Submitted by afb432 on
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The precision of OSIRIS Level 2 data is a measure of the uncertainty in the values retrieved from OSIRIS measurements of light scattering in the atmosphere.  This uncertainty comes from measurement noise and random noise generated through the SASKTRAN forward model in the SaskMART retrieval algorithm.  Using other retrieval methods the precision information is generated as a biproduct naturally in the form of a covariance matrix but by its nature SaskMART does not. The covariance matrix can be obtained after the retrieval using the original measrements' uncertainty and the retrieved result. This method has been validated using matching pair statics.  In this method stratospheric ozone in the tropics is considered to be stable over the timescale of a day so retrieved ozone profiles in close geographical proximity and within 1.01 days were compared.  The variation in these matching pairs compared favorably with the precision values.  This is the expected result because the precision should be a measure of the random error in the retrievals.