[asac] [almanews] ALMA Memo 352 Released

[Carolyn White]

ALMA Memo No. 352

Design and Development of 183 GHz Water Vapour Radiometers

R. Hills(MRAO), H. Gibson(MRAO/SAO), J. Richer(MRAO), H. Smith(MRAO), 
V. Belitsky(OSO/Chalmers), R. Booth(OSO/Chalmers), D. Urbain(OSO/Chalmers)

March 06, 2001

This memo describes the plans for the development of the prototype 183 GHz
radiometers for ALMA.  It is planned that such radiometers will be used to
correct for the phase errors introduced by water vapour in the atmosphere.
One radiometer will be mounted on each of the antennas and will provide
real-time measurements of the brightness temperature of the atmosphere at
frequencies near the 183 GHz emission line of water.  These measurements
will be used to estimate the path fluctuations that are caused by the
variations in the amount of water vapour along the line of sight from each
antenna.  Even on a good site corrections for these fluctuations will be
needed for much of the time, especially at ALMA higher frequency bands and
on long baselines.  A substantial amount of work on the design of the
radiometers has already been carried out, so this document contains a
description of the instruments to be built, at the level of a conceptual
design.  Two radiometers of somewhat different designs, but with most
components in common, will be built and tested.  The intention is to
develop a cost-effective and reliable final design suitable for production
in quantity.  It is expected that the prototype radiometers constructed
here will subsequently be used for tests in the field, both to sort out
compatibility issues with the rest of the ALMA system and to develop the
phase-correction techniques further.  The project is being carried out as
a collaboration between Chalmers and MRAO.

View a pdf version of ALMA Memo 352:
     
     http://www.alma.nrao.edu/memos/html-memos/alma352/memo352.pdf

Download a postscript version of ALMA Memo 352

     http://www.alma.nrao.edu/memos/html-memos/alma352/memo352.ps
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