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# Source code for astropy.timeseries.io.kepler

    # Licensed under a 3-clause BSD style license - see LICENSE.rst
    import warnings

    import numpy as np

    from astropy.io import fits, registry
    from astropy.table import MaskedColumn, Table
    from astropy.time import Time, TimeDelta
    from astropy.timeseries.sampled import TimeSeries

    __all__ = ["kepler_fits_reader"]

    def kepler_fits_reader(filename):
        """
        This serves as the FITS reader for KEPLER or TESS files within
        astropy-timeseries.

        This function should generally not be called directly, and instead this
        time series reader should be accessed with the
        :meth:`~astropy.timeseries.TimeSeries.read` method::

            >>> from astropy.timeseries import TimeSeries
            >>> ts = TimeSeries.read('kplr33122.fits', format='kepler.fits')  # doctest: +SKIP

        Parameters
        ----------
        filename : `str` or `pathlib.Path`
            File to load.

        Returns
        -------
        ts : `~astropy.timeseries.TimeSeries`
            Data converted into a TimeSeries.
        """
        hdulist = fits.open(filename)
        # Get the lightcurve HDU
        telescope = hdulist[0].header["telescop"].lower()

        if telescope == "tess":
            hdu = hdulist["LIGHTCURVE"]
        elif telescope == "kepler":
            hdu = hdulist[1]
        else:
            raise NotImplementedError(
                f"{hdulist[0].header['telescop']} is not implemented, only KEPLER or TESS"
                " are supported through this reader"
            )

        if hdu.header["EXTVER"] > 1:
            raise NotImplementedError(
                f"Support for {hdu.header['TELESCOP']} v{hdu.header['EXTVER']} files not"
                " yet implemented"
            )

        # Check time scale
        if hdu.header["TIMESYS"] != "TDB":
            raise NotImplementedError(
                f"Support for {hdu.header['TIMESYS']} time scale not yet implemented in"
                f" {hdu.header['TELESCOP']} reader"
            )

        tab = Table.read(hdu, format="fits")

        # Some KEPLER files have a T column instead of TIME.
        if "T" in tab.colnames:
            tab.rename_column("T", "TIME")

        for colname in tab.colnames:
            unit = tab[colname].unit
            # Make masks nan for any column which will turn into a Quantity
            # later. TODO: remove once we support Masked Quantities properly?
            if unit and isinstance(tab[colname], MaskedColumn):
                tab[colname] = tab[colname].filled(np.nan)
            # Fix units
            if unit == "e-/s":
                tab[colname].unit = "electron/s"
            if unit == "pixels":
                tab[colname].unit = "pixel"

            # Rename columns to lowercase
            tab.rename_column(colname, colname.lower())

        # Filter out NaN rows
        nans = np.isnan(tab["time"].data)
        if np.any(nans):
            warnings.warn(f"Ignoring {np.sum(nans)} rows with NaN times")
        tab = tab[~nans]

        # Time column is dependent on source and we correct it here
        reference_date = Time(
            hdu.header["BJDREFI"],
            hdu.header["BJDREFF"],
            scale=hdu.header["TIMESYS"].lower(),
            format="jd",
        )
        time = reference_date + TimeDelta(tab["time"].data)
        time.format = "isot"

        # Remove original time column
        tab.remove_column("time")

        hdulist.close()

        return TimeSeries(time=time, data=tab)

    registry.register_reader("kepler.fits", TimeSeries, kepler_fits_reader)
    registry.register_reader("tess.fits", TimeSeries, kepler_fits_reader)