Computer Science – Performance
Scientific paper
Nov 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993pasp..105.1334b&link_type=abstract
Astronomical Society of the Pacific, Publications (ISSN 0004-6280), vol. 105, no. 693, p. 1334-1341
Computer Science
Performance
12
Antenna Design, Parabolic Antennas, Performance Prediction, Radio Telescopes, Subreflectors, Efficiency, Sidelobes, Surface Distortion, Temperature Effects
Scientific paper
In this paper we describe a program to upgrade the Haystack 37-m radio telescope for operations at lambda 3 mm. Attainment of useable antenna efficiency at these relatively short wavelengths (Haystack was originally designed for use at lambda 3 cm) required, in addition to extensive and careful resetting of the surface panels, two critical developments for control or correction of surface distortions. One is a system for active thermal control of a crucial element of the antenna structure--the splice plate, a heavy aluminum ring that serves to join the inner and outer antenna panels. Thermal lags in this ring relative to the panels previously caused high amplitude, ring-like deformations on the surface. The other development was necessitated by the early, nonhomologous, antenna design, which led to astigmatic and ring-like deformations with elevation angle. Part of the ring distortions can be corrected by the active thermal-control system, but one full ring and part of another do not respond to thermal control. A novel deformable subreflector was developed to correct phase errors arising on the antenna as a result of astigmatism and ring distortions. Haystack is now fully operational across the 86-115 GHz frequency range, with a nearly diffraction-limited primary beam (20 arcsecs at 115 GHz), and moderate efficiency--13% aperture and 18% beam efficiency at 15 GHz. The current 115 GHz sensitivity of 50 mK/Jy is the highest of any lambda 3-mm antenna in the U.S. The highest sidelobes are below - 15 dB. A sensitive, two-channel SIS mixer radiometer has been developed, with system temperatures of 200-400 K (depending on frequency) under dry conditions, followed by a flexible new autocorrelation spectrometer with 4096 lags and 160 MHz bandwidth.
Ball John A.
Barvainis Richard
Ingalls Richard P.
Salah Joseph E.
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