The Met Office Meteorological Research Unit at Cardington, Bedforshire, operated a Radiometrics TP/WVP-3000 microwave radiometer used a neural network to retrieve profiles of water vapour and temperature. The TP/WVP-3000 was set up to take readings in the vertical approximately every 8 s. Regular tipping curve scans were done over a range of zenith angles (30, 45, 90, 135, 150 degrees) to compare the atmospheric radiances to that of known values at relatively opaque water vapour frequencies (with the opacity being a linear function of the slant path), in addition using frequent views of an internal temperature-controlled black body. Absolute calibrations for the absorbing channels were done periodically using a black body cooled with liquid nitrogen.