A Michelson-type Radio Interferometer for University Education

TL;DR

This paper presents a simple, affordable radio interferometer designed for educational purposes, enabling students to learn interferometry by measuring the Sun's diameter using a low-cost setup at radio frequencies.

Contribution

It introduces a novel, practical radio interferometer model suitable for university labs, making interferometry accessible and hands-on for students.

Findings

Successfully measured the Sun's diameter in a classroom setting

Demonstrated the interferometer's capability with commercial satellite signals

Provided a practical educational tool for understanding radio interferometry

Abstract

We report development of a simple and affordable radio interferometer suitable as an educational laboratory experiment. With the increasing importance of interferometry in astronomy, the lack of educational interferometers is an obstacle to training the future generation of astronomers. This interferometer provides the hands-on experience needed to fully understand the basic concepts of interferometry. The design of this interferometer is based on the Michelson & Pease stellar optical interferometer, but operates at a radio wavelength (~11 GHz; ~2.7cm); thus the requirement for optical accuracy is much less stringent. We utilize a commercial broadcast satellite dish and feedhorn. Two flat side mirrors slide on a ladder, providing baseline coverage. This interferometer resolves and measures the diameter of the Sun, a nice daytime experiment which can be carried out even in marginal weather (i.e., partial cloud cover). Commercial broadcast satellites provide convenient point sources for comparison to the Sun's extended disk. We describe the mathematical background of the adding interferometer, the design and development of the telescope and receiver system, and measurements of the Sun. We present results from a students' laboratory report.