Project: Lunar Occultation of the diffuse radio sky

What has the Moon got to do with observations of the early Universe? The answer lies in an interesting quirk of interferometry. Interferometers basically measure spatial fluctuations in the sky. They are insensitive to anything that is uniformly bright everywhere- like the global component of the 21-cm signal. However, I demonstrated in this project that an interferometer is sensitive to the ovvultation (eclispse) of a global signal by the Moon. I show that interferometers measure the brightness contrast between the background and the Moon. Since we know the lunar brightness to 1st order (230 Kelvin blackbody), we can now use the many desirable properties of interferometry (easy of calibration for instance) to measure the global 21-cm signal from the early Universe! While making the first lunar images at low frequencies, I also discovered a point-like emission at the center of the Moon. This turned out to be man-made interference (communication signals etc) reflected from the Moon! Thus, this project also provided estimates of how bright the Earth looks in the radio frequency part of the electromagnetic spectrum .... just in case aliens are looking for us!

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Lunar Eclipse