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| Paper: |
Analysis of Space Coronagraphic Images : Application to Ten Years of SOHO/LASCO Data |
| Volume: |
351, Astronomical Data Analysis Software and Systems XV |
| Page: |
275 |
| Authors: |
Burtin, M.; Llebaria, A.; Lamy, P. |
| Abstract: |
Since 1996, the LASCO Coronagraphs of the ESA/NASA SOHO mission have been providing the solar astronomical and geophysical communities with an unprecedented view of the solar corona. The photometric restitution of the huge amount of data is of prime importance for understanding the physics of the corona, its evolution over a solar cycle as well as its consequences on the Earth environment, and represents a major challenge. The combination of ground calibrations, continuous in-flight calibrations and the implementation of novel procedures has been necessary to disentangle the strong intercorrelation between many instrumental effects such as vignetting, polarization, straylight, optical distortion and timing. Geometricals parameters are extracted in a first pass. The vignetting correction relies on a detailed model of the instrument supplemented by a comparison with ground-based observations of the inner corona during the 1998 total eclipse. The polarimetric response based on the Mueller method was finely corrected thanks to polarized images obtained during specific maneuvers of the SOHO spacecraft. The straylight has been deduced on a yearly basis using the unpolarized component extracted from polarization sequences. The photometric calibration and its temporal evolution relies on several hundreds stars observed over ten years of operation. We will describe the overall software and database architectures of these calibration-pipeline chains, and the final products made available on our LASCO website. |
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