Exploring the Moon over HERA as a Source of Radio Frequency Interference
Abstract
The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer located in South Africa. This array seeks to detect the Epoch of Reionization, an event in the early Universe when the neutral intergalactic medium became ionized with the emergence of the first stars. This detection relies on extremely faint background radio signals, which are dwarfed by the strong foregrounds of local radio communications. The Moon is the closest celestial body to Earth. Its reflection of light, while helpful illuminating nightly darkness, has historically affected astronomical measurements as a bright foreground polluting the dark sky. HERA's location is helpful with this since the Moon rarely comes close to HERA's zenith at -30 degrees. However, the Moon's orbital plane oscillates relative to the ecliptic over a period of 18.6 years, resulting in a maximum declination of +/-28.5 degrees. This presents the issue of the Moon's flux density being detected by HERA as it approaches its zenith. Additionally, transmissions can be reflected by the Moon and be picked up by HERA. These can include Earth-Moon-Earth communications (EME), transmissions that use the Moon's reflective property to bounce signals back to Earth. This investigation approaches this problem by tracking the Moon's path along the sky and simulating radio communications using specifications for a traditional EME at 144MHz.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23334923D