Across-track scanner terminology (memorize all four):

• IFOV (Instantaneous Field of View) — the angle within which incident energy is focused on the detector at one moment. Combined with altitude, it determines spatial resolution (the ground pixel size).
• Field of view (FOV) — the full sweep angle of the mirror, defining a complete scan line.
• Swath width — on-ground width of one scan line; set by FOV × altitude.
• Diagram labels: A = rotating mirror, B = detector, C = IFOV, D = spatial resolution, E = FOV, F = swath width.