Optical sensor for active control of antenna surfaces

Abstract

The ability to accurately monitor the shape of antenna surfaces is likely to play a critical role in future radar systems. Errors in surface figure are particularly troublesome in applications that require high antenna gains at short wavelengths. For robust operation, these tolerances must be maintained against many outside influences, including the variation of gravitational distortion with elevation angle, bending and vibrations due to antenna motion or wind, and thermal distortions due to radiative heating from the Sun or temperature variations of the surrounding air. Attempts at building large antennas that meet the surface-tolerance specifications based on passive structures alone may be impractical or prohibitively expensive. A more cost-effective approach is to actively control the antenna shape using an array of actuators controlled by feedback signals obtained from surface-shape monitoring. An additional motivation for actively controlling antenna surfaces is to reduce the cost of deploying space-based radars by minimizing the weight of the antenna surface and its supporting mechanical structure.