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GPS Block II

In the aftermath of the Challenger accident, the Air Force decided to remove the Navstars from the Shuttle manifest, and to launch them on an improved version of the proven Delta launch vehicle, known as the Delta II. A total of 20 of these rockets were ordered. Block II SVs were built by Rockwell International.

Significant Block II SV enhancements to the signal-in-space (SIS) interface were:

With the launch of five new Navstar satellites in 1989, the Air Force began to implement the full complement of 21 active and 3 spare satellites will be required for the system can provide nearly continuous global coverage.(1) The first of 28 Block II SVs, SV PRN number 14, was launched on 14 February 1989 from Cape Canaveral AFS, FL using a Delta II MLV and was set "healthy" in its broadcast 50 Hz navigation message for global use on 15 April 1989. Although the first two satellites launched had been nicknamed Elvis (Presley) and Janis (Joplin), this practice ceased with the third and subsequent launches.(2) Rockwell International was also the prime contractor for Block IIA. The design life of the operational satellites is seven and one-half years.(3)

Navstar GPS Specifications
Weight: 1,860 pounds (in orbit)
Orbit altitude: 10,900 miles
Power plant: Solar panels generating 700 watts
Dimension: 5 feet wide, 17.5 feet long (length includes wingspan)
Launch vehicle: Delta II
Primary contractor: Rockwell International - Block I, IIA


1. Kolcum, Edward, "First USAF/McDonnell Douglas Delta 2 Launch Begins New Military Space Era," Aviation Week & Space Technology, 20 February 1989, page 18-19.

2. "News and Comment," Air Force Magazine, October 1989, page 29.

3. Maj Michael J. Muolo, Maj Richard A. Hand, Maj Bonnie Houchen and Maj Lou Larson, Space Handbook A War Fighter's Guide to Space -- Volume One, AU-18, Air University Air Command and Staff College, (Air University Press, Maxwell Air Force Base, Alabama, December 1993).

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Implemented by Charles P. Vick, Sara D. Berman, and
Christina Lindborg, 1997 Scoville Fellow
Maintained by Robert Sherman
Originally created by John Pike
Updated Sunday, April 13, 1997