Based on experience with Landsat, 
we believe we are entering a new 
era of automated satellites that will c 
ombine the electronic gathering be « 
Of data, with highly sophisticated ground computer Processing bas: 
capabilities to provide a truly new and continuing look at our planet. ton: 
pre 
Skylab (Colvocoresses, 1975), unlike Landsat, did not provide for to 
the systematic collection of earth 
ing program. A wide variety of ins 
experimental collection of data which has been successfully tested for thai 
cartographic purposes. There are also reports of successful applica- 
tions in the geological sciences. The nonsystematic nature of the data 
has generally precluded an assessment of direct benefit or potential 
continuing application. In an indirect sense, however, Skylab has 
proved valuable by providing quantities of experimental data at higher 
Spatial resolutions and in Spectral bands not collected by Landsat. 
Skylab experimental sensors, for example, have shown that wavelengths God« 
somewhat shorter than those recorded by Landsat can successfully pene- 
resources data nor was it a continu- 
truments were employed for the 
lim: 
ava: 
trate water and view subaqueous features. Skylab-acquired data also pro: 
demonstrate that by recording wavelengths somewhat longer than those nif. 
recorded by Landsat cloud Penetration is substantially improved. In res] 
Summary, Skylab data will be useful in the design of future systems. nav: 
A number of additional measurement capabilities are being 
developed that will greatly add to our ability to understand the Earth. not 
don: 
as i 
Precision Measurements of Intercontinental Distances net 
(Re 
Geological and geophysical studies have shown that large movements obt. 
of portions of the Earth's crust have taken place during geologic time. ava 
Some areas are subject to geologic hazards as a result of movements anoi 
taking place at the present time. The occurrence of mineral and energy anoi 
resources is closely linked to geologic structures that have resulted men 
from these movements. cau 
ass 
The rates, direction, location, and causes of crustal movement have 
been a puzzle in geology. A major difficulty in understanding crustal 
movements has been the inability to make precise measurements over large ind 
distances and to be able to repeat these measurements at intervals of app 
every few years. Hypotheses concerning plate tectonics and sea floor How 
Spreading have been a major step forward in Providing the capability to men 
design meaningful experiments. New capabilities for precise measurements, sur 
rferometry and laser ranging to satellites, alt 
and 
hypotheses. The U.S. Geological Survey (1965, p. 27) states that hori- geo 
zontal and vertical displacements "would have to be determined within less 
than 1 dm; if coordinates could be determined more precisely, movements 
could be detected over shorter intervals." In many cases it will require the 
a decade or more of data acquisition using these measurement techniques to Dep 
establish the precise rates of crustal motions. These measurements will 
20 
ten Ea mm SE OR SE TW SRK WAC