Primary Beam and Dish Surface Characterization at the Allen Telescope Array by Radio Holography
Creators: name: ATA GROUP
name: Atkinson, Shannon
name: Backer, D. C.
name: Backus, P. R.
name: Barott, William
name: Bauermeister, Amber
name: Blitz, Leo
name: Bock, D. C. -J.
name: Bower, Geoffrey C.
name: Bradford, Tucker
name: Cheng, Calvin
name: Croft, Steve
name: Dexter, Matt
name: Dreher, John
name: Engargiola, Greg
name: Fields, Ed
name: Heiles, Carl
name: Helfer, Tamara
name: Jordan, Jane
name: Jorgensen, Susan
name: Kilsdonk, Tom
name: Gutierrez-Kraybill, Colby
name: Keating, Garrett
name: Law, Casey
name: Lugten, John
name: MacMahon, D. H. E.
name: McMahon, Peter
name: Milgrome, Oren
name: Siemion, Andrew
name: Smolek, Ken
name: Thornton, Douglas
name: Pierson, Tom
name: Randall, Karen
name: Ross, John
name: Shostak, Seth
name: Tarter, J. C.
name: Urry, Lynn
name: Werthimer, Dan
name: Williams, Peter K. G.
name: Whysong, David
name: Harp, G. R.
name: Ackermann, R. F.
name: Nadler, Z. J.
name: Blair, Samantha K.
name: Davis, M. M.
name: Wright, M. C. H.
name: Forster, J. R.
name: DeBoer, D. R.
name: Welch, W. J.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The Allen Telescope Array (ATA) is a cm-wave interferometer in California, comprising 42 antenna elements with 6-m diameter dishes. We characterize the antenna optical accuracy using two-antenna interferometry and radio holography. The distortion of each telescope relative to the average is small, with RMS differences of 1 percent of beam peak value. Holography provides images of dish illumination pattern, allowing characterization of as-built mirror surfaces. The ATA dishes can experience mm-scale distortions across -2 meter lengths due to mounting stresses or solar radiation. Experimental RMS errors are 0.7 mm at night and 3 mm under worst case solar illumination. For frequencies 4, 10, and 15 GHz, the nighttime values indicate sensitivity losses of 1, 10 and 20 percent, respectively. The ATA.s exceptional wide-bandwidth permits observations over a continuous range 0.5 to 11.2 GHz, and future retrofits may increase this range to 15 GHz. Beam patterns show a slowly varying focus frequency dependence. We probe the antenna optical gain and beam pattern stability as a function of focus and observation frequency, concluding that ATA can produce high fidelity images over a decade of simultaneous observation frequencies. In the day, the antenna sensitivity and pointing accuracy are affected. We find that at frequencies greater than 5 GHz, daytime observations greater than 5 GHz will suffer some sensitivity loss and it may be necessary to make antenna pointing corrections on a 1 to 2 hourly basis.
description: 19 pages, 23 figures, 3 tables, Authors indicated by an double dagger ({\ddag}) are affiliated with the SETI Institute, Mountain View, CA 95070. Authors indicated by a section break ({\S}) are affiliated with the Hat Creek Radio Observatory and/or the Radio Astronomy Laboratory, both affiliated with the University of California Berkeley, Berkeley CA