After 26 years an era came to end at DLR’s Earth Observation Center (EOC) on 21 June 2017. The endeavour that came to a successful conclusion involved processing and archiving satellite data from the ERS and Envisat missions and was one of EOC’S longest-duration projects. The ERS-1/-2 Envisat D-PAF/D-PAC (Processing and Archiving Facility/Center) at DLR, commissioned by ESA, existed continuously since 1991.
It all began in July 1991 with the launch of the ESA satellite ERS-1 (in operation until 2000), whose payload data was acquired at GARS O’Higgins, DLR’s German Antarctic Receiving Station, among other locations. In the course of the project, data from ERS-2 (1995 – 2011) and Envisat (2002 – 2012) were also secured.
As part of the project, SAR data from ESA earth observation satellites were processed, archived long-term, and provided to a global user community, at first on physical media and later electronically via FTP. Besides SAR data, another focus of activity was on processing and distributing data on the atmosphere recorded by a variety of science instruments, such as GOME on ERS-2, and GOMOS, MIPAS and SCIAMACHY on the Envisat satellite. Data from the SCIAMACHY instrument, for example, contributed significantly to monitoring the size of the ozone hole over Antarctica. Subsequently, EOC also proved its capabilities in a total of 14 complex reprocessing campaigns for a diverse range of atmosphere data.
As a consequence of the long duration of the project, it was necessary to migrate this valuable data inventory several times. In other words, it was transferred onto the latest generation data media, from the GRAU AML-2 robot library to Oracle StorageTek Powderhorn to the Oracle StorageTek SL3000 data library, which was used up to the end. Data delivery technology also changed over the years. What began with the dispatch of CDs, DVDs and exabyte media was handled online from 2010 using FTP or HTTP servers. At peak periods up to 30 TB of data, or up to half a million data sets, were delivered every month. Per year over 30,000 ESA orders were processed. Worth mentioning is also the continued use of ERS and Envisat data by the user community long after the end of the active mission phases.
Starting in 2012, after the unexpected end of the Envisat mission, ESA began a data return operation, which involved extracting overs 600 TB of ERS-1/-2 and Envisat data from the DLR archives in order to make them available to users through ESA’s (A)SAR On-The-Fly Service. By the end of the project some 4.1 million data sets comprising over 800 TB of data had passed through the data archives.
EOC continues this successful work with the Sentinel-1A Processing and Archiving Center (PAC) that went into operation beginning of 2015 under contract with ESA. In July 2016 the operational phase began for the Sentinel-1B satellite and for OLCI data from Sentinel-3A. At the present stage of planning the Sentinel PAC will be completed by March 2018 when Sentinel-3B is launched into orbit. As impressive as the amount of data from the three historic ESA mission may be, the fleet of Sentinel satellites collects earth observation data at an entirely different order of magnitude. A little more than three years after the launch of the first Sentinels, the Sentinel PAC at EOC had already processed and archived 2.7 million data sets. The amount of data processed to date is over 4,300 terabytes (4.2 petabytes), thus exceeding already now the amount of data that was accumulated during the 26-year lifetime of the ERS/Envisat project by more than five times.