Study and application of superresolution techniques on the OSIRIS cameras onboard Rosetta Khallefi Leïla © esa Supervisors: J. L. Vazquez M. Küppers trainee project 2009

Mission Instrument Superresolution Goals My Work Agenda - Mission - Instrument - SR - Goals - My Work Mission Instrument Superresolution Goals My Work

A key in the comprehension of the solar system formation Agenda - Mission - Instrument - SR - Goals - My Work Rosetta Mission Why studying comets? A key in the comprehension of the solar system formation 3rd Cornerstone Mission of the ESA Horizon 2000 Program © esa © esa Launch 2004 – encounter 2014 Target Comet Churyumov-Gerasimenko Rosetta Space Probe Lander Philae Asteroid Steins

OSIRIS Optical, Spectroscopic and Infrared Remote Imaging System Agenda - Mission - Instrument - SR - Goals - My Work OSIRIS Optical, Spectroscopic and Infrared Remote Imaging System WAC wide angle camera NAC narrow angle camera Provide images of the near nucleus environnement 14 filters between 250-1000 nm Resolution of 101 µrad px-1 Provide High resolution images 12 filters Resolution of 18.6 µrad px-1 Shape and volume Surface mineralogy Landing spot for Philae Nature of the cometary nuclei … Provide information on :

How to find a way to increase the current resolution ? Superresolution Agenda - Mission - Instrument - SR - Goals - My Work How to find a way to increase the current resolution ? Limitations Maintain the complete nucleus within the FOV of the WAC Mass requirements for a longer Focal length system Limited the data volume that can be transmitted Cost of the CCD © xkcd A solution: Image processing techniques

Exploit the new information in each image Superresolution Agenda - Mission - Instrument - SR - Goals - My Work Exploit the new information in each image Multiple images scene … spacecraft Subpixel Shifts Aliasing Motion estimation S. Park, M. Park, M. Kang IEEE signal processing magazine may 2003 spacecraft scene …

Study and comparison of algorithms Agenda - Mission - Instrument - SR - Goals - My Work I) Bibliography Study and comparison of algorithms II) Implementation of algorithms /tests III) Use on the images of the Asteroid Steins IV) Specifications on images V) Search engine development

Step one Study and Comparision construction of a model: Agenda - Mission - Instrument - SR - Goals - My Work Step one Study and Comparision construction of a model: Wk X + nk = Wk X X ? sampling Continuous to Discrete Without Aliasing Continuous scene HR image x Kth Observed LR image warping blurring downsampling Translation Rotation Blur noise +

Step one Study and Comparision construction of a model: Agenda - Mission - Instrument - SR - Goals - My Work Step one Study and Comparision construction of a model: the HR image Yk = Wk X + nk noise the kth LR image Warping blurring subsampling Matrix gathers - estimation of the motion - noise statistics - Sensing S. Park, M. Park, M. Kang, IEEE signal processing magazine may 2003 knowledge

Step one Study and Comparision Agenda - Mission - Instrument - SR - Goals - My Work Step one Study and Comparision 6 main different approaches Non uniform Interpolation More sophisticated models for registration error (than just gaussian) Differents weights according to the contribution of the LR images 2 algorithms + improvement: Frequency domain + Not constrain noise and blur + Reduce effect of registration error + Theoretically simple Lack of correlation in the frequency domain Regularized reconstruction + Flexible + Use of prior knowledge + Use when small number of LR images available Frequency domain + Not constrain noise and blur + Reduce effect of registration error + Theoretically simple Lack of correlation in the frequency domain Projection onto convex sets + Simple - Non uniqueness of the solutions - High computational cost Adaptative filtering + Really efficient - Computational complexity Regularized reconstruction + Flexible + Use of prior knowledge + Use when small number of LR images available Iterative back projection + simplicity - Non uniqueness of the solution - Choice of the parameter + Real time - Same noise and blur in all the images - Ignore error of interpolation stage

Step two Implementation Agenda - Mission - Instrument - SR - Goals - My Work Step two Implementation The Bayesian Approach compute the MAP grid use a prior (smooth) estimation of parameters of regularisation use an image for reference interpolate pixels values at the desired resolution test HR image

Step two Implementation Agenda - Mission - Instrument - SR - Goals - My Work Step two Implementation The Bayesian Approach S. Park, M. Park, M. Kang, IEEE signal processing magazine may 2003 step 1: use an image - images of same filter? - resize them - estimation of the motion with spice - choosing the resolution? - create a new picture by interpolation - interpolation method coherent with the sensing: bilineare, Spline,… - opening/closing - using of spice - center of mass - Type of motion - estimation or knowledge

Step two Implementation Agenda - Mission - Instrument - SR - Goals - My Work Step two Implementation The Bayesian Approach step 2: iterative process - estimation of the parameters By minimisation of the square error - creation of a new image - re-evaluation of the parameters Issues with band choices Number of images used Issue with the bond choice of the interpolation process Size of the interpolation grid Number of iterations Estimation of the noise, modification

Agenda - Mission - Instrument - SR - Goals - My Work TO BE CONTINUED…