orbital speed
Technical term in astronomy for the speed at which a celestial body moves along its orbit.
惑星によって公転速度は異なる。
Orbital speed varies depending on the planet.
自転速度 refers to rotational speed (spinning on an axis), while 公転速度 refers to orbital speed (revolution around another body).
Compound of 公転 (revolution, orbit) and 速度 (speed).