Every satellite depends on antennas on the ground. They receive telemetry and payload data and send commands back. The right ground station antenna depends on the orbit, the frequency band and how much data a mission needs to bring down.
The main types of ground station antennas
Parabolic dish
The classic ground station antenna. According to NASA's Small Spacecraft Technology State of the Art report, a dish uses a parabolic reflector to collect signals from the spacecraft and focus them onto a feed antenna, typically a horn. NASA uses high-gain parabolic dishes for S-, X- and Ka-band links with small satellites.
Yagi and other UHF antennas
Many university and amateur ground stations use UHF Yagi antennas. They are cheap, light and easy to point with a small rotator, which makes them common for CubeSat telemetry at low data rates.
Phased arrays
A phased array steers its beam electronically instead of moving a dish. NASA describes phased array ground systems and free-space optical links as emerging solutions for constellations, because one array can potentially serve several satellites at once.
Optical ground terminals
Laser communication uses telescopes instead of radio antennas. It offers very high data rates but depends on clear skies.
How big are ground station antennas?
Size scales with distance and data rate. LEO ground stations often use dishes of a few metres. For deep space, NASA's Deep Space Network uses much larger antennas: each of its three complexes, at Goldstone in California, near Madrid and near Canberra, has one 70 m (230 ft) antenna, one 26 m (85 ft) antenna and several 34 m (112 ft) antennas. The 70 m Deep Space Station 43 in Canberra, shown on the cover, is described by NASA as the largest steerable parabolic antenna in the Southern Hemisphere.
Why frequency band matters
For a dish of the same size, higher frequencies give more gain and a better G/T, the figure of merit for receive performance. That is why high-volume data moves from S-band to X-band and Ka-band. Higher bands also demand more precise pointing and suffer more from rain. Our guide to satellite frequency bands explains the trade-offs.
Tracking a moving satellite
A satellite in LEO crosses the sky in minutes, so mechanical antennas need fast azimuth and elevation mounts. Pass length and the number of contacts per day depend on the station's latitude and the orbit. Operators often combine stations worldwide or buy contacts through Ground Station as a Service instead of building their own.
Frequently asked questions
What antenna is used in a ground station?
Most professional stations use parabolic dishes. Small university stations often use UHF Yagi antennas, and newer stations add phased arrays or optical terminals.
How large is a satellite ground station antenna?
From under a metre for simple UHF setups to several metres for LEO data downlink, and up to 70 m for NASA's deep space antennas.
What is G/T?
Gain over system noise temperature. It describes how well a receiving station can pick up weak signals.
Can one antenna track several satellites?
A dish tracks one satellite at a time. Phased arrays can form several beams and are being developed for this purpose.
Related reading
- Ground Station as a Service explained
- Satellite frequency bands: S, X and Ka
- How many MEO satellites are there?
Sources
- NASA: Small Spacecraft SOA, Ground Data Systems and Mission Operations
- NASA: Deep Space Network
- NASA/JPL: A Big Crane for a Big Dish (PIA23797)
Cover image: Deep Space Station 43 in Canberra, Australia. Credit: NASA/JPL-Caltech (PIA23797), public domain.