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What vpmanager does:

Set a Given Telescope’s VP/PB model

The vpmanager recognizes the names of several telescopes: ATCA, GBT, GMRT, HATCREEK, NMA, NRAO12M, NRAO140FT, OVRO, VLA, WSRT. New telescopes and their default VP/PB models will need to be added to the system.

Common VP/PB Models

Many common voltage pattern (vp) and primary beam (pb) models have been coded into CASA. Currently, the recognized models include DEFAULT, ATCA_L1, ATCA_L2, ATCA_L3, ATCA_S, ATCA_C, ATCA_X, GBT, GMRT, HATCREEK, NRAO12M, NRAO140FT, OVRO, VLA, VLA_INVERSE, VLA_NVSS, VLA_2NULL, VLA_4, VLA_P, VLA_L, VLA_C, VLA_X, VLA_U, VLA_K, VLA_Q, WSRT, and WSRT_LOW. In all cases, the VP/PB model and the beam squint (if present) scale linearly with wavelength. If DEFAULT is selected, the appropriate VP/PB model is selected for the telescope and observing frequency.

1-D Beam Models

Most beam models are rotationally symmetric (excepting beam squint). From the beam parameterization in terms of the various coefficients and other terms, an internal lookup table with 10000 elements is created for application of the VP/PB to an image.

Beam Squint

The VP/PB models include beam squint. The VLA_L, VLA_C, VLA_X, VLA_U, VLA_K, and VLA_Q models (which are the defaults for those VLA bands), have the appropriate squint magnitude and orientation, though the orientation has not been verified through processing actual data.

Multiple VP/PB Models for one MS

The VPManager can have VP information for multiple telescopes. However, the internals of imager cannot yet deal with VP/PB’s for multiple telescopes. In the case of a MS with multiple telescopes present, the primary beam of the first telescope present in the MS will be used, even if it is not the first telescope specified in the VP description table produced by vpmanager.

Antenna-dependent Voltage Patterns

are not yet supported.

Two-dimensional Voltage Pattern Images

are supported via setpbimage.

Methods

Description

The vpmanager, or voltage pattern manager, creates a table with the description of one or more voltage patterns (vp) or primary beams (pb). There is a mapping between telescope name and the vp or pb description. The vp description table can be read by imager’s setvp method, which instantiates the corresponding voltage patterns from the descriptions and applies them to the images. While the vp description table can have multiple telescopes in it, limitations to the internal visibility buffers currently limit the functionality within imager to a single telescope.

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Copyright © 2008 Associated Universities Inc., Washington, D.C.

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