The Allen Telescope Array (ATA), formerly known as the One Hectare Telescope (1hT), is a
radio telescope
A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
dedicated to astronomical observations and a simultaneous
search for extraterrestrial intelligence
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other pl ...
(SETI). The array is situated at the
Hat Creek Radio Observatory
The Hat Creek Radio Observatory (HCRO) is operated by SRI International in the Western United States. The observatory is home to the Allen Telescope Array designed and owned by the SETI Institute in Mountain View, CA.
Location
Hat Creek Radio ...
in
Shasta County
Shasta County (), officially the County of Shasta, is a county in the northern portion of the U.S. state of California. Its population is 182,155 as of the 2020 census, up from 177,223 from the 2010 census. The county seat is Redding.
Shasta ...
, northeast of
San Francisco
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
, California.
The project was originally developed as a joint effort between the
SETI Institute
The SETI Institute is a not-for-profit research organization incorporated in 1984 whose mission is to explore, understand, and explain the origin and nature of life in the universe, and to use this knowledge to inspire and guide present and futu ...
and the
Radio Astronomy Laboratory The Radio Astronomy Lab (RAL) is an Organized Research Unit (ORU) within the Astronomy Department at the University of California, Berkeley. It was founded by faculty member Harold Weaver in 1958.
Until 2012, RAL maintained a radio astronomy observ ...
(RAL) at the
University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
(UC Berkeley), with funds obtained from an initial 12.5 million donation by the
Paul G. Allen Family Foundation
Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American business magnate, computer programmer, researcher, investor, and philanthropist. He co-founded Microsoft Corporation with childhood friend Bill Gates in 1975, which ...
and
Nathan Myhrvold
Nathan Paul Myhrvold (born August 3, 1959), formerly Chief Technology Officer at Microsoft, is co-founder of Intellectual Ventures and the principal author of ''Modernist Cuisine'' and its successor books. Myhrvold was listed as co-inventor o ...
. The first phase of construction was completed and the ATA finally became operational on 11 October 2007 with 42 antennas (ATA-42), after
Paul Allen
Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American business magnate, computer programmer, researcher, investor, and philanthropist. He co-founded Microsoft Corporation with childhood friend Bill Gates in 1975, which h ...
(co-founder of
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
) had pledged an additional $13.5 million to support the construction of the first and second phases.
Although overall Allen has contributed more than $30 million to the project, it has not succeeded in building the 350 6.1 m (20 ft) dishes originally conceived, and the project suffered an operational hiatus due to funding shortfalls between April and August 2011, after which observations resumed.
Subsequently, UC Berkeley exited the project, completing divestment in April 2012. The facility is now managed by
SRI International
SRI International (SRI) is an American nonprofit scientific research institute and organization headquartered in Menlo Park, California. The trustees of Stanford University established SRI in 1946 as a center of innovation to support economic d ...
(formerly Stanford Research Institute), an independent, nonprofit research institute. As of 2016, the
SETI Institute
The SETI Institute is a not-for-profit research organization incorporated in 1984 whose mission is to explore, understand, and explain the origin and nature of life in the universe, and to use this knowledge to inspire and guide present and futu ...
performs observations with the ATA between the hours of 6 pm and 6 am daily.
In August 2014, the installation was threatened by a forest fire in the area and was briefly forced to shut down, but ultimately emerged largely unscathed.
Overview
First conceived by
SETI
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other p ...
pioneer
Frank Drake
Frank Donald Drake (May 28, 1930 – September 2, 2022) was an American astrophysicist and astrobiologist.
He began his career as a radio astronomer, studying the planets of the Solar System and later pulsars. Drake expanded his interests t ...
, the idea has been a dream of the
SETI Institute
The SETI Institute is a not-for-profit research organization incorporated in 1984 whose mission is to explore, understand, and explain the origin and nature of life in the universe, and to use this knowledge to inspire and guide present and futu ...
for years. However, it was not until early 2001 that research and development began, after a donation of $11.5 million by the
Paul G. Allen Family Foundation
Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American business magnate, computer programmer, researcher, investor, and philanthropist. He co-founded Microsoft Corporation with childhood friend Bill Gates in 1975, which ...
