2.2 Ryle Telescope 

The RT is used almost exclusively for CMBR studies. Since the commissioning of CAT, approximately half of all RT time has been spent mapping CAT fields to allow subtraction of the many contaminating foreground sources -- subtraction of foreground radio sources from the CAT data would be impossible without the higher sensitivity and resolution of the Ryle Telescope. Pooley has developed control and data-analysis software for the RT which allow it rapidly to survey the large () field of the CAT. The RT time that remains is used for Sunyaev-Zel'dovich imaging. The performance of the RT for these programmes has been excellent - see sections 1.1.1 and 1.1.3 respectively.

Technical advances during the period of this report include:

1. Development of a rastering scheme (and control and data handling software) to allow efficient mapping of CAT fields ( FWHM) with the RT primary beam (6 arcmin FWHM). An area of 0.5 degrees square can be mapped in 12hr.

2. Improvements to receivers and cryostats: modification of the matching unit between feed horn and waveguide; a redesigned waveguide thermal break in the cryostat; and renovation of the second-stage amplifier. These changes have reduced the total antenna temperature from 75 to 65K. Modified units are gradually being fitted and will speed up observations to a given sensitivity by 30%.