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 65 of 350
capabilities on ground and restore the dual 280Mbps data-streams ready
for front-end processing. The dual 280Mbps channels restored after the
EDRS ground equipment will be clear of any encryption.
[Assumption-12] The apportioned availability to Sentinel-2 for data-relay downlinks via the
EDRS constellation will be pre-defined at static times phased along the
Sentinel-2 orbit repeat cycle, following a preliminary agreement with the
EDRS exploitation segment in coordination with Sentinel-1.
[Assumption-13] The Sentinel-2 mission can use operationally the EDRS 230Mbps datarepatriation
multicast link for a third of the total time (cf. [RD-46]).
[Assumption-14] The operation constraints of the OCP will be later characterised by a welldefined
operation duty-cycle and an overall limit to the overall number of
operation switches sized for the OCP lifetime, similarly to the XBS.
[Assumption-15] The MSI timeline received on-ground after downlink will be provided with a
granularity of exactly one MSI on-board scene (corresponding to 3.48
seconds of instrument operation and about 23km on ground along-track)
as corresponding to the minimum indivisible packet size of the MSI. A
playback-stop commanded while an MSI scene is being downlinked will
effectively stop the playback and transmission only after the MSI scene
has been entirely transmitted.
[Assumption-16] The on-board recording of the ancillary data does not require specific
scheduling at PDGS mission-planning level as being either entirely
autonomous on-board or systematically triggered and maintained through
FOS flight operation procedures. The ancillary data is recorded
continuously including when the MSI is not operating, or when it is
operating in standby or idle modes.
[Assumption-17] 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 e.g. during the time separating two successive data-downlinks
to ground-stations. In this case, it is assumed idle transfer frames are
transmitted instead.
[Assumption-18] During orbit control and in case of attitude problems, the MSI shutter shall
be closed to protect the instrument. This constraint will be managed by the
FOS.
[Assumption-19] In response to potential X-Band access conflicts between Sentinels, a
conflict-free coordination among Sentinels will result in a predefined
allocation of downlink passes available for Sentinel-2. This allocation will
be static to a large extent (e.g. on a six to three months basis at least) and
will be settled after the selection of the CGS network, or in-any case at the
time of the Sentinel-2 PDGS deployment phase.
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