NationMaster - Encyclopedia: Allen Telescope Array

The Allen Telescope Array (ATA), formerly known as the One Hectare Telescope (1hT), is a joint effort by the SETI Institute and the Radio Astronomy Laboratory at the University of California, Berkeley to construct a radio interferometer that is dedicated to astronomical and simultaneous search for extra-terrestrial intelligence observations. It is being constructed at the Hat Creek Radio Observatory, 290 miles northeast of San Francisco, California and, when completed, is expected to be composed of 350 antennas. The SETI Institute is a private, nonprofit organization dedicated to scientific research, education and public outreach to explore, understand, and explain the nature and origin of the Universe. ... Sather tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... Interferometry is the applied science of combining two or more input points of a particular data type, such as optical measurements, to form a greater picture based on the combination of the two sources. ... This article is about the search for extra-terrestrial intelligence. ... Constructing 85-foot dish The Hat Creek Radio Observatory (HCRO) is operated by the Radio Astronomy Laboratory (an Organized Research Unit of the Astronomy Department at the University of California, Berkeley). ... â€œSan Franciscoâ€ redirects here. ... Official language(s) English Capital Sacramento Largest city Los Angeles Largest metro area Greater Los Angeles Area Ranked 3rd - Total 158,302 sq mi (410,000 kmÂ²) - Width 250 miles (400 km) - Length 770 miles (1,240 km) - % water 4. ...

Background

First conceived by SETI pioneer Frank Drake, the idea has been a dream of the SETI Institute for years. However, it was not until early 2001 that research and development commenced after a donation of $11.5 million USD by the Paul G. Allen Family Foundation. In March 2004, the SETI Institute unveiled a three tier construction plan for the telescope, following a successful completion of a three-year research and development phase. Construction began right after, due to the donation pledge of $13.5 million USD by Paul Allen (co-founder of Microsoft) to support the construction of the first and second phases. The SETI Institute named the telescope in his honor. Professor Frank Drake Frank Drake (born May 28, 1930, Chicago, Illinois) is an American astronomer and astrophysicist. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... â€œUSDâ€ redirects here. ... The Paul G. Allen Family Foundation is a private foundation located at in Seattle, Washington. ... 2004 : January - February - March - April - May - June - July - August - September - October - November - December Deaths â€¢ 08 Abu Abbas â€¢ 20 Queen Juliana â€¢ 28 Peter Ustinov â€¢ 30 Alistair Cooke More March 2004 deaths Ongoing events EU Enlargement Exploration of Mars: Rovers Haiti Rebellion Israeli-Palestinian conflict Occupation of Iraq Same-sex marriage in... For other persons named Paul Allen, see Paul Allen (disambiguation). ... Microsoft Corporation, (NASDAQ: MSFT, HKSE: 4338) is a multinational computer technology corporation with global annual revenue of US$44. ...

Overview

The ATA will be a centimeter-wave array that pioneers the Large-Number Small-Diameter (LNSD) concept of building radio telescopes. Compared to a large dish antenna, large numbers of smaller dishes are cheaper for the same collecting area. However, to get similar sensitivity, the signals from each telescope must be combined. This requires high performance electronics, and has been impractically expensive up until now. However, due to Moore's Law, (an empirical law saying the electronics becomes twice as capable every two years for the same price), the required electronics are now practical, resulting in a large cost saving over telescopes of more conventional design. This is informally referred to as replacing steel with silicon. Interferometry is the applied science of combining two or more input points of a particular data type, such as optical measurements, to form a greater picture based on the combination of the two sources. ... Gordon Moores original graph from 1965 Growth of transistor counts for Intel processors (dots) and Moores Law (upper line=18 months; lower line=24 months) For the observation regarding information retrieval, see Mooers Law. ...

The ATA has four primary advantages for scientific studies over all major radio telescopes built to date: a very wide field-of-view (2.45° at λ = 21 cm), complete instantaneous frequency coverage from 0.5 to 11.2 GHz, multiple simultaneous backends, and active interference mitigation. The instantaneous area of sky imaged is 17 times that of the Very Large Array (VLA). The instantaneous frequency coverage of more than 4 octaves is unprecedented in radio astronomy and is the result of a unique feed, input amplifier, and signal path design. Active interference mitigation will make it possible to observe even at frequencies of many terrestrial radio emitters. The field of view is the part of the observable world that is seen at any given moment. ... The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. U.S. Route 60 passes through the complex. ...

