OPS 5118, also known as Navstar 6, GPS I-6 and GPS SVN-6, was an American
navigation satellite launched in 1980 as part of the
Global Positioning System
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
development programme. It was the sixth of eleven
Block I GPS satellites to be launched.
Background
Global Positioning System (GPS) was developed by the
U.S. Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55°. These vehicles are placed in 6 orbit planes with four operational satellites in each plane.
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Spacecraft
The first eleven spacecraft (GPS Block 1) were used to demonstrate the feasibility of the GPS system. They were 3-axis stabilized, nadir pointing using
reaction wheel
A reaction wheel (RW) is used primarily by spacecraft for three-axis attitude control, and does not require rockets or external applicators of torque. They provide a high pointing accuracy, and are particularly useful when the spacecraft must be ...
s. Dual solar arrays supplied over 400 watts. They had
S-band
The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional ...
communications for control and
telemetry and
Ultra high frequency (UHF) cross-link between spacecraft. They were manufactured by
Rockwell Space Systems, were 5.3 meters across with
solar panels
A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a phot ...
deployed, and had a design life expectancy of 5 years. Unlike the later operational satellites, GPS Block 1 spacecraft were inclined at 63°.
Launch
OPS 5118 was launched at 22:00 UTC on 26 April 1980, atop an
Atlas F
The SM-65F Atlas, or Atlas-F, was the final operational variant of the Atlas missile, only differing from the Atlas E in the launch facility and guidance package used. It first flew on 8 August 1961, and was deployed as an operational ICBM between ...
launch vehicle with an SGS-1
upper stage. The Atlas used had the serial number 34F, and was originally built as an Atlas F.
The launch took place from
Space Launch Complex 3E at
Vandenberg Air Force Base,
and placed OPS 5118 into a transfer orbit. The satellite raised itself into
medium Earth orbit using a
Star-27 apogee motor.
Mission
By 16 May 1980, OPS 5118 had been raised to an orbit with a
perigee of , an
apogee of , a
period of 717.94 minutes, and 62.8° of
inclination to the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
.
The satellite had a design life of 5 years and a mass of .
It broadcast the PRN 09 signal in the GPS demonstration constellation, and was retired from service on 6 March 1991.
References
{{Orbital launches in 1980
Spacecraft launched in 1980
GPS satellites