The Radio Communications Research Unit (RCRU) is part of the Rutherford Appleton Laboratory’s Engineering Department. It consists of some thirty scientists and engineers engaged on a wide ranging interdisciplinary programme of radio communications research. The expertise of the Unit covers basic electromagnetic theory, communication systems, microwave system design, meteorology and geophysics. Much of the experimental work of the RCRU is conducted at Chilbolton, Hampshire, UK. where facilities include multi-frequency, multi-parameter radar systems installed on the 25m steerable antenna, experimental mm-wave systems, meteorological sensors and a UV vertical sounding lidar. A multi-frequency satellite receiving system associated with ITALSAT F1 is located 8 km from Chilbolton at Sparsholt.

The more analytical studies, undertaken at the Rutherford Appleton Laboratory, lead to the development of improved propagation models and novel communications concepts, essential for radio communications planning and spectrum management. Support for this work is given by the Radiocommunication Agency through the National Radio Propagation Programme of the UK.

Relevant expertise:

• Individuals within RCRU have many years of experience in the measurement, and interpretation, of sky brightness temperatures collected with microwave radiometers.

Relevant facilities:

• Chilbolton meteorological radars

  The Chilbolton rain radar is a world leader in dual-linear-polarisation measurement techniques. The 25m antenna on which the radar is mounted gives a high spatial resolution (0.25^o ), whilst the operating frequency of 3 GHz ensures that the data suffer negligible effects from attenuation. The characterisation of the rain drop size distribution using the differential-reflectivity technique allows prediction of propagation effects up to at least 30 GHz.

  A 94 GHz radar that is designed to make reflectivity measurements of clouds was installed on the rim of the 25m antenna during 1998. (The 0.5m antenna of the radar has a beamwidth of 0.4^o .) This is a fully-coherent radar that is capable of measuring the full velocity spectra of cloud particles.

• Microwave radiometers

  Ground-based, vertically pointing, Dicke switched radiometers are being used to measure sky brightness temperatures from the Chilbolton Observatory. At present radiometers operating at 22.2, 28.8 and 93 GHz are available. Estimates of the total cloud liquid water path and the total water vapour path can be made from these measurements.

• Lidar ceilometer

  A zenith pointing ceilometer operating at 905nm provides information relating to the base height of cloud passing over Chilbolton.

Participation in earlier EU-proposals:

• 'Flood hazard control by multi-sensor storm tracking in Mediterranean areas', 1993.

  Role:- Development of multi-sensor storm tracking techniques for flood prediction

• 'Clouds and Climate', 1994.

  Role:- Obtain reflectivity measurements from a variety of cloud types using 3, 35 & 94 GHz radars

• 'MEFFE', 1996.

  Role:- Collection of 3 GHz radar reflectivity data at time of overpasses by SSM/I satellite

• 'EUROTRMM', 1998.

  Role:- Collection of radar reflectivity data from sites in Papua New Guinea and Singapore to compare with data collected from the TRMM satellite.