(1) A non-photographic imaging system, which utilises an oscillating mirror and fibre optic sensor array. The mirror sweeps from side to side, transmitting incoming energy to a detector array which sequentially outputs brightness values (that is, signal strengths) for successive pixels one swath at a time. The forward motion of the sensor platform carries the instrument to a position along its path where an adjacent swath can be imaged (2) For Landsats 1,2,3, 4, and 5 the Multispectral Scanner sensed radiation simultaneously by an array of six detectors in each of four spectral bands from 0.5 to 1.1 µm. See radiometer.