GPS Grows Up (1980–1989).

Efforts to expand the fledgling GPS program suffered
some growing pains during the development phase.
The first setback was brought on by a 1979 decision by the Office of the
Secretary of Defense (OSD) to cut $500 million (approximately 30 percent) from
the budget over the period FY81–FY86.19 As a result, the GPS program was restructured
and the scope of the program reduced. The final satellite constellation
was cut from 24 to 18 satellites (plus three satellites serving as on-orbit
spares); Block II development satellites were dropped; and the design was
scaled down in terms of weight, power, and nuclear and laser hardening.20
Plans for attainment of an early limited two-dimensional capability in 1981
were also dropped.

Funding for GPS was somewhat unstable during the early stages of the program
even though it received support from many elements of the services. Because
GPS is a support system and not a standard weapon system with a clear mission
and a history of well-defined operational concepts, early understanding of the
value of the system was less straightforward than with tanks or aircraft. This increased
the need to sell the program, particularly to potential users. The JPO
addressed this problem, especially during Phase I, by emphasizing one of the
more tangible capabilities of the system: increased bombing accuracy. The fact
that GPS was a joint program also increased the need to sell the program to
multiple services. No one service was anxious to bear the entire financial load
for a support system that was to be used by all services. As a result, GPS had
service support difficulties. For example, the program was zeroed out in 1980
through 1982, but was reinstated by OSD.21 It appears that OSD support contributed
to the survival of the program.

GPS suffered another setback as a result of the Space Shuttle Challenger accident
in 1986. As the only planned launch vehicle for GPS satellites at that time,
the loss of the shuttle caused a 24-month delay in the scheduled launch of the
second generation of GPS satellites, the Block IIs. Originally, the JPO planned to
launch the first 12 satellites (Phase I) on refurbished Atlas F boosters and to use
the McDonnell-Douglas Delta for the next series of launches (Phase II). Around 1979, the JPO had responded to DoD decisions which designated the Space
Shuttle as the principal launch vehicle for Air Force missions. Although the
Block IIs were built to be compatible with shuttle deployment, the JPO decided
to switch back to the Delta II as the GPS launch vehicle following the Challenger
disaster.

The first Block II satellite was eventually launched in February 1989 from Cape
Canaveral AFS, and became operational for global use in April 1989. Since then,
there have been 23 more Block II satellite launches. Like the Block I satellites,
the Block IIs were produced by Rockwell International. The Block II satellites
differ from the Block Is in shape and weight and incorporate design differences
that affect security and integrity.22 Significant Block II satellite enhancements
include:

• Radiation-hardened electronics to improve reliability and survivability
• Full selective availability (SA) and anti-spoofing (AS) capabilities to provide
system security
• Automatic detection of certain error conditions and switching to nonstandard

code transmission or default navigation message data to protect users
from tracking a faulty satellite and to maximize system integrity.
Block II satellites launched after 1989 have the additional capability of operating
for up to 180 days without contact from the control segment. They are
called Block IIAs. This represents a significant improvement over the earlier
Block I and II satellites, which required updating from the control segment after
only 3.5 days.

Further progress was made on the control and user equipment segments of GPS
during this period. As part of the transition to an operational and sustainable
system, the control segment was transferred to a new master control station located
at Falcon AFB, CO. System testing was completed, and successful interoperability
was demonstrated between the ground control stations, the satellites,
and the “user” navigation equipment. Rockwell-Collins was chosen as the
contractor for the production GPS user equipment. By the turn of the century,
an estimated 17,000 U.S. military aircraft will be equipped with GPS, and 60,000
portable receivers will be in use by U.S. ground forces and on military
vehicles.