GSC Sentinel-2 PDGS OCD - Emits - ESA

GSC Sentinel-2 PDGS OCD
Issue 1 Revision 2 (draft) - 25.07.2010
GMES-GSEG-EOPG-TN-09-0008
page 176 of 350
○ Polar X-Band stations (typically one or two) able as a whole to receive the data from
Sentinel-2 spacecrafts once per orbit. They will additionally be equipped to retransmit
the data in near-real-time through EDRS 220Mbps data-repatriation transponders;
○ A network of a TBD number of Ka/Ku-Band stations spread throughout Europe in the
EDRS reception footprints of both the data-relay and the data-repatriation
transponders. Those stations will be able to receive the complementary Sentinel-2
downlinks via the OCP and EDRS as well as the data repatriated by multicast in Ku-
Band from polar stations.
Taking benefit from the compound usage described above, the repatriation capability will be
used to multicast in near-real-time the raw-data acquired at polar-stations throughout Europe
which will amount to half of the overall mission data. Coupled with the data-relay downlinks
securing the other half in multicast directly from the spacecrafts, this operation configuration
will lead to a fully flexible ground network bringing the huge Sentinel-2 data volumes nearly
anywhere in Europe for local processing and distribution close to the users.
The repatriated data volume from polar-stations, amounting in average to 8 minutes of
payload data from each spacecraft, can be multicast within about 18 minutes on the EDRS
220Mbps bandwidth repatriation path. Considering two Sentinel-2 units in orbit, usage of the
link will be limited to 36 minutes in average per every 100 minutes which is about a third of
the assumed time-shared capacity allocated to Sentinel-2.
This scenario is hence deemed achievable while providing NRT access to the global Sentinel-
2 data anywhere in Europe, provided the repatriation path is available to the Sentinel-2
mission at the right time. Beyond the noteworthy benefits that such scenario would bring in
terms of flexibility, reliability and performance, it would also considerably reduce the needs for
operating high-bandwidth point-to-point ground-lines to move the large volumes of Sentinel-2
data throughout Europe.
The global multicast data will be filtered in input to each centre (e.g. divided by geographical
regions) while providing for the necessary redundancy between centres to ensure global
reliability. Each centre will autonomously bring the raw data to higher-levels by local
processing and distribute it into a federated data-access network.
End-users will mostly rely on the ground network infrastructure, possibly enhanced to their
needs, to access the data from the local centres via the federated network. In complement,
the
data-broadcast capability will be used to reach locations that are poorly served otherwise.
This operation configuration is depicted below:
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