Internal schematic of HIRDLS (High Resolution Dynamic Limb Sounder) instrument created in 1992 at NCAR. HIRDLS is an infrared limb-scanning radiometer designed to sound the upper troposphere, stratosphere, and mesosphere to determine temperature; the concentrations of O3, H2O, CH4, N2O, NO2, HNO3, N2O5, ClONO2, CFCl2, CFCl3, and aerosols; and the locations of polar stratospheric clouds and cloud tops. (Image courtesy of Earth Observing Laboratory, NCAR).