. In March 2004, following the successful completion of a three-year research and development phase, the SETI Institute unveiled a three-tier construction plan for the telescope. Construction began immediately, thanks to the pledge of $13.5 million by
Paul Allen
Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American business magnate, computer programmer, researcher, investor, and philanthropist. He co-founded Microsoft Corporation with childhood friend Bill Gates in 1975, which h ...
(co-founder of
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
) to support the construction of the first and second phases. The SETI Institute named the telescope in Allen's honor. Overall, Paul Allen contributed more than $30 million to the project.
The ATA is a centimeter-wave
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
which pioneers the Large-Number Small-Diameter concept of building
radio telescope
A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...
s. Compared to a large
dish antenna
A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or par ...
, large numbers of smaller dishes are cheaper for the same collecting area. To get similar sensitivity, the signals from all telescopes must be combined. This requires high-performance electronics, which had been prohibitively expensive. Due to the declining cost of electronic components, the required electronics became practicable, resulting in a large cost-saving over telescopes of more conventional design. This is informally referred to as "replacing steel with silicon".
The ATA has four primary technical capabilities that make it well suited for a range of scientific investigations: a very wide
field of view
The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation.
Humans a ...
(2.45° at λ = 21 cm, the wavelength of the
hydrogen line
The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , w ...
), complete instantaneous frequency coverage from 0.5 to 11.2
gigahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one h ...
(GHz), multiple simultaneous backends, and active interference mitigation. The area of sky which can be instantaneously imaged is 17 times that obtainable by the
Very Large Array
The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twen ...
telescope. The instantaneous frequency coverage of more than four
octaves
In music, an octave ( la, octavus: eighth) or perfect octave (sometimes called the diapason) is the interval between one musical pitch and another with double its frequency. The octave relationship is a natural phenomenon that has been refer ...
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 the frequencies of many terrestrial
radio emitters.
All-sky surveys are an important part of the science program, and the ATA will have increased efficiency through its ability to conduct
extraterrestrial intelligence searches (SETI) and other
radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming f ...
observations simultaneously. The telescope can do this by splitting the recorded signals in the control room prior to final processing. Simultaneous observations are possible because for
SETI
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other p ...
, wherever the telescope is pointed, several target stars will lie within the large field of view afforded by the 6 m dishes. By agreement between the UC Berkeley
Radio Astronomy Laboratory The Radio Astronomy Lab (RAL) is an Organized Research Unit (ORU) within the Astronomy Department at the University of California, Berkeley. It was founded by faculty member Harold Weaver in 1958.
Until 2012, RAL maintained a radio astronomy observ ...
(RAL) and the
SETI Institute
The SETI Institute is a not-for-profit research organization incorporated in 1984 whose mission is to explore, understand, and explain the origin and nature of life in the universe, and to use this knowledge to inspire and guide present and futu ...
, the needs of conventional radio astronomy determined the pointing of the array up until 2012.
The ATA is planned to comprise 350 6 m dishes and will make possible large, deep radio surveys that were not previously feasible. The telescope design incorporates many new features, including
hydroformed
Hydroforming is a cost-effective way of shaping ductile metals such as aluminium, brass, low alloy steel, and stainless steel into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automot ...
antenna surfaces, a
log-periodic feed covering the entire range of frequencies from 500
megahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, me ...
(MHz) to 11.2 GHz, and low-noise,
wide-band amplifiers with a flat response over the entire band, thus 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 via
optical fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...
cables. This means that as electronics improve and wider bandwidths are obtainable, only the central processor needs to change, and not the antennas or feeds.
The instrument was operated and maintained by RAL until development of the array was put on hold in 2011. RAL worked hand in hand with the SETI Institute during design and prototyping and was the primary designer of the feed, antenna surfaces,
beamforming
Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles e ...
, correlator, and imaging system for radio astronomy observations.
