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Advances in Astronomy
Volume 2012, Article ID 623709, 5 pages
Research Article

Preliminary Results on Irradiance Measurements from Lyra and Swap

1Department of Physics, Auden Technology and Management Academy (ATMA), Bangalore 562112, India
2Indian Institute of Astrophysics, Bangalore 560 034, India
3Royal Observatory of Belgium (ROB), Circular Avenue 3, B-1180 Brussels, Belgium
4LATMOS, 11 Boulevard d'Alembert, 78280 Guyancourt, France
5Department of Physics, Bangalore University, Bangalore 560056, India

Received 14 November 2011; Accepted 9 December 2011

Academic Editor: J. Javaraiah

Copyright © 2012 S. T. Kumara et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The first and preliminary results of the photometry of Large Yield Radiometer (LYRA) and Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard PROBA2 are presented in this paper. To study the day-to-day variations of LYRA irradiance, we have compared the LYRA irradiance values (observed Sun as a star) measured in Aluminum filter channel (171 Å–500 Å) with spatially resolved full-disk integrated intensity values measured with SWAP (174 Å) and Ca II K 1 Å index values (ground-based observations from NSO/Sac Peak) for the period from 01 April 2010 to 15 Mar 2011. We found that there is a good correlation between these parameters. This indicates that the spatial resolution of SWAP complements the high temporal resolution of LYRA. Hence SWAP can be considered as an additional radiometric channel. Also the K emission index is the integrated intensity (or flux) over a 1 Å band centered on the K line and is proportional to the total emission from the chromosphere; this comparison clearly explains that the LYRA irradiance variations are due to the various magnetic features, which are contributing significantly. In addition to this we have made an attempt to segregate coronal features from full-disk SWAP images. This will help to understand and determine the actual contribution of the individual coronal feature to LYRA irradiance variations.