VHF-band RFI in Geographically Remote Areas

1. VHF-band RFI in Geographically Remote Areas Judd D. BowmanHubble Fellow, CaltechAlan E. E. RogersHaystack Observatory With support from: CSIRO/MRO and Curtin University Thanks to: The organizers and Murray Lewis and the NSF31 March 2010 RFI2010 Groningen

2. Outline • Experiment to Detect the Global EoR Signature (EDGES) • RFI at Murchison Radio-astronomy Observatory (MRO) • Quick surveys in the US Rural New England Catlow Valley, Oregon • A few words on meteor scattering

3. Experiment to Detect the Global Epoch of Reionization Signature (EDGES)

4. Exotic Telescopes Prepare to Probe Era of First Stars and Galaxies Science, Vol. 325. no. 5948, pp. 1617 – 1619, 25 September 2009

5. The approach for LOFAR, MWA, PAPER, SKA… “Science with the MWA” Greenhill, Bowman, et al. (2010, in prep) Figure by Matt McQuinn

6. The approach for EDGES  [MHz] 10 50 100 500 50 0 -50 -100 Tb [mK] 21 cm global brightness temperature 100 10 z [redshift] Pritchard & Loeb 2008

7. EDGES

8. EDGES Bowman & Rogers (in prep)

10. Deep VHF-band integrations at the MRO

11. Murchison Radio-astronomy Observatory

12. Radio Frequency Interference (RFI)

13. Integrated spectrum at MRO by EDGES Murchison Radio-Astronomy Observatory (MRO) Aug 20 – Oct 20, 2009 1440 wall-clock hours on sky ~50 hours actual integration +15 dB +40 dB

14. Orbcomm LEO satellite constellation (136-138 MHz)

15. Total power in band vs. time Sum antenna temperature 90-205 MHz Orbcomm band ~138 MHz

17. Anomalous propagation – DTV 7 and 9 EDGES Memo#058, AEER, 2010

18. Integrated RFI(time excision only – by broadband power level in FM, Orbcomm, DTV bands: 30% removal) Note: shows every channel that ever had RFI over 3 months Conservatively excise any channel that had RFI: 11% removal

19. Example excision rates

20. Shallow surveys in remote areas of the US

21. US TV and FM radio “pollution” West Forks, Maine D1 Array – Haystack Obs.

22. Rural New England, US D1 Array – Haystack Obs. West Forks, Maine EDGES Memo#044, AEER, 2009

23. US TV and FM radio “pollution”

25. Catlow Valley, Oregon, US EDGES Memo#052, AEER, JDB, 2009 60 dB 80 MHz 200 10 dB

26. Meteor scattering

27. Time-variable FM RFI FM band

28. Meteor scatter rates vs. elevation angle horizon zenith EDGES Memo#054, AEER, 2009

29. Summary • 3 month deployment in MRO • Deepest broadband spectrum ever acquired: 5 mK rms (-220 dBW/m2/Hz) • First redshifted 21 cm EoR science • Simple time and spectral flagging sufficient to remove RFI • FM band a good indicator of anomalous transmission events • Total power in band varies strongly with Orbcomm and aircraft • Quiet sites in US – not as good as MRO • Meteor scatter a significant source of RFI, dependent on elevation angle of sky coverage

30. Aircraft at MRO

31. FM at MRO

32. RFI observed in Oregon, US

33. Summary • 3 month deployment in MRO • Deepest broadband spectrum ever acquired: 5 mK rms (-220 dBW/m2/Hz) • First redshifted 21 cm EoR science • Simple time and spectral flagging sufficient to remove RFI • FM band a good indicator of anomalous transmission events • Total power in band varies strongly with Orbcomm and aircraft • Quiet sites in US – not as good as MRO • Meteor scatter a significant source of RFI, dependent on elevation angle of sky coverage