Sensor

Revisit rate — theoretical vs real

How often a given point on Earth can be imaged. The number on a spec sheet is the theoretical maximum; real revisit at acceptable quality is usually half that.

d1d2d3d4d5d6d7d8d9d10d11d12d13d1414-day window over a single point1-SAT · THEORETICALevery 5 days1-SAT · REAL QUALITY2 usable / 14 dayscloudy6-SAT · THEORETICAL< 1 day6-SAT · REAL QUALITY5 usable / 14 daysusableopportunitycloudy / off-nadir > 20°
Fig. 1 Revisit is how often a given point on Earth sits under an accessible pass. Theoretical revisit (spec sheet) assumes maximum off-nadir pointing and any-quality capture. Real revisit at acceptable quality (<20° off-nadir, <30% cloud) is usually 2–3× worse. Constellation size is the single biggest lever.

Revisit rate is how often a given point on Earth can be imaged by the constellation. A spec sheet might say 'every 5 days,' but that is the theoretical maximum assuming the satellite tilts to its maximum off-nadir angle and you accept any image regardless of quality.

Real revisit at acceptable quality

If you require less than 20° off-nadir, less than 30% cloud, and reasonable sun elevation, real revisit is usually half the theoretical figure or worse. A 5-day theoretical revisit becomes 10–14 days at acceptable quality in cloudy regions. A 1-day theoretical revisit becomes 2–4 days at quality.

Why constellations matter

A single satellite will almost never give you frequent quality-acceptable monitoring. Constellation size is the single biggest lever on how fast a provider can respond to tasking. When you see 'sub-daily revisit' on a spec sheet, check how many satellites are involved.