A spacecraft antenna that provides a high amplification of radio-frequency signals that it transmits or receives. It is usually a parabolic dish, and the larger the collecting area the greater the increase in amplification. An HGA requires a high directional accuracy. The dish may be fixed to the spacecraft, as was the HGA on the Magellan probe, whose attitude had to be manoeuvred to point its antenna towards the Earth. The Mars Global Surveyor, however, had a moveable HGA on an articulated arm, enabling the dish to point towards the Earth regardless of the position of the spacecraft.
Subjects: Astronomy and Astrophysics.