Radiometers detect radio wavelength electromagnetic radiation and typically
have an antenna (16), an amplifier (18) and a detector (20).
All three of these components have response characteristics that may be dependent
on temperature, and in the case of systems using radiometer arrays dependent upon
temperatures throughout the system. Different temperatures across a multi-channel
antenna and differential channel temperature response can result in poor image
quality from imaging radiometers. Resolution of a linear array of detector horns
is limited by the size of the horns. An imaging radiometer (10) uses a focussing
polariser (36), a quarter wave plate (32), a rotating inclined disk
(28), and a detector feed array (16) to perform a conical scan, and
compensates for variations in operating temperature of a radiometer using one or
more of a variety of techniques including calibrating channels relative to each
other, calibrating channels using reference temperatures in situo, and calibrating
channels using temperature response predictions stored in the radiometer signal
processor (22). Aspects of the invention also optimise image resolution,
image quality and allow calibration.
