Filter responses for MKO NIR filters as specified in Tokunaga+ 2002 (see
        also Tokunaga+ 2005). I downloaded the L' profile from
        http://irtfweb.ifa.hawaii.edu/~nsfcam/hist/filters.2006.html.

        Pivot wavelengths from Tokunaga+ 2005 (Table 2) confirm that the
        profile is in QE convention, although my calculation of the pivot
        wavelength for L' is actually closer if I assume otherwise. M' and K_s
        are substantially better in QE convention, though, and based on the
        paper and nomenclature it seems more appropriate.

def _load_data(self, band):
        """Filter responses for MKO NIR filters as specified in Tokunaga+ 2002 (see
        also Tokunaga+ 2005). I downloaded the L' profile from
        http://irtfweb.ifa.hawaii.edu/~nsfcam/hist/filters.2006.html.

        Pivot wavelengths from Tokunaga+ 2005 (Table 2) confirm that the
        profile is in QE convention, although my calculation of the pivot
        wavelength for L' is actually closer if I assume otherwise. M' and K_s
        are substantially better in QE convention, though, and based on the
        paper and nomenclature it seems more appropriate.

        """
        # `band` should be 'Lp'.
        df = bandpass_data_frame('filter_mko_' + band + '.dat', 'wlen resp')
        # Put in increasing wavelength order:
        df = df[::-1]
        df.index = np.arange(df.shape[0])
        df.wlen *= 1e4 # micron to Angstrom
        df.resp *= df.wlen # QE to equal-energy response.
        return df