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The SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration |
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| Authors: | J-P Halain D Berghmans D B Seaton B Nicula A De Groof M Mierla A Mazzoli J-M Defise P Rochus |
| Institution: | 1. Centre Spatial de Liège, Université de Liège, Avenue Pré Aily, 4031, Angleur, Belgium 2. Royal Observatory of Belgium, Avenue Circulaire 3, 1180, Brussels, Belgium 3. Department of Science and Robotic Exploration, European Space Agency, Noordwijk, The Netherlands 4. Institute of Geodynamics of the Romanian Academy, Jean-Louis Calderon 19-21, Bucharest-37, Romania 5. Research Center for Atomic Physics and Astrophysics, Faculty of Physics, University of Bucharest, Bucharest, Romania 6. Institut d’Astrophysique et de Géophysique, Université de Liège, 4000, Liège, Belgium |
| Abstract: | The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar corona every one to two minutes for more than two years. The most important technological developments included in SWAP are a radiation-resistant CMOS-APS detector and a novel onboard data-prioritization scheme. Although such detectors have been used previously in space, they have never been used for long-term scientific observations on orbit. Thus SWAP requires a careful calibration to guarantee the science return of the instrument. Since launch we have regularly monitored the evolution of SWAP’s detector response in-flight to characterize both its performance and degradation over the course of the mission. These measurements are also used to reduce detector noise in calibrated images (by subtracting dark-current). Because accurate measurements of detector dark-current require large telescope off-points, we also monitored straylight levels in the instrument to ensure that these calibration measurements are not contaminated by residual signal from the Sun. Here we present the results of these tests and examine the variation of instrumental response and noise as a function of both time and temperature throughout the mission. |
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