ATMOSPHERIC EMISSION IN THE 20-MICRON WINDOW FROM MAUNA KEA

The emission spectrum within the 20-?m window of the atmosphere above Mauna Kea has been measured to a resolution of 0.01 cm-1 with a Michelson interferometer and compared to a single-layer synthetic spectrum in order to test the feasibility of observing fine-structure emission lines from astronomical sources from this site. It is demonstrated that the observed spectrum can be very closely simulated by the inclusion of CO2, H2O, and N2O in the synthetic spectrum, a situation which is presumed to hold for other high, dry observing sites. The present data indicate that large telescopes equipped with high-resolution spectrometers can still be used to advantage in the observation of selected fine-structure lines against the background emission from these sites, particularly when careful background subtraction techniques are used.