The LOFAR radio environment

Aims. This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods. We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz wi...

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Main Authors:	Offringa, A., De Bruyn, A., Zaroubi, S., Van Diepen, G., Martinez-Ruby, O., Labropoulos, P., Brentjens, M., Ciardi, B., Daiboo, S., Harker, G., Jelic, V., Kazemi, S., Koopmans, L., Mellema, G., Pandey, V., Pizzo, R., Schaye, J., Vedantham, H., Veligatla, V., Wijnholds, S., Yatawatta, S., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, M., Beck, R., Bell, M., Bentum, M., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H., Conway, J., De Vos, M., Dettmar, R., Eisloeffel, J., Falcke, H., Fender, R., Frieswijk, W., Gerbers, M., Griessmeier, J., Gunst, A., Hassall, T., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., Karastergiou, A., Kondratiev, V., Koopman, Y., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McKean, J., Meulman, H., Mevius, M., Mol, J., Nijboer, R., Noordam, J., Norden, M., Paas, H., Pandey, M., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., Röttgering, H., Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, Charlotte, Stappers, B., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Van Ardenne, A., Van Cappellen, W., Van Duin, A.
Format:	Journal Article
Published:	EDP Sciences 2012
Online Access:	http://hdl.handle.net/20.500.11937/52548

