 News |
FAQ
|
| Search
|
Home
|
| Getting Started | Documentation | Glish | Learn More | Programming | Contact Us |
|
| Version 1.9 Build 803 |
|
When solving for visibility-plane calibration components, the calibrater tool compares the observed DATA column with the MODEL_DATA column. The first time that an imager or calibrater tool is constructed for a given MS, the MODEL_DATA column is created and initialized with unit point source flux density visibilities (unpolarized) for all sources (e.g. AMP=1, phase=0o). The Imager.setjy function is then used to set the proper flux density for flux density calibrators. For sources that are recognized flux density calibrators (listed in Table 1.3), Imager.setjy will calculate the flux densities, Fourier transform the data and write the results to the MODEL_DATA column. For the VLA, the default source models are customarily point sources defined by the Baars or Perley-Taylor flux density scales, or point sources of unit flux density if the flux density is unknown. The MODEL_DATA column can also be filled with a model generated from an image of the source (e.g. the Fourier transform of an image generated after initial calibration of the data).