Analysis and Optimization of the AUT 30-metre Radio Telescope: Pointing and Surface
Rasha, Asif Rayhan
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The purpose of this research is to analyze, evaluate and improve the current pointing performance of AUT’s 30-metre radio telescope. The telescope currently uses the "fivept" pointing procedure of the NASA Field System (used for scheduling and operation of the 30-metre) to collect pointing offsets. “pdplt”, another pro- gram in the Field System, is used to process, generate and apply a pointing model to correct for errors in pointing. The Field System pointing model allows up to 30 terms to account for various pointing errors, of which 8 terms are currently being used. Previous research had identified a sinusoidal pattern in the residual pointing offsets that significantly reduces pointing accuracy . We develop an alternative pointing methodology that significantly improves the pointing accuracy by (a) applying a source selection method, (b) applying an outlier removal procedure and (c) using additional terms to remove the sinusoidal pattern. The “fivept” pointing procedure is used to build the pointing database. A script written in Bash is used to preprocess the offsets and the R programming language is used to process, analyze and evaluate new pointing models. Three new terms are added to the existing model that effectively suppress the sinusoidal pattern. The end result improves the pointing accuracy significantly, with the RF axis being able to point within an error ellipse that is smaller than 10% of the FWHM. We speculate about possible reasons for the origin of the sinusoidal pattern of the pointing offsets. A major speculation was gravitational deformation in Elevation of the primary reflector surface. We use the laser scanning method to study the surface of the primary reflector. A FARO Laser scanner is used for collecting data. SCENE, an industry standard program and Matlab are used for processing and analyzing the data. We conclude that the main reflector has a good quality of surface with rms of ∼ 3 mm, and does not demonstrate any noticeable gravitational deformation when studied at different Elevation angles.