Abstract: In an embodiment, an antenna subsystem includes a sparse receive antenna and an electronically steerable transmit antenna. The sparse receive antenna includes an array of electronically steerable receive elements each configured to receive a respective signal having a wavelength and each spaced apart from each adjacent one of the receive elements by a respective first distance that is more than one half of the wavelength, has an aperture, and is configured to generate a receive beam pattern. And the electronically steerable transmit antenna includes an array of transmit elements each configured to radiate a respective signal having the wavelength and each spaced apart from each adjacent one of the transmit elements by a respective second distance that is less than one half of the wavelength, has an aperture that is significantly smaller than the aperture of the sparse receive antenna, and is configured to filter, spatially, the receive beam pattern.

Abstract: A wide-angle infrared cloud imager that comprises a first and second mirrors driven by first and second stepping motors is disclosed. The first and second mirrors are rotated by the steps motors at axes orthogonal to each other. The first mirror directs reflected infrared radiation to the second mirror. Infrared radiation reflected from the second mirror is directed to an infrared radiation detector that outputs a signal directly proportional to the intensity of incident infrared radiation. The signal is provided to a computer for recording. The computer also provides the driving signal to drive the first and second motors.