2007A&A...465..685N


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.18CEST07:03:07

2007A&A...465..685N - Astronomy and Astrophysics, volume 465, 685-693 (2007/4-2)

Out-of-focus holography at the Green Bank Telescope.

NIKOLIC B., PRESTAGE R.M., BALSER D.S., CHANDLER C.J. and HILLS R.E.

Abstract (from CDS):

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 7mm. We use the technique with parameterization of the aperture in terms of Zernike polynomials and employing a large defocus, as described by Nikolic et al. (2007A&A...465..679N). Individual measurements take around 25min 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 λ/100. 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.

Abstract Copyright:

Journal keyword(s): telescopes

Simbad objects: 5

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Number of rows : 5

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 3C 84 Sy2 03 19 48.1597607660 +41 30 42.114155434   13.10 12.48 11.09   ~ 3460 3
2 3C 279 QSO 12 56 11.1664521013 -05 47 21.531840471   18.01 17.75 15.87   ~ 2634 2
3 3C 345 QSO 16 42 58.8100340220 +39 48 36.999540578   16.81 16.59 16.84   ~ 1532 2
4 4C 06.69 QSO 21 48 05.4585565234 +06 57 38.605396596   16.85 16.47 15.06   ~ 582 1
5 3C 454.3 QSO 22 53 57.74798 +16 08 53.5611   16.57 16.10 15.22   ~ 2439 2

    Equat.    Gal    SGal    Ecl

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2019.10.18-07:03:07

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