Judd D. BowmanHubble Fellow, Caltech

Alan E. E. RogersHaystack Observatory

With support from:CSIRO/MRO and Curtin University

Thanks to:The organizers and Murray Lewis and the NSF

31 March 2010 RFI2010 Groningen

VHF-band RFI VHF-band RFI in Geographically Remote Areasin Geographically Remote Areas

Outline

• Experiment to Detect the Global EoR Signature (EDGES)• RFI at Murchison Radio-astronomy Observatory (MRO)• Quick surveys in the US

Rural New EnglandCatlow Valley, Oregon

• A few words on meteor scattering

Experiment to Detect the Global Epoch of Reionization Signature

(EDGES)

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

The approach for LOFAR, MWA, PAPER, SKA…

“Science with the MWA”Greenhill, Bowman, et al. (2010, in prep)

Figure by Matt McQuinn

The approach for EDGES

Pritchard & Loeb 2008

100 10 z [redshift]

50

0

-50

-100

Tb [

mK

]

21 cm global brightness temperature

5001005010

[MHz]

EDGES

EDGES

Bowman & Rogers (in prep)

Deep VHF-band integrations at the MRO

Murchison Radio-astronomy Observatory

Radio Frequency Interference (RFI)

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

Orbcomm LEO satellite constellation (136-138 MHz)

Total power in band vs. time

Sum antenna temperature 90-205 MHzOrbcomm band ~138 MHz

Anomalous propagation – DTV 7 and 9

EDGES Memo#058, AEER, 2010

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 monthsConservatively excise any channel that had RFI: 11% removal

Example excision rates

Shallow surveys in remote areas of the US

US TV and FM radio “pollution”

D1 Array – Haystack Obs.D1 Array – Haystack Obs.

West Forks, Maine

Rural New England, US

D1 Array – Haystack Obs. West Forks, Maine

EDGES Memo#044, AEER, 2009

US TV and FM radio “pollution”

Catlow Valley, Oregon, US60 dB

10 dB 80 MHz 200

EDGES Memo#052, AEER, JDB, 2009

Meteor scattering

Time-variable FM RFI

FM band

Meteor scatter rates vs. elevation angle

EDGES Memo#054, AEER, 2009

horizon

zenith

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

Aircraft at MRO

FM at MRO

RFI observed in Oregon, US

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