Array2k Project Update
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| For the past two years, the SETI community has marveled at the development of the ambitious Paul Allen Telescope, a mini-Cyclops consisting of up to a thousand phased satellite TV-type dishes. While saluting the efforts of our California colleagues, The SETI League has been hard at work on its own phased array design, more modest in scope but quite as technologically audacious. When completed, Array2k will employ a unique mix of analog and digital techniques to operate in five distinct modes simultaneously. Optimized as a drift-scan sky survey instrument in the proud tradition of Ohio State's Big Ear, it will serve as its own Follow-Up Detection Device, verifying its own findings in real time. |  |
| Since the earliest days of the Project Argus search, our members have been discussing technologies required to combine multiple small dishes into a meaningful SETI array. SETI League member and noted space artist Jon Lomberg has contributed this artist's conception of Array2k, the next-generation radio telescope now in preliminary design phase at SETI League headquarters. |
 Jon Lomberg |
| In January 2000, Executive Director H. Paul Shuch met in Sri Lanka with Advisory Committee member Sir Arthur C. Clarke, to discuss the design of our Array2k SETI antenna. Though well known as a novelist, Clarke has an impressive engineering background, and is considered the father of communications satellites (as celebrated in song). |
 SETI League |
| At the Powai campus of India Institute of Technology, Prof. Govind Swarup, the father of Indian radio astronomy, met with SETI League executive director H. Paul Shuch early in 2000 to critique design details of the Array2k SETI antenna. This current initiative is based in part on an array Swarup designed with Prof. Ron Bracewell at Stanford University forty years prior. It is documented by them in "The Stanford Microwave Spectroheliograph Antenna: A Microsteradian Pencil Beam Interferometer," IRE Trans Ant Prop vol AP-9 pp 22-30, January 1961. |
 SETI League |
| Dr. Shuch has also met several times over the past couple of years with Prof. Ron Bracewell at Stanford University, to discuss the latter's 32-dish array, circa 1960. Paul's question for Bracewell has been, "If you were building this array today, what would you do differently? Because that's what we want to do!" |
 SETI League |
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The seven dishes of the SETI Institute's Rapid Prototype Array provide a test bed for new technology to be used in their ambitious Paul Allen Array (formerly called the One Hectare Telescope). Technology sharing is allowing SETI League engineers to apply some of these concepts in the development of our own (somewhat more modest) Array2k design. More RPA photos are available here. |
 SETI League |
| This wooded acerage in Warren County, NJ is future home toThe SETI League's planned Array2k radio telescope. Our experimental phased array will share the land with an ostrich farm. "This is compatible land use," points out SETI League president Richard Factor, "because ostriches emit no electromagnetic interference." The twin metaphor is not lost on us: ostriches represent the heads-in-the-sand attitude of those politicians who saw fit to terminate the NASA SETI program, whereas SETI League members have our heads planted firmly in the stars. |
 SETI League |
| TVRO polar mount modified for remote control of both Right Ascension and Declination. Two-axis rotation is considerably more complex than the meridian-transit mounts contemplated for Array2k. The RA rotor is a standard satellite TV horizon-to-horizon chain drive. Elevation rotation is provided by replacing the usual Dec turnbuckle with a motorized jack screw (the kind of "dish mover" often used for RA rotation). Note the counterweight, required to keep the dish balanced so as to prolong the life of the elevation rotor bearings. |
 SETI League |
| This detail shows one way of mounting the SETI League hydrogen-line feedhorn to a surplus TVRO dish antenna. Four 1/4 inch holes are drilled in the outer walls of the choke ring, as far back toward its shorted end as possible, and 1/4-20 screws and nuts are used to attach the feed assembly to the dish's existing mounting arms. The feedhorn is then slid in and out of the rigidly mounted choke ring until proper illumination is achieved. A similar feed design is contemplated for the Array2k design. |
 N6TX photo |
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As design work continues on our Array2k radio telescope project, it is possible to add a bit more detail to our artist's conception. This new sketch by SETI League intern Aurore Simonnet provides a perspective view of the planned dish placement. See more of Aurore's work on her personal website. |
 A. Simonnet |
| The SETI League has received a very generous donation of a significant quantity of high-quality, commercial grade 1.8 meter dishes with C-band feeds and az-el mounts. Here our executive director has set up the first of the lot at SETI League Hq., and is preparing to test its performance. Although somewhat smaller than the dishes we had originally envisioned for Array2k, the price is certainly right, thus we are rethinking the array design. |
 SETI League |
| Offset-fed dishes such as those donated for our Array2k project (see photo above) require feed geometries different from that used on prime focus dishes (background). At the left side of this picture is the C-band feed we received along with each of our 47 contributed dishes. At right is Big Brother, an L-band extrapolation of that design, constructed from a three-pound coffee tin, a galvanized steel 10" to 6" stovepipe reducer ($4.59 at the local hardware store), two type N connectors, and a four inch length of 1/8" OD brass hobby tubing. The offset feed works well from 1296 to about 1535 MHz (with its response rolling off pretty well at 1575, which should help to eliminate GPS interference). |
 SETI League |
 | Engineers at CSIRO in Australia have developed some elegant corrugated waveguide feedhorns for use by the SETI Institute's Project Phoenix targeted search. The one at left, installed on a 100 foot dish at the Georgia Tech Woodbury Research Facility, covers 1 to 7 GHz with dual polarizations. For our Array2k effort, The SETI League is developing much narrower-band corrugated feedhorns. At right is an L-band feed constructed out of surplus materials, at a cost many orders of magnitude below the feeds made by our Australian colleagues. |
 SETI League |
| SETI League executive director Dr. H. Paul Shuch explains the latest Array2k feed design at the Society of Amateur Radio Astronomers conference at NRAO Green Bank WV. See more SARA photos here. |
 SETI League |
| First testing of an Array2k corrugated cylindrical waveguide feedhorn prototype on one of the offset-fed 1.8-meter dishes was begun in August, 2001. The large feedhorn aperture would have significantly reduced overall antenna gain, if a conventional blocked-aperture prime focus dish had been used. |
 SETI League |
See also photos of our Very Small Array (VSA) prototype.
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