≡ Menu

Low Frequency Musings on Extraterrestrial Life

When it comes to SETI investigations, the Low Frequency Array (LOFAR) being built in Europe offers intriguing possibilities. With a plan to encompass roughly 25,000 small antennae, arranged in clusters spread out over an area 350 kilometers in diameter, LOFAR may prove sensitive enough to detect the radiation leakage of transmitters in the radio and television bands from extraterrestrial civilizations. The array will operate between 10 and 240 MHz. When completed, it will offer not only myriad astronomical possibilities but SETI opportunities with a difference.

Michael Garrett (Leiden University) is general director of ASTRON, the Netherlands Institute for Radio Astronomy, now involved in building the new array. Garrett makes note of what’s possible if LOFAR’s formidable resources are turned to SETI:

“LOFAR can extend the search for extra-terrestrial intelligence to an entirely unexplored part of the low-frequency radio spectrum, an area that is heavily used for civil and military communications here on Earth. In addition, LOFAR can survey large areas of the sky simultaneously – an important advantage if SETI signals are rare or transient in nature.”

This story has a particular resonance for me. Back in the 1970’s, I put together a shortwave listening post that had it all — three receivers, including radioteletype capability, and all sorts of filters and peripheral equipment. I loved DXing the tropical bands, my specialty, looking for faint Indonesian local stations that would drift into the eastern US usually around sunrise for their brief window of receivability. In the evenings, I would hunt unusual, low-power South American stations, including the holy grail for shortwave listeners, the Falkland Islands, a fabulous catch that only a few old hands had made (I never did log the Falklands).

Even harder to get was Tristan da Cunha — I knew of no one other than a few South African DXers who could lay claim to that one. It occurred to me one night as I was logging a new station in my book that the right kind of equipment might catch a signal from another star. Back then, knowing little about these matters, I just assumed that signal would be a radio or TV signal, and that we would be listening in to the traffic of a civilization not so different from our own. I pondered what kind of antenna it would take, and wrote a speculative piece called ‘Where the Real DX Is’ for Glenn Hauser’s Review of International Broadcasting.

LOFAR’s frequency range covers areas I used to scan, but no one today is as naive as I was about expecting other civilizations to be like ours. But whatever we find, a SETI attempt via LOFAR is worth doing. Sure, nearby civilizations would be unlikely to be at the same level of electromagnetic development — radio and TV — that we are. On the other hand, it seems reasonable to search broadly through the spectrum in case we’re missing something obvious. It’s not as if SETI is LOFAR’s raison d’etre, but making researchers aware of SETI possibilities is only common sense.

Symbolic view of LOFAR

So what is LOFAR about? The plan is to survey the universe with higher resolution and sensitivity than any previous surveys at these wavelengths, mapping everything from the reionization of hydrogen in the early universe to the formation of galaxies and the clusters that house them. Throw in the distribution of cosmic rays, the study of pulsars and transient events of all descriptions and you have an observatory that deepens our understanding in these frequency ranges and is certain to make serendipitous discoveries.

Image: A typical galaxy like the Milky Way contains as many stars as there are grains of sand on all the worlds beaches. Most of these stars have planetary systems and many will have the right conditions for life to flourish. LOFAR can potentially search for artificial radio signals from intelligent civilizations in nearby stellar systems. Credit: LOFAR.

Serendipity as in the discovery of ETI? LOFAR’s SETI potential has been under discussion in the Netherlands this past week at a workshop held in Dwingeloo. With stations spread throughout northern Europe, the observatory will be inspiring various SETI observing proposals as the project’s Phase I progresses to full capability. Prepare for the unexpected, even if it’s not the signature of an extraterrestrial transmitter. Every time we push into higher-resolution instrumentation or look at the universe in less studied wavelengths, something unusual tends to happen. Who knows what LOFAR’s version of gamma-ray bursts may turn out to be?

Comments on this entry are closed.

  • James Brown June 11, 2008, 20:27

    I wish the LOFAR folks well but I can’t for the life of me envision how it would work. Even a casual spin over the low frequency bands produces so many birds, harmonics, spurs, bleeps bloops and blops that sorting them all out will be a real test of computing power.