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author	Offringa, A. De Bruyn, A. Zaroubi, S. Van Diepen, G. Martinez-Ruby, O. Labropoulos, P. Brentjens, M. Ciardi, B. Daiboo, S. Harker, G. Jelic, V. Kazemi, S. Koopmans, L. Mellema, G. Pandey, V. Pizzo, R. Schaye, J. Vedantham, H. Veligatla, V. Wijnholds, S. Yatawatta, S. Zarka, P. Alexov, A. Anderson, J. Asgekar, A. Avruch, M. Beck, R. Bell, M. Bell, M. Bentum, M. Bernardi, G. Best, P. Birzan, L. Bonafede, A. Breitling, F. Broderick, J. Brüggen, M. Butcher, H. Conway, J. De Vos, M. Dettmar, R. Eisloeffel, J. Falcke, H. Fender, R. Frieswijk, W. Gerbers, M. Griessmeier, J. Gunst, A. Hassall, T. Heald, G. Hessels, J. Hoeft, M. Horneffer, A. Karastergiou, A. Kondratiev, V. Koopman, Y. Kuniyoshi, M. Kuper, G. Maat, P. Mann, G. McKean, J. Meulman, H. Mevius, M. Mol, J. Nijboer, R. Noordam, J. Norden, M. Paas, H. Pandey, M. Pizzo, R. Polatidis, A. Rafferty, D. Rawlings, S. Reich, W. Röttgering, H. Schoenmakers, A. Sluman, J. Smirnov, O. Sobey, Charlotte Stappers, B. Steinmetz, M. Swinbank, J. Tagger, M. Tang, Y. Tasse, C. Van Ardenne, A. Van Cappellen, W. Van Duin, A.
author_facet	Offringa, A. De Bruyn, A. Zaroubi, S. Van Diepen, G. Martinez-Ruby, O. Labropoulos, P. Brentjens, M. Ciardi, B. Daiboo, S. Harker, G. Jelic, V. Kazemi, S. Koopmans, L. Mellema, G. Pandey, V. Pizzo, R. Schaye, J. Vedantham, H. Veligatla, V. Wijnholds, S. Yatawatta, S. Zarka, P. Alexov, A. Anderson, J. Asgekar, A. Avruch, M. Beck, R. Bell, M. Bell, M. Bentum, M. Bernardi, G. Best, P. Birzan, L. Bonafede, A. Breitling, F. Broderick, J. Brüggen, M. Butcher, H. Conway, J. De Vos, M. Dettmar, R. Eisloeffel, J. Falcke, H. Fender, R. Frieswijk, W. Gerbers, M. Griessmeier, J. Gunst, A. Hassall, T. Heald, G. Hessels, J. Hoeft, M. Horneffer, A. Karastergiou, A. Kondratiev, V. Koopman, Y. Kuniyoshi, M. Kuper, G. Maat, P. Mann, G. McKean, J. Meulman, H. Mevius, M. Mol, J. Nijboer, R. Noordam, J. Norden, M. Paas, H. Pandey, M. Pizzo, R. Polatidis, A. Rafferty, D. Rawlings, S. Reich, W. Röttgering, H. Schoenmakers, A. Sluman, J. Smirnov, O. Sobey, Charlotte Stappers, B. Steinmetz, M. Swinbank, J. Tagger, M. Tang, Y. Tasse, C. Van Ardenne, A. Van Cappellen, W. Van Duin, A.
author_sort	Offringa, A.
building	Curtin Institutional Repository
collection	Online Access
description	Aims. This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods. We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz/1 s resolution. Results. We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions. Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills. © 2012 ESO.
first_indexed	2025-11-14T09:52:10Z
format	Journal Article
id	curtin-20.500.11937-52548
institution	Curtin University Malaysia
institution_category	Local University
last_indexed	2025-11-14T09:52:10Z
publishDate	2012
publisher	EDP Sciences
recordtype	eprints
repository_type	Digital Repository
spelling	curtin-20.500.11937-525482017-09-13T15:39:23Z The LOFAR radio environment Offringa, A. De Bruyn, A. Zaroubi, S. Van Diepen, G. Martinez-Ruby, O. Labropoulos, P. Brentjens, M. Ciardi, B. Daiboo, S. Harker, G. Jelic, V. Kazemi, S. Koopmans, L. Mellema, G. Pandey, V. Pizzo, R. Schaye, J. Vedantham, H. Veligatla, V. Wijnholds, S. Yatawatta, S. Zarka, P. Alexov, A. Anderson, J. Asgekar, A. Avruch, M. Beck, R. Bell, M. Bell, M. Bentum, M. Bernardi, G. Best, P. Birzan, L. Bonafede, A. Breitling, F. Broderick, J. Brüggen, M. Butcher, H. Conway, J. De Vos, M. Dettmar, R. Eisloeffel, J. Falcke, H. Fender, R. Frieswijk, W. Gerbers, M. Griessmeier, J. Gunst, A. Hassall, T. Heald, G. Hessels, J. Hoeft, M. Horneffer, A. Karastergiou, A. Kondratiev, V. Koopman, Y. Kuniyoshi, M. Kuper, G. Maat, P. Mann, G. McKean, J. Meulman, H. Mevius, M. Mol, J. Nijboer, R. Noordam, J. Norden, M. Paas, H. Pandey, M. Pizzo, R. Polatidis, A. Rafferty, D. Rawlings, S. Reich, W. Röttgering, H. Schoenmakers, A. Sluman, J. Smirnov, O. Sobey, Charlotte Stappers, B. Steinmetz, M. Swinbank, J. Tagger, M. Tang, Y. Tasse, C. Van Ardenne, A. Van Cappellen, W. Van Duin, A. Aims. This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods. We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz/1 s resolution. Results. We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions. Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills. © 2012 ESO. 2012 Journal Article http://hdl.handle.net/20.500.11937/52548 10.1051/0004-6361/201220293 EDP Sciences unknown
spellingShingle	Offringa, A. De Bruyn, A. Zaroubi, S. Van Diepen, G. Martinez-Ruby, O. Labropoulos, P. Brentjens, M. Ciardi, B. Daiboo, S. Harker, G. Jelic, V. Kazemi, S. Koopmans, L. Mellema, G. Pandey, V. Pizzo, R. Schaye, J. Vedantham, H. Veligatla, V. Wijnholds, S. Yatawatta, S. Zarka, P. Alexov, A. Anderson, J. Asgekar, A. Avruch, M. Beck, R. Bell, M. Bell, M. Bentum, M. Bernardi, G. Best, P. Birzan, L. Bonafede, A. Breitling, F. Broderick, J. Brüggen, M. Butcher, H. Conway, J. De Vos, M. Dettmar, R. Eisloeffel, J. Falcke, H. Fender, R. Frieswijk, W. Gerbers, M. Griessmeier, J. Gunst, A. Hassall, T. Heald, G. Hessels, J. Hoeft, M. Horneffer, A. Karastergiou, A. Kondratiev, V. Koopman, Y. Kuniyoshi, M. Kuper, G. Maat, P. Mann, G. McKean, J. Meulman, H. Mevius, M. Mol, J. Nijboer, R. Noordam, J. Norden, M. Paas, H. Pandey, M. Pizzo, R. Polatidis, A. Rafferty, D. Rawlings, S. Reich, W. Röttgering, H. Schoenmakers, A. Sluman, J. Smirnov, O. Sobey, Charlotte Stappers, B. Steinmetz, M. Swinbank, J. Tagger, M. Tang, Y. Tasse, C. Van Ardenne, A. Van Cappellen, W. Van Duin, A. The LOFAR radio environment
title	The LOFAR radio environment
title_full	The LOFAR radio environment
title_fullStr	The LOFAR radio environment
title_full_unstemmed	The LOFAR radio environment
title_short	The LOFAR radio environment
title_sort	lofar radio environment
url	http://hdl.handle.net/20.500.11937/52548

The LOFAR radio environment

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