19 research outputs found
Evaluation of the ALMA Prototype Antennas
The ALMA North American and European prototype antennas have been evaluated
by a variety of measurement systems to quantify the major performance
specifications. Nearfield holography was used to set the reflector surfaces to
17 microns RMS. Pointing and fast switching performance was determined with an
optical telescope and by millimeter wavelength radiometry, yielding 2 arcsec
absolute and 0.6 arcsec offset pointing accuracies. Path length stability was
measured to be less than or approximately equal to 20 microns over 10 minute
time periods using optical measurement devices. Dynamical performance was
studied with a set of accelerometers, providing data on wind induced tracking
errors and structural deformation. Considering all measurements made during
this evaluation, both prototype antennas meet the major ALMA antenna
performance specifications.Comment: 83 pages, 36 figures, AASTex format, to appear in PASP September 2006
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The paraboloidal reflector antenna in radio astronomy and communication: theory and practice
Reflector antennas are widely used in the microwave and millimeter wavelength domain. Radio astronomers have developed techniques of calibration of large antennas with radio astronomical methods. These have not been comprehensively described. This text aims to fill this gap. The Paraboloidal Reflector Antenna in Radio Astronomy and Communication: Theory and Practice takes a practical approach to the characterization of antennas. All calculations and results in the form of tables and figures have been made with Mathematica by Wolfram Research. The reader can use the procedures for the implementation of his/her own input data. The book should be of use to all who are involved in the design and calibration of large antennas, like ground station managers and engineers, practicing radio astronomers, and finally, graduate students in radio astronomy and communication technology