    It will make the junk I hear in the waterhole tame by comparision

  • Ron S June 12, 2008, 0:05

    Paul, many moons ago you posted the paper by Loeb where he proposes just this sort of search (the one that Shostak panned). Any news as to whether that proposal has progressed, or perhaps that it quietly died? I wonder if they’ll only talk about the SETI possibilities of LOFAR rather than spend the time/money on it.

    And per another discussion a bit more recently, there would be a better chance for success at the high end of the frequency range.

  • Administrator June 12, 2008, 8:31

    Right you are, Ron. That paper is “Eavesdropping on Radio Broadcasts from Galactic Civilizations with Upcoming Observatories for Redshifted 21cm Radiation,” available here:


    Loeb has a grant to look for extraterrestrial transmissions in more or less the same frequency range as LOFAR is talking about. He wants to use the Murchison Widefield Array (formerly Mileura), but the array is still in development, and has in fact shifted its location slightly to move to a quieter radio environment. I share James Brown’s concern over harmonics, spurs and all the rest, and it’s obviously a major concern here. To my knowledge, the MWA couldn’t start work on anything like Loeb’s project until 2010, but if anyone has anything different on that, please post here.

  • dad2059 June 12, 2008, 12:47

    While it makes sense not to over-look the obvious at times, I see where this system could be prone to ‘false positives’ unless some sophisticated filtering out algorithm is employed.

    I see the chances of actually catching ET low-band TV signals about zero, but you never know when a “Wow! I could’ve had a V8 moment!” might occur!

  • Ron S June 12, 2008, 19:59

    Loeb, and for that matter a lot of astronomical and spacecraft reception, uses long integration times, so that transient stuff tends to gets filtered out naturally. Unfortunately that also can filter out a lot of signals since there is inevitable frequency drift, far in excess of typical receiver bandwidth, due to planetary and orbital motion (both the source and us). I alluded to this in a comment some time ago when I provided a calculation on interstellar path loss of a TV carrier.

    Regardless, the folks doing this sort of work are intimately familiar with unwanted noise and signals, intermittent and other varieties. Dealing with it is routine.

  • ljk June 27, 2008, 11:16

    Cluster listens to the sounds of Earth

    The first thing an alien race is likely to hear from Earth is chirps
    and whistles, a bit like R2-D2, the robot from Star Wars. In reality,
    they are the sounds that accompany the aurora.

    Now ESA’s Cluster mission is showing scientists how to understand
    this emission and, in the future, search for alien worlds by listening
    for their sounds.

    More at:


  • ljk November 6, 2008, 0:57

    F.C.C. to Open Radio Spectrum

    New York Times Nov. 4, 2008


    The FCC has approved unlicensed
    wireless devices that operate in the
    empty “white space” between TV
    channels, opening up the possibility
    of low-cost, high-speed Internet
    access and new wireless devices,
    such as mobile broadband access in
    rural locations….


  • ljk February 4, 2009, 11:21

    Science with a lunar low-frequency array: from the dark ages of the Universe to nearby exoplanets

    Authors: Sebastian Jester (MPIA Heidelberg), Heino Falcke (ASTRON / Radboud Universiteit Nijmegen)

    (Submitted on 3 Feb 2009)

    Abstract: Low-frequency radio astronomy is limited by severe ionospheric distortions below 50 MHz and complete reflection of radio waves below 10-30 MHz. Shielding of man-made interference from long-range radio broadcasts, strong natural radio emission from the Earth’s aurora, and the need for setting up a large distributed antenna array make the lunar far side a supreme location for a low-frequency radio array.

    A number of new scientific drivers for such an array, such as the study of the dark ages and epoch of reionization, exoplanets, and ultra-high energy cosmic rays, have emerged and need to be studied in greater detail.

    Here we review the scientific potential and requirements of these and other new scientific drivers and discuss the constraints for various lunar surface arrays. In particular we describe observability constraints imposed by the interstellar and interplanetary medium, calculate the achievable resolution, sensitivity, and confusion limit of a dipole array using general scaling laws, and apply them to various scientific questions.

