The Removal of Artificially Generated Polarization in SHARP Maps

TL;DR

This paper addresses artificial polarization in SHARP maps caused by instrument misalignments and pointing drifts, proposing a correction algorithm that effectively reduces artificial signals in observational data.

Contribution

It introduces a correction algorithm for artificial polarization in SHARP data, validated through simulations and real observations, improving data accuracy.

Findings

The correction algorithm removes up to 60% of artificial polarization in tests.

Application to real data reduces polarization by approximately 0.15% and 0.03%.

Artificial polarization depends on source size and misalignment measurements.

Abstract

We characterize the problem of artificial polarization for the Submillimeter High Angular Resolution Polarimeter (SHARP) through the use of simulated data and observations made at the Caltech Submillimeter Observatory (CSO). These erroneous, artificial polarization signals are introduced into the data through misalignments in the bolometer sub-arrays plus pointing drifts present during the data-taking procedure. An algorithm is outlined here to address this problem and correct for it, provided that one can measure the degree of the sub-array misalignments and telescope pointing drifts. Tests involving simulated sources of Gaussian intensity profile indicate that the level of introduced artificial polarization is highly dependent upon the angular size of the source. Despite this, the correction algorithm is effective at removing up to 60% of the artificial polarization during these tests. The analysis of Jupiter data taken in January 2006 and February 2007 indicates a mean polarization of 1.44%+/-0.04% and 0.95%+/-0.09%, respectively. The application of the correction algorithm yields mean reductions in the polarization of approximately 0.15% and 0.03% for the 2006 and 2007 data sets, respectively.