A remote-sensing instrument that measures microwave thermal emission from the limb (edge) of the Earth's atmosphere in order to sense vertical profiles of atmospheric gases, temperature, and pressure. The first MLS was launched in 1991 on NASA's Upper-Atmosphere Research Satellite to investigate ozone depletion. The 280-kg instrument has a sensor, spectrometer, and power supply. An advanced MLS, developed for the 2004 Aura mission, will help increase our understanding of global climate changes. MLS experiments are also carried on balloons and aircraft.