Because all-sky surveys are an important part of the science program, the efficiency of the ATA will be increased by doing radio astronomy and SETI searches simultaneously. The telescope will do this by splitting the signals in the control room prior to final processing. Simultaneous observations are possible because for SETI, several target stars will lie within the large field-of-view afforded by the 6m dishes wherever the telescope is pointed. Thus, by agreement between the RAL and the SETI Institute, the needs of conventional radio astronomy will determine the pointing of the array. Image File history File links Download high resolution version (1280x960, 416 KB)Artist rendering of completed ATA-350. ... Image File history File links Download high resolution version (1280x960, 416 KB)Artist rendering of completed ATA-350. ...

The ATA is planned to comprise 350 six-meter dishes and will make possible large, deep radio surveys that were not previously feasible. The telescope incorporates many new design features including hydroformed antenna surfaces, a log-periodic feed covering the entire range of frequencies from 500 MHz to 11.2 GHz, and low noise, wide-band amplifiers with a flat response over the entire band making it possible to amplify the sky signal directly. This amplified signal, containing the entire received bandwidth, is brought from each antenna to the processing room on optical fiber cables. This means that as electronics improve and wider bandwidths are feasible, only the central processor needs to change, and not the antennas or feeds. Hydroforming (or hydramolding) is a cost-effective way of shaping malleable metals such as aluminum into lightweight, structurally stiff and strong pieces. ... Log-periodic dipole array In telecommunication, a log-periodic antenna (LP, also known as a log-periodic array) is a broadband, multielement, unidirectional, narrow-beam antenna that has impedance and radiation characteristics that are regularly repetitive as a logarithmic function of the excitation frequency. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ...

The instrument will be operated and maintained by the Radio Astronomy Laboratory (RAL) at the University of California, Berkeley. The RAL has worked hand in hand with the SETI Institute during design and prototyping and is the primary designer of the feed, antenna surfaces, beam forming, correlator and imaging system for Radio Astronomy observations. Sather tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ...

The astronomy decadal panel, Astronomy and Astrophysics in the New Millennium, endorsed SETI and recognized the ATA (then, the 1 Hectare Telescope) as an important stepping-stone to the Square Kilometer Array (SKA). A hectare (symbol ha) is a unit of area, equal to 10 000 square metres, commonly used for measuring land area. ... The Square Kilometre Array, once complete will be a radio telescope with a planned collecting area of a square kilometre. ...

The ATA aspires to be among the world's largest and fastest observing instruments. It will also permit astronomers to search for many different target stars simultaneously. When completed as originally envisioned, it will be one of the largest and most powerful telescopes in the world.

Although cost estimates of unbuilt projects are always dubious, and the specs are not identical (the conventional telescopes have lower noise temperature, but the ATA has a larger field of view, for example), the ATA has potential promise as a much cheaper radio telescope technology for a given effective aperture. For example, the amount spent on the first ATA-42 phase, including technology development, is roughly 1/3 of the cost of a new copy of a Deep Space Network 34 meter antenna of similar collecting area. Similarly, the estimated total cost of building the remaining 308 dishes is estimated (as of October 2007) at about $41 million^[1]. This is about a factor of 2 cheaper than the 85 million dollar cost^[2] of the last large radio astronomy antenna built in the USA, the Green Bank Telescope, of similar collecting area. Noise temperature: At a pair of terminals, the temperature of a passive system having an available noise power per unit bandwidth at a specified frequency equal to that of the actual terminals of a network. ... The field of view is the part of the observable world that is seen at any given moment. ... Deep Space Network (DSN) is an international network of radio antennas that supports interplanetary spacecraft missions, and radio and radar astronomy observations for the exploration of the solar system and the universe. ... The Robert C. Byrd Green Bank Telescope (GBT) is the worlds largest fully steerable radio telescope. ...

Status

The ATA was originally planned to be constructed in 4 stages, the ATA-42, ATA-98, ATA-206, and ATA-350; each number representing the number of dishes in the array at a given time (See Table 1).

SETI operations with 42 dishes started on 11 October 2007^[1]. Funding for building out additional antennas is currently being sought by the RAL from various sources, including the US Navy and DARPA and private donors.

Astronomical data has been acquired since July 2006 that is scientifically useful^[3] and to help commission the array.

Since its inception, the ATA has been a development tool for array technology (specifically, for the Square Kilometer Array). Future progress depends on the technical performance of the sub-array already under construction, and the procurement of additional funding. The Square Kilometre Array, once complete will be a radio telescope with a planned collecting area of a square kilometre. ...

Correlator development continues, with deployment of two 4 baseline (or antenna) correlators in 2006 and in January 2007, the delivery of two 8 baseline correlators from the RAL. An additional two 32 baseline correlators are planned to be deployed by mid-year 2007.

