GSC Sentinel-2 PDGS OCD - Emits - ESA
GSC Sentinel-2 PDGS OCD - Emits - ESA
GSC Sentinel-2 PDGS OCD - Emits - ESA
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<strong>GSC</strong> <strong>Sentinel</strong>-2 <strong>PDGS</strong> <strong>OCD</strong><br />
Issue 1 Revision 2 (draft) - 25.07.2010<br />
GMES-GSEG-EOPG-TN-09-0008<br />
page 50 of 350<br />
3.5 Space Segment<br />
3.5.1 SENTINEL-2 SPACECRAFT OVERVIEW<br />
The <strong>Sentinel</strong>-2 spacecraft depicted on Figure 3-2 is a 3-axis stabilised earth polar-orbiting<br />
satellite weighting 1.2 tons. It features an accurate Attitude and Orbit Control System (AOCS)<br />
based on a multi-head star-tracker and fibre optic gyroscopes, as well as a dual frequency<br />
GPS receiver to provide precise on-board determination of the satellite position.<br />
It carries on-board the Multi-Spectral Instrument (MSI) payload of 280kg and about 1m 3<br />
volume hosting the attitude sensors in order to minimise the thermo-elastic perturbations to<br />
the attitude measurements.<br />
Figure 3-2 <strong>Sentinel</strong>-2 Spacecraft<br />
The payload data, GPS & AOCS ancillary data and spacecraft housekeeping telemetry data<br />
(HKTM) can be buffered on board into a 2.4 Tbits mass storage system before being<br />
downlinked to ground receiving stations using an X-Band data distribution equipment<br />
featuring two concurrently operating 280 Mbps Travelling Wave Tube Amplifiers (TWTA) for<br />
an overall effective downlink rate capacity of 520Mpbs for payload-data. Alternatively, the X-<br />
Band distribution system can be used to transmit the payload data in real-time to groundstations<br />
while buffering the same data for later playback to other stations.<br />
The current satellite design, mass and power budgets currently make provision for future<br />
integration of a Optical Communication Payload (OCP) to be procured through the European<br />
Data Relay Satellite (EDRS) <strong>ESA</strong> program to allow transmission of the same mission data via<br />
EDRS provided geo-stationary data-relay satellites, hence substantially augmenting the datadownlink<br />
capacity of the mission through still EDRS-pointing ground Ka-Band antennas.<br />
The spacecraft operations are controlled from ground via a Telemetry and Tele-command<br />
(TMTC) subsystem operating in S-Band and interfacing the On-board Computer (OBC).<br />
The OBC software includes an on-board scheduler supporting both the MTL-based<br />
scheduling (Mission Timeline based on UTC), and the GPS coupled OPS (Orbit Position<br />
Schedule) scheduling capability allowing for long periods (>15 days) autonomy of the<br />
spacecraft operations.<br />
<strong>ESA</strong> UNCLASSIFIED – For Official Use<br />
© <strong>ESA</strong><br />
The copyright of this document is the property of <strong>ESA</strong>. It is supplied in confidence and shall not be reproduced, copied or<br />
communicated to any third party without written permission from <strong>ESA</strong>.
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