Odin is a 250 kg class satellite built in co-operation between Sweden, Canada, France, and Finland and launched in February 2001. It carries two instruments: a 4-band sub-millimetre radiometer used for both astronomy and atmospheric science and an optical spectrometer and infrared imaging system for purely atmospheric observations. As part of the joint mission Odin will observe the atmospheric limb for 50% of the observation time producing profiles of many species of interest in the middle atmosphere with a vertical resolution of 1–2 km. These species include, among others, ozone, nitrogen dioxide, chlorine monoxide, nitric acid, water vapour, and nitrous oxide. An overview of the mission and the planned measurements is given. PACS Nos.: 42.68Mj, 94.10Dy, 95.55Fw

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The optical spectrograph and infrared imager system (OSIRIS) on board the Odin spacecraft is designed to retrieve altitude profiles of terrestrial atmospheric minor species by observing limb-radiance profiles. The grating optical spectrograph (OS) obtains spectra of scattered sunlight over the range 280-800 nm with a spectral resolution of approximately 1 nm. The Odin spacecraft performs a repetitive vertical limb scan to sweep the OS 1 km vertical field of view over selected altitude ranges from approximately 10 to 100 km. The terrestrial absorption features that are superimposed on the scattered solar spectrum are monitored to derive the minor species altitude profiles. The spectrograph also detects the airglow, which can be used to study the mesosphere and lower thermosphere. The other part of OSIRIS is a three-channel infrared imager (IRI) that uses linear array detectors to image the vertical limb radiance over an altitude range of approximately 100 km. The IRI observes both scattered sunlight and the airglow emissions from the oxygen infrared atmospheric band at 1.27 µm and the OH (3-1) Meinel band at 1.53 µm. A tomographic inversion technique is used with a series of these vertical images to derive the two-dimensional distribution of the emissions within the orbit plane.Résumé : Le système de spectrographie optique et d'imagerie infrarouge (OSIRIS) à bord du satellite Odin est conçu pour enregistrer les profils en altitude des éléments mineurs de l'atmosphère en observant les profils de radiance du limbe. Le spectrographe optique à réseau (OS) obtient les spectres de la lumière solaire diffusée sur le domaine entre 280-800 nm, avec une résolution spatiale approximative de 1 nm. Le satellite Odin balaye verticalement le limbe de façon répétée, de telle sorte que l'ouverture verticale de 1 km du OS parcoure les domaines voulus entre 10 et 100 km. Nous analysons les spectres solaires diffusés en superposition avec les caractéristiques terrestres d'absorption, afin de déterminer les profils en altitude des éléments mineurs de l'atmosphère. Le spectrographe détecte aussi la luminescence nocturne atmosphérique qui peut être utilisé pour étudier la mésosphère et la thermosphère. L'autre partie d'OSIRIS est un imageur infrarouge (IRI) à trois canaux qui utilise une banque linéaire de détecteurs pour imager la radiance du limbe sur un domaine d'altitude d'approximativement 100 km. L'IRI observe à la fois la lumière solaire diffusée et les émissions de luminescence nocturne atmospérique provenant de la bande infrarouge de l'oxygène atmosphérique à 1.27 µm et la bande de Meinel de l'OH (3-1) à 1.53 µm. Nous utilisons une technique d'inversion tomographique avec une série de ces images verticales pour obtenir la distribution bidimensionnelle des émissions à l'intérieur de l'orbite.[Traduit par la Rédaction] Can.

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[1] The validation of the collection 2 level 1b radiance and irradiance data measured with the Ozone Monitoring Instrument (OMI) on NASA's Earth Observing System (EOS) Aura satellite is investigated and described. A number of improvements from collection 2 data to collection 3 data are identified and presented. It is shown that with these improvements in the calibration and in the data processing the accuracy of the geophysically calibrated level 1b radiance and irradiance is improved in the collection 3 data. It is shown that the OMI level 1b irradiance product can be reproduced from a high-resolution solar reference spectrum convolved with the OMI spectral slit functions within 3% for the Fraunhofer structure and within 0.5% for the offset. The agreement of the OMI level 1b irradiance data product with other available literature irradiance spectra is within 4%. The viewing angle dependence of the irradiance and the irradiance goniometry are discussed, and improvements in the collection 3 data are described. The in-orbit radiometric degradation since launch is shown to be smaller than 0.5% above 310 nm and increases to about 1.2% at 270 nm. It is shown how the viewing angle dependence of the radiance is improved in the collection 3 data. The calculation of the surface albedo from OMI measurement data is discussed, and first results are presented. The OMI surface albedo values are compared to literature values from the Total Ozone Mapping