Beam forming electronics are also planned for mid-2007 deployment which will allow for simultaneous astronomical and SETI observations.

Key science goals

The science goals listed here represent the goals of the most important projects that will be conducted over the next three years with the ATA. Each of these goals is associated with one of the 4 stages of development (see Table 1). The bulleted items are the projects that will be undertaken and the subtopics are some of the science that will be produced. The ATA will:

Opportunistic science

After array construction, a few science goals that were not explicitly designed have been mentioned.

For a very different science goal, the Allen Telescope Array has offered to provide the downlink for any contestants in the Google Lunar X Prize^[4]. This is practical since the array, with no modifications, covers the main space communications bands (S-band and X-band). A telemetry decoder would be the only needed addition. The Google Lunar X PRIZE, sometimes referred to as simply Moon 2. ...

Also, the Allen array was mentioned as a candidate^[5] for searching for a new type of radio transient. It is an excellent choice for this because of a large field of view and wide instantaneous bandwidth.

Instrument details

The ATA-42 configuration will provide a maximum baseline of 300 m (and ultimately the ATA-350, 900 m). A cooled log-periodic feed on each antenna is designed to provide a system temperature of ~ 45 K from 1 to 10 GHz, with reduced sensitivity in the range 0.5–1.0 GHz and 10–11.2 GHz. Four separate frequency tunings (IFs) are available to produce 4x100 MHz intermediate frequency bands. Two IFs support correlators for imaging; two will support SETI observing. All tunings can produce four dual polarization phased array beams which can be independently pointed within the primary beam and can be used with a variety of detectors. The ATA can therefore synthesize up to 32 phased array beams.

The wide field of view of the ATA gives it an unparalleled capability for large surveys (Fig. 4). The time required for mapping a large area to a given sensitivity is proportional to (ND)², where N is the number of elements and D is the diameter of the dish. This leads to the surprising result that a large array of small dishes can outperform an array with smaller number of elements but considerably greater collecting area at the task of large surveys. As a consequence, even the ATA-42 is competitive with much larger telescopes in its capability for both brightness temperature and point-source surveys. For point source surveys, the ATA-42 is comparable in speed with Arecibo and the Green Bank Telescope (GBT), but slower by a factor of 3 than the Very Large Array (VLA). The ATA-350, on the other hand, will be an order of magnitude faster than the Very Large Array for point-source surveys and is comparable to the Expanded VLA (EVLA) in survey speed. For surveys to a specified brightness temperature sensitivity, the ATA-98 will exceed the survey speed of even the VLA-D configuration. The ATA-206 should match the brightness temperature sensitivity of Arecibo and the GBT. The ATA, however, provides better resolution than either these single dish telescopes. Image File history File linksMetadata ATA-gregorian. ... Image File history File linksMetadata ATA-gregorian. ... Look up point source in Wiktionary, the free dictionary. ... The Robert C. Byrd Green Bank Telescope (GBT) is the worlds largest fully steerable radio telescope. ... The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. U.S. Route 60 passes through the complex. ...

The antenna for the ATA is a 6.1 m × 7.0 m hydroformed offset Gregorian telescope with a 2.4-meter subreflector with an effective f/D of 0.65. (DeBoer, 2001). The offset geometry eliminates blockage, which increases the efficiency and decreases the sidelobes. It also allows for the large subreflector, providing good low frequency performance. The hydroforming technology used to make these surfaces is the same hydroforming technique used to generate low-cost satellite reflectors by Andersen Manufacturing (Idaho Fall, ID). The unique, interior frame rim-supported compact mount allows excellent performance at a low cost. The drive system employs a spring-loaded passive anti-backlash azimuth drive train. The Gregorian telescope is a type of reflecting telescope designed by Scottish mathematician and astronomer, James Gregory in the 17th century. ...

References

^ ^a ^b Dennis Overbye, Stretching the Search for Signs of Life, New York Times, 11 October 2007
^ FROM THE GROUND UP: BALANCING THE NSF ASTRONOMY PROGRAM Report of the National Science Foundation, Division of Astronomical Sciences Senior Review Committee October 22 2006. The $85M cost is stated in section 4.4.2.3. This is what the NSF paid, but the true cost might be higher - the contractor filed for a $29M overrun, but only $4M of this was allowed.
^ See, for example, GRB 070612A: Allen Telescope Array Observations
^ Google X prize strategic alliances
^ Big Radio from the Stars, Science Now Magazine

The Search Continues with the Allen Telescope Array. Mountain View, CA: SETI Institute. March 25, 2004.
Radio Astronomy Laboratory, Univ of Cal, Berkeley: NSF proposal, June 15th, 2005.

External links

News articles

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