USA-5
Tenth Block I GPS satellite; last Block I decommissioned.
USA-5—also designated Navstar 10, GPS I-10, and GPS SVN-10—was an American navigation satellite that launched in 1984 as part of the Global Positioning System development effort. It was the tenth of eleven Block I GPS satellites to go up. Built by Rockwell Space Systems, the spacecraft was three-axis stabilized and nadir-pointing, using reaction wheels for attitude control. Its twin solar arrays generated more than 400 watts of power. The satellite communicated via S-band for control and telemetry, and used UHF cross-links to talk to other spacecraft. With its solar panels deployed, it measured 5.3 meters across and had a design life of five years. Unlike later operational GPS satellites, Block I vehicles like USA-5 flew in orbits inclined at 63 degrees.
The launch occurred at 21:41:00 UTC on 8 September 1984 from Space Launch Complex 3W at Vandenberg Air Force Base. An Atlas E rocket—serial number 14E, originally built as an Atlas E—with an SGS-2 upper stage carried the satellite into a transfer orbit. From there, USA-5 used a Star-27 apogee motor to raise itself into medium Earth orbit. By 3 October 1984, it had settled into an orbit with a perigee of 19,962 km, an apogee of 20,403 km, a period of 718.00 minutes, and an inclination of 63.20 degrees. The satellite weighed 758 kg and broadcast the PRN 12 signal within the GPS demonstration constellation. It was retired from service on 18 November 1995, making it the last Block I satellite to be decommissioned.
Quick Facts
- Names list
- Navstar 10
- GPS I-10
- GPS SVN-10
- Operator
- U.S. Air Force
- Satcat
- 15271
- Mission duration
- 5 years (planned); 11 years (achieved)
- Spacecraft
- Navstar
- Manufacturer
- Rockwell Space Systems
- Launch mass
- 758 kg / 1,671 lb
- Dimensions
- 5.3 meters of long
Facts from the source article.
Lore & Background
USA-5 was launched atop an Atlas E launch vehicle with an SGS-2 upper stage from Space Launch Complex 3W at Vandenberg Air Force Base. The Atlas used had the serial number 14E and was originally built as an Atlas E. The satellite was placed into a transfer orbit and raised itself into medium Earth orbit using a Star-27 apogee motor. By 3 October 1984, it had been raised to an orbit with a perigee of 19962 km, an apogee of 20403 km, a period of 718.00 minutes, and an inclination of 63.20° to the equator. The spacecraft was 3-axis stabilized, nadir pointing using reaction wheels, with dual solar arrays supplying over 400 watts. It had S-band communications for control and telemetry and UHF cross-link between spacecraft. Manufactured by Rockwell Space Systems, it was 5.3 meters across with solar panels deployed and had a design life expectancy of 5 years. Unlike later operational satellites, Block I spacecraft were inclined at 63°.
Reader's Guide
USA-5 was part of the initial Block I series of GPS satellites, which were used to demonstrate the feasibility of the Global Positioning System. As the tenth of eleven Block I satellites, it helped validate the concept of a space-based navigation system providing all-weather round-the-clock capabilities for military and later civilian use. The satellite broadcast the PRN 12 signal in the GPS demonstration constellation. It was retired from service on 18 November 1995, making it the last Block I satellite to be decommissioned. Its long operational life—over a decade beyond its 5-year design life—underscored the robustness of the early GPS spacecraft. The Block I program laid the groundwork for the operational GPS constellation of 24 spacecraft in 20,200 km circular orbits inclined at 55°, placed in 6 orbit planes with four operational satellites in each plane. USA-5's contribution to proving the system's reliability and accuracy was essential to the eventual global adoption of GPS for military, commercial, and recreational applications.
Frequently Asked Questions
When and where was USA-5 launched?
USA-5 lifted off on 8 September 1984 at 21:41:00 UTC from Space Launch Complex 3W at Vandenberg Air Force Base, carried into orbit by an Atlas E rocket topped with an SGS-2 upper stage (serial 14E).
What was USA-5's role in the GPS program?
As the tenth Block I satellite, USA-5 was part of the initial proof-of-concept constellation that demonstrated the feasibility of satellite-based positioning for the U.S. military. It holds the distinction of being the last of the eleven Block I spacecraft to be retired from service.
What were USA-5's key physical and orbital specifications?
With its solar panels deployed, the satellite had a mass of 758 kg and was designed for a five-year operational life. It orbited at a 63.20° inclination, a typical mid-latitude trajectory for the early GPS constellation.
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