The prototype M-AERI mounted on NOAA S Discoverer during the Combined Sensor Cruise. With the protective cover removed, the two black-body calibration targets and scan mirror drive motor can be seen (above). The field of view, scanning from zenith to the ocean at 35^o zenith angle, requires a large aperture on the seaward side of the instrument (below). The MAERI is mounted so that its field of view intersects the sea surface ahead of the ship’s bow wave.