indicates weekly 
and seasonal distribution of biomass at spatial resolutions on the order of seven kilometres. 
Data diskettes are available free of charge to users on request, and complete data files are 
routinely provided by NOAA to the United Nations Environment Program Global Resource 
Information Database [GRID 1988]. 
This example might be considered as an encouraging precedent for remote sensing 
data policy applied to active global monitoring. However, it is unique, and has evolved by 
accident, rather than by intent. At the time that (land) remote sensing data was 
commercialized by the United States, AVHRR was considered to be a weather instrument, 
so that its data was treated as other weather data, therefore deemed to be available to the 
public free of charge. It is in the public interest that research has developed a parameter 
useful for land applications from this "weather" instrument, but the practice of making this 
data freely available remains an embarrassment to those who believe that all remotely 
sensed land data should be sold at value in the market place. 
ESA 
The European Space Agency (ESA) is embarking on a microwave remote sensing 
satellite program [ESA 1989], operation of which will begin with the launch of ERS-1 early 
in 1991. ESA has been studying ways in which data policy for ERS-1 may be extended in 
the interests of the environment and developing countries. It is noteworthy, subject to 
review of proposals, that a limited amount of data from the satellite is to be made available 
to developing countries and/or for specific purposes (such as pollution monitoring or 
national resource monitoring) on terms similar to those applied to participating scientists 
from ESA nations, namely, free data (subject to copyright, third party transfer restrictions, 
etc.) [Duchossois 1989]. One example cited in discussion by ESA officials is the use of ERS- 
1 C-band radar data for selected forestry sites in the Brazilian Amazon. These 
investigations would also be contributions by Brazil (and ESA) to the International Space 
Year (1992), for which Brazil is the lead nation for a tropical forestry application of satellite 
data. 
Initiatives in the United States 
There are many Congressional actions in response to the issue of Global Change, 
some of which may impact directly the field of remote sensing. Several legislative initiatives