Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz

H K Vedantham, L V E Koopmans, A G de Bruyn, S J Wijnholds, M Brentjens, F B Abdalla, K M B Asad, G Bernardi, S Bus, E Chapman, B Ciardi, S Daiboo, E R Fernandez, A Ghosh, G Harker, V Jelic, H Jensen, S Kazemi, P Lambropoulos, O Martinez-RubiG Mellema, M Mevius, A R Offringa, V N Pandey, A H Patil, R M Thomas, V Veligatla, S Yatawatta, S Zaroubi, J Anderson, A Asgekar, M E Bell, M J Bentum, P Best, A Bonafede, F Breitling, J Broderick, M Brüggen, H R Butcher, A Corstanje, F de Gasperin, E de Geus, A Deller, S Duscha, J Eislöffel, D Engels, H Falcke, R A Fallows, R Fender, C Ferrari, W Frieswijk, Michael Garrett, J Grießmeier, A W Gunst, T E Hassall, G Heald, M Hoeft, J Hörandel, M Iacobelli, E Juette, V I Kondratiev, M Kuniyoshi, G Kuper, G Mann, S Markoff, R McFadden, D McKay-Bukowski, J P McKean, D D Mulcahy, H Munk, A Nelles, M J Norden, E Orru, M Pandey-Pommier, R Pizzo, A G Polatidis, W Reich, A Renting, H Röttgering, D Schwarz, A Shulevski, O Smirnov, B W Stappers, M Steinmetz, J Swinbank, M Tagger, Y Tang, C Tasse, S ter Veen, S Thoudam, C Toribio, C Vocks, M W Wise, O Wucknitz, P Zarka

    Research output: Contribution to journalArticlepeer-review

    92 Downloads (Pure)


    We present radio observations of the Moon between 35 and 80 MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies 35 <ν <80 MHz since it is `colder' than the diffuse Galactic background it occults, (ii) using the (negative) flux of the lunar disc, we can reconstruct the spectrum of the diffuse Galactic emission with the lunar thermal emission as a reference, and (iii) that reflected RFI (radio-frequency interference) is concentrated at the centre of the lunar disc due to specular nature of reflection, and can be independently measured. Our RFI measurements show that (i) Moon-based Cosmic Dawn experiments must design for an Earth-isolation of better than 80 dB to achieve an RFI temperature 2 at 800 km height, or 15 m2 at 400 km height. Currently, our diffuse background spectrum is limited by sidelobe confusion on short baselines (10-15 per cent level). Further refinement of our technique may yield constraints on the redshifted global 21 cm signal from Cosmic Dawn (40 > z > 12) and the Epoch of Reionization (12 > z > 5).
    Original languageEnglish
    Pages (from-to)2291-2305
    Number of pages15
    JournalMonthly Notices of the Royal Astronomical Society
    Publication statusPublished - 2015


    • methods: observational
    • techniques: interferometric
    • Moon
    • dark ages
    • reionization
    • first stars


    Dive into the research topics of 'Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz'. Together they form a unique fingerprint.

    Cite this