different platforms. The British Skylark rocket was recently 
tested as an earth resource survey vehicle (Anon. 1972). 
Airborne remote sensing systems are undoubtedly the most 
flexible. As shown in Figure 2, they operate in a range of 
altitude from a few meters to 10 or 15 kilometers. Aircraft are 
available nearly everywhere. Many can provide the room and power 
output sufficient for the largest variety of sensors. NASA's 
RB-57F high-altitude capability is a good example of the flexibility 
possible (Park 1971). If problems develop in the operation of 
airborne sensors, re-flights are relatively inexpensive. Usually 
tests can be made with more rigid control over experimental con- 
ditions than can be achieved with balloons, rockets and earth- 
orbiting satellites. The results of airborne tests can be readily 
used as feedback to improve, modify or adjust equipment for further 
  
  
tests without major reinvestments of time and money. 
From a training standpoint, airborne systems offer the best 
means of initiating a remote sensing program. A small aircraft 
and an aerial camera might be all that are required to carry out a 
large number of practical experiments, train personnel and develop 
well-defined procedures for collecting image data and extracting 
useful information. As expertise, equipment and procedures are 
developed, more ambitious programs can be undertaken until all the 
ingredients are available for space involvement. During the learn- ? 
ing and development process, it is noteworthy that useful informa- 
tion is being collected. Thus, close contact with the interrelation- * 
ship between means and ends of acquiring the remote sensing data 
is maintained, 
A well-conceived airborne program can have three important 
roles other than training. It may stand by itself as the mainstay 
for acquiring remote sensing data. Airborne programs will play a 
supporting role for most space programs. For many applications, 
the complementary relationship between airborne and space sensing © o