Allen Telescope Array
The ATA is under construction at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California. When completed, the array is expected to consist of 350 antennas. The first phase with 42 antennas (ATA-42) is complete and became operational on 11 October 2007. However, in April 2011, the ATA was placed in operational hibernation due to funding shortfalls. In August 2011, short-term funding was found Operation of the ATA was resumed on December 5, 2011.
Organization: | SETI Institute & Radio Astronomy Laboratory |
Location : | Hat Creek Radio Observatory |
Coordinates : | Coordinates: 40.817°N 121.470°W |
Website : | seti.org |
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 by the Paul G. Allen Family Foundation. In March 2004, following successful completion of a three-year research and development phase, the SETI Institute unveiled a three-tier construction plan for the telescope. Construction began right after, due to the pledge of $13.5 million 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. Overall Paul Allen has contributed more than $30 million to the project.
In other words, cost cutting measures by US government meant it was taken offline. A lack of some $2.5 million means those running it* have to stop taking data, and shut down the array.
This has engendered screams of horror from people around the world. And, I might add, not just those of us who believe that there’s life out there.
The ATA is a ‘Large Number of Small Dishes’ (LNSD) Array. Its first phase went online in 2007, with 42 dishes. The idea was that it would eventually be made up of 350.
The dishes are small – only 6m in diameter – with smaller dishes being cheaper for the same collecting area that larger dishes. There are technical issues, however: to get the same sensitivity as larger dishes, the signals from all the telescopes need to be combined. This, happily, is now possible with the increasingly low cost of the necessary electronics.
All these beautiful dishes meant that the ATA was going to be able to conduct large, deep radio surveys of our skies which were previously not possible. Simultaneously, it was also going to scan the sky for SETI (the Search for Terrestrial Intelligence).
It was going to one of the world’s largest and most powerful telescopes.
And projects like SETI (as well as rather a lot of other science initiatives) are under increasing amounts of funding pressure.
Today, a friend pinged me a link to the infographic below, demonstrating beautifully how misaligned people’s pecuniary priorities can be. It compares the cost of running SETI for a year to, well, cruise missiles and bailing out banks. Franky, its embarassing.
The Allen Telescope Array Search for Electrostatic Discharges on Mars
After hibernating for more than seven months, a set of radio telescopes run by the SETI (Search for Extraterrestrial Intelligence) Institute has once again begun listening for signals from the many alien planet candidates discovered by NASA's Kepler space telescope, researchers announced Monday (Dec.5).
The antennas are offset Gregorian Telescope. The big dish (the primary reflector) is 6.1 meters (20 feet) in diameter and is a segment of a paraboloid. The axis (center) of the paraboloid is near the bottom edge of the dish - just like Dish TV. A big advantage of the offset is that the secondary reflector (the smaller dish (about 6 feet in diameter) does not obstruct the view of the primary. Radio "light" bounces off the primary onto the secondary, then off the secondary to the Log Periodic antenna, not shown, but at the V of the blue lines. An advantage of the large size of the secondary is its ability to reflect and focus lower frequencies than the usual radio telescope. Note that the aluminum is not shiny - as a condition of land usage by the National Park Service, the aluminum is made dull by "soda blasting". Dimensioned drawing.
Radio telescope
A radio telescope is form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes. In their astronomical role they differ from optical telescopes in that they operate in the radio frequency portion of the electromagnetic spectrum where they can detect and collect data on radio sources. Radio telescopes are typically large parabolic ("dish") antennas used singly or in an array. Radio observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, TV, radar, and other EMI emitting devices. This is similar to the locating of optical telescopes to avoid light pollution, with the difference being that radio observatories are often placed in valleys to further shield them from EMI as opposed to clear air mountain tops for optical observatories.
Early radio telescopes
The first radio antenna used to identify an astronomical radio source was one built by Karl Guthe Jansky, an engineer with Bell Telephone Laboratories, in 1931. Jansky was assigned the job of identifying sources of static that might interfere with radio telephone service. Jansky's antenna was an array of dipoles and reflectors designed to receive short wave radio signals at a frequency of 20.5 MHz (wavelength about 14.6 meters). It was mounted on a turntable that allowed it to rotate in any direction, earning it the name "Jansky's merry-go-round". It had a diameter of approximately 100 ft (30 m). and stood 20 ft (6 m). tall. By rotating the antenna on a set of four Ford Model-T tires, the direction of the received interfering radio source (static) could be pinpointed. A small shed to the side of the antenna housed an analog pen-and-paper recording system. After recording signals from all directions for several months, Jansky eventually categorized them into three types of static: nearby thunderstorms, distant thunderstorms, and a faint steady hiss of unknown origin. Jansky finally determined that the "faint hiss" repeated on a cycle of 23 hours and 56 minutes. This period is the length of an astronomical sidereal day, the time it takes any "fixed" object located on the celestial to come back to the same location in the sky.
An amateur radio operator, Grote Reber, was one of the pioneers of what became known as radio astronomy when he built the first parabolic "dish" radio telescope (9 meters (30 ft) in diameter) in his back yard in Illinois in 1937. He was instrumental in repeating Karl Guthe Jansky's pioneering but somewhat simple work at higher frequencies, and he went on to conduct the first sky survey at very high radio frequencies. The rapid development of radar technology during World War II was easily translated into radio astronomy technology after the war, and the field of radio astronomy began to blossom.
Status of ATA
Ø 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.
Ø The ATA was originally planned to be constructed in four 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.
Ø Regular operations with 42 dishes started on 11 October 2007. Funding for building additional antennas is currently being sought by the RAL from various sources, including the US Navy, DARPA, NSF and private donors.
Ø Astronomical data has been acquired since May 2005, utilizing a four-input correlator (four antennas, dual polarization) and then updated in January 2007 with two eight-input (16 antennas, dual polarization).Scientifically useful data has been acquired and is helping commission the array
Ø As of April 2011, the ATA has been placed in hibernation mode due to funding shortfalls, meaning that it is no longer available for use.
Ø Operation of the ATA was resumed on December 5, 2011.
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 ~45K from 1 GHz to 10 GHz, with reduced sensitivity in the range 0.5 GHz to 1.0 GHz and 10 GHz to 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 antennae for the ATA are 6.1 m × 7.0 m hydro formed offset Gregorian telescopes, each with a 2.4-meter sub reflector with an effective f/D of 0.65. (DeBoer, 2001). The offset geometry eliminates blockage, which increases the efficiency and decreases the side lobes. It also allows for the large sub reflector, providing good low frequency performance. The hydro forming technology used to make these surfaces is the same hydro forming technique used to generate low-cost satellite reflectors by Andersen Manufacturing of Idaho Falls, Idaho. 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.
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