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Allen Telescope Array

Ata logo.png

The Allen Telescope Array (ATA) is a Radio Interferometer that is dedicated to astronomical and simultaneous search for extra-terrestrial intelligence observations. It's construction was a joint effort by the SETI Institute and the UC Berkeley Radio Astronomy Laboratory (RAL) with major funding from Paul Allen.

Contents

The ATA is located at the existing Hat Creek Radio Observatory (HCRO) and it is managed by SRI International. Hat Creek is located in the Cascades just north of Mt. Lassen[1] at an elevation of 1280m (4200 ft) above sea level. Hat Creek is 290 miles northeast of San Francisco, California.

Ata panorama.jpeg

The ATA is being constructed in stages. The initial array has 42 six-meter (6.1m) antennas and the final configuration will have 350 of these relatively small antennas. The ATA-42 is complete and became operational on October 11th 2007. The total collecting area of the ATA-42 is 1100 square meters with an aperture efficiency of 63%.[2] The ATA-42 has the equivalent collecting area of a larger 39.5m single dish.[3] Each antenna has a log-periodic feed which is cooled for a system temperature of 45 K.

The Full-Width Half-Maximum (FWHM) response of the primary beam is 3.5°/frequency in GHz. At 1.42 GHz the size of the primary beam is 2.46° in diameter. For reference the Moon is 0.5° in diameter.

Collection

RF converter board.jpg

An innovative feed and cryogenic receiver system on each antenna provides continuous frequency coverage from 0.5 to 11 GHz. This entire bandwidth is brought from each antenna over fiber optic cables to the control building, and there as much of the bandwidth as possible is digitized, with current-epoch ADCs (104.8576 MHz, dual-polarization in 4 independent frequency channels today). The digitized signals received from individual antennas are combined in two ways; to form a radio map or image of the entire field of view of the array using a spectral-imaging correlator, and to form a synthesized, full-resolution beam for pointing at a specific target on the sky using a phased-up beamformer. There are four independent IF tunings available at the ATA. Today two correlators are attached to two of the frequency tunings, and three beamformers work from the other two tunings. Eventually multiple beamformers and correlators could populate all of the IF tunings, if the scientific case for such commensal observations is strong enough. The three beamformers used by SETI currently each produce 104.8576 MHz bandwidth dual-polarization beams.

Operations

The ATA was a shared resource between the RAL at Berkeley and the SETI Institute. On April 15th 2011 a funding crisis caused UC Berkeley to back out of its ATA obligations. This forced the ATA into a state of hibernation until December 5th 2011 when it was relaunched[4] thanks to SETIstars and Air Force funding.[5] On April 13th 2012 it was announced that SRI had taken over ATA management duties from UC Berkeley.[6][7][8]

Observation proposals are sent to the ATA steering committee. The committee approves or rejects proposals and allocates telescope time accordingly.

In general either one astronomical survey or one SETI survey (SonATA) will control the pointing of the array as the primary user, with other secondary users able to access different IF tunings, correlators, beamformers, or other backend processors for their observations. This is what is meant by commensal observing at the ATA; the direction on the sky must be shared, but the multiple back end instruments and the frequency agility of the array permit many different science programs to be conducted at one time utilizing that same piece of sky.

Nodes

The antennas are grouped into 5 "nodes", 1,2,3,4,5. Each antenna in a node has a set of antennas that are assigned a letter. The naming convention is node:letter. There are 42 antennas. Here is a list of all the antennas:

1a,1b,1c,1d,1e,1f,1g,1h,1j,1k,2a,2b,2c,2d,2e,2f,2g,2h,2j,2k,2l,2m,3d,3e,3f,3g,3h,3j,3l,4e,4f,4g,4h,4j,4k,4l,5b,5c,5e,5g,5h

Each antenna has 2 pols, x and y. The convention for referring to a particular antenna pol is node:letter:pol. Example: 1ax, 1ay, etc.

Occasionally antennas are referred to as "ant3a" or "ant2e".

The term "ant" or "ants" is commonly used to mean "antenna" or "antennas".

See also

References

  1. http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=hat+creek,+ca+allen+telescope+array&aq=&sll=43.2205,5.533848&sspn=0.012916,0.015407&t=h&ie=UTF8&hq=hat+creek,+ca+allen+telescope+array&hnear=&radius=15000&ll=40.817504,-121.470037&spn=0.006707,0.011791&z=17&vpsrc=6
  2. http://www.nhao.jp/~narusawa/oseti/dorothy-inform.html
  3. sqrt(42 * (6.1m/2)^2)) * 2 = 39.5m
  4. http://setiquest.org/blog/ata-relaunch-dec-5-2011
  5. http://setiquest.org/setiquest/ata-relaunch-press-release.pdf
  6. http://www.sri.com/news/releases/041312.html
  7. http://www.spaceref.com/news/viewpr.html?pid=36718
  8. http://www.marketwatch.com/story/sri-international-to-manage-the-hat-creek-radio-observatory-and-conduct-space-research-using-the-allen-telescope-array-2012-04-13

External links


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