Glossary — G
14 terms
Guidance
The process of determining and commanding a vehicle's path.
Example: Guidance computed steering to reach the target orbit.
GEO
Geostationary Orbit: a circular geosynchronous orbit directly above the equator at about 35,786 km, where a satellite appears fixed over one longitude.
Example: Weather and broadcast satellites typically occupy geostationary orbit to serve a fixed coverage area.
GSO
Geosynchronous Orbit: an orbit with a period equal to Earth's sidereal day of about 23 hours 56 minutes, regardless of inclination or eccentricity.
Example: A satellite in geosynchronous orbit returns to the same point in the sky each sidereal day.
GNC
Guidance, Navigation, and Control: the integrated discipline steering a vehicle along its path.
Example: The GNC team tuned the ascent algorithm before flight.
Gravity turn
A launch trajectory that lets gravity gradually bend the path over.
Example: After clearing the tower, the rocket began its gravity turn.
GPS
Global Positioning System: a satellite constellation providing position and timing globally.
Example: The vehicle used GPS to refine its state after liftoff.
Gravity assist
Using a planet's gravity to change a spacecraft's speed and direction.
Example: A gravity assist around Jupiter flung the probe toward the outer planets.
Gas generator cycle
An engine cycle that burns a small propellant flow in a gas generator to drive the turbopump.
Example: The F-1 engine used a gas generator cycle to power its turbopump.
Gyroscope
A device measuring or maintaining orientation using angular momentum.
Example: Gyroscopes sense rotation for the guidance system.
Grid fin
A lattice-like aerodynamic fin used for steering and drag.
Example: Grid fins steered the booster during its descent.
Ground track
The path a satellite's subpoint traces on Earth's surface.
Example: The ground track shifts westward each orbit because of Earth's rotation.
Gimbal
A pivoting mount that swivels the engine to steer by vectoring thrust.
Example: Engine gimbaling provided pitch and yaw control during ascent.
Graveyard orbit
A disposal orbit above geostationary altitude where retired satellites are parked.
Example: End-of-life geostationary satellites are boosted into the graveyard orbit.
g-force
The load on a body expressed in multiples of Earth's gravity.
Example: The crew withstood peak g-forces near reentry.