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

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.

[1] The Sub-Millimetre Radiometer (SMR) on board the Odin satellite, launched on 20 February 2001, observes key species with respect to stratospheric chemistry and dynamics such as O 3 , ClO, N 2 O, and HNO 3 using two bands centered at 501.8 and 544.6 GHz. We present the adopted methodology for level 2 processing and the achieved in-orbit measurement capabilities of the SMR radiometer for these species in terms of altitude range, altitude resolution, and measurement precision. The characteristics of the relevant level 2 data versions, namely version 1.2 of the operational processor as well as versions 222 and 223 of the reference code, are discussed and differences are evaluated. An analysis of systematic retrieval errors, resulting from spectroscopic and instrumental uncertainties, is also presented.

Aims. We investigate the physical and chemical conditions in a typical star forming region, including an unbiased search for new molecules in a spectral region previously unobserved. Methods. Due to its proximity, the Orion KL region offers a unique laboratory of molecular astrophysics in a chemically rich, massive star forming region. Several ground-based spectral line surveys have been made, but due to the absorption by water and oxygen, the terrestrial atmosphere is completely opaque at frequencies around 487 and 557 GHz. To cover these frequencies we used the Odin satellite to perform a spectral line survey in the frequency ranges 486−492 GHz and 541−577 GHz, filling the gaps between previous spectral scans. Odin's high main beam efficiency, η mb = 0.9, and observations performed outside the atmosphere make our intensity scale very well determined.

The Odin satellite, launched in Feb. 2001, is equipped with a 1.1-m submillimetre telescope. Odin was used to observe the 557 GHz line of water with high spectral resolution in 12 comets between 2001 and 2005. Line shapes and spatial mapping provide information on the anisotropy of the outgassing and constraints on water excitation, enabling accurate measurements of the water production rate. Five comets were regularly observed over periods of more than one month to monitor the variation of their water outgassing rate with heliocentric distance. Observing campaigns have been generally coordinated with ground-based observations of molecular lines at Nançay, CSO or IRAM 30-m telescopes to obtain molecular abundances relative to water.Thanks to Odin's frequency coverage, it was also possible to detect the H