GB-Stockbridge: UKRI-3547 Supply of a X-band Cassegrain Feed Tower & Frequency Selective Sub-Reflector for Chilbolton Observatory

The Chilbolton observatory operates a 25m diameter, prime focus, parabolic reflector antenna with an F/d ratio of 0.36. The antenna was commissioned in 1967 and has for many years been used with an S-band radar fed from the prime focus point. The main feed is undergoing an upgrade to implement monopulse tracking. At the same time the observatory would like to add a wide band X-band radar to the antenna for simultaneous operation with the S-band radar. The intention is to use the S-band radar for tracking and ranging of satellites while the wide bandwidth X-band radar is used for imaging.

The antenna was commissioned in 1967 and there are no CAD drawings for the structure. Contractors may wish to visit the site to conduct a survey of the structure and check mounting points, access to the backing structure etc that will become important in the design, installation and alignment of the feed tower and the sub-reflector.

It is not thought possible to integrate an X-band feed with the S-band monopulse feed at prime focus. The solution proposed is one used in satellite communications ground stations of having the S-band feed at the prime focus of the reflector and the X-band feed in a tower mounted in the centre of the dish forming a cassegrain arrangement with a frequency selective sub reflector.