-28- 
per minute. Both beams point 3-1/2 degrees down for all azimuth 
positions when the aircraft assumes its mean level flight attitude. 
The ground data processing equipment associated with the digi 
tal computer is one of the keys to the effective utilization of the USQ-28. 
There would be little advantage to a system capable of mapping 30 to 
40 thousand square miles a day if it took weeks or months to determine 
the success of each mission and the areas that required re-flight. The 
digital ground data processing subsystem not only performs all of the 
primary computations, but it summarily reviews the mission immed 
iately after landing. Any areas requiring re-flight, due to cloud cover, 
equipment malfunction, or pilot error are immediately printed out. 
Such areas are then scheduled for re-flight the next day. 
The computer chosen for the digital ground data reduction sys 
tem is the SDS 910. The primary specifications of this computer are 
presented below in Table VI. 
TABLE VI 
Basic core memory 8, 192 words 
In-Out rate 250,000 characters/sec. 
Fixed point execution rate ..... 16 microseconds - add 
248 " - multiply 
Floating point exec, rate 832 microseconds. - add 
(39-bit fraction, 9-bit 1,696 " -multiply 
exponent) 
The basic data processing program consists of nine program 
units. Three of these include an index of refraction subroutine. The 
nine program units are: 
a. The Control Program 
This program unit provides; 
1. Controls for all start sequence procedures. 
2. Controls for all ending sequence procedures. 
3. Sequential selection of all control parameters 
and units required for complete mission data 
reduction.