do_wide_field_pos_cor

do_wide_field_pos_cor(fitsname: str, date_time: EpochDict | None = None, obs_long: QuantityDict | None = None, obs_lat: QuantityDict | None = None) → None[source]

Applies mean wide field position correction to FITS WCS in place.

Apply a mean correction to the FITS WCS reference position as a function of mean hour angle of observation and mean declination (see PIPE-587, PIPE-700, SRDP-412, and VLASS Memo #14).

The correction is intended for VLASS-QL images. It is performed as part of the hifv_exportvlassdata task call in the VLASS-QL pipeline run. It can also be executed outside of the pipeline.

CRVAL1, CUNIT1, CRVAL2, CUNIT2 and HISTORY keywords are updated in place in the input FITS image header. ZD and TELMJD keywords describe the zenith distance value and time of zenith distance, respectively.

Parameters:

  • fitsname -- name (and path) of FITS file to be processed.

  • date_time --

    Mean date and time of observation in casa_tools.measure.epoch format, if None use DATE-OBS FITS header value. e.g. {'m0': {'unit': 'd', 'value': 58089.83550347222},

    'refer': 'UTC', 'type': 'epoch'}

  • obs_long -- Geographic longitude of observatory, casa_tools.quanta.quantity format. If None, then use VLA coordinate. e.g. {'value': -107.6, 'unit': 'deg'}.

  • obs_lat -- Geographic latitude of observatory, casa_tools.quanta.quantity format. If None, then use VLA coordinate. e.g. {'value': 34.1, 'unit': 'deg'}.

Example

file = "VLASS1.1.ql.T19t20.J155950+333000.10.2048.v1.I.iter1.image.pbcor.tt0.subim.fits" # Mean time of observation datetime = pipeline.infrastructure.casa_tools.measures.epoch('utc', '2017-12-02T20:03:07.500') # VLA coordinates obslong = {'unit':'deg','value':-107.6} obslat = {'unit':'deg','value':34.1} # Correct reference positions in fits header do_wide_field_pos_cor(file, date_time=datetime, obs_long=obslong, obs_lat=obslat)