Surface Accuracy Improvement of the Yebes 40 Meter Radiotelescope Using Microwave Holography

The surface improvement of the Centro Astronómico de Yebes (CAY) 40 m radiotelescope with the use of coherent (with-phase) microwave holography is shown. For this purpose, a dual channel Ku-band receiver in prime focus has been developed. It allows holography measurements with unmodulated beacons from geostationary satellites in the Clarke belt. Initial surface measurements revealed an accuracy of 485 μm amplitude-weighted RMS (WRMS) with respect to the best-fit paraboloid. After a few iterations of the measurement and surface adjustment cycle, the accuracy has been improved to 194 μm WRMS. This means an estimated aperture efficiency improvement from 2.6% to 38.2% at 86 GHz for a prime-focus receiver with an illumination equal to the one produced by the holography receiver test feed.