scan speed

The term scan speed is (I presume) the rate at which a telescope's direction is shifted to a new portion of the celestial sphere during an observation. I see it cited as an angle per second, e.g., 30"/s. The concept is relevant to surveys (e.g., slew surveys) and observations of extended targets, in both cases where the telescope's direction moved during the observation. There is presumed to be a tradeoff between the scan speed used and the quality of the observation, with the integration time also being a factor.

I presume a scan speed is generally used to indicate the angular distance shifted across the celestial sphere (per unit time), but I suppose it might cited in relation to the telescope's aim in relation to its mount, in which case the aim is further affected by the spacecraft's or (for a ground telescope) the Earth's rotation. For rapid scans, Earth rotation might make little contribution; on the ecliptic, it would affect the rotation at a rate of 15"/s.

Some space telescopes and probes are designed to observe while (slowly) spinning, with a fixed scan speed.