GSC Sentinel-2 PDGS OCD - Emits - ESA

ESA UNCLASSIFIED – For Official Use
GSC Sentinel-2 PDGS OCD
Issue 1 Revision 2 (draft) - 25.07.2010
GMES-GSEG-EOPG-TN-09-0008
page 85 of 350
As introduced in section 3.5.4.3 and in order to simplify the PDGS operations, the MMFU
supports through appropriate commanding (cf. [RD-41]), the functionality of appending a
margin of three imaging scenes at the discontinuity boundaries. This enhanced functionality
shall be used by the PDGS mission planning element such that data circulation on ground
between processing stations or centres, which otherwise would be required for dataprocessing,
is avoided.
4.3.8.3 MSI Duty Cycle
It is anticipated [AD-03] that the MSI shall not stay longer than 50 min [TBC] continuously in
idle mode or any measurement mode during an orbit for derating reasons. This constraint is
at present TBC and will be better qualified at a later stage.
4.3.8.4 X-Band Operation Constraints
Two main constraints are highlighted for the X-Band subsystem operations as per [AD-03]:
○ Duty-Cycle: As per the current baseline, the satellite thermal and power/energy
accommodation of the X-Band System is capable of at least 24 minutes of continuous
downlink per orbit.
This limit figure will be better qualified at a later stage and it is already expected that 30
minutes should be achievable after characterisation and tuning of system parameters
(e.g. Albedo factor, operational temperature range of the modulators, X-Band OPS-
STDBY duty cycles).
○ Lifetime Number of Cycles: The X-Band system is specified for an overall number of
operation cycles (from standby to operation and back) equal to 100000 (one hundred
thousand) for the mission lifetime. Considering the extended lifetime of 12 years, this
figure derives into an average number of continuous X-Band transmissions per orbit of
about one and two third (1.6).
Within the above duty-cycle constraint, it is assumed the XBS can remain in operation mode
without the necessity of a temporary transition to standby even when the MMFU is not
feeding data to the XBS during the time separating two successive data-downlinks to groundstations.
In this case, it is assumed the carrier will be automatically switched off.
This approach is aimed at minimising the number of XBS switches during nominal operations
that will generally require two station contacts per orbit. The X-Band ground reception system
will hence be constrained such that it is as a whole narrowed to some extent within 24
minutes of satellite over-fly time for one third of the orbits, with a margin allowing for one
additional operation cycle to reach station contact beyond the 24 minutes for the remaining
orbits.
The above constraints will be considered in particular for the selection of the CGS network to
be operated for Sentinel-2 and for the further accommodation of LGS opportunities.
4.3.8.5 Asynchronous Management of Ancillary and MSI Data
As outlined in paragraph 3.5.4.3, the satellite ancillary data is required to perform MSI dataprocessing
on-ground. This data is continuously recorded on-board into a dedicated packet-
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