Mid‐Infrared Observing Conditions at the South Pole

Abstract

Measurements of the mid-infrared sky brightness at the South Pole throughout the winter of 1998 show that the sky background is extremely low and stable. For 50% of the time, the flux in the 8.78 to 9.09 μm window is below 50 Jy per square arcsecond. Typical background levels in this window during clear conditions are of the order of 20 Jy per square arcsecond. This is almost an order of magnitude better than any other site on earth. The lower limit to the sky background across most of the N window appears to be set by the aerosol content of the sky rather than by residual water vapor. These data were acquired remotely using an automated instrument housed in the AASTO (Automated Astrophysical Site-Testing Observatory).