GPS Block 1

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GPS Block 1
Credit - USAF

Other Designations: Global Positioning System. Code Name: Navstar. Class: Navigation. Destination: Medium Earth Orbit. Nation: USA. Agency: U.S. Air Force. Manufacturer: North American.

GPS Block 1 prototype satellites formed the GPS Demonstration system and were followed by the Block 2 operational system.

The spacecraft was 3-axis stabilized, nadir pointing using reaction wheels. Dual solar arrays supplied over 400 watts (EOL) and charged NiCd batteries. S-Band (SGLS) communications were used for control and telemetry. A UHF channel provided cross-links between spacecraft. A hydrazine propulsion system was used for orbital correction. The payload included two L-Band navigation signals at 1575.42 MHz (L1) and 1227.60 MHz (L2)

Block I satellites cost $ 20 million each. In 1974 Rockwell was awarded a contract to build 8 satellites. A 1978 contract amendment added 4 additional satellites. This was subsequently modified in 1981 for the twelfth satellite to be produced as the first GPS Block 2 qualification model.

Design Life: 5 years. Typical orbit: 20,200 km / 12 hr period; 63 deg inclin; 6 planes. Span: 5.30 m (17.30 ft). Mass: 759 kg (1,673 lb). Main Engine: Star 27. Electrical System: 2 solar panels. Electric System: 0.40 average kW.

GPS Block 1 Chronology

1978 February 22 - Navstar 1 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. Mass: 759 kg (1,673 lb). Perigee: 20,249 km (12,582 mi). Apogee: 20,560 km (12,770 mi). Inclination: 64.50 deg. Period: 727.00 min.
Also known as Navigational Development Satellite 1. Technology prototype of Navstar satellite.

1978 May 13 - Navstar 2 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. Mass: 759 kg (1,673 lb). Perigee: 19,523 km (12,131 mi). Apogee: 20,653 km (12,833 mi). Inclination: 63.60 deg. Period: 714.20 min.
Also known as Navigational Development Satellite 2. Technology prototype of Navstar satellite.

1978 October 7 - Navstar 3 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. Mass: 759 kg (1,673 lb). Perigee: 20,706 km (12,866 mi). Apogee: 20,941 km (13,012 mi). Inclination: 63.30 deg. Period: 744.20 min.
Technology prototype of Navstar satellite.

1978 December 11 - Navstar 4 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 20,750 km (12,890 mi). Apogee: 21,012 km (13,056 mi). Inclination: 64.60 deg. Period: 746.50 min.
Global Positioning System. First pre-opertional Navstar satellite.

1980 February 9 - Navstar 5 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 19,805 km (12,306 mi). Apogee: 20,560 km (12,770 mi). Inclination: 64.90 deg. Period: 718.00 min.
Global Positioning System.

1980 April 26 - Navstar 6 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 19,387 km (12,046 mi). Apogee: 20,471 km (12,720 mi). Inclination: 62.80 deg. Period: 707.80 min.
Global Positioning System.

1981 December 19 - Navstar 7 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3E. Launch Vehicle: Atlas. FAILURE: Failure. Mass: 770 kg (1,690 lb).
Global Positioning System.

1983 July 14 - Navstar 8 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3W. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 20,757 km (12,897 mi). Apogee: 21,229 km (13,191 mi). Inclination: 64.20 deg. Period: 751.10 min.
Global Positioning System.

1984 June 13 - USA 1 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3W. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 20,681 km (12,850 mi). Apogee: 21,194 km (13,169 mi). Inclination: 64.20 deg. Period: 748.80 min.
Global Positioning System.

1984 September 8 - USA 5 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3W. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 20,612 km (12,807 mi). Apogee: 21,203 km (13,174 mi). Inclination: 61.90 deg. Period: 747.60 min.
Global Positioning System.

1985 October 9 - USA 10 - Program: Navstar. Launch Site: Vandenberg. Launch Complex: SLC3W. Launch Vehicle: Atlas. Mass: 770 kg (1,690 lb). Perigee: 20,765 km (12,902 mi). Apogee: 21,673 km (13,466 mi). Inclination: 65.00 deg. Period: 760.40 min.
Global Positioning System.

Bibliography:

McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: http://www.planet4589.org/jsr.html.
Krebs, Gunter, Gunter's Space Page, University of Frankfurt, 1996. Web Address when accessed: http://www.skyrocket.de/space.
JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: http://msl.jpl.nasa.gov/home.html.
Lockheed Martin Coporation, Atlas Family Fact Sheets, September 1998.. Web Address when accessed: http://www.lmco.com/ILS/txtmain/ils_lsysinfo.htm.

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