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USA-1 (satellite)

From Wikipedia, the free encyclopedia

NamesNavstar 9
Mission typeNavigation
OperatorU.S. Air Force
COSPAR ID1984-059A
SATCAT no.15039
Mission duration5 years (planned)
10 years (achieved)
Spacecraft properties
Spacecraft typeGPS Block I
ManufacturerRockwell Space Systems
Launch mass758 kg (1,671 lb)
Dimensions5.3 meters of long
Power400 watts
Start of mission
Launch date13 June 1984, 11:37 UTC
RocketAtlas E / SGS-2
Launch siteVandenberg, SLC-3W
General Dynamics
Entered service19 July 1984
End of mission
Deactivated20 June 1994
Orbital parameters
Reference systemGeocentric orbit[1]
RegimeMedium Earth orbit
Perigee altitude19,917 km (12,376 mi)
Apogee altitude20,446 km (12,705 mi)
Period718.00 minutes
← OPS 9794 (Navstar 8)
USA-5 (Navstar 10) →

USA-1, also known as Navstar 9, GPS I-9 and GPS SVN-9, was an American navigation satellite launched in 1984 as part of the Global Positioning System development programme. It was the ninth of eleven Block I GPS satellites to be launched,[2] and the first satellite to receive a USA designation.


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.[3]


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 wheels. Dual solar arrays supplied over 400 watts. They had S-band 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 deployed, and had a design life expectancy of 5 years. Unlike the later operational satellites, GPS Block 1 spacecraft were inclined at 63°.[3]


USA-1 was launched at 11:37 UTC on 13 June 1984, atop an Atlas E launch vehicle with an SGS-2 upper stage. The Atlas used had the serial number 42E, and was originally built as an Atlas E.[4] The launch took place from Space Launch Complex 3W at Vandenberg Air Force Base,[5] and placed USA-1 into a transfer orbit. The satellite raised itself into medium Earth orbit (MEO) using a Star-27 apogee motor.[2]


By 19 July 1984, USA-1 had been raised to an orbit with a perigee of 19,917 km (12,376 mi), an apogee of 20,446 km (12,705 mi), a period of 718.00 minutes, and 62.80° of inclination to the equator.[6] The satellite had a design life of 5 years and a mass of 758 kg (1,671 lb).[2] It broadcast the PRN 13 signal in the GPS demonstration constellation, and was retired from service on 20 June 1994.


  1. ^ "Trajectory: Navstar 9 1984-059A". NASA. 14 May 2020. Retrieved 21 November 2020. This article incorporates text from this source, which is in the public domain.
  2. ^ a b c Krebs, Gunter. "GPS (Navstar)". Gunter's Space Page. Retrieved 12 July 2012.
  3. ^ a b "Navstar 9 1984-059A". NASA. 14 May 2020. Retrieved 21 November 2020. This article incorporates text from this source, which is in the public domain.
  4. ^ McDowell, Jonathan. "Launch Log". Jonathan's Space Report. Retrieved 12 July 2012.
  5. ^ McDowell, Jonathan. "Launch List". Launch Vehicle Database. Jonathan's Space Report. Retrieved 12 July 2012.
  6. ^ McDowell, Jonathan. "Satellite Catalog". Jonathan's Space Page. Retrieved 12 July 2012.
This page was last edited on 24 June 2021, at 03:27
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