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 83 of 350
4.3.8.1 MSI Detectors Parallax
As outlined in section 3.5.2.2, the MSI includes two distinct arrays of 12 detectors mounted on
different focal-planes (VNIR & SWIR) each one distributing the detectors onto two alternate
lines on the focal-plane. This design makes the sensing footprint on the start and end of each
acquisition not homogeneous between the spectral bands and detector modules.
This derives into an operation constraint for the MSI acquisition planning such that previous
data to the area of interest (data around to the “advanced switch-on” showed in the figure
below) and next adjacent data (next to the “delayed switch-off”) will be required to avoid gaps
in the PDGS production timeline due to the sensor different viewing conditions.
Figure 4-4: Sentinel-2 MSI footprint
4.3.8.2 MSI Data Downlink Discontinuities
RT direct-downlinks to core stations or the NRT prioritisation of the MSI data takes in the
MMFU data-store, together with the need for several X-Band station visibilities (nominally two
per orbit revolution) to recover the data on-ground, will after playback generate discontinuities
on the timeline received at the CGSs.
Figure 4-5 depicts a typical MSI acquisition timeline with several continuous imaging
segments and the MSI packet store playback timeline onto two distinct ground-stations where
some MSI data-takes are transmitted in RT and others have been prioritised for NRT
downlink.
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