OPS 5112
Second Block I GPS satellite, launched in 1978.
OPS 5112—also designated Navstar 2, NDS-2, GPS I-2, and GPS SVN-2—was an American navigation satellite that launched in 1978 as part of the Global Positioning System’s early development. It was the second of eleven Block I GPS satellites to fly, and it transmitted the PRN 07 signal within the GPS demonstration constellation.
The U.S. Department of Defense created the Global Positioning System to give military forces on land, at sea, and in the air continuous, all-weather navigation. Over time, GPS became essential for many civilian uses worldwide, including recreation (like boating, flying, and hiking), corporate fleet tracking, and surveying. The system relies on 24 spacecraft in circular orbits 20,200 kilometers high, inclined at 55°, arranged in six orbital planes with four active satellites each.
The first eleven spacecraft, known as GPS Block 1, proved the GPS concept. These satellites were three-axis stabilized, pointed toward Earth, and used reaction wheels for orientation. Twin solar arrays generated more than 400 watts of power. They communicated via S-band (SGLS) for control and telemetry and used UHF cross-links between spacecraft. Built by Rockwell Space Systems, each measured 5.3 meters across with its solar panels deployed, and had a design life of five years. Unlike later operational satellites, Block 1 spacecraft flew in orbits inclined at 63°.
OPS 5112 lifted off at 10:34 UTC on 13 May 1978, aboard an Atlas F launch vehicle with an SGS-1 upper stage. That Atlas, serial number 49F, was originally built as an Atlas F. The launch occurred from Vandenberg Air Force Base’s Space Launch Complex 3 (SLC-3E), placing the satellite into a transfer orbit. OPS 5112 then used a Star-27 apogee motor to raise itself into medium Earth orbit.
By 14 July 1978, the satellite occupied an orbit with a perigee of 19,952 kilometers, an apogee of 20,084 kilometers, a period of 711.30 minutes, and an inclination of 63.10°. It weighed 758 kilograms and was designed to operate for five years. OPS 5112 was taken out of service on 16 July 1981.
Quick Facts
- Names list
- Navstar 2
- NDS-2
- GPS I-2
- GPS SVN-2
- Operator
- U.S. Air Force
- Satcat
- 10893
- Mission duration
- 5 years (planned); 3 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
OPS 5112 was manufactured by Rockwell Space Systems and was 3-axis stabilized, nadir pointing using reaction wheels. Dual solar arrays supplied over 400 W, and the satellite measured 5.3 m across with solar panels deployed. It had S-band (SGLS) communications for control and telemetry and UHF cross-link between spacecraft. Unlike later operational satellites, GPS Block I spacecraft were inclined at 63°.
The satellite was launched atop an Atlas F launch vehicle with an SGS-1 upper stage, the Atlas having serial number 49F and originally built as an Atlas F. The launch occurred from Vandenberg Space Launch Complex 3 (SLC-3E) at Vandenberg Air Force Base, placing OPS 5112 into a transfer orbit. The satellite then raised itself into medium Earth orbit using a Star-27 apogee motor.
By 14 July 1978, OPS 5112 was in an orbit with a perigee of 19952 km, an apogee of 20084 km, a period of 711.30 minutes, and 63.10° of inclination to the equator. It had a design life of 5 years and a mass of 758 kg. The satellite was retired from service on 16 July 1981.
Reader's Guide
OPS 5112 was part of the first eleven spacecraft (GPS Block I) used to demonstrate the feasibility of the GPS system. The Global Positioning System 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 use (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. GPS employs 24 spacecraft in 20,200 km circular orbits inclined at 55°, placed in 6 orbit planes with four operational satellites in each plane. As the second Block I satellite, OPS 5112 helped validate the satellite design and orbital concepts that would later be used in the operational GPS constellation. Its retirement in 1981 came after roughly three years of service, well within its 5-year design life.
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