Nature on the Allen Telescope Array

27 Jul 2011
Posted by colby

At the risk of some copyright infringement, I link to an article published in Nature today (27 July 2011). First, please read the article. All the way through. It's 3 pages. I'll wait.

The article points out that the Allen Telescope Array was a big effort compared to other SETI related research. Fair enough. The scale at the ATA is larger than anything else being done that involves SETI research. The article also downplays that the ATA was designed to be exceptionally good as a multi-role instrument.

Waldrop is correct in saying that the NSF cut off funding to the ATA because it was not big enough. That's right. You heard me. Had the ATA been able to have, say, another 40-86 antennas (yes, there's a magical 128 number in there), then the power of the instrument would and could justify larger operating funds from the NSF. The ATA has an exceptional potential for doing fundamental astronomy research. The work on the ATA has already made huge contributions to the next generation of radio telescopes (especially the Square Kilometer Array or SKA). And yet, the conceit of the article is that the ATA is and was too big and that perhaps it is better to do SETI research in cheaper ways. The dissonance here is frustrating.

Don't just take my word for it. About 147 of the top astrophysicists and astronomers in the United States put together a report called the 2010 Astronomy and Astrophysics Decadal Survey and included:

"Progress on development of the SKA-mid pathfinder instruments---the Allen Telescope Array in the United States ... will provide crucial insight in the optimal path toward a full SKA." [page 92] and that the ATA is amongst, "...radio observatories [that] have been judged as world-leading, on the basis of both their technical performance and the desire of radio astronomers to use them. ... The small facilities provide unique scientific capabilities, training and technical development..." [pages 168-170] (my emphasis) while those same small facilities receive a pittance in funding ($10 million/year across a dozen facilities vs hundreds of millions spent on ALMA and the NRAO supported big instruments like the EVLA [again, pages 169-170]). (see: Astro2010: The Astronomy and Astrophysics Decadal Survey)

The Nature article is also correct in pointing out that Arecibo has almost half a dozen receivers working at the same time to gather data. 5 independent and different receivers, looking at a slightly different soda straw sized part of the sky and in different parts of the radio spectrum. The ATA antennas look at an area of the sky that is 50 times larger, because of the ATA's smaller dish size, while the receivers on the ATA dishes simultaneously see a huge 10GHz of of the radio spectrum. Really, go look at other designs for radio telescopes and you'll see "wide-band" defined in terms of 2, 4 and 8 GHz. (EVLA Frequency Bands and Tunability).

The ATA can already provide 4 independent data streams from within those 10GHz, and if fully built out could provide many more, simultaneously.

There are modifications to the current ATA receiver designs that boost the bandwidth even wider, while bringing their efficiency into the realm of the multi-million dollar receivers put on the EVLA and very little extra cost to each receiver.

That $200,000 per antenna is stupendously cheap compared to almost all other radio astronomy related construction (ALMA, $6.0 million/antenna, see: Long Latin American Millimeter Array Costs Section V).

Keep in mind this isn't just good for SETI research, it's good for basic radio astronomy research, the sort that has had the support of the federal government, state governments and private universities with a couple of billion dollars spent on them over the last 20 years.

The current estimate for completing the array to 350 telescopes is, according to the article, $60 million. The cost of each antenna would come down with economies of scale, so a raw estimate of $200K per antenna to get to that number seems off, but, you still have to factor in extra spending on infrastructure to actually do something with the signals coming from the antennas.

I am, of course, biased about this. The "two caretakers" mentioned at the start of the article includes me. I was laid off from the Radio Astronomy Lab on July 1st after 10 years and 2 weeks of working for them.

I am now waiting for news on when or if I have to move off of the observatory soon. There's something in the works to keep me employed doing what I love, helping support basic research, while having the privilege of living on the site of one of the most ambitious, sophisticated and cost efficient radio instruments in the world.

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