National Radio
Astronomy Observatory

5.2.13 Primary beams in imaging

The CASA imaging task and tools use primary beams based on models for each observatory’s antenna types. In addition to different antenna diameters, different functions may be used.

The voltage patterns are based on the following antenna primary beams, based on the TELESCOPE_NAME keyword in the OBSERVATION table:

VLA

— Airy disk fitted to measurement. Note that a R/L beam squint is also included with feed dependent angle;

ALMA

— Airy disk for 12m dish with a blockage of 1m;

ATA

— Airy disk for 6m dish;

ATCA

— polynomial fitted to measurement of main lobe;

BIMA, HATCREEK

— Gaussian with halfwidth of λ/2D;

CARMA

— Airy patterns for the BIMA or OVRO dish sizes as appropriate;

GBT

— polynomial fitted to measurement of main lobe;

GMRT

— VLA Airy disk scaled to 45.0m;

IRAMPDB

— Airy disk for dish of 15m with a blockage of 1m;

NRAO12M

— VLA beam scaled to 12m;

OVRO

— VLA Airy disk scaled to 10.4m;

SMA

— Spheroidal function fit to FWHM;

WSRT

— polynomial fitted to measurement of main lobe;

If the telescope name is unknown, or is CARMA or ALMA, then the DISH_DIAMETER in the ANTENNA table is used with a scaled VLA pattern.

Note that for the purposes of mosaicing in clean, the primary beams that are Airy or spheroidal are best-behaved (see § 5.3.15).

More information about CASA may be found at the CASA web page

Copyright © 2010 Associated Universities Inc., Washington, D.C.

This code is available under the terms of the GNU General Public Lincense