Evaluating The Temperature of The Sky: The L-Band All-Sky Survey

  • Duncan Zerafa

Student thesis: Phd


In this thesis the construction and commissioning of the L-BASS instrument is described. The L-BASS (L-Band All-Sky Survey) is an instrument that is designed to produce an absolutely calibrated map of the sky at a wavelength of 21cm, with a measured radiometric accuracy of less than or equal to 0.1 K. The angular resolution of the two horn antennae beams is 22 plus or minus 0.5 degrees. The motivation for this is to produce improved temperature calibration for higher resolution maps and to investigate the possibility of a new steep radio background component observed by the ARCADE-2 team experiment. The instrument has two horn type antennae that scan independently of each other in elevation. The horns produce an circularly polarised output signal. The design of the receiver is a pseudo-correlation type with a digital back-end spectrometer differencing the signals from the two horns. Stability and calibration will be key to the success of the L-BASS project. Testing of all individual components is described as well as the performance of the complete receiver in the laboratory. A detailed description of how isolation between the channels in the correlation receiver was achieved. The movable antennas are connected to the receiver with flexible cables. Extensive tests on the performance of these cables under different physical conditions are described. In order to achieve absolute calibration one of the horns will need to be disconnected from the receiver and replaced by a cryogenic load. This needs to be done reproducibly so a series of tests were done on different connector types. A custom thermometry system was designed for accurate temperature monitoring of the receiver, horns and cables is also described. Measurements of the properties of the horn antennas and polarisers are described. These include VNA measurement of S-parameters and beam patterns using a test range at Jodrell Bank Observatory. Finally, first-light measurements of the fully assembled telescope system are described. These include scans across the Sun to check beam-width and the detection of Galactic hydrogen 21cm emission.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorIan Browne (Supervisor), Peter Wilkinson (Supervisor) & Paddy Leahy (Supervisor)

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