GSC Sentinel-2 PDGS STBD - emits - ESA

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GSC Sentinel-2 PDGS STBDIssue 1 Revision 2 (draft) - 25.07.2010GMES-GSEG-EOPG-TN-09-0031page 5 of 602 RECALL OF THE MAIN DRIVERS APPLICABLE TO PDGSSIZING2.1 Mission Data VolumesThe Sentinel-2 mission calls for the systematic acquisition with two twin satellites of all landsurfaces with a 290 km instrument swath in 13 spectral bands at 10m, 20m and 60mresolution. This corresponds to an average continuously sustained raw-data supply rate ofabout 160Mbps for the constellation. On ground, this implies a very large data volume tomanage with appropriate processing, archiving and networking resources.2.2 Systematic Processing and Product AvailabilityTimelinessThe PDGS operation baseline [RD-02] imposes strong constraints on the Level-1C producttimeliness provided to end-users:- Real-Time acquired data shall be available on-line within 100 minutes from dataacquisition on ground;- Data prioritised on-board for Near-Real-Time downlink shall be available on-linewithin 3 hours from data sensing;- All other data shall be available on-line within 24 hours from data sensing.The overall amount of RT/NRT data should range between 5 and 25% of the totalamount acquired.2.3 Product QualityThe stringent quality requirements imposed on the PDGS products (cf. [RD-01] and [RD-02])impose a complex and high-performance image processing workflow. In particular thegeolocation accuracy of the level-1 products have led to a complex processing algorithm upto Level-1C as defined in [RD-03] with associated preliminary benchmarks which isdimensioning the processing system.2.4 PDGS Distributed ArchitectureFor data reception, archiving and dissemination goals, The PDGS is designed as a networkof distributed ground stations and complementary centres imposing product data exchangesamongst PDGS remote locations and between the PDGS and its users. This implies anadequate dimensioning of internal data circulation resources between centres (electronicallyor else), complemented by data dissemination resources between the various archivelocations and end users (electronic only).ESA UNCLASSIFIED – For Official Use© 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.
3 PDGS PROCESSING BUDGET ANALYSISESA UNCLASSIFIED – For Official UseGSC Sentinel-2 PDGS STBDIssue 1 Revision 2 (draft) - 25.07.2010GMES-GSEG-EOPG-TN-09-0031page 6 of 60This chapter provides an analysis of the data processing budget for the Sentinel-2 PDGS.After this introductory part, the Sentinel-2 Level-0 and Level-1 processing benchmarks aredescribed. The next section provides an overview of the parallelisation opportunitiesassociated to every processing step. In a last section, preliminary processing budget figuresare estimated together with a description of the rationale of the calculations and associatedassumptions.3.1 Introduction3.1.1 PDGS PROCESSING SYSTEMThe PDGS processing system will be composed of hardware and software elements whichcan be mapped one another into processes which gradually carry out the overall processingin a controlled stepwise approach. In this model, every software element will implement a“processing step” using a given hardware element as work horse.Recalling the PDGS functional decomposition presented in [RD-02], the unitary processingstepsimplement the Instrument Data Processing (IDP) functional element while the DataProcessing Control (DPC) element structures, triggers and controls every step within theoverall workflow.In this framework, the Instrument Processing Facility (IPF) is the realisation of the IDPfunctionality into independently controlled processes hereafter referred to as “IPFcomponents”. In counterpart, the DPC functionality will be translated into a supervisioninfrastructure which composes and executes the workflow by means of separately controlledIPF components on the available hardware resources.3.1.2 PROCESSING RATIONALE AND TIMELINE CONSTRAINTSThe study of the PDGS operational processing scenarios to meet the various timelinessconstraints summarised in section 2.2 has led to a simple model in which:- The data is processed systematically up to Level-1C from every raw-data acquisitionperformed at every station. The collection of MSI data received at one station at aparticular orbit is hereafter referred to as a “datastrip”;- The processing follows a FIFO rule in which the data received first is processed firstwithin the datastrip. This model ensures that the processing strictly follows the prioritiesset in the downlink sequence (RT downlink or prioritised downlink via the NRT store),hence resulting in a product availability timeliness directly inherited from the downlinkplan;- The data processing resource is sized such as to ensure that the end-to-end timelinessconstraints are fulfilled after every datastrip processing, and that the resource issystematically freed for the next datastrip processing at the same station.Because of the need for Satellite Ancillary Data (SAD) to complete the MSI data processing,the processing sequence is driven by two triggers: the MSI data downlink and the SAD© 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.
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