What is the diameter of Voyager's main high-gain antenna?

Voyager’s main high-gain antenna has a diameter of 3.7 meters. The large dish-shaped antenna lets the spacecraft exchange radio signals with NASA’s Deep Space Network across enormous distances.

The antenna is a Cassegrain design and supports the spacecraft’s long-range communications. Voyager uses an X-band transmitter for its primary downlink, with an S-band system serving as backup. Commands travel from Earth to the spacecraft, while scientific measurements and engineering data return through the same network of ground stations.

A narrow radio beam is essential because the signal becomes dramatically weaker as distance increases. Voyager’s antenna has an approximate beamwidth of 0.5 degrees in X-band and 2.3 degrees in S-band. Ground antennas must point extremely accurately to maintain contact with a probe billions of kilometres away.

The 3.7-meter figure describes the antenna’s diameter, not the spacecraft’s total height or the distance across its solar-panel-like structures. Voyager’s power comes from radioisotope thermoelectric generators, since it travels too far from the Sun for ordinary solar panels to remain practical.