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What equipment makes up the space segment of the Navstar GPS system?
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GPS
U.S. Navstar Global Positioning System (GPS) satellite in orbit over Earth, shown in an artist's conception.
The space segment of the Navstar GPS system is composed of a constellation of satellites in orbit around Earth. These satellites, which include various production models such as the Block II series, are arranged in six circular orbital planes to ensure that at least five satellites are visible from most locations on Earth at any given time.1
A typical satellite in the constellation weighs approximately 900 kg (2,000 pounds) and features several key pieces of equipment:1
- Solar arrays: Winglike panels that extend from the main body to generate electrical power from sunlight.1
- Navigation antennas: A set of 12 helical antennas used to transmit navigation pulses to users on the ground.1
- Radio antenna: A long, spearlike antenna designed to receive instructions from control engineers on the ground.1
- Onboard thrusters: Mechanisms used by ground control to adjust the satellite's position when it drifts from its intended configuration.1
The satellite's main body is designed to pivot continuously to keep the navigation antennas pointed toward Earth and the solar arrays aligned with the Sun.1