OCT is a technique which uses IR to get "through" tissue using beam in the near infrared (roughly 950 nm, with a spread of roughly 100 nm). The return is passed through interferometer and what amounts to a diffraction grating to produce the "spread" that the line camera sees. After some signal processing (FFT is a big one), you can get the intensity at depth. If you sweep in X,Y somehow, usually deflecting the beam with a mirror, you can obtain a volumetric image like an MRI or sonogram. Very useful for imaging the eye, particularly the back of the retina where the blood vessels are.
Data stops being written as the sat rotates the camera away from the planet and resumes once it has rolled over enough to again point at the earth.
It may seem like a pedantic difference; a "line scan camera" is stationary while mirrors inside it spin or another mechanism causes it to "scan" a complete vertical line - perhaps all at once, perhaps as the focal point moves Vs a camera in a satellite that has no moving parts that just records a single point directly in front of the instrument .. and the entire satellite spins and moves forwards.