Platform Deformation Phase Correction for the AMiBA-13 Co-planar Interferometer

TL;DR

This paper introduces a new method to correct platform deformation in co-planar interferometers, significantly improving image quality and flux recovery in the AMiBA-13 array by modeling and compensating for deformation-induced phase errors.

Contribution

The paper develops a platform deformation correction model based on photogrammetry and optical pointing data, applicable to co-planar and single dish telescopes, enhancing phase accuracy and imaging performance.

Findings

Recovered 50-70% of flux loss after phase correction.

Restored over 90% of source flux with the correction method.

Applicable to other telescopes with deformation issues.

Abstract

We present a new way to solve the platform deformation problem of co-planar interferometers. The platform of a co-planar interferometer can be deformed due to driving forces and gravity. A deformed platform will induce extra components into the geometric delay of each baseline, and change the phases of observed visibilities. The reconstructed images will also be diluted due to the errors of the phases. The platform deformations of The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) were modelled based on photogrammetry data with about 20 mount pointing positions. We then used the differential optical pointing error between two optical telescopes to fit the model parameters in the entire horizontal coordinate space. With the platform deformation model, we can predict the errors of the geometric phase delays due to platform deformation with given azimuth and elevation of the targets and calibrators. After correcting the phases of the radio point sources in the AMiBA interferometric data, we recover 50% - 70% flux loss due to phase errors. This allows us to restore more than 90% of a source flux. The method outlined in this work is not only applicable to the correction of deformation for other co-planar telescopes but also to single dish telescopes with deformation problems. This work also forms the basis of the upcoming science results of AMiBA-13.