Winter 2008 Issue


Millimeter Magic

By Dr. H. Paul Shuch, N6TX

SETI League member Peter Vekinis, LX1QF, on site at the 12-meter diameter millimeter-wave radio telescope on Kitt Peak, near Tucson, Arizona, in November 2006 scanning for intelligent extraterrestrial signals. Peter conducted a two-day observing run in the 170-GHz spectral region. His raw data, recorded as audio .WAV files, was made available for SETI League members to download and analyze. So far, no signal of obvious intelligent extrater-restrial origin has been found buried in the mm-wave noise.

Where, exactly, within the vast electromagnetic spectrum are we most likely to detect radio evidence of our cosmic companions? The question is important to practitioners of SETI science, professional and amateur alike, because our terrestrial technology is limited. Wouldnít it be wonderful if we could view the whole spectrum, DC to daylight, in real time? Weíre talking about the ultimate panadaptor. However, thatís a little like trying to monitor every frequency on every ham band simultaneously in order not to miss the next opening to that elusive DX station.

The DX that SETIzens seek, however, is even more elusive than the rarest uninhabited island which might some day be activated. At least, when a trek is mounted to a remote corner of planet Earth, we know the DXpeditionís destination, what bands the team members plan to operate, what callsign they will use, their preferred modulation modes, and how long they plan to be there. With interstellar DX, we donít even know for sure that they exist, much less the particulars of their QTH, operating schedule, or band plan. Lacking any a priori knowledge, all we can do is guess, and the better we guess, the greater our chance of success.

The first scientific paper proposing modern SETI, co-authored by Prof. Phil Morrison, W8FIS, back in 1959, appeared in the prestigious British science journal Nature. In it, Morrison and his colleague Giuseppi Cocconi grappled with the concept of magic frequencies, those calling channels that Nature has carved into the cosmic bandplan, which would be obvious to any thinking creature on a planet orbiting any star. The assumption of mediocrity suggests that if we on Earth can figure out the bandplan, then our potential DX (being, we presume, more intelligent than we) will have figured it out as well. Morrisonís and Cocconiís suggestion, the neutral hydrogen emission line at 1420.405751692 MHz, has been the starting point for nearly all the SETI searches that have followed. Hydrogen is, after all, the most abundant element in interstellar space, and it emits a clearly detectable, narrow-band calibration signal for all who care to tune its way. Surely if we can see that, so can they.

After nearly half a century of trying, though, we have yet to detect the interstellar CQ, on the hydrogen line or the myriad other magic frequencies we have monitored with Earthís best radio telescopes. Could it be weíre listening on the wrong channel?

Peter Vekinis, LX1QF, thinks so. He speculates that advanced extraterrestrial civilizations will announce their presence in the millimeter-wave spectrum. Peter recently concluded two days of SETI observations from the 12-meter diameter radio telescope on Kitt Peak, Arizona. He selected ten frequencies between 115 and 177 GHz, associated with natural emission lines from molecules of biological significance on Earth. If organic processes are similar throughout the cosmos, Peter reasoned, then one or more of these frequencies might be obvious to the beings we seek to detect.

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