The RTS Southern Centre was privileged to visit the Science and Technology Facilities Council's Chilbolton Observatory site on July 16th. The Station Manager, Darcy Ladd, opened the visit with a presentation about the history of the site, and the work currently being undertaken. We were then split into groups and given a very thorough conducted tour of the site. The staff were very helpful, answering questions as we went, and we were able to take photographs without hindrance.
The site is an old WW2 airfield located between Winchester and Andover, and after it became disused, in the early sixties it was planned that a radio observatory be built there for scientific purposes. The observatory was commissioned in 1967, the centrepiece of which is a 25 metre steerable dish antenna. The site was chosen as it has a clear view all around to the horizon, and is away from major populated areas, which would cause radio interference.
Early uses of the dish during the cold war period was for tracking Soviet "Sputniks", and for radio astronomy. The dish is now mostly used as a high power weather radar. RF energy is beamed into the atmosphere, and reflections from clouds and other water droplets received and measured. The transmitter used has a power of 700kW at 3GHz., but 1.275GHz is used as well. These radars help to increase the understanding of rain and snowfall, and aid the science of weather forecasting. The 25m dish is also being used to evaluate the performance of the Gallileo test satellites GIOVE-A and GIOVE-B. This is in preparation for the launch of the main Gallileo satellites which will provide a European navigational satellite system by 2014, similar to the American GPS, but superior in performance. This will be available to SATNAV devices.
The site also has a radio propagation range, 500 metres in length. Transmission on different frequencies from a cabin at one end of this range to another ar the other end allows atmospheric effects on the propagation of the radio signals to be measured. There is a rainfall measurement area, which is key to the success of the tests. The presence of water droplets in the atmosphere attenuates radio signals ("water absorbtion"), and the data gleaned from the tests provides useful information for planning mobile phone and other networks.
There is also a 4.5 metre dish which is being used in conjunction with the STEREO satellites, which observe the sun from space. The purpose is to help predict solar events such as solar flares, which could impact communications and power distribution on Earth.
During the tour we were able to see the main control room, and the big dish turning. We also were able to go inside the dish internal technical areas, reached via steep and narrow stairs. Hard hats were donned for this part of the tour! One of the surprising things was the small size of the motor that turns the dish. We also visited the propagation range and saw the rainfall monitoring system, one of the main operational problems of which is the unwanted attention of birds!
The visit took an hour-and-a-half, and provided a fascinating insight into the cutting edge research being conducted by the STFC at Chilbolton. Our thanks are due to the staff, who gave up their time to make a most interesting and enjoyable morning for us.
You can see some more pictures from the visit in the form of a slide show, by clicking here (opens in a new window).
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Peter Wright