The Water Vapor Monitor Instrument of SOFIA

Although SOFIA flies above greater than 95% of the Earth's atmospheric water vapor, the residual water can still affect the infrared signals seen by the SOFIA science instruments. A small dedicated instrument has been developed to measure this residual water vapor so that the astronomical IR signals can be properly corrected. The Water Vapor Monitor is permanently mounted in the upper deck of the SOFIA aircraft and observes the 183 GHz atmospheric water line in emission through a custom window. This talk will describe the design of the WVM instrument, its calibration, and the issues that have been discovered in properly modeling the effects of telluric water vapor in the IR signals.