- The Thermovision 750 shall be used primarily for 
oblique registrations of limited areas, or of 
curvilinear objects such as rivers, shores, roads, 
powerlines, etc. For thermal mapping of wider areas 
thermal-IR line scanners may be more advantageous. 
- Helicopters shall be used as camera platforms, permitting 
studies of the objects under whichever conditions of 
distance, oblique angle, time of day, instrument control 
settings, etc. the operator finds most suitable. 
- The thermal image shall be superimposed upon the ordinary 
visible-light view of the recorded area, to make orienta- 
tion and identification of the sources of thermal radi- 
ation easier. 
- A system for rapid, continuous registration of the infor- 
mation presented on the display screen together with 
spoken comments ought to be developed. 
THE HYBRID VIEWING AIRBORNE INSTRUMENT ASSEMBLY 
The above conclusions stimulated the subsequent development 
of the portable airborne instrument assembly - on the 
basis of the following general specifications: Instrument 
assembly to be easily taken in and out of modern (i.e. gas- 
turbine powered) utility helicopters, antivibration suspen- 
sion integrity conforming to accepted aircraft safety norms, 
composed of commercially available subsystems wherever 
possible, incorporate superposition viewing with options 
for closed circuit television (CCTV) monitoring, video 
tape recording (VTR) and photographic recording using 
off-the-shelf equipment. 
The thermal infrared imagery is provided by a standard 
AGA Thermovision 750 system, consisting of separate IR 
camera and display units. 
IR Camera Unit: 
The IR camera scans (in the present hybrid system) a 
7x7 angular degree rectangular field of view (fov) at 
25 raster fields per second, in a 4-field interlace 
pattern. The single InSb point-detector, in common with 
coated IR optics, responds to thermal radiation in the 
3-5 um middle infrared wavelengths, corresponding to 
an atmospheric transmission there. The infrared imagery 
is derived from about 70 scanning lines per field, with 
the 4-field interlacing plus spot wobbling-overlap 
between lines, providing a complete thermal picture 
frame, of (effectively) 210 scanning lines. With the 
spatial resolution along the scanning lines about 100 
TV-lines, the number of pixels per scanning frame is 
approximately 21,000 per 1/6th second.