IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 44, NO. 5, MAY 2006 1093 The Ozone Monitoring Instrument Pieternel F. Levelt, Gijsbertus H. J. van den Oord, Marcel R. Dobber, Anssi Mälkki, Huib Visser, Johan de Vries, Piet Stammes, Jens O. V. Lundell, and Heikki Saari Abstract—The Ozone Monitoring Instrument (OMI) flies on the National Aeronautics and Space Adminsitration’s Earth Observing System Aura satellite launched in July 2004. OMI is a ultraviolet/visible (UV/VIS) nadir solar backscatter spectrometer, which provides nearly global coverage in one day with a spatial resolution of 13 km 24 km. Trace gases measured include O , NO , SO , HCHO, BrO, and OClO. In addition, OMI will mea- sure aerosol characteristics, cloud top heights, and UV irradiance at the surface. OMI’s unique capabilities for measuring important trace gases with a small footprint and daily global coverage will be a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change. OMI’s high spatial resolution is unprecedented and will enable detection of air pollution on urban scale resolution. In this paper, the instrument and its performance will be discussed. Index Terms—Air quality, atmospheric research, ozone layer, ul- traviolet/visible (UV/VIS) satellite instruments. I. INTRODUCTION T HE Ozone Monitoring Instrument (OMI), a contribution of The Netherlands and Finland to the National Aeronau- tics and Space Adminsitration’ (NAS) Aura mission, is flown on the Aura spacecraft. Aura is part of the NASA’s long-term Earth Observing System (EOS) mission and was launched July 15, 2004, from Vandenberg Air Force base in California. The Aura spacecraft circulates in a 98.2 inclination, sun-synchronous polar orbit at 705-km altitude, with a local afternoon equator crossing time at 13:45 (ascending node), providing 14 orbits a day. The mission has a design lifetime of five years once in orbit. The Aura spacecraft also carries three other instru- ments: the Microwave Limb Sounder (MLS) [1], the High Res- olution Dynamics Limb Sounder (HIRDLS) [2], and Tropo- spheric Emission Spectrometer (TES) [3]. MLS and HIRDLS are limb sounding instruments. TES has both limb sounding and nadir sounding modes. Manuscript received May 20, 2005; revised October 7, 2005. This work was supported in part by The Netherlands Agency for Aerospace Programmes (NIVR). P. F. Levelt, G. H. J. van den Oord, M. R. Dobber, and P. Stammes are with the Royal Dutch Meteorological Institute (KNMI), KS/AS, 3730 AE De Bilt, The Netherlands (e-mail: llevelt@knmi.nl; oordvd@knmi.nl; dobber@knmi.nl; stammes@knmi.nl). A. Mälkki is with Geophysical Research, Finnish Meteorological Institute, Earth Observation, FIN-00101 Helsinki, Finland FIN-00101 Helsinki, Finland (e-mail: Anssi.Malkki@fmi.fi). H. Visser is with Netherlands Organisation for Applied Scientific Research TNO-TPD, NL 2600 AD Delft, The Netherlands (e-mail: hvisser@tpd.tno.nl). J. de Vries is with Dutch Space BV, NL 2303 DB Leiden, The Netherlands (e-mail: j.de.vries@dutchspace.nl). J. O. V. Lundell is with Patria Finavitec Oy Systems, FIN-33100 Tampere, Finland (e-mail: jens.lundell@patria.fi). H. Saari is with VTT Automation, FIN-02044 VTT, Finland (e-mail: heiki.saari@vtt.fi). Digital Object Identifier 10.1109/TGRS.2006.872333 Fig. 1. Conceptual design of OMI with the large field of view out of the plane of the paper. The OMI instrument is composed of the following three elements: 1) Optical Assembly, consisting of the Optical Bench (OPB), two Detector Modules, and Thermal Hardware; 2) the Electronics Unit , performing CCD readout control and analog-to-digital conversion; 3) Interface Adaptor Module, performing Command Buffering as well as the data formatting and satellite bus interface functions. OMI is a heritage instrument of the European Global Ozone Monitoring Experiment (GOME) [4] and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments [5], which introduced the concept of measuring the complete spectrum in the ultraviolet/vis- ible/near-infrared (UV/VIS/NIR) wavelength range with a high spectral resolution. This enables one to retrieve several trace gases at the same time for the same air mass. The American predecessor of OMI is NASA’s Total Ozone Mapping Spec- trometer (TOMS) instrument. TOMS uses a different retrieval algorithm with only six wavelength bands, from which the ozone column can be obtained very accurately [6]. TOMS has the advantage that it has a fairly small ground-pixel size (50 km 50 km) in combination with a daily global coverage. OMI combines the advantage of GOME and SCIAMACHY with the advantage of TOMS, measuring the complete spectrum in the UV/VIS wavelength range with a very high spatial resolution (13 km 24 km) and daily global coverage. This is possible by using a two-dimensional (2-D) detector, as has been used, for example, in the GOMOS satellite instrument [7] in comparable wavelength ranges. The small pixel size enables OMI to look “in between” the clouds, which is very important for retrieving tropospheric information [8]. OMI was built by Dutch Space and TNO TPD in The Nether- lands in cooperation with Finnish VTT and Patria Advanced Solutions Ltd. The Royal Netherlands Meteorological Institute (KNMI) is the Principal Investigator Institute. Overall respon- sibility for the OMI mission lies with The Netherlands Agency for Aerospace Programmes (NIVR) with the participation of the Finnish Meteorological Institute (FMI). II. MEASUREMENT TECHNIQUE UV/VIS spectrometers detect the solar irradiance scattered and absorbed by the constituents of the Earth atmosphere. For 0196-2892/$20.00 © 2006 IEEE