Galileo 94 GHz radar
10 Mar 2011



Galileo is a 94 GHz (3.2 mm wavelength) cloud radar. It is a fully coherent, dual polarisation Doppler radar.

​The Galileo radar is designed to complement the 35 GHz (9 mm) Copernicus cloud radar currently operating at the Observatory for observations of cloud microphysics and climatology. It has operated since 1994. The radar provides real-time measurement and display of the full Doppler spectrum, and the moments Z, v, and w.

The latest results from Galileo can be viewed on the Chilbolton weather web.

Millimetre-wave cloud radars exploit the fact that the echo intensity of Rayleigh scatter increases with the inverse-fourth power of the wavelength. These radars normally operate in the windows in the atmospheric absorption spectrum at 35 GHz and 94 GHz.

The shorter-wavelength radar (94 GHz) is sensitive to a small amount of Mie scattering from the largest cloud particles. The 35 GHz backscatter, however, is overwhelmingly due to the Rayleigh mechanism. A comparison of measurements at the 2 frequencies, given by the dual-wavelength ratio (DWR) provides a measure of the size of the scattering particles. Together with measurements of radar reflectivity, this allows ice water content to be derived in cirrus clouds.

The radar is currently on the ground within 100 m of the 25 m steerable antenna. Copernicus, the 35 GHz cloud radar is also located within 5 m of Galileo. Galileo is installed in a positioning unit that can be manually adjusted in azimuth and elevation. The most common mode of operation is vertically pointing, but the radar can be pointed at lower elevations for calibration purposes, and for operation along the same path as the radars on the 25 m antenna.

Technical specification of the Galileo radar

Contact: Hooper, David (STFC,RAL,RALSP)