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TOPIC: Green Bank Telescope


L

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RE: Green Bank Telescope
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The Robert C. Byrd Green Bank Telescope is the most overbooked telescope in the world. The waiting list to get some time on the telescope is long and prestigious. And with good cause: Its sensitivity to radio signals is unparalleled.
The telescope is so sensitive, in fact, that the National Radio Astronomy Observatory (NRAO) has a van that drives around the surrounding countryside asking people to stop using their wireless speaker systems, electric fences, broadband wireless modems, military radar, etc. - anything that might interfere with the telescopes readings.

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An Indian scientist, Dr Srikanta Pal, has rectified the problem of satellite signals interfering with the observation of the universe by the world's largest telescope in the US.
The Robert C Byrd Green Bank Telescope located at the National Radio Astronomy Observatory's site at Pocahontas County in West Virginia, had been exhibiting the problem  since August 2000.

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Of all the threats to scientific research Wesley Sizemore has stymied over the years, satellites and cell phone towers don't stick in his memory quite like the possessive old hound and its treasured heating pad.
Sizemore is an interference hunter, vigilantly pursuing stray electromagnetic signals that bedevil researchers at the National Radio Astronomy Observatory, which sits on 13,000 square miles tucked away in the nation's only radio-free quiet zone.

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L

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Of all the threats to scientific research Wesley Sizemore has stymied over the years, satellites and cell phone towers don't stick in his memory quite like the possessive old hound and its treasured heating pad.
Sizemore is an interference hunter, vigilantly pursuing stray electromagnetic signals that bedevil researchers at the National Radio Astronomy Observatory, which sits on 13,000 square miles tucked away in the nation's only radio-free quiet zone.
Radio observatories need interference-free zones like optical observatories need clear night skies.
Though buffered by ridgetops in a West Virginia mountain valley, 50 miles from the nearest town of any size, the Green Bank observatory is under an audio assault unlike any it's faced in the 50 years since Congress created the quiet zone. Wireless computers and other gadgets are cluttering the same frequencies occupied by signals from neutron stars.

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This is a video made from a spot under the dish of the Robert C. Byrd Green Bank Telescope, the largest fully steerable radio telescope in the world.



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L

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Green Bank Telescope in Lightning Storm (Hi-Res)



Green Bank Telescope in Lightning Storm (Lo-Res)



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L

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Astronomy in Green Bank, West Virginia
A new book published by the National Radio Astronomy Observatory (NRAO) tells the story of the founding and early years of the Observatory at Green Bank, West Virginia. But it was Fun: the first forty years of radio astronomy at Green Bank, is not a formal history, but rather a scrapbook of early memos, recollections, anecdotes and reports. But it was Fun... is liberally illustrated with archival photographs. It includes historical and scientific papers from symposia held in 1987 and 1995 to celebrate the birthdays of two of the radio telescopes at the Observatory.
The National Radio Astronomy Observatory was formed in 1956 after the National Science Foundation decided to establish an observatory in the eastern United States for the study of faint radio signals from distant objects in the Universe. But it was Fun... reprints early memos from the group of scientists who searched the mountains for a suitable site -- an area free from radio transmitters and other sources of radio interference -- "in a valley surrounded by as many ranges of high mountains in as many directions as possible," which was "at least 50 miles distant from any city or other concentration of people." The committee settled on Green Bank, a small village in West Virginia, and the book documents the struggles that followed to create a world-class scientific facility in an isolated area more accustomed to cows than computers.

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National Radio Astronomy Observatory
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National Radio Astronomy Observatory celebrates milestone
The National Radio Astronomy Observatory celebrated the 50th anniversary of the groundbreaking for its first facility last week.
On June 14, staff members cut cakes at Socorro's Array Operations Centre; the Very Large Array; Green Bank, W. Va.; Charlottesville, Va.; and the Atacama Large Millimeter Array, in Chile, said Socorro centre Public Information Officer David Finley. They watched each other's events via video feed.
Public Education Officer Robyn Harrison said the celebration honoured the first groundbreaking in Green Bank, the earliest NRAO facility.

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Green Bank Telescope
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Title: Out-Of-Focus Holography at the Green Bank Telescope
Authors: B. Nikolic, R. M. Prestage, D. S. Balser, C. J. Chandler, R. E. Hills

We describe phase-retrieval holography measurements of the 100-m diameter Green Bank Telescope using astronomical sources and an astronomical receiver operating at a wavelength of 7 mm. We use the technique with parameterisation of the aperture in terms of Zernike polynomials and employing a large defocus, as described by Nikolic, Hills & Richer (2006). Individual measurements take around 25 minutes and from the resulting beam maps (which have peak signal to noise ratios of 200:1) we show that it is possible to produce low-resolution maps of the wavefront errors with accuracy around a hundredth of a wavelength.
Using such measurements over a wide range of elevations, we have calculated a model for the wavefront-errors due to the uncompensated gravitational deformation of the telescope. This model produces a significant improvement at low elevations, where these errors are expected to be the largest; after applying the model, the aperture efficiency is largely independent of elevation. We have also demonstrated that the technique can be used to measure and largely correct for thermal deformations of the antenna, which often exceed the uncompensated gravitational deformations during daytime observing.
We conclude that the aberrations induced by gravity and thermal effects are large-scale and the technique used here is particularly suitable for measuring such deformations in large millimetre wave radio telescopes.

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