    Whichever science is deemed most important, pathfinder arrays are needed to test the feasibility of these experiments in the not too distant future. Lunar low-frequency arrays are thus a timely option to consider, offering the potential for significant new insights into a wide range of today’s crucial scientific topics. This would open up one of the last unexplored frequency domains in the electromagnetic spectrum.

    Comments: 36 pages, many figures, accepted for publication by New Astronomy Reviews

    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Earth and Planetary Astrophysics (astro-ph.EP); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)

    Cite as: arXiv:0902.0493v1 [astro-ph.CO]

    Submission history

    From: Sebastian Jester [view email]

    [v1] Tue, 3 Feb 2009 12:44:58 GMT (499kb)


  • ljk September 19, 2009, 21:22

    Building LOFAR – status update

    Authors: M.A. Garrett (1,2,3) ((1) ASTRON – Netherland Institute for Radio Astronomy, (2) Sterrewacht Leiden, Leiden University, NL, (3) Centre for Astrophysics and Supercomputing, University of Swinburne, Australia)

    (Submitted on 17 Sep 2009)

    Abstract: The Low Frequency Array (LOFAR) is a new generation of electronic radio telescope based on aperture array technology and working in the frequency range of 30-240 MHz. The telescope is being developed by ASTRON, and currently being rolled-out across the Netherlands and other countries in Europe.

    The plan is to build at least 36 stations in the Netherlands (with baseline lengths of up to 100 km), 5 stations in Germany, and 1 station in each of Sweden, France and the UK. With baseline lengths of up to 2000 km, sub-arcsecond resolution will be possible at the highest frequencies. The Key Science Projects being addressed by the project include: deep, wide-field cosmological surveys, transients, the epoch of re-ionisation and cosmic ray studies.

    We present the current status of the project, including the development of the super-core in Exloo and the completion of the first 3 stations. ‘First fringes’ from these stations is also presented.

    Comments: 6 pages, invited review presented at “Science and Technology of Long Baseline Real-Time Interferometry: The 8th International e-VLBI Workshop – EXPReS09” Madrid, Spain June 22-26, 2009. To be published in Proceedings of Science (PoS)

    Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

    Cite as: arXiv:0909.3147v1 [astro-ph.IM]

    Submission history

    From: Mike Garrett [view email]

    [v1] Thu, 17 Sep 2009 06:11:00 GMT (3441kb)


  • ljk June 3, 2011, 8:12

    LOFAR So Far… Digging Deep Into Our Universe

    by Tammy Plotner on June 2, 2011

    A very small part of the raw LOFAR image of the field centered on the bright quasar 3C196. It shows tens of discrete sources, the faintest having a flux density of only a few mJy at 150 MHz.The image has an angular resolution of 8 arcseconds. The image still needs to be deconvolved. The data was processed by Dr. Panos Labropoulos on the EoR-cluster at the University of Groningen.

    The International LOFAR telescope is a Pan-European collaborative project led by ASTRON Netherlands Institute for Radio Astronomy. The radio telescope integrates thousands of simple dipole receivers with effective digital signal processing and high-performance computing. LOFAR can rapidly take in wide areas of the sky, aiming in multiple directions simultaneously. It also utilizes unexplored low frequencies, around around 150 MHz, which allows astronomers new insights. What has LOFAR done so far? Try capturing faint radio sources never revealed before.

    An international team led by astronomers at ASTRON and the Kapteyn Institute of the University of Groningen have used the LOFAR telescope, designed and constructed by ASTRON, to make the deepest wide-field images of the sky to date. At the conference, the trouble of dealing with foreground noise was the topic – foreground noise that makes it nearly impossible to get a good radio view of the distant Universe.

    What researchers are looking for is the Epoch of Reionization (EoR) – a time which is postulated to have occurred in the period between about 400 and 800 million years after the Big Bang. Says the team, “During the EoR the neutral hydrogen was slowly disappearing, probably as a result of the strong ‘ionizing’ power of the first stars and quasars. Detecting the EoR is one of the hottest projects in astronomy today.”

    Full article here:


  • ljk January 11, 2012, 1:16

    Radio array starts work

    Giant low-frequency sensor system on track to probe the birth of the first stars.

