eJected an appreciable distance from the missile before ig- 
nition. A strobe lamp, on the other hand, is attached to the 
missile and has a flash duration of the order of 0.2 milli- 
seconds. A major disadvantage is the heavier weight of the 
strobe unit. The limiting photographic range of existing 
strobe lamps sultable for missile work is far less than of 
Dalsy flares, being about 250 to 300 nautical miles with a camera 
of 4 inch aperture. 
The telemetered response of a missile-borne photocell 
establishes the time of occurrence of each flash to an accuracy 
of the order of one millisecond. Accuracies approaching 0.1 
milliseconds are anticipated from ground based photomultiplier 
systems being developed. 
Since the precise times of the stellar exposures are re- 
corded on a chronograph, the directions of any selected stars 
at the various instants of exposure can be computed from the 
known astronomical coordinates of the stars, as reduced from 
Star catalogue data, and from the known geographical coordinates 
of the station. While it is possible to compute both the ro- 
tational and the interior orientation of a camera from a minimum 
of three stars, 1t is the practice in missile photogrammetry to 
exploit redundancy to minimize the effect of measuring errors. 
Consequently, the calibration of orientation is based upon a 
least squares solution carrying as control points a total of 
20 to 30 stars, compactly distributed about the flashing light 
11