The executables bin/antab2sefd and bin/applycal, use routines in eat.postproc to perform a priori amplitude calibration and field-angle rotation correction. antab2sefd reads Tsys values for all timestamps for each station from the ANTAB files and computes SEFDs for each station and source over time, with the outputs organised as SEFD/SEFD_<band>/<expt_no>/<source>_<station.txt>.
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If Tsys measurements are missing for some timestamps for a given (source, station) combination, then the corresponding timestamps are missing from the output text files containing SEFDs. When applycal is invoked, the SEFDs are interpolated or extrapolated (using the same interpolation scheme) as necessary during calibration.
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If no Tsys measurements are found for a given (source, station) combination in the ANTAB files (i.e. if multiple chunks of timestamps are missing so that all scans for a given source are missing Tsys measurements), then the corresponding <source>_<station>.txt file is never created, even if the station is known to have observed the source. In this case, the SEFD is set to unity during calibration.
Either of the above two cases can explain unexpectedly high/low a priori calibrated amplitudes. Has this behaviour been observed in past EHT data/metadata? If so, what is the best way to handle/improve apriori amplitude calibration when Tsys values are missing?
The executables
bin/antab2sefdandbin/applycal, use routines ineat.postprocto perform a priori amplitude calibration and field-angle rotation correction.antab2sefdreads Tsys values for all timestamps for each station from the ANTAB files and computes SEFDs for each station and source over time, with the outputs organised asSEFD/SEFD_<band>/<expt_no>/<source>_<station.txt>.If Tsys measurements are missing for some timestamps for a given (source, station) combination, then the corresponding timestamps are missing from the output text files containing SEFDs. When
applycalis invoked, the SEFDs are interpolated or extrapolated (using the same interpolation scheme) as necessary during calibration.If no Tsys measurements are found for a given (source, station) combination in the ANTAB files (i.e. if multiple chunks of timestamps are missing so that all scans for a given source are missing Tsys measurements), then the corresponding
<source>_<station>.txtfile is never created, even if the station is known to have observed the source. In this case, the SEFD is set to unity during calibration.Either of the above two cases can explain unexpectedly high/low a priori calibrated amplitudes. Has this behaviour been observed in past EHT data/metadata? If so, what is the best way to handle/improve apriori amplitude calibration when Tsys values are missing?