kepler.py

"""Reader for official Kepler light curve FITS files produced by the Ames pipeline."""
from ..lightcurve import KeplerLightCurve
from ..utils import KeplerQualityFlags

from .generic import read_generic_lightcurve


def read_kepler_lightcurve(filename,
                           flux_column="pdcsap_flux",
                           quality_bitmask="default"):
    """Returns a KeplerLightCurve.

    Parameters
    ----------
    filename : str
        Local path or remote url of a Kepler light curve FITS file.
    flux_column : 'pdcsap_flux' or 'sap_flux'
        Which column in the FITS file contains the preferred flux data?
    quality_bitmask : str or int
        Bitmask (integer) which identifies the quality flag bitmask that should
        be used to mask out bad cadences. If a string is passed, it has the
        following meaning:

            * "none": no cadences will be ignored (`quality_bitmask=0`).
            * "default": cadences with severe quality issues will be ignored
              (`quality_bitmask=1130799`).
            * "hard": more conservative choice of flags to ignore
              (`quality_bitmask=1664431`). This is known to remove good data.
            * "hardest": removes all data that has been flagged
              (`quality_bitmask=2096639`). This mask is not recommended.

        See the :class:`KeplerQualityFlags` class for details on the bitmasks.
    """
    lc = read_generic_lightcurve(filename,
                                 flux_column=flux_column,
                                 quality_column='sap_quality',
                                 time_format='bkjd')

    # Filter out poor-quality data
    # NOTE: Unfortunately Astropy Table masking does not yet work for columns
    # that are Quantity objects, so for now we remove poor-quality data instead
    # of masking. Details: https://github.com/astropy/astropy/issues/10119
    quality_mask = KeplerQualityFlags.create_quality_mask(
                                quality_array=lc['sap_quality'],
                                bitmask=quality_bitmask)
    lc = lc[quality_mask]

    lc.meta['targetid'] = lc.meta.get('keplerid')
    lc.meta['quality_bitmask'] = quality_bitmask
    lc.meta['quality_mask'] = quality_mask
    return KeplerLightCurve(data=lc)