What term describes camera roll as it point tword the planet as it passes?

[ncc1701d]

First off from what I understand the term "nadir" is the camera direction on a satellite when it is pointed tword the center of gravity that the satellite is orbiting which would be the planet.
Does anyone know the term, if there is one that describes the roll or rotation of the camera as it points tword the planets center of gravity? Is it locked to the satellite shape and the orbit path determines the alignment as it passes or both?
Cant research it much on google because not sure how to ask it in such a way to find the answer. Can someone elighten me on how this works?
thanks

 

[Urwumpe]

Depends on the coordinate system you use.

It is either surface relative: Heading, Pitch, Bank
Or in general: Yaw, Pitch, Roll

In your case, with the camera pointing nadir, heading would be the best term to describe the camera angle - since it is that in surface relative coordinates.

 

[Quick_Nick]

I would consider measuring the angle between your prograde vector (adjusted to the horizon for elliptical orbits) and the 'up' vector of the camera.
I think this might remain constant so long as you use yaw and pitch to keep facing nadir. (at least in the universe containing spherical cows)