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 129 of 350
○ The Scene Duplication Flag will be activated at every recording NRT/Nominal
transition provided the MSI is operating during that transition (cf. case-B in the figure
depicted below);
○ The Scene Duplication Flag will be activated in case of Playback-RT operations on the
following cases (cf. case-C in the figure depicted below):
‣ The Scene Duplication Flag will be activated at every Playback-RT-With-
Memory-Freed transition provided the MSI is operating immediately before that
time (i.e. at the entry point of the RT segment).
‣ The Scene Duplication Flag will be activated at every interruption of Playback-
RT-With-Memory-Freed operations provided the MSI is operating immediately
after that time (i.e. at the exit point of the RT segment).
Figure 4-20: MMFU Scenes Duplication Cases
As justified in [RD-30], this strategy will result in sufficient MSI data received at every groundstation
to cover the discontinuities between stations and ensure consistency of the global
processing. It will also fulfil the MSI spatial registration constraint described in section
4.3.9.2.3 requiring that the MSI downlink in every CGS does not create orphan MSI segments
of less that 60km along-track. As a matter of fact, the appended three scenes will ensure that
although one station may receive trunks of data of less than three scenes, another one will
necessarily receive the same data in a larger set to cover the processing needs.
4.5.4.2.2.3 Playback Management
The accommodation of the Playback-Regular sequence within the station contact period will
differ based on whether the MSI packet store can be emptied at the term of the contact or
whether it must be explicitly suspended to let a subsequent playback operation recover the
remains of the buffer. This implies that the evolution of the MMFU memory is modelled by the
PDGS with sufficient accuracy as part of mission planning activities.
Figure 4-21 depicts these two distinct approaches simulating identical initial conditions of the
memory at the time of Acquisition-Of-Signal (AOS) with different lengths of the visibility
segment available for playback.
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