    Eric Hand

    10 January 2012

    he Netherlands, one of the most densely populated countries in Europe, would seem to be an inauspicious place to detect radio whispers from the distant Universe. Mobile-phone towers, television transmissions, planes overhead and even the odd burst of noise from a windmill create a background din in the radio sky.

    But the builders of LOFAR, the Low-Frequency Array of radio receivers centred around the tiny village of Exloo, say that they have found ways to ignore the noise. In doing so, Dutch astronomers at ASTRON, the Netherlands Institute for Radio Astronomy in Dwingeloo, are opening up a region of the electro­magnetic spectrum that should hold clues to one of the earliest phases of cosmic history, when the first stars formed — an era beyond the ken of even the biggest optical telescopes.

    “Many of the radio astronomers said this couldn’t be done,” says Heino Falcke, an astronomer at Radboud University in Nijmegen and chairman of the International LOFAR Telescope Board, the five-nation foundation that governs the €150-million (US$192-million) project. Yet Falcke and his colleagues defied the doubters by presenting their first results on 9 January at a meeting of the American Astronomical Society in Austin, Texas. “The message today is: the basic things all work. We can do this,” he said.

    Full article here:


  • francisco May 10, 2012, 6:56


    I might indicate someone who is expected sensitivity of LOFAR system once completed for narrowband signals as

    which supposedly would use SETI civilizations.

    Several parameters are needed.

    1) Effective Area of ​​the entire network of antennas.
    – In my case I see interesting use of the low bands, about 30 Mhz so is to calculate the effective area Ae.
    first in a single antenna.

    – According to some article, the total equivalent area can be 1 km square.

    – A dipole antenna tuned to 30 Mhz its area is 12 square meters according to load and without considering additional gain

    for example the inclusion of a ground plane, any loss, etc.

    – Use double polarization antennas and do not know if this affects the effective area of ​​communications signals, I guess not.
    Rather I think that mitigates losses by depolarization.

    – It seems that there are 36 stations with 96 elements = 3,456 antennas. The items include ground planes, so the

    actual gain of each element is to calculate with precision.

    – In the system LOFAR low band antennas are tuned around 50 MHz, so that the yield will be more

    low 30 MHz, and therefore less than the theoretical Ae due to performance.

    2) noise in the receivers.
    Since the galactic is dominant, little affect the technology used for the LNA.
    Reach between 21,000 ° k to 28/30 MHz up to 30,000 ° K, but of course this is the temperature that will see a dipole softened slightly

    management, temperature can vary a lot when we use the whole stage and look antenna sites

    different. Much higher in the galactic Ecuador and much lower at the poles.

    With these two data we would have the key parameter Ae / Tsys.

    3) Bandwidth of emission. logically if the scope should be the highest possible speed to be slow.
    Let’s say we use CW with 1 bit per second, so that on average we could assign B = 1 Hz.
    So we should not integrate the signal to pass information.

    I said that I have done my calculations, who knows a little about the subject knows it is very easy, but as I said

    above the dispersion of values ​​is very high.

    I have not located any work on the Internet about this, at least for SETI. Nor accurate information on the

    sensitivity, but lately an article entitled “In Situ Antenna Performance Evaluation of the Phased Array LOFAR Radio

    Telescope “is at least an attempt to calibrate the antennas.

    Apart from the above I believe that LOFAR will revolutionize the field of radio astronomy because it can not observe processes

    such as thermal magnetic fields, transient phenomena of short duration, galaxies with very high shifts to

    Besides being very likely to be used for communication, because naturally the ionosphere makes spotlight and much

    signal escapes into space using at least us high power and without any preferred direction, so

    Statistically it is easy to be received.
    The two only drawback is ofcourse the one hand the noise and other interstellar dispersion is very high at low

    frequencies destroying information, at least the noise is mitigated by the large effective areas that can be used,

    especially since it is affordable and digitaliazacion massive digital signal processing.
    As for the dispersion problem is difficult but I guess there will be areas clean galactic ionized gas, which is the

    causes dispersion.
    As seen is a whole new world to investigate.

    My email is: fdiaz_montano@hotmail.com
    Name: Francisco