The panel for the
Astronomy and Astrophysics Decadal Survey
The Astronomy and Astrophysics Decadal Survey is a review of astronomy and astrophysics literature produced approximately every ten years by the National Research Council of the National Academy of Sciences in the United States. The report surve ...
in its fifth report,
''Astronomy and Astrophysics in the New Millennium'' (2001), endorsed SETI and recognized the ATA (then called the 1-
Hectare
The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...
Telescope) as an important stepping stone towards the building of the
Square Kilometer Array
The Square Kilometre Array (SKA) is an intergovernmental international radio telescope project being built in Australia (low-frequency) and South Africa (mid-frequency). The combining infrastructure, the Square Kilometre Array Observatory (SKA ...
telescope (SKA). The most recent Decadal report recommended ending the US's financial support of the SKA, although US participation in SKA precursors such as
MeerKAT
MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas in the Meerkat National Park, in the Northern Cape of South Africa. In 2003, South Africa submitted an expression of interest to host the Square Kilom ...
, the
Hydrogen Epoch of Reionization Array
The Hydrogen Epoch of Reionization Array (HERA) is a radio telescope dedicated to observing large scale structure during and prior to the epoch of reionization. HERA is a Square Kilometre Array (SKA) precursor instrument, intended to observe the ...
and the
Murchison Widefield Array
The Murchison Widefield Array (MWA) is a joint project between an international consortium of organisations to construct and operate a low-frequency radio array. 'Widefield' refers to its very large field of view (on the order of 30 degrees ac ...
.
Although cost estimates of unbuilt projects are always dubious, and the specifications are not identical (conventional telescopes have lower
noise temperature
In electronics, noise temperature is one way of expressing the level of available noise power introduced by a component or source. (This is to be distinguished from Temperature Noise in Thermodynamics or Principal Interferrometric Analysis Over C ...
, but the ATA has a larger
field of view
The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation.
Humans a ...
, 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 one third of the cost of a new copy of a
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that suppo ...
34 m antenna of similar collecting area. Similarly, the estimated total cost of building the remaining 308 dishes was estimated () at about $41 million.
This is about two times cheaper than the $85 million cost of the last large radio astronomy antenna built in the US, the
Green Bank Telescope
The Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia, US is the world's largest fully steerable radio telescope, surpassing the Effelsberg 100-m Radio Telescope in Germany. The Green Bank site was part of the National Radio ...
, of similar collecting area. The contractor filed for a $29 million overrun, but only $4 million of this was allowed.
The ATA aspires to be among the world's largest and fastest observing instruments, and to permit astronomers to search many different target stars simultaneously. If completed as originally envisioned, it will be one of the largest and most powerful telescopes in the world.
History
Since its inception, the ATA has been a development tool for
astronomical interferometer
An astronomical interferometer or telescope array is a set of separate telescopes, mirror segments, or radio telescope antenna (radio), antennas that work together as a single telescope to provide higher resolution images of astronomical objects ...
technology (specifically, for the
Square Kilometer Array
The Square Kilometre Array (SKA) is an intergovernmental international radio telescope project being built in Australia (low-frequency) and South Africa (mid-frequency). The combining infrastructure, the Square Kilometre Array Observatory (SKA ...
).
The ATA was originally planned to be constructed in four stages, 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). The ATA is planned to comprise 350 dishes with a diameter of 6 m each.
Regular operations with 42 dishes started on 11 October 2007.
Funding for building additional antennas is currently being sought by the
SETI Institute
The SETI Institute is a not-for-profit research organization incorporated in 1984 whose mission is to explore, understand, and explain the origin and nature of life in the universe, and to use this knowledge to inspire and guide present and futu ...
from various sources, including the
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
,
Defense Advanced Research Projects Agency
The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military.
Originally known as the Adv ...
(DARPA),
National Science Foundation
The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National I ...
(NSF) and private donors.
Simultaneous astronomical and SETI observations are performed with two 32-input dual
polarization imaging correlators. Numerous articles reporting conventional radio astronomy observations have been published.
