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 125 of 350
To account for potential conflicts with other Sentinel missions in utilising the X-Band and
EDRS resources, the available downlink-budget will be further characterised by a database of
constraints applicable separately to each satellite and including:
○ A list of X-Band Silent Segments: a static pattern of time segments with an N-cycles
repeatability during which the XBS shall not be operating due to conflicting RF
simultaneous operations with other Sentinel satellites;
○ A list of Station Unavailability Segments: a static pattern of time segments with an N-
cycles repeatability during which downlink activities to a given ground-station are not
permitted due to conflicting acquisitions by other Sentinel satellites requiring the station
resources (e.g. antenna) simultaneously;
○ A list of EDRS Availability Segments: a pre-defined pattern of time segments with an
N-cycles repeatability during which EDRS spacecrafts are available to relay Sentinel-2
data (cf. section 4.3.11).
The above constraints will be defined outside of the strict scope of the Sentinel-2 PDGS.
4.5.4.2.1.3 Detailed Downlink Planning
This step will define the effective downlink scenario applicable to each satellite based on the
associated MSI acquisition scenario and comprehensively ensuring that all operation
constraints are fulfilled. It will be applied recurrently as required by the mission planning and
scheduling loop with the FOS (cf. section 4.5.3.1.1).
The dynamics of the downlink scenario will be constrained by:
○ The static Coarse Downlink Budget as characterised in the previous step with all its
embedded constraints defining ground station, OCP and XBS usability;
○ The plans for station temporary unavailability provided by the ground station operators
(e.g. during maintenance periods);
○ The strict satellite operation constraints related to the use of the X-Band data
transmission subsystem described in sections 4.3.8.4 and the ones related to the
operations of the OCP as anticipated in section 4.3.8.6.
In particular, the number of on-off transitions imposed on the XBS and OCP
subsystems will be minimised on a repeat-cycle basis within the duty-cycle constraints
of each subsystem imposed at orbit-level. This will impose when relevant the merging
of non overlapping opportunities into one single transmission segment within the dutycycle
constraints. In turn, it may further reduce from the coarse figure the downlink
budget available at specific orbits whenever the duty-cycle does not allow full merging
of the downlink opportunities.
Additional TBC conflicts brought in by OCP operations with respect to MSI imaging (cf.
section 4.3.8.6) or the satellite power budget, coupled with the required TBD transitory
operations of the OCP itself, will further constrain the usage of EDRS/OCP contact
opportunities.
○ The effective zone coverage partitioning into NRT, RT and nominal data defined in the
HLOP and intersecting the MSI acquisition scenario defined in section 4.5.4.1.1.
ESA UNCLASSIFIED – For Official Use
© ESA
The copyright of this document is the property of ESA. It is supplied in confidence and shall not be reproduced, copied or
communicated to any third party without written permission from ESA.