High precision refraction measurements by solar imaging during occultation: Results from SOFIE

Abstract

A new method for measuring atmospheric refraction angles is presented, with in-orbit measurements demonstrating a precision of ±0.02 arcsec(±0.1, μrad). Key advantages of the method are the following:(1) Simultaneous observation of two celestial points during occultation(i.e., top and bottom edges of the solar image) eliminates error from instrument attitude uncertainty.(2) The refraction angle is primarily a normalized difference measurement, causing only scale error, not absolute error.(3) A large number of detector pixels are used in the edge location by fitting to a known edge shape. The resulting refraction angle measurements allow temperature sounding up to the lower mesosphere. © 2009 Optical Society of America.