Three phased array
beamformers utilizing the Berkeley Emulation Engine 2 (BEE2) were deployed in June 2007 and have been integrated into the system to allow for simultaneous astronomical and SETI observations. As of April 2008, the first
pulsar
A pulsar (from ''pulsating radio source'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Ea ...
observations were conducted using the beamformer and a purpose-built pulsar
spectrometer
A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...
.
The workhorse SETI search system
(SETI on ATA or SonATA) performs fully automated SETI observations. SonATA follows up on detected signals in real time and continues to track them until 1) the signal is shown to have been generated on Earth or rarely, 2) the source sets, which triggers follow up the next day. As of 2016, more that two hundred million signals have been followed up and classified using the ATA. Not one of these signals had all the characteristics expected for an ETI signal. The results of SETI Institute's observations are published in a number of papers.
In April 2011, the ATA was put into hibernation owing to funding shortfalls, meaning that it was no longer available for use. Operation of the ATA resumed on 5 December 2011.
Efforts are now led by
Andrew Siemion.
Status
In 2012, the ATA was funded by a $3.6 million philanthropic donation by Franklin Antonio, cofounder and Chief Scientist of
Qualcomm Incorporated
Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, ...
. This gift supports upgrades of all the receivers on the ATA dishes to have dramatically greater sensitivity (2 − 10× from 1–8 GHz) than before and support sensitive observations over a wider frequency range, from 1–15 GHz, when initially the radio frequency electronics went to only 11 GHz. By July 2016, the first ten of these receivers had been installed and proven. Full installation on all 42 antennas is planned .
In November 2015, the ATA studied the anomalous star
KIC 8462852
Tabby's Star (also known as Boyajian's Star and WTF Star, and designated KIC 8462852 in the Kepler Input Catalog) is an F-type main-sequence star in the constellation Cygnus (constellation), Cygnus approximately from Earth. Unusual ligh ...
, and in autumn 2017 the Allen Telescope Array examined the interstellar asteroid
'Oumuamua for signs of technology, but detected no unusual radio emissions.
Key science goals
The science goals listed below represent the most important projects to be conducted with the ATA. Each of these goals is associated with one of the four stages of development mentioned earlier. (See Table 1). Also listed is some of the science that it is hoped each will produce.
* Determine the
hydrogen line
The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , w ...
(HI) content of
galaxies
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
out to ''z'' ~ 0.2 over 3π
steradian
The steradian (symbol: sr) or square radian is the unit of solid angle in the International System of Units (SI). It is used in three-dimensional geometry, and is analogous to the radian, which quantifies planar angles. Whereas an angle in radian ...
s, in order to measure how much
intergalactic gas
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and Earth atmosphere, its atmosphere and between astronomical object, celestial bodies. Outer space is not completely empty—it is a Ultra-high vacuum, near-per ...
external galaxies are accreting; to search for dark, starless galaxies; to lay the foundation for
dark energy
In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
detection by the
Square Kilometer Array
The Square Kilometre Array (SKA) is an intergovernmental international radio telescope project being built in Australia (low-frequency) and South Africa (mid-frequency). The combining infrastructure, the Square Kilometre Array Observatory (SKA ...
.
* Classify 250,000 extra-galactic radio sources as
active galactic nuclei
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not prod ...
or
starburst galaxies
A starburst galaxy is one undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies. For example, the star formatio ...
, in order to probe and quantify star formation in the
Local Universe
The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acco ...
; to identify high
redshift
In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in f ...
objects; to probe large-scale structure in the Universe; to identify gravitational lens candidates for
dark matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
and
dark energy
In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
detection.
* Explore the
transient sky, in order to probe accretion onto
black hole
A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
s; to find orphan
gamma ray burst
In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milli ...
afterglows; to discover new and unknown transient phenomena.
* Survey 1,000,000 stars for
SETI
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other p ...
-related emission with enough sensitivity to detect an
Arecibo
Arecibo (; ) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about west of San Juan, the ...
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
out to 300
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s within the range of 1–10
GHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
.
