Zodiacal Infrared Foreground Prediction for Space Based Infrared Interferometer Missions

Abstract

The zodiacal foreground for a highly sensitive space infrared interferometer is predicted for various observing locations. For the predictions we use a model that was derived from measurements of the Cosmic Background Explorer (COBE). We find that at a wavelength of $10{\rm \mu m}$ 96% of the sky is darker than $1{MJy}{\rm sr}^{-1}$ for observations in the ecliptic plane at $5{\rm AU}$, and 83% is darker than $0.1{\rm MJy}{\rm sr}^{-1}$. At $1{\rm AU}$, however, always more than 50% of the sky are brighter than $1{\rm MJy}{\rm sr}^{-1}$, even if the observations are made from $30^\circ$ or $60^\circ$ of latitude above the ecliptic plane, at 10 or $20{\rm \mu m}$. Thus, according to the employed model, the foreground reduction by increasing the heliocentric distance of the observing location is more effective than by increasing the latitude.