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Temperatures in the mesosphere--lower thermosphere region (MLT) have been derived from the Optical Spectrograph and InfraRed Imaging System (OSIRIS) observations of [O.sub.2] A-band ([b.sup.1][∑.sup.+.sub.g]-[X.sup.3] [∑.sup.-.sub.g])O-O emission spectra. The observed OSIRIS spectra are inverted pixel by pixel, producing inverted volume emission rate spectra at altitudes between 90 and 110 km, which are compared to modelled temperature dependent [O.sub.2] A-band spectra. The estimated accuracy of the retrieved temperatures is approximately ± 2 K near 90 km and up to ± 6 K at higher altitudes. The developed temperature retrieval technique is presented, and some initial retrieval results are briefly discussed. Nous obtenons les temperatures dans la mesosphere-region de basse thermosphere (la basse atmosphere) a partir des observations, par le spectrographe optique et le systeme d'imagerie infrarouge (OSIRIS), des spectres d'emission ([b.sup.1][[suma].sup.+.sub.g][X.sup.3][[suma].sup.-.sub.g])O-O de la bande A de [O.sub.2]. Les spectres observeis par OSIRIS sont inverses pixel par pixel, produisant des spectres de taux d'emission en volume inverse; a des altitudes entre 90 et 110 km, qui sont alors compare;sa des spectres modelises dependant en temperature de la bande A de [O.sub.2]. Les precisions estimeees des temperatures obtenues est approximativement ±2 K pres de 90 km, jusqu'a ±6 K aux altitudes plus elevees. Nous presentons la technique pour obtenir les temperatures et nous discutons quelques resultats preliminaires. [Traduit par la Redaction], 1. Introduction A detailed understanding of the physics and chemistry of the mesosphere--lower thermosphere (MLT) region of the Earth's atmosphere requires an accurate knowledge of the temperature profile in the [...]

The two optically forbidden lines of atomic oxygen, O(¹S-¹D) at 557.7 nm and O([1.sup.S] - ³P) at 297.2 nm, serve as important diagnostics in atmospheric, planetary, and cometary studies. Originating from the same upper state, the emission brightness ratio, B(557.7)B(297.2), must necessarily be constant. The reported emission ratio of these two lines from both theoretical and experimental investigations varies by approximately a factor of two. These two emissions are observed simultaneously in aurora] spectra by the OSIRIS spectrograph on the Odin spacecraft, offering another opportunity to perform the ratio measurement. Because of the considerable wavelength separation between these two atomic lines, precise instrumental relative response calibrations can be problematic. To maintain accurate on-orbit spectral calibrations, an atmospheric radiation model with multiple Rayleigh scatter is employed to constantly track instrumental response. An example of a calibrated single bright aurora] spectrum over the full OSIRIS wavelength range of 275 to 815 nm, limb tangent altitude 105 km, is presented. Using a number of individual auroral spectra, the observed 01557.7 nm brightness is plotted versus the observed 01297.2 nm brightness to both verify the required linear relationship and to experimentally determine the brightness ratio. Spectral contamination by other auroral emission features is removed. From the linear fit, the observed B(557.7)B(297.2) ratio is 9.3 ± 0.5. By comparison, a ratio of 9.8 ± 1 was recently reported, determined by combining results from a number of observational databases separated in time and in wavelength coverage. PACS Nos: 32.30-r, 32.70.Fw, 92.60.hc, 92.60.hw Les deux lignes optiques de l'atome d'oxygene, O(¹S - ¹D) a 557,7 nm et O(¹S - ³P) a 297,2 nm sont d'importants outils de diagnostique dans les etudes sur l'atmosphere, les planetes et les cometes. Provenant du meme etat superieur, le rapport d'emission B(557,7) / B(297,2) doit necessairement etre constant. Il y a un facteur de pres de deux entre les valeurs experimentale et theorique du rapport d'emission de ces deux lignes. Elles sont obseevves simultanement par le spectrographe OSIRIS a bord du satellite Odin, ce qui offre une autre possibilite de mesurer ce rapport. A cause de la grande difference en longueur d'onde entre ces deux lignes atomiques, une calibration instrumentale precise sera problematique. Dans le but de maintenir une calibration precise en orbite, nous utilisons un modele de radiation atmospherique avec diffusion Rayleigh multiple, afm de faire un suivi constant de la reponse instrumentale. Nous presentons un exemple d'un spectre auroral calibre sur l'ensemble du domaine spectral d'OSIRIS, de 275 nm a 815 nm, pris dans le limbe tangent a 105 km d'altitude. Utilisant un certain nombre de spectres d'aurore individuels, nous comparons les graphes d'observation de la brillance d'OI 557,5 et de OI 297,2, pour verifier la linearite et determiner experimental ement le rapport de brillance. Nous eliminons la contamination spectrale provenant d'autres emission aurorales. A partir d'un ajustement numerique lineaire, nous avons determine la valeur du rapport B(557,7) / B(297,2) = 9,3 ± 0,5. Pour fin de comparaison, on a recemment rapporte un rapport de 9,8 ± 1, obtenu en combinant des bases de donnees experimentales separees dans le temps et portant sur diverses longueurs d'onde. [Traduit par la Redaction], 1. Introduction The ratio between the O(¹S-¹D) and O(¹S - ³P) transitions has been the subject of numerous investigations. Some of the early theoretical calculations were conducted by Condon [1] [...]

Abstract: A new algorithm, SaskMART, is presented that uses observations of limb-scattered sunlight and a radiative transfer model to determine the ozone number-density profile up to 35 km altitude. In [...]

Abstract: A simple radiative transfer model is developed to calculate the contribution of sea-glint to limb radiance. It is shown that the absolute sea-glint signal peaks between 70. and 80. [...]

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