1 November 2001 Highly accurate photometric equalization of long sequences of coronal images
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The LASCO-C2 and C3 coronagraphs aboard the SOHO solar observatory have been providing for the last five years an unprecedented long sequence of coronal images at high cadence (about 100 images/day). To build temporal sequences for movie displays as well as for science analysis purpose, we need a photomety having a relative accuracy better than 0.1 percent. In this paper we address this problem showing how image to image regression as well as long term correction of drifts induced by Wiener-Levy stochastic processes are able to solve this challenge. The use of time derivatives of synoptic maps to correct and verify the full procedure and comparison with more classical methods like star calibration are discussed. Difficulties due to brightening events as coronal mass ejections, showers of cosmic rays, etc., as well as those due to telemetry gaps are also addressed.
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Antoine Llebaria, Antoine Llebaria, Arnaud Thernisien, Arnaud Thernisien, } "Highly accurate photometric equalization of long sequences of coronal images", Proc. SPIE 4477, Astronomical Data Analysis, (1 November 2001); doi: 10.1117/12.447183; https://doi.org/10.1117/12.447183

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