SATELLITE-TRACKING PROGRAM — HAYES 287 



perhaps 20°. Dr. Baker had then suggested that the fihn in the 

 camera could be mounted to wind across a curved focal surface (the 

 back-up plate) ; he had earlier used this method for a 6-inch f/1 

 Schmidt camera, one of his wartime projects. 



In February of the following year, having formally accepted from 

 the Observatory the assignment to design the optical system. Dr. 

 Baker ran a family of rays through a classical Schmidt system on an 

 IBM computer as a preliminary step toward determining possible 

 improvements. The over-all problem was a formidable one. An f/1 

 Schmidt system had never been built for an aperture greater than 8 

 inches, and the classical Schmidt system has only one corrector 

 plate. This new camera might require complex plates with strong 

 aspheric optical powers and would have a much larger aperture. 



To complicate matters, in the spring the Navy announced that the 

 diameter of the Vanguard satellite had been lowered from 30 to 20 

 inches. This was a most critical decision. It meant that even closer 

 attention would have to be given to the optical performance of the 

 camera and that the factor of safety, already so narrow in the original 

 choice, had now vanished. In addition, it became apparent that 

 the camera had to track the satellite, rather than remain stationary 

 and permit the satellite to record itself on the exposed film. 



At this point Wliipple, Hynek, and Baker decided upon a larger 

 instrument. To restore the desired factor of safety for recording the 

 faint image of the satellite, they found it necessary to increase the 

 aperture to 20 inches, to hold the speed to f/1, and to seek an image 

 diameter no larger than 20 microns. (A human hair has a diameter 

 of about 75 microns.) At the same time they increased the desired 

 field of view to 30° to guarantee that, despite the uncertainties of 

 initial positions, the faint satellite image could be detected against 

 the background of stars. They recognized that the cost of the camera 

 would be substantially greater than had been considered before and 

 that the classical Sclimidt system was inadequate to do the job. No 

 one, however, was fully aware then that the trail toward the goal 

 of a satisfactory camera would be long and difficult. 



The next step was to design the mechanical elements of the camera. 

 In February Wliipple and Hynek discussed the problem with Joseph 

 Nunn of South Pasadena, Calif., who was known and highly recom- 

 mended to them. The essential question was precisely whether, and if 

 so how, the camera was to move. There were three possibilities : the 

 first, which already seemed doubtful, was to have the camera remain 

 stationary and let the satellite make a track on the filni; the second 

 was simply to have the camera track the satellite, w th the stars 

 appearing on the film as chopped trailed images, and the satellite 

 as a "point" ; the third was a rather complicated oscillating movement. 



