Success Has Many Fathers - GPS Declassified: From Smart Bombs to Smartphones - page 46

Fig. 3.5. Transforming celestial navigation to satellite ranging. This diagram helped to
explain how navigation based on time signals from satellites compared to the angular
sightings used in celestial navigation. (Courtesy Naval Research Laboratory)
nrl launched the Timation I satellite in May 1967 and conducted initial
tests internally. Researchers gave Pentagon officials the first outside demon-
stration at the John Ericsson statue near the Lincoln Memorial in October of
that year. They selected the location for several reasons. First, good sightlines
were important, given that the satellite would be visible for only about thir-
teen minutes (it was in orbit about seven hundred miles above the surface of
the earth). Second, Ericsson's invention of the screw propeller and the uss
Monitor , the first ironclad battleship, made this an appropriate setting for dem-