OMI Algorithm Theoretical Basis Document Volume IV OMI Trace Gas Algorithms

Preface Background The Ozone Monitoring Instrument OMI is a Dutch-Finnish ozone monitoring instrument that will fly on NASA's Aura Mission, part of the Earth Observation System (EOS), scheduled for launch in January 2004. OMI's measurements of ozone columns and profiles, aerosols, clouds, surface UV irradiance, and the trace gases NO 2 , SO 2 , HCHO, BrO, and OClO fit well into Aura's mission goals to study the Earth's atmosphere. OMI is a wide swath, nadir viewing, near-UV and visible spectrograph which draws heavily on European experience in atmospheric research instruments such as GOME (on ERS-2), SCIAMACHY and GOMOS (both flying on Envisat). Purpose The four OMI-EOS Algorithm Theoretical Basis Documents (ATBDs) present a detailed picture of the instrument and the retrieval algorithms used to derive atmospheric information from the instrument's measurements. They will provide a clear understanding of the data-products to the OMI scientists, to the Aura Science Team, and the atmospheric community at large. Each chapter of the four ATBDs is written by the scientists responsible for the development of the algorithms presented. These ATBDs were presented to a group of expert reviewers recruited mainly from the atmospheric research community outside of Aura. The results of the reviewer's study, critiques and recommendations were presented at the ATBD panel review on February 8 th , 2002. Overall, the review was successful. All ATBDs, except the Level 1b ATBD, have been modified based on the recommendations of the written reviews and the panel, which were very helpful in the development of these documents. An updated level 1b ATBD is expected in the near future. Contents ATBD 1 contains a general description of the instrument and its measurement modes. In addition, there is a presentation of the Level 0 to 1B algorithms that convert instrument counts to calibrated radiances, ground and in-flight calibration, and the flight operations needed to collect science data. It is critical that this is well understood by the developers of the higher level processing, as they must know exactly what has been accounted for (and how), and what has not been considered in the Level 0 to 1B processing.