🛰️ Space Glossary

Spacecraft Systems

The subsystems that make up a satellite — from the bus and payload to attitude control, power, thermal management, and communications. 21 terms, each explained in plain language with key data and links to live trackers.

AG Antenna Gain Measure of how focused an antenna's signal is Spacecraft Systems AC Attitude Control Keeping a satellite pointed in the right direction 0.01°0.05–0.1° C C&DH The satellite's onboard computer and data system RAD750, LEON, FPGAFDIR (fault detection) C CubeSat A standardised small satellite built in 10 cm cube units 10 × 10 × 11.35 cm≤ 2 kg D Downlink The space-to-Earth half — where every satellite earns its keep Space → groundSpacecraft power ES Earth Sensor Infrared sensor detecting Earth's thermal horizon 0.05–0.5°Scanning, static array IT Ion Thruster An electric propulsion system that accelerates ionised gas to produce thrust 2,000–5,000 s20–50 km/s M Magnetorquer Electromagnetic coil for attitude control using Earth's field NoneLow (1–5°) MW Momentum Wheel Constantly spinning wheel providing gyroscopic stability CMG (ISS uses 4) P Payload The mission-specific equipment aboard a satellite Atomic clocksThe whole spacecraft PS Power Subsystem Generating, storing, and distributing electrical power Lithium-ion batteriesPCU holds bus voltage RW Reaction Wheel Spinning wheel used to precisely rotate a satellite None — electric motorMomentum saturation SB Satellite Bus The main structural and support platform of a satellite 10 cm cube, ~1–2 kg SA Solar Array Panels that convert sunlight into electrical power 1,361 W/m² at 1 AULi-ion batteries ST Star Tracker Camera that determines orientation by identifying stars 1–10 arcsecondsStar pattern matching SS Sun Sensor Optical sensor that detects the Sun's direction 5° accuracy0.01–0.1° TC Thermal Control Keeping satellite temperatures within safe limits 120°C+−150°C T Transponder Communications relay unit on a satellite C, Ku, Ka, V24–72 per GEO sat T TT&C Communications link between satellite and ground control Uplink of instructionsS-band (~2 GHz) T TT&C The housekeeping link that keeps a satellite a satellite Works while tumblingRange + range-rate U Uplink The Earth-to-space half of every satellite link Ground → spaceHigher sub-band up

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