Flux Density Models for Solar System Bodies in CASA

Flux Density Models for Solar System Bodies in CASA

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ALMA Memo # 594


Flux Density Models for Solar System Bodies in CASA

B. Butler

NRAO

2012-12-05

CASA 4.0 introduces a modification to the way that the flux densities of solar system bodies are calculated, in order to use them for setting the flux density scale in ALMA observations. The bodies included are: Venus, Mars, Jupiter, Uranus, Neptune, Io, Europa, Ganymede, Callisto, Titan, Ceres, Vesta, Pallas, and Juno. These models may be extended to work for other wavelengths (particularly for VLA), but for now they should only be used for ALMA. The main difference from how it was done previously in CASA is in the brightness temperature models for these bodies, but there is also a change in the way that their sky brightness model is calculated, since setjy no longer writes directly into the deprecated MODEL column. This memo describes how the previous flux densities were calculated, and how that has changed in CASA 4.0. The new models are called “Butler-­‐JPL-­‐Horizons 2012” while the old ones were called “Butler-­‐JPL-­‐Horizons 2010”. Many of the “m odels” in the 2010 version were not true models at all, but rather put in by CASA programmers with little to no oversight. This has been remedied in the 2012 versions, for all supported bodies (though the asteroids are still poorly modeled). The detailed description for each body in Appendix A describes the provenance of its model.

View a pdf version of ALMA Memo #594.

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