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Point source sensitivity (PS sensitivity) is a determination of how sensitive an observation is detecting point sources. For instruments such as CCDs with pixels, it can be a statistically-based quantity based upon signal-to-noise ratio (SNR) threshold aiming to separate actual sources from random noise (e.g., photon noise). Such a threshold merely produces a probability of a point source, and a probability threshold must be chosen, in effect, based upon a probability, such as "80% chance that this is a point source". Additional integration time which improves the SNR, in turn improves this sensitivity. Even for the same instrument and observation, separate thresholds might be chosen for confirming/measuring a point source versus discovering one. For radio telescopes and radio interferometers that aren't simply arrays of sensors, there is analogous analysis yielding such point source sensitivity. Surface brightness sensitivity is a similar analysis of an instrument's ability to determine surface brightness, which has additional challenges.