Ok, I looked at the wrong instrument.

Regarding the MMS, here (page 3) it says:

MSS sensor, the oldest operational multispectral digital sensor

Then I found this diagram (with some explanations on this link):

If I understand correctly, that means it has a 6 pixel-row resolution that it uses to scan a 2D area.

Finally, I realized I was using a wrong idea of “digital camera”. There is no true “digital sensor”, all sensors are analog and always need a postprocess to convert to digital… right?

As always, it’s impossible to provide a non-ambiguous definition. Is a 6-pixel row res instrument on a satelite a “digital camera”? … kind of :)

Anyway, fascinating topic. Thanks for the input!