A New Technique to Enhance SODISM Images based on the Modified Undecimated Wavelet Transform

There are many satellites and ground-based observatories providing continuous observations of our Sun, of which the PICARD microsatellite is one. PICARD is a space-based satellite observatory holding the Solar Diameter Imager and Surface Mapper (SODISM), which has been continuously monitoring solar activities on five wavelengths, at 215nm, 393 nm, 535 nm, 607 nm and 782, from July 2010 to April 2014. Due to the noise associated with SODISM images, their clarity and the appearance of solar features are affected. In this paper, a Modified Undecimated Discrete Wavelet Transform (M-UDWT) technique is used to de-noise and enhance the quality of the SODISM images depending on the five wavelengths monitored by the SODISM instrument. The proposed method is robust and effectively improves the quality of SODISM images, so that the resulting images become more suitable for further analysis than the original (noised image). Subjective and objective measurements that were conducted on the performance of the proposed algorithms show greater clarity of the solar features in the image, than the input one. Moreover, differences between the conventional DWT and M-UDWT methods are stated in this paper.