Success Has Many Fathers - GPS Declassified: From Smart Bombs to Smartphones - page 49

By the critical year of 1973, when the initial gps system was configured, the
proposed Timation configuration was twenty-seven satellites in three planes,
in eight-hour circular orbits, with ground stations in the United States or secure
U.S. territories.
The differences between the rival services' navigation proposals reflected
their different needs. The Navy had a worldwide fleet, which included surface
ships, submarines, and aircraft carriers. A worldwide three-dimensional sys-
tem was important to meet the Navy's needs. The Air Force wanted to be able
to put five missiles in the same hole. A worldwide system was not as critical a
requirement for the Air Force.
The Air Force and its private research arm, the Aerospace Corporation, devel-
oped a space-based navigation system called Project 621b. Some sources assert
that it started in 1963; however, a 1966 briefing report (declassified in 1979)
by Aerospace engineers J. B. Woodford and H. Nakamura includes a chronol-
ogy that dates “ssd/Aerospace identification of potential need for a new nav-
igation satellite” to June 1, 1964. 34 The date is probably an approximation. The
study envisioned regional constellations of geosynchronous or near-
geosynchronous satellites and characterized putting atomic clocks in the sat-
ellites as a “growth item.” 35 A paper presented by Woodford and two other
engineers from Aerospace at the 1969 eascon (Electronics and Aerospace
Systems Convention) proposed three or four regional constellations around
the globe, each with one satellite in geosynchronous orbit and three or four
satellites in inclined elliptical orbits. 36
The other 1960s range measurement system was the Army's secor, short
for sequential correlation of range. secor satellites used transponders to return
radio signals sent from three ground stations at known, surveyed positions to
compute the position of a station at an unknown position. 37 It was designed
primarily for geodetic purposes.
Toward the latter half of the 1960s there was pressure to consolidate space-
based navigation system efforts and produce a system with three-dimensional
capability that would be available worldwide and around the clock. Finding
agreement on the design and deployment of a single shared system produced
what Washington does best—multilayered committees, subtle infighting, bud-
get wrangling, secret meetings, and afterward, differing accounts of what was
accomplished and who should get credit.