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The Implementation of Ionospheric Corrections in CASA

Thursday September 11, 2014
2:00 pm


 Presenter:  Jason Kool (Iowa)
 Series:  Center for Astrophysics Research and Technologies Seminar Series
 Abstract:  In order to provide a means of externally calibrating low frequency (< 8 GHz) data, it has become common practice to use global ionospheric models derived from the Global Positioning System (GPS). The Common Astronomy Software Applications (CASA) package, which was developed to meet the data post-processing needs of next generation telescopes such as the Karl G. Jansky Very Large Array, does not currently have the capability to mitigate ionospheric effects. However, in order to support the needs of the low frequency radioastronomical community, we have developed a new calibration method in CASA to facilitate GPS-based ionospheric corrections. We investigated two data centers as potential sources for global ionospheric models: the International Global Navigation Satellite System Service (IGS) and the MIT Automated Processing of GPS (MAPGPS) stored on the Madrigal database. We elected to use the IGS data because the MAPGPS data is too sparse to use without additional interpolation schemes. The prototype code to implement ionospheric corrections is written in both Python and C++. The Python module produces a TEC data cube (with axes of longitude, latitude, and time) that is then used at the C++ level to mitigate the first and second order ionospheric effects (dispersion delay and Faraday rotation, respectively). In this talk, we will discuss this implementation as well as a set of test observations designed to demonstrate (1) the presence of ionospheric effects and (2) the ability of our newly developed code to reduce these effects.
 Location:  PAIS-2540, PAIS

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