PROGRESS REPORT ON TRANSIT 
by R. B. KERSHNER 
The Johns Hopkins University 
Applied Physics Laboratory 
Silver Spring, Maryland 
"TRANSIT" is the code name for a program to develop 
and establish in being a system of near-earth satellites to provide 
a means for establishing locations (navigating) anywhere on the 
surface of the earth. The development phase is being carried out 
for the Bureau of Naval Weapons primarily by the Applied Physics 
Laboratory of The Johns Hopkins University with cooperative efforts 
by the Naval Weapons Laboratory at Dahlgren, Virginia, the Naval 
Ordnance Test Station at China Lake, and the Pacific Missile Range. 
The launching of the satellites is conducted by the Air Force 
Ballistic Missile Division. 
As a navigation system, TRANSIT will have the virtue 
of true global coverage, all weather operation, relative immunity 
to interference (either natural or man-made), unlimited traffic 
handling, frequent availability of fixes (every 100 minutes or 
oftener), and very high accuracy. On the other hand, since posi- 
tion is available only intermittently and not continuously, for 
some purposes TRANSIT may not replace the various radio aids that 
do provide continuous position fixing in the areas where such aids 
are available. However, it Should be noted that a relatively 
modest quality inertial system would suffice to provide continuous 
interpolation between TRANSIT fixes. 
The principle on which the design of the TRANSIT system 
is based is quite simple. Briefly stated, the entire system is 
based on the fact that a constant frequency radio transmission from 
an earth satellite is received by a ground station at the surface 
of the earth with an apparent variation of frequency. This variation 
in received frequency, the result of the well known Doppler effect, 
is an accurate measure of the rate of change of the slant range 
91 
