The OSIRIS spectra of limb scattered sunlight are used to retrieve the ozone number density vertical profiles over the altitude range from 10 to 60 km at a vertical resolution of approximately 1.5 km using the SaskMART Multiplicative Algebraic Reconstruction Technique, which is a one dimensional modification of a two-dimensional tomographic retrieval algorithm. This technique allows for the consistent merging of the absorption information from radiance measurements at wavelengths in the Chappuis and the Hartley-Huggins bands at each iteration of the inversion. A set of weighting factors is used to determine the importance of each line of sight and each element of the measurement vector for the retrieved state at each altitude.

OSIRIS ozone profile measurements show agreement with coincident SAGE II occultation measurements to within 2% from 18 to 53 km altitude over a large range of geolocations and solar zenith angles.

This retrieval is regularly processed at the University of Saskatchewan for all OSIRIS stratospheric limb scan measurements. Data from November, 2001, to the current date is available for download as an OSIRIS Level 2 Product in HDF-EOS5 format. OSIRIS remains fully operational and processing of this algorithm will be maintained into the foreseeable future.


Figure from Shaw, T.A. and T.G. Shepherd, Atmospheric Science: Raising the Roof, Nature Geoscience 1, 12 - 13, doi:10.1038/ngeo.2007.53, 2008.