 A Block I GPS satellite (Navstar 1) | |
| Names | Navstar 1 NDS-1 GPS I-1 GPS SVN-1 |
|---|---|
| Mission type | Navigation Technology |
| Operator | U.S. Air Force |
| COSPAR ID | 1978-020A[1] |
| SATCATno. | 10684 |
| Mission duration | 5 years (planned) 7.25 years (achieved) |
| Spacecraft properties | |
| Spacecraft | Navstar |
| Spacecraft type | GPS Block I |
| Manufacturer | Rockwell Space Systems[2] |
| Launch mass | 758 kg (1,671 lb) |
| Dimensions | Solar panel span: 5.3 m (17.4 ft) |
| Power | 400 watts |
| Start of mission | |
| Launch date | 22 February 1978, 23:44:00UTC |
| Rocket | Atlas F / SGS-1 (Atlas-64F) |
| Launch site | Vandenberg,SLC-3E |
| Contractor | Convair General Dynamics |
| Entered service | 29 March 1978 |
| End of mission | |
| Deactivated | 17 July 1985 |
| Orbital parameters | |
| Reference system | Geocentric orbit[3] |
| Regime | Medium Earth orbit (Semi-synchronous) |
| Perigee altitude | 20,095 km (12,486 mi) |
| Apogee altitude | 20,308 km (12,619 mi) |
| Inclination | 63.3° |
| Period | 718.70 minutes |
OPS 5112 (Navstar 2) → | |
OPS 5111, also known asNavstar 1,NDS-1,GPS I-1 andGPS SVN-1, was an Americannavigation satellite launched in 1978 as part of theGlobal Positioning System development program. It was the first GPS satellite to be launched, and one of elevenBlock I demonstration satellites.[2]
Global Positioning System (GPS) was developed by theU.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.[1]
The first eleven spacecraft (GPS Block 1) were used to demonstrate the feasibility of the GPS system. They were 3-axis stabilized, nadir pointing usingreaction wheels. Dual solar arrays supplied over 400 watts. They hadS-band communications for control and telemetry andUltra high frequency (UHF) cross-link between spacecraft. They were manufactured byRockwell Space Systems, were 5.3 meters across withsolar panels deployed, and had a design life expectancy of 5 years. Unlike the later operational satellites, GPS Block 1 spacecraft were inclined at 63°.[1]
OPS 5111 was launched at 23:44 UTC on 22 February 1978, atop anAtlas Flaunch vehicle with an SGS-1 upper stage. The Atlas used had the serial number 64F, and was originally built as anAtlas F.[4] The launch took place fromVandenberg Space Launch Complex 3 (SLC-3E) atVandenberg Air Force Base,[5] and placed OPS 5111 into a transfer orbit. The satellite raised itself intomedium Earth orbit using aStar-27apogee motor.[2]
By 29 March 1978, OPS 5111 was in an orbit with aperigee of 20,095 km (12,486 mi), anapogee of 20,308 km (12,619 mi), aperiod of 718.70 minutes, and 63.3° ofinclination to theequator.[6] The satellite had a design life of 5 years and a mass of 758 kg (1,671 lb).[2] It broadcast the PRN 04 signal in the GPS demonstration constellation, and was retired from service on 17 July 1985.
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