Measuring Tianlai's primary beam using sky model

TL;DR

This paper measures the Tianlai Cylinder Pathfinder Array's primary beam pattern by exploiting the Sun's motion, decomposing the beam into E-W and N-S components, and validating results with sky models.

Contribution

It introduces a method to measure and decompose the primary beam of a drift-scan radio telescope using solar observations and sky modeling.

Findings

Beam pattern is factorizable into E-W and N-S components.

E-W beam profiles are obtained at various elevations.

Results align with previous expectations.

Abstract

We present the beam pattern measurement of the Tianlai Cylinder Pathfinder Array. As it is a pure drift-scan instrument, we exploit the North-South motion of the Sun to demonstrate that the primary beam is factorizable. Leveraging this property, we decompose the primary beam into independent East-West (E-W) and North-South (N-S) components. Using the Sun as a calibration source, we obtain the E-W beam profiles at various elevations, applying normalization to eliminate the effects of solar activity. Subsequently, we simulate the observed signals using a sky map model to derive the best-fit N-S beam. The results of this work are consistent with previous expectations.