RFI Flagging, Demixing and Visibilities Compression
The raw correlated visibility data that comes out of the correlator contains radio-frequency interference: signal originating not from celestial sources but, for example, television signals. To enable removing the unwanted interference, the raw data is stored at very high resolution. On this high resolution, the data can be flagged. Also, some more unwanted signal can be removed, namely from very strong celestial sources that are not in the field of view. Demixing is a technique to remove their signal in a relatively cheap way. Once the unwanted signals are removed at high resolution, the data can be averaged down in time and or frequency. All these steps will be discussed in this chapter.
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