Commissioning and Data-Handling for the L-BASS Instrument

Abstract

In this thesis I describe the development and outputs of a data handling and analysis program for L-BASS (L-Band All-Sky Survey). L-BASS is a twin horn, pseudo-correlation instrument with a digital back end, generating simultaneous time streams of radiometer data proportional to the signal detected by each horn. Initially creating maps of the sky differenced to the NCP (North Celestial Pole), this design will ultimately allow for the production of absolutely calibrated, low resolution observations of the northern sky at 1.4 GHz. L-BASS outputs will provide a high quality reference which other higher res- olution surveys can use to enhance their temperature calibration. It will also support (or otherwise) the controversial results from the ARCADE2 measurement of excess radio brightness at 3 GHz. The software developed, named L-BASS.DH, uploads multiple data sets, including radiometer data output from a digital spectrometer, instrument temperature data and meteorological data. Time streams of these data are variously processed and used to eval- uate attenuation in the atmosphere, and attenuation and gain effects in the signal paths through the L-BASS instrument. In particular, a model of the signal path and attenua- tion effects in the passive components prior to amplification is coded and incorporated into L-BASS.DH. This functionality allows gain changes and the additional radiometric contribution from passive components to L-BASS measurements to be predicted for each minute of data taking. A suite of analysis tools offered by L-BASS.DH has proven invaluable during the com- missioning of the L-BASS instrument. This includes the characterisation of temperature- dependent gain effects in several crucial components. Using L-BASS.DH, unanticipated instances of microphonics were detected in the receiver. Microphonic events are shown not to affect the total power measurements on the bandpass, however the short timescale gain variations within individual frequency bins pose a challenge to L-BASS calibration processes.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Paddy Leahy (Supervisor) & Clive Dickinson (Supervisor)