# Correlation plots of the Siberian radioheliograph

## TL;DR

This paper discusses the upgrade of the Siberian Solar Radio Telescope to a radioheliograph, focusing on correlation plots and their relation to spatial spectra for imaging solar radio sources.

## Contribution

It introduces the analysis of correlation plots in the Siberian Radioheliograph and relates covariance of signals to spatial frequency spectra in radio imaging.

## Key findings

- Correlation of signals relates to spatial frequency spectra.
- Correlation plots are sums of complex correlations for antenna pairs.
- Covariance up to Van Vleck correction is a correlation coefficient.

## Abstract

The Siberian Solar Radio Telescope is now being upgraded. The upgrading is aimed at providing the aperture synthesis imaging in the 4-8 GHz frequency range, instead of the single-frequency direct imaging due to the Earth rotation. The first phase of the upgrading is a 48-antenna array - the Siberian Radioheliograph. One type of radioheliograph data represents correlation plots. In evaluating the covariance of two-level signals, these plots are sums of complex correlations, obtained for different antenna pairs. Bearing in mind that correlation of signals from an antenna pair is related to a spatial frequency, we can say that each value of the plot is an integral over a spatial spectrum. Limits of the integration are defined by the task. Only high spatial frequencies are integrated to obtain dynamics of compact sources. The whole spectrum is integrated to reach maximum sensitivity. We show that the covariance of two-level variables up to Van Vleck correction is a correlation coefficient of these variables.