Exploring the Unknown - NASA's History Office

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recommended that continuity of data collection be maintained with another
experimental satellite (ERTS-C) until an operational satellite system becomes available.
However, even if neither an operational system nor ERTS-C is approved at
this time, ERTS-B should nevertheless be launched in 1974 to extend the experimental
operations conducted with ERTS-1. If there has to be a gap, it would be
preferable to get a stronger experimental base sooner and accept a hiatus between
a more meaningful experimental phase and the operational system, rather than
introduce an unnecessary hiatus into the middle of the experimental phase.
3. The acceleration of ERTS-B, even if combined with a decision to proceed with
ERTS-C for launch in 1976, as I have separately recommended, does not have
budgetary implications that go beyond previously planned committed levels for
space research and technology. The additional cost of ERTS-C can easily be
accommodated within a total NASA budget well below the planning level of
$3.2–3.4 billion (1971 dollars) agreed to in January 1972, as shown in my FY 1975
budget letter of September 28, 1973.
Now let me explain more fully the reasons for shifting the launch date of ERTS B to
1974, independent of the related considerations discussed above.
R&D Strategy
OBSERVING THE EARTH FROM SPACE
The research and development strategy for the ERTS program, for which NASA and
the associated technical agencies are responsible, must be based on recognition of the fact
that a multipurpose development program like ERTS cannot be treated like a classical
hardware systems development with clearly identifiable decision points for separate phases
of research, development, test, evaluation, and operations. We are dealing with a system
and many potential applications [3] in which the experimental phase has to include
(in different ways for each application) a whole variety of activities, including among others:
• Development and test of sensor performance capabilities.
• Development and test of satellite hardware capabilities.
• Development and test of data collection and relay capabilities.
• Development and test of ground data processing to provide data in useful form
for each of many applications.
• Development of data analysis aids and methodologies to convert data into useful
information.
• Test of information utility in each application for management and decision-making.
Two key points must be stressed: First, the satellite data requirements for experimentation
necessary to achieve an adequate basis for evaluation are different for each class of
potential application; and second, some of the most important potential applications
require a data base of repetitive coverage extending over several years and/or quasioperational
testing using current, near-real-time data.
There are two major areas of ERTS applications that clearly appear to have great nearterm
potential value and which illustrate the importance of the continuity of data an
ERTS-B 1974 launch would provide. These are the areas of vegetation and water boundary
discrimination. It has been demonstrated, for example, that ERTS data can be used to
identity and separate different crops, monitor crop vigor, end measure crop acreage. To
be useful in the development of systematic crop yield [4] predictions, these techniques
need to be applied to current growing seasons that are influenced by current climatology.
The same holds true for measurement of forest stress under insect attack and for exact
delineation of coastal wetlands by grass species discrimination: the dynamic nature of the
problem requires current data for current use. For hydrology applications like flood mapping,
seasonal lake and pond assessments, water sedimentation and pollution measure-