GSC Sentinel-2 PDGS STBD - emits - ESA

3.3.2 ANALYSIS OF PARALLELISATION OPPORTUNITIESESA UNCLASSIFIED – For Official UseGSC Sentinel-2 PDGS STBDIssue 1 Revision 2 (draft) - 25.07.2010GMES-GSEG-EOPG-TN-09-0031page 22 of 60This section analyses the parallelisation opportunities associated to each step of the Level-0and Level-1 processing algorithm.Referring to the decomposition into processing steps outlined in [RD-02], the parallelisationopportunities applicable to each one are explained and classified for outer and/or innermode of parallelisation. For opportunities classified for outer parallelisation, the processingunit is defined accordingly.The parallelisation opportunities are described according to the following terminology:- By Detector, referring to the opportunity of processing the image data of every MSIDetector independently.This opportunity will result into a processing performance scalability figure of 12 as perthe number of independent MSI detectors.- By Band, referring to the opportunity of processing the image data of every MSI spectralband independently.This opportunity will result into a processing performance scalability figure of 13 to benormalised according to processing applied. E.g. For processing steps with predominantpixel-based processing applicable to all 13 bands (e.g. radiometry processing), thedensity of pixels specific to each band shall be taken into account into a normalisedglobal scalability figure of 5.58 (4 + 6 x 1/2 2 + 3 x1/6 2 ).- By Along-Track Fragment, referring to the opportunity of processing the image data infragments of MSI data split along the orbit.This opportunity will result into a processing performance scalability figure directlyproportional to the number of independent fragments to be scaled down depending onthe processing margins top be applied. Assuming a minimum fragment size equivalent to12 MSI on-board scenes (i.e. about 300km along-track), a coarse scalability figure of 22can be assumed for the processing of an average orbit segment of 6640km along-track(22 ≈ 6640/300).- By Block of Target Image, referring to the opportunity of processing the Level-1Cgeocoded image pixels in independent blocks of pixels in geocoded space, by default anentire Level-1C tile area of 100 km x 100 km.This opportunity will result into a processing performance scalability figure directlyproportional to the number of independent (and equally sized) blocks to be scaled downdepending on the processing margins top be applied. Assuming a processing split byentire level-1C tiles, a coarse scalability figure of about 200 can be assumed for theprocessing of an average orbit segment of 6640km along-track and 290km across track.- By Tile, referring to the opportunity of processing the image data in independent Level-1C tile fragments.All types of parallelisation defined above are independent from each other and will result in amultiplication of the opportunities when cumulated. E.g. an opportunity for parallelisation byDetector and Along-Track Fragment will result into an overall scalability figure of 12 timesthe one associated to the along-track fragmentation.© ESAThe copyright of this document is the property of ESA. It is supplied in confidence and shall not be reproduced, copied orcommunicated to any third party without written permission from ESA.