Low-frequency observations of the moon with the Murchison Widefield Array

Benjamin McKinley, Frank Briggs, David L Kaplan, Lincoln Greenhill, Gianni Bernardi, Judd D Bowman, Angelica de Oliveira-Costa, Steven John Tingay, Bryan Malcolm Gaensler, Divya Oberoi, Melanie Johnston-Hollitt, Wayne Arcus, David Graeme Barnes, John Bunton, Roger Cappallo, Brian E Corey, Avinash Deshpande, Ludovico deSouza, David Emrich, Robert F GoekeBryna J Hazelton, David Edwin Herne, Jacqueline N Hewitt, Justin C Kasper, Barton B Kincaid, Ronald Koenig, Eric Kratzenberg, Colin J Lonsdale, Mervyn John Lynch, Stephen Russell McWhirter, Daniel A Mitchell, Miguel F Morales, Edward H Morgan, Stephen M Ord, Joseph Pathikulangara, Thiagaraj Prabu, Ronald A Remillard, Alan E E Rogers, Anish A Roshi, Joseph E Salah, Robert John Sault, Natarajan Udaya-Shankar, K S Srivani, Jason A Stevens, Ravi Subrahmanyan, Randall B Wayth, Mark F Waterson, Rachel Lindsey Webster, Alan R Whitney, Andrew J Williams, Christopher L Williams, J Stuart B Wyithe

Research output: Contribution to journalArticleResearchpeer-review

20 Citations (Scopus)

Abstract

A new generation of low-frequency radio telescopes is seeking to observe the redshifted 21cm signal from the epoch of reionization (EoR), requiring innovative methods of calibration and imaging to overcome the difficulties of wide-field low-frequency radio interferometry. Precise calibration will be required to separate the expected small EoR signal from the strong foreground emission at the frequencies of interest between 80 and 300MHz. The Moon may be useful as a calibration source for detection of the EoR signature, as it should have a smooth and predictable thermal spectrum across the frequency band of interest. Initial observations of the Moon with the Murchison Widefield Array 32 tile prototype show that the Moon does exhibit a similar trend to that expected for a cool thermally emitting body in the observed frequency range, but that the spectrum is corrupted by reflected radio emission from Earth. In particular, there is an abrupt increase in the observed flux density of the Moon within the internationally recognized frequency modulated (FM) radio band. The observations have implications for future low-frequency surveys and EoR detection experiments that will need to take this reflected emission from the Moon into account. The results also allow us to estimate the equivalent isotropic power emitted by the Earth in the FM band and to determine how bright the Earth might appear at meter wavelengths to an observer beyond our own solar system.
Original languageEnglish
Article number23
Number of pages9
JournalThe Astrophysical Journal
Volume145
DOIs
Publication statusPublished - 2013
Externally publishedYes

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