* Survey the 4×10
10 stars of the inner
galactic plane
The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms ''galactic plane'' and ''galactic poles'' usuall ...
from 1.42–1.72 GHz for very powerful
transmitters
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
.
* Measure the
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
s in the
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
and other
Local Group
The Local Group is the galaxy group that includes the Milky Way.
It has a total diameter of roughly , and a total mass of the order of .
It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...
galaxies, in order to probe the role of magnetic fields in star formation and
galaxy formation and evolution
The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have ge ...
.
* Detect the
gravitational wave
Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1 ...
background from massive
black holes
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...
through
pulsar
A pulsar (from ''pulsating radio source'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Ea ...
timing.
* Measure
molecular cloud
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen ...
and
properties using new molecular tracers, in order to map star formation conditions on the scale of entire
giant molecular clouds (GMCs); to determine the
metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
gradient of the Milky Way.
Opportunistic science
Since construction of the
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
began, a few science goals not specifically drawn up for it have been suggested.
For example, the Allen Telescope Array has offered to provide the mooncast data downlink for any contestants in the
Google Lunar X Prize
The Google Lunar XPRIZE (GLXP), sometimes referred to as Moon 2.0,
was a 2007–2018 inducement prize space competition organized by the X Prize Foundation, and sponsored by Google. The challenge called for privately funded teams to be th ...
. This is practical, since the array, with no modifications, covers the
main space communications bands (S-band and X-band). A
telemetry
Telemetry is the in situ data collection, collection of measurements or other data at remote points and their automatic data transmission, transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Gr ...
decoder would be the only needed addition.
Also, the ATA was mentioned as a candidate for searching for a new type of radio
transient. It is an excellent choice for this owing to its large field of view and wide instantaneous bandwidth. Following this suggestion,
Andrew Siemion and an international team of astronomers and engineers developed an instrument called "Fly's Eye" that allowed the ATA to search for bright radio transients, and observations were carried out between February and April 2008.
Instruments
The ATA-42 configuration will provide a maximum baseline of 300 m (and ultimately for the ATA-350, 900 m). A cooled log-periodic feed on each antenna is designed to provide a system temperature of ~45K from 1–10 GHz, with reduced sensitivity in the ranges of 0.5–1.0 GHz and 10–11.2 GHz. Four separate frequency tunings (IFs) are available to produce 4 x 100 MHz intermediate frequency bands. Two IFs support correlators for imaging; two will support
SETI
The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other p ...
observing. All tunings can produce four dual polarization
phased array
In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving th ...
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 a smaller number of elements but considerably greater collecting area in 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
A point source is a single identifiable ''localised'' source of something. A point source has negligible extent, distinguishing it from other source geometries. Sources are called point sources because in mathematical modeling, these sources can ...
surveys. For point source surveys, the ATA-42 is comparable in speed to
Arecibo
Arecibo (; ) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about west of San Juan, the ...
and the
Green Bank Telescope
The Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia, US is the world's largest fully steerable radio telescope, surpassing the Effelsberg 100-m Radio Telescope in Germany. The Green Bank site was part of the National Radio ...
(GBT), but three times slower than the
Very Large Array
The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twen ...
(VLA). The ATA-350, on the other hand, will be one order of magnitude faster than the Very Large Array for point source surveys, and is comparable to the
Expanded Very Large Array (EVLA) in survey speed. For surveys up 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
Arecibo (; ) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about west of San Juan, the ...
and the GBT. The ATA, however, provides better resolution than either of these single-dish telescopes.
The antennas for the ATA are 6.1 x 7.0 meters (20.0 ft x 23.0 ft)
hydroformed
Hydroforming is a cost-effective way of shaping ductile metals such as aluminium, brass, low alloy steel, and stainless steel into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automot ...
offset
Gregorian telescope
The Gregorian telescope is a type of reflecting telescope designed by Scottish mathematician and astronomer James Gregory in the 17th century, and first built in 1673 by Robert Hooke. James Gregory was a contemporary of Isaac Newton. Both often ...
s, each with a 2.4 meter sub-reflector with an effective
focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative foca ...
