EOS MLS Instrument Calibration Report Volume 1

<p>The Microwave Limb Sounder experiment (MLS) on the Earth Observing System (EOS) Aura spacecraft measures thermal limb emission from molecules and radicals of special interest in the stratosphere and upper troposphere, with some measurements extending into the mesosphere. By measuring emission spectra as a function of limb altitude it is possible during ground processing to infer concentration profiles of various species including ClO, BrO, HNO3, N2O, CO, H2O, H2O2, HO2, O3, OH, HCl, HCN and SO2. Measurement of O2 emission provides pressure and temperature data necessary for accurate constituent retrievals, and the spacecraft inertial reference unit (IRU) provides the pointing reference necessary for measurement of geopotential height. An overview of the EOS MLS experiment is given in.</p> <p>This document assumes a reasonable degree of familiarity with the EOS MLS instrument, its operation and internal timing, and with the terminology used to describe both the instrument and its operation. It is not the intention of this document to serve as an MLS tutorial. A detailed description of instrument operation and timing is provided in the EOS MLS Level 1 Data Processing Algorithm Theoretical Basis document.</p> <p>This report is divided into four volumes. Volume 1 describes the calibrations, the calibration data analyses, and the measured instrument performance. For those desiring a deeper view into EOS MLS calibration data, Volume 2 provides a comprehensive presentation of the data, with the voluminous high-resolution spectral sweep data presented in Volume 3. All post-launch updates are presented in Volume 4 in order to allow the majority of this report (i.e., the first 3 volumes) to remain stable. Volume 4 of this report must be referenced by those wishing to fully understand the in-orbit refinements to calibration of EOS MLS, as well as its observed performance in its intended operating environment. For an instrument which operates exclusively in a total-power observing mode (like this one) it is extremely difficult to accurately predict in-orbit sensitivity, since environmental conditions have a strong impact on the behavior of time-series data from the individual measurement channels.</p>