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Report - Mullard Observatory Cambs, Sept 2011

Discussion in 'Other Sites' started by Tassadar, Oct 16, 2011.

  1. Tassadar

    Tassadar 28DL Full Member
    28DL Full Member

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    While in the area would have been rude to miss out on these, the nice security dude dint seem to object to us roaming either

    Mullard Radio Astronomy Observatory is home to a number of large aperture synthesis radio telescopes, including the One-Mile Telescope, 5-km Ryle Telescope, and the Arcminute Microkelvin Imager. Radio interferometry started in the mid-1940s on the outskirts of Cambridge, but with funding from the Science Research Council and a donation of £100,000 from Mullard Limited, construction of the Mullard Radio Astronomy Observatory commenced at Lord's Bridge, a few kilometres to the west of Cambridge and was opened by Sir Edward Victor Appleton on 25 July 1957. This group is now known as the Cavendish Astrophysics Group.

    The Half-Mile Telescope was constructed in 1968 (2 aerials) at the Mullard Radio Astronomy Observatory with two more aerials being added in 1972, using donated dishes (total cost was £70,000). Two of the dishes are fixed, while two are moveable and share the One-Mile's rail track; to obtain information from the maximum number of different baselines, 30 days of observing were required. Observing frequency 1.4 GHz (21 cm wavelength), bandwidth 4 MHz. Used for Hydrogen Line studies of nearby galaxies and produced the first good radio maps of hydrogen distribution (as a function of its velocity), for M33 and M31 (also produced nearly 20 PhDs and 50 published papers). The telescope was operated by the Radio Astronomy Group of the Cambridge University.

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    The 4C Array is a cylindrical paraboloid radio telescope at the Mullard Radio Astronomy Observatory. It is similar in design to the Molonglo Observatory Synthesis Telescope. It is 450 m long, 20 m wide, with a second, moveable element (now mostly removed; some of it is still visible, beyond COAST). The first large aperture synthesis telescope (1958), it was also the first new instrument to be built at Lord's Bridge, after the Observatory was moved there in 1957, and needed 64 km (40 mi) of reflector wire (since removed). The 4C operated at 178 MHz (1.7 m), and located nearly 5000 sources of the 4C (4th Cambridge) catalogue published in 1965 and 1966, which helped establish the evolution of the radio galaxy population of the universe. The telescope is now inoperable.
    It is flanked to the northwest by the Cosmic Anisotropy Telescope enclosure and to the south by the One-Mile and Half-Mile Telescopes

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    The Interplanetary Scintillation Array (IPS Array or Pulsar Array) was built at the Mullard Radio Astronomy Observatory in 1967 and originally covered four acres (16,000 m²). It was extended in 1978 to nine, and re-furbished in 1989. It operates at 81.5 MHz (3.7 m wavelength), and is made up of 4096 dipoles in a phased array. 14 beams can map the northern sky in one day. Sheep are used to keep grass away from the aerials as a lawnmower would not fit. It was designed by Antony Hewish to measure the high-frequency fluctuations of radio sources, originally for monitoring interplanetary scintillation. Antony Hewish received a Nobel prize after the high time-resolution of the array allowed the detection of pulsars by Jocelyn Bell in 1967. The IPS has more recently been used to track and help forecast interplanetary weather, and specifically to monitor the solar wind. It is now essentially retired, and has lost significant fraction of its area. The telescope was operated by the Cavendish Astrophysics Group.

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    The One Mile Telescope was completed by the Radio Astronomy Group of Cambridge University in 1964. The telescope was used to produce the 5C catalogue of radio sources.
    Observations with larger incremental spacings were used to observe individual radio sources with unprecedented sensitivity, angular resolution, and image quality. These surveys required intensive use of inverse Fourier Transforms, and were made possible by development of a new generation of computers such as the Titan.
    In 1971, Sir Martin Ryle described why, in the late 1950s, radio astronomers at MRAO decided on the construction of the new One Mile telescope: "Our object was twofold. First we wanted to extend the range of our observations far back in time to the earliest days of the Universe, and this required a large increase in both sensitivity and resolution. With greater resolution we hoped that we might be able to draw radio maps of individual radio sources with sufficient detail to give some indication of the physical processes which brought them into being."
    One of the One Mile Telescope dishes was temporarily used to improve the resolution of MERLIN (then MTRLI) from 1987 until Autumn 1990.

    The One-Mile Telescope, was the first to use Earth-rotation aperture synthesis (described by Ryle as "super-synthesis") and the first to give radio maps with a resolution better than that of the human eye. The telescope was made up of three 120 ton dishes, each of which is 18 m in diameter. Two of the dishes are fixed, while the third can be moved along an 800 m long (half mile) rail track, at speeds of up to 6.4 km/h. There were 60 different stations along the track, which is straight to within 0.9 cm, and whose far end was raised by 5 cm to allow for the curvature of the Earth over its length. The observing frequencies were usually 408 MHz (75 cm; the resolution was 80 arcsec)and 1.4 GHz (21 cm; the resolution was 20 arcsec, three times better than that of the unaided eye).

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    The Cosmic Anisotropy Telescope CAT was a three-element interferometer for cosmic microwave background radiation (CMB/R) observations at 13 to 17 GHz, based at the Mullard Radio Astronomy Observatory. In 1995, it was the first instrument to measure small-scale structure in the cosmic microwave background. When the more sensitive Very Small Array came online, the CAT telescope was decommissioned in a ceremonial bonfire.

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    Control room for the One mile array

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    Thanks


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