GMES Space Component

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GMES Space Component Coordinated Data Access
System Sentinels Missions E. Monjoux, A.
Buongiorno, O. Colin, B. Rosich, A.
Tassa Earth Observation Ground Segment
Department
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Global Monitoring for Environment and Security
GMES is established to fulfil the growing need
amongst European policy-makers to access accurate
and timely information services to better
manage the environment, understand and mitigate
the effects of climate change and ensure civil
security