The spectral response for the CO J 1-0 transition region. The spectral resolution has been oversampled by a factor of  ~10 for a window surrounding each of the CO transitions listed in Table E.1, the asterisks show the spacing of independent spectral data points. This region was selected to include the rest frequency (± 300 km s^-1 – vertical dotted lines) for each of the CO, C¹³O, CO¹⁷, and CO¹⁸ isotopes. Also shown is the band average spectrum for each region.