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a gaseous nitrogen system will be provided. This will also prevent 
static electricity buildup and film brittleness. While the film is 
held in contact with the platen, the platen will be translated in the 
direction of flight to provide forward motion compensation. The FMC 
range is 0.010 to .045 radians per second, which is adequate for all 
normal operating altitudes of the Space Shuttle. This FMC will per- 
mit the long exposure times required by high resolution films. The 
platen will also contain a reseau at 5 cm intervals. The reseau will 
be provided by 0.05 mm holes, illuminated by light emitting diodes 
from the rear of the platen. The reseau can be switched on or off on 
command. It will probably be used for a few frames at the beginning 
and end of each photographic pass. 
The photograph format is illustrated in Figure 4. Fiducials at the mid- 
points of the leading and trailing edge and both sides of the film will 
define the principal reference system. Additional fiducials will be 
provided to define any 23 x 23 cm portion of the overall frame. Digital 
data blocks will provide the time of exposure, mission, and frame numbers. 
Camera Operation 
The normal operating mode will be 80% forward overlap, but 60% and 10% 
are also available on command. As illustrated in Figure 5, appropriate 
selection of frames can provide stereomodels with a B/H ratio of 0.3 to 
1.2. It is worthy of note that when the camera is operated in the 807 
forward overlap mode, the central 23 x 23 cm portions of consecutive 
frames have a forward overlap of 60% with a B/H ratio of 0.3. The 
central portions are thus amenable for plotting in any standard photo- 
grammetric instrument capable of handling 30.5 cm focal length.  Maxi- 
mum advantage of the full frame overlap with maximum B/H ratio can be 
obtained with analytical plotters in which the principal point can be 
offset from the center of the 23 x 23 cm diapositive. 
As shown in Figure 6, the terrain coverage available from orbital alti- 
tude is enormous. At the nominal altitude of 300 km, for example, each 
frame covers 225 x 450 km (120 x 240 n.mi.) with the long dimension in 
the direction of flight. 
Figure 7 shows the positioning capability, presuming measurements are 
made with a precision of 0.015 mm on the photograph. At 300 km altitude, 
this is equivalent to 15 meters on the ground which is more than adequate 
for map compilation at scale 1:50,000. Figure 8 shows the elevation 
accuracy obtainable.at various B/H ratios. A precision of better than 
10 meters is available at 300 km altitude. This should be adequate for 
compiling contours at 30 m vertical interval. 
Spacecraft Mounting 
For the initial flight the camera will be mounted in its own environmental 
enclosure on the ERNO pallet which will be carried in the aft end of the 
Shuttle cargo bay as shown in Figure 9. A study has been completed to 
define the interface between the camera controls and the Shuttle systems. 
It is contemplated that the camera will be operated whenever the Shuttle