A calculation of confusion noise due to infrared cirrus

General expressions are developed for the statistical errors to be expected in photometric measurements due to confusion in a background of fluctuating surface brightness. Backgrounds actually observed in the far infrared by the IRAS satellite are used to calculate tables of these error expressions for two simple measurement techniques. The confusion noise limited sensitivities for NASA's planned Space Infrared Telescope Facility and the European Space Agency's Infrared Space Observatory are estimated at a wavelength of 100 μm from these tables