Photographic "Footprints", definitions thereof Options

[ncc1701d]

Concerning the definition of a "footprint"
Say a spacecraft flying overhead of planet is pointing its camera rectangular shaped FOV down at the surface. If 1 or more of the 4 corner boundary rays stops intercepting with the surface, is the area under the FOV still considered a "footprint"? Perhaps it only matters if the borsight ray of the FOV intercepts with the planet to qualify as a "footprint" ?
I tend to think all of those 4 cornors rays would have to be intecepting the surface to qualify as a "footprint" but
I just wanted some clarification maybe from an expert.

Thank you.