L-BASS: A project to produce an absolutely calibrated 1.4 GHz sky map. II -- Technical Description of the System

Abstract: L-BASS is an instrument designed to make radiometric temperature measurements of the sky with an absolute accuracy of better than 0.1 K at 1.4 GHz. This will be achieved in two steps: first by measuring the sky temperature relative to that of the North Celestial Pole, using two horn-based antennas, and second with the sky antenna replaced with a calibrated cryogenic load to measure the absolute brightness temperature of the North Celesial Pole. Here we describe the design of the L-BASS two-antenna system and report on laboratory measurements to establish its performance at component and sub-system level.