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 153 of 350
4.5.4.10.2.1 Dark Signal Assessment
The assessment of dark signal will be performed through acquisition of images over oceans
during night time. This will allow determining the radiometric calibration parameters for
removing the offset due to dark current.
This operation will be automatic and data-driven based on the reception of the Dark-Signal
Calibration data which will be commanded every 3 repeat cycles (30 days).
Such acquisitions will be optimised such as to cover areas without lucent plankton (e.g.
Pacific Ocean close to Chile) and to avoid full moon conditions. Based on the selected
calibration sites, the repeat-cycle orbit will be selected such as to minimise the impact on the
on-board memory evolution.
Figure 4-29 shows the coverage extracted from [RD-19] of typical image acquisitions
optimised for this purpose by simulation during summer and winter.
The result of both seasonal simulations overlap substantially such that it will be possible to
select a common site providing equal conditions for the continuity of this calibration process in
the long-term.
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