The Microwave Limb Sounder instrument was launched aboard NASA's EOS AURA satellite in July, 2004. The overall scientific objectives for MLS are to measure temperature, pressure, and several important chemical species in the upper troposphere and stratosphere relevant to ozone processes and climate change. MLS consists of a suite of radiometers designed to operate from 118 GHz to 2.5 THz, with two antennas (one for 2.5 THz, the other for the lower frequencies) that scan vertically through the atmospheric limb, and spectrometers with spectral resolution of 6 MHz at spectral line centers. This paper describes the on-orbit commissioning the MLS instrument which includes activation and engineering functional verifications and calibrations.
The Microwave Limb Sounder (MLS) instrument, launched in July of 2004 on NASA's EOS Aura satellite, has been in its nominal science operating mode since August 2004. The objective of EOS MLS is to obtain measurements of atmospheric composition, temperature and pressure through observations of millimeter- and submillimeter-wavelength thermal emission as the instrument field-of-view is scanned through the atmospheric limb. The MLS instrument has completed activation, in-orbit calibrations have been performed leading to adjustments to radiometric calibration (Level 1) algorithms, a software upgrade was implemented for more robust operation of the laser local oscillator, and engineering performance trends have been established. This paper discusses the current status of the MLS instrument which now continuously provides data to produce global maps of targeted chemical species as well as temperature, cloud ice, and gravity wave activity. Performance trends are assessed with respect to characterization during initial on-orbit activation of the instrument, and with data from ground test verification prior to launch.