We continue to work with the staff of the JCMT on improving the accuracy of the antenna surface. Analysis of 94GHz `holography' maps of JCMT showed that the individual panels that make up the reflector were slightly more steeply curved than the overall surface with the nominal focal length. The dish has now been adjusted to a shorter focal length to reduce this mismatch, leading to a considerable increase in sensitivity at the shortest wavelengths. Hills advised on problems with non-homologous deflections in the backing structure, and helped to correct a serious deterioration in performance that occurred in September 1994, which was probably due to distortion of the secondary mirror.
Hills also worked with Morris at IRAM on the 30-metre telescope and was able to identify paths of spurious signals which were adversely affecting the surface measurements there.
A major revision of the software used for antenna measurements is being undertaken by Debenham, who joined MRAO recently to work on the software in this and related areas. A more `user-friendly' and flexible package is being produced and alternative algorithms tested.
Hills (1994) discussed some of the possibilities opened up by the use of new materials and active controls in the construction of very large telescopes. He has also been working with the project team on refining the specifications of the telescope for ESA's FIRST mission.