Fast Surface Error Diagnosis for Radiotelescopes Using Linearized Microwave Holography

Abstract

Radiotelescopes are typically composed of large reflector antennas located outdoors. These antennas are designed to achieve high levels of gain, which is possible due to their large size and RF systems designed for working at high frequencies. However, various sources of errors (such as mounting imperfections or deformations caused by gravity and weather effects) are difficult to identify and can significantly degrade the performance of the radiotelescope, reducing its gain. The correct diagnosis of these errors has been a challenge in radio astronomy. The most widely used technique is microwave holography, in which mechanical errors are detected through long electromagnetic acquisitions. The measured far-field is processed to obtain the aperture field, thus the errors affecting the surface or the phase distribution. In this article, a novel methodology is proposed to diagnose reflector errors using holography. The proposed approach defines a system that models all possible aperture errors as a combination of basis functions, directly relating the errors to the acquired far field and reducing the number of samples required for analysis.