Ask Dr. SETI ®
I have a conceptual problem with Project Argus that somebody might be able to help me with.
A list of the nearest twenty stars shows that they occupy a region within 12 light years (11.8 to be precise) of the earth. It seems to me that with a dish a mere few meters across there would be little hope of picking up any signal of consequence outside that range. But instead of pointing the dishes at realitistic targets, non-steerable dishes will spend most of their time pointing into deep space missing even our own galaxy. For virtually all of the search time the receivers have no realistic hope of detecting anything.
The processing problem (that the FFT takes too long on a Pentium) could thus be eliminated simply by including software that calculates where the dish is pointing at the time of data collection, and junking the data that is collected when the probability of receiving anything useful approaches zero.
The BETA project of the Planetary Society claims to be able to scan a quarter of a BILLION channels simultaneously. This alone is far more than the Project Argus stations could ever hope to achieve even if all 5000 were operational. What's more the BETA survey can selectively look at high probability regions at all times.
But let's assume that the 5000 toy stations cost an average of $5000 each to build...a total of $25,000,000. Wouldn't that money be much better spent on a much smaller number of larger and more capable stations?
NJB (via email)
The Doctor Responds:
The odds of amateur SETI success are admittedly long. On the other hand, we have shown our "toys" to have sensitivities on a par with that of the Ohio State University 'Big Ear' radio telescope 20 years ago, when the "Wow!" event was detected. (see this article.) That signal did not come from a nearby star. In fact, the nearest star within the beamwidth of the OSU antenna at the time of the "Wow!" detection was 225 LY (at any given instant, about 5 stars are in its beam), and did not appear on anybody's candidate star list for targeted searches.
You say our dishes will spend most of their time pointing into deep space. This is precisely what Big Ear (and for that matter, Project BETA) do! Most of the three dozen or so candidate signals detected by the world's SETI projects over the last 40 years have been detected by "pointing off into deep space."
Yes, BETA scans about 250,000,000 channels simultaneously. (That's 10-milliHertz channels, as opposed to our 10-Hertz ones, so the frequency span is 1,000 times less than you might assume. Still, it's damned good.) But let's look at costs. BETA's predecessor, META, cost $100,000. BETA probably cost 10 times as much. (I can directly identify some $400,000 in funding, and that doesn't count the free labor provided by Harvard University). And it only sees 1 part in 1,000,000 of the sky. We desire full-sky coverage in real time. So let's see, a million BETAs is $1,000,000,000,000. Now add the tens of millions of dollars needed for each of the million radio telescope antennas which we're going to attach to each of those million BETA receivers, and we've just exceeded the Gross Planetary Product.
You are correct in saying that BETA could selectively look at high probability regions of space at all times. But in fact it doesn't! BETA is actually (and quite deliberately) used in the All-Sky Survey mode. See their Web site for an explanation of why they choose this strategy.
Sure, BETA covers far more frequencies than we can (for now -- read here for a look at what's planned). But one (or even a dozen) large telescopes can never compete with a global network of thousands of small dishes, as far as sky coverage is concerned. Furthermore, the true strength of BETA resides in its digital signal processing hardware and software -- techniques which are compatible with any telescope of any size, employed in any search strategy which we may choose. And our members, all amateurs, are indeed adopting much of that technology in their own stations. The creator of BETA is, after all, a radio amateur himself.
You estimate the cost of each Argus station at $5000, for a total cost of $25 Million. I think that's a greatly exaggerated figure. You'll probably find that the average sum spent by our members is closer to $500. But even if your estimates were right, that cost would be spread out over thousands of members, over tens of years. The late NASA SETI program was spending half that total every year, and looking at tiny slices of sky from only two telescopes! And for all the money spent, the NASA HRMS sky survey ran for only 1000 hours before Congress pulled the plug. No political body is going to terminate a grass-roots survey such as ours.
But here's another reason why The SETI League will not be in a position to build "a much smaller number of larger and more capable stations," even if we found that approach desirable. Regardless of the actual cost of Project Argus stations (let's call that k) and the number ultimately built (which we can call n), the sum $n*k is not ours to spend. After all, it is our individual n participants around the world who are each choosing to spend $k apiece on their hobby! I doubt that we as a volunteer organization would get very far if we tried to direct our members' discretionary funds toward anything other than each acquiring his or her own radio telescope. How many amateur optical astronomers do you suppose cash in their binoculars and 20 cm Schmidt cassegrain telescopes each year, so some membership-supported nonprofit can build another Mount Palomar? You could probably count them on the thumbs of one hand.
I venture to guess that hobbyists are unlikely to give up their "toy" telescopes so someone else can build a "real" one. And just as it is the amateur optical astronomers with their "toys" who are discovering all the comets, who do you suppose has the best chance of detecting ETI? I suspect it is he or she who owns the equipment in use, and cannot be turned off by Government edict.
I do appreciate your comments, because they indicate that we haven't done a very good job explaining the extensive cost/benefit analysis which went into the design of our survey. Most important, even if your figures were correct, is to realize that a global amateur effort can indeed put 5000 modestly equipped observers on the air, without spending any public funds in the process. That's 4995 more stations than we've ever had on at any prior time. We hope to make up in strength of numbers what we lack in sophistication or budget. I certainly hope you'll be joining us.
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this page last updated 28 December 2002
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