A description of the general principles involved in remote sensing is followed by a review of instruments designed to sense properties of the earth's atmosphere and surface from near-earth orbiting and geostationary satellites. These include instruments for measuring atmospheric temperature, clouds, winds, precipitation and composition (water vapour and trace constituents). Emphasis is on general principles, but a few instruments are described in detail as examples. A list of space-borne atmospheric remote-sensing instruments is included. Methods for data reduction are outside the scope of this review.