Battle of Midway [spoilers]

[Robin Landseadel]

Still more on E. Imperial Highway, El Segundo, TRW & usw:

	Besides Transit, GPS had two immediate programmatic
	ancestors: a technology program called 621B, started by
	SAMSO in the late 1960s, and a parallel program called
	Timation, undertaken by the Naval Research Laboratory in the
	same period.  621B envisioned a constellation of 20 satellites in
	synchronous inclined orbits, while Timation envisioned a
	constellation of 21 to 27 satellites in medium altitude orbits.  In
	1973, elements of the two programs were combined into the
	GPS concept, which employed the signal structure and
	frequencies of 621B and medium altitude orbits similar to those
	proposed for Timation.

http://www.losangeles.af.mil/shared/media/document/AFD-060912-025.pdf