/diameter (f/D) ratio of 0.65. (See DeBoer, 2001). The offset geometry eliminates blockage, which increases efficiency and decreases the
side lobe
In antenna engineering, sidelobes are the lobes (local maxima) of the far field radiation pattern of an antenna or other radiation source, that are not the ''main lobe''.
The radiation pattern of most antennas shows a pattern of "''lobes'' ...
s. It also allows for the large sub-reflector, providing good low frequency performance. The hydroforming technology used to make these surfaces is the same as that used by Andersen Manufacturing of Idaho Falls, Idaho to generate low-cost satellite reflectors. The unique interior frame rim-supported compact mount allows excellent performance at low cost. The drive system employs a spring-loaded passive anti-backlash azimuth drive train. Most components designed by Matthew Fleming and manufactured at Minex Engineering Corp. in
Antioch, CA
Antioch is the third-largest city in Contra Costa County, California, United States. Located in the East Bay region of the San Francisco Bay Area along the Sacramento–San Joaquin River Delta. The city's population was 115,291 at the 2020 cens ...
.
Data management
As with other
arrays
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
{{TOC right
Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
, the huge amount of incoming sensory information requires real-time
array processing
Array processing is a wide area of research in the field of signal processing that extends from the simplest form of 1 dimensional line arrays to 2 and 3 dimensional array geometries. Array structure can be defined as a set of sensors that are sp ...
capability in order to reduce data volume for storage. For ATA-256, the average data rates and total data volume for the correlator are estimated to be 100
Mbyte/s and 15
Pbyte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
s for the five-year survey period.
Experiments such as
transient surveys will exceed this rate significantly. The
beamformers produce data at a much higher rate (8
gigabytes
The gigabyte () is a multiple of the unit byte for digital information. The prefix ''giga'' means 109 in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB.
This definiti ...
per second (Gb/s)) but only a very small fraction of this data is archived. In 2009, the signal detection hardware and software was called Prelude, which was
composed of rack-mounted PCs augmented by two custom accelerator cards based on
digital signal processing
Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...
(DSP) and
field-programmable gate array
A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware d ...
(FPGA) chips. Each Programmable Detection Module (one of 28 PCs) can analyze 2 MHz of dual-polarization input data to generate spectra with spectral resolution of 0.7 Hz and time samples of 1.4 seconds.
In 2009, the array had a 40
Mbit/s
In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are multi ...
internet connection, adequate for remote access and transferring of data products for ATA-256. An upgrade to 40
Gbit/s
In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are multi ...
was planned, which would enable direct distribution of raw data for offsite computing.
Computational complexity and requirement
Like other array systems the ATA has a computational complexity and cross-connect which scales as
O(N
2) with the number of antennas
.
The computation requirement, for example, for correlating the full ATA bandwidth (
= 11 GHz) for the proposed
= 350 dual-polarization antenna build-out, using an efficient frequency-multiply
(FX) architecture and a modest 500 kHz channel width (with number of channels
= 2200), is given by:
[
]
= 44
Peta-
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pre ...
OPs per second
where
is an
operation
Operation or Operations may refer to:
Arts, entertainment and media
* ''Operation'' (game), a battery-operated board game that challenges dexterity
* Operation (music), a term used in musical set theory
* ''Operations'' (magazine), Multi-Ma ...
. Note that since each dish has a dual polarization antenna, each signal sample is actually a two data set, hence
.
See also
*
*
*
*
*
*
References
External links
*
*
The Search Continues with the Allen Telescope Array Mountain View, CA: ''SETI Institute''. March 25, 2004.
* Radio Astronomy Laboratory, University of California, Berkeley: NSF proposal, June 15, 2005.
* https://web.archive.org/web/20111006031806/https://setistars.org/
{{Portal bar, California, Astronomy, Stars, Spaceflight, Outer space, Solar System
Astronomical observatories in California
Radio telescopes
Search for extraterrestrial intelligence
Interferometric telescopes