Abstract

We report development of a simple and affordable radio interferometer suitable as an educational laboratory experiment. The design of this interferometer is based on the Michelson and Pease stellar optical interferometer, but instead operates at the radio wavelength of ∼11 GHz (∼2.7 cm), requiring much less stringent optical accuracy in its design and use. We utilize a commercial broadcast satellite dish and feedhorn with two flat side mirrors that slide on a ladder, providing baseline coverage. This interferometer can resolve and measure the diameter of the Sun, even on a day with marginal weather. Commercial broadcast satellites provide convenient point sources for comparison to the Sun's extended disk. The mathematical background of an adding interferometer is presented, as is its design and development, including the receiver system, and sample measurements of the Sun. Results from a student laboratory report are shown. 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.

Highlights

  • The future of radio astronomy relies strongly on interferometers (e.g., ALMA, VLA, VLTI, aperture masking techniques).1–3 From our experience at interferometer summer schools at the Nobeyama Radio Observatory4 and at the CARMA Observatory,5 we are convinced that hands-on experiments are critical to a full understanding of the concepts of interferometry

  • The design of this interferometer is based on the Michelson and Pease stellar optical interferometer, but instead operates at the radio wavelength of $11 GHz ($2.7 cm), requiring much less stringent optical accuracy in its design and use

  • With the increasing importance of interferometry in astronomy, the lack of educational interferometers is an obstacle to training the future generation of astronomers

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Summary

A Michelson-type radio interferometer for university education

We utilize a commercial broadcast satellite dish and feedhorn with two flat side mirrors that slide on a ladder, providing baseline coverage. This interferometer can resolve and measure the diameter of the Sun, even on a day with marginal weather. 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.

INTRODUCTION
MATHEMATICAL BACKGROUND
Geometric delay
Total power
Point source
Extended source and visibility
Visibility measurements and sun’s diameter
Receiver system
SETUP AND MEASUREMENTS
75-50 Ohm Adaptor
Measurements
RESULTS
Miscellaneous
Full Text
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