How is the Allen Telescope Array used for Space Surveillance

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High on a plateau in north eastern California, boarded on the east by the most northern extent of the Sierra Nevada and to the west by volcanic peaks of the southern most extent of the Cascade range, is a little valley named after a creek that begins on the north east face of Mt Lassen and meanders down through the valley below it. The people who live there know this place as Hat Creek. It is a special place for many reasons, but one unique aspect of the valley is that radios TVs and cell phones don't work there, it is a radio dead-zone because the mountains block almost all humanly generated electromagnetic radiation. The air in Hat Creek is remarkably clear, free of the smog that obscures the sky in other places. On a moonless night the Milky Way is a bright ribbon of stars traversing the sky and it is a light intense enough to cast shadows. It is an ideal place to do astronomy, and that's why the University of California built a radio astronomy observatory there in the late 1950's.

Since the 1950's the Hat Creek Radio Observatory (HCRO) has been a place that has produce innovations in radio-astronomy technology and made discoveries that have brought about whole new perceptions of the universe. One of the original instruments at the facility was an 85 foot dish antenna used to study many distant objects including the crab nebula, the remnant of a supernova. Over the years many discoveries were made with this radio telescope but in the 1990's it was destroyed by wind and replace with a 10-element telescope array called BIMA. The new array continued to make discovery after discovery, but in 2003 was moved to a location in the Mohave desert to make room for an all new and revolutionary telescope array. The new system was called the Allan Array Telescope(ATA), named after Microsoft cofounder Paul Allen who donated 26 million dollars to its construction.

The ATA will eventually consist of 350 small 20 meter dishes, about twice the diameter of TV satellite dishes popular in the 1980's and 90's. These dishes are a lot more inexpensive to build, and provide several advantages over a larger radio telescope dish. The dishes can be configured to operate independently or in unison. When the dishes are all focused on a single celestial radio source, they effectively represent one very big dish about 2700 feet wide, thus offering great amplification. Focused on different objects the telescope can be used to scan large areas of the sky for radio sources in a relatively short time. This bifurcation of capability makes the ATA and ideal instrument for both astronomy and for the search for extra terrestrial intelligence. Today, the HCRO ATA facility is a joint project of the University of California at Berkeley and an organization called the SETI (Search for Extra Terrestrial Intelligence) Institute. Fourty two of the eventual 350 dish antennas are installed and operational, and can be used by SETI to do its thing, at the same time astronomers are doing scientific research with the array.

Another unique capability of the ATA, particularly considering its SETI application, is its ability to listen to literally millions of N-band frequencies at the same time. In addition, as SETI director Dr. Jill Tarter points out in a documentary produced by San Francisco PBS Channel KQED (See it at the SETI web site : SETI's capabilities in the past decade have allowed about 1000 star systems to be investigated, but within the next ten years, ATA will provide the capability to search a million more. Considering that there are more than 300 billion stars in the Milky Way galaxy, SETI may be busy for generations to come. But according to astronomer Frank Drake's equation, which got the original NASA SETI project going in the 1960's, there could be as many as 100,000 other worlds right in the Milky Way galaxy where life is evolving.

Since 2007 when the HCRO's ATA installation came on line, SETI scientist have been searching the sky 24-7 looking for that proverbial needle in the cosmic hay stack, that one instance of an intelligible radio signal which will alert all humanity to the fact that we are not alone in this immense universe. If your interested in astronomy or the search for extra terrestrial intelligence, HCRO is open to the public and Hat Creek is a great destination for a lot of other fantastic recreational activities. Burney Falls State Park and Lassen Volcanic National Park are located about 20 miles away respectively, north and south of HCRO on HWY 89. There are plenty of camping facilities, and lodging and other facilities can be found about 15 miles away in the town of Burney. One great perspective of the ATA, this quaint listening post tuned in to the electromagnetic harmonies of the cosmos, is to take the hike to the top of Lassen Peak and look down at it in the valley below. For some it is a totally spiritual experience and for all and event to be remembered and recalled for the rest of our brief human existence.



There is a lot more to learn about HCRO, the SETI organization, and the strategies to radio eavesdrop on some extra terrestrial alien presence. You can find more technical information about the ATA at the SETI web site and more about HCRO at their web site at:

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