The Falcon aircraft. The orange spear above the nose collects meteorological data. For this mission, three remote sensing instruments collect data as the airplane flies in the lowermost stratosphere. A dual wavelength laser-lidar system measures profiles of ozone and the optical properties of clouds and aerosols; a Differential Optical Absorption Spectrometer (DOAS) system measures stratospheric species such as BrO and OClO that are important for quantifying how quickly ozone depletion is expected to occur; and an Airborne Submillimeter Radiometer (ASUR) measures key constituents such as chlorine monoxide and nitric acid. The laser-lidar and DOAS systems collect data using the ports on the roof of the aircraft (the lidar can be reconfigured to send the beam through the bottom of the aircraft for studying tropospheric clouds) and the ASUR system obtains measurements through a special window designed to allow the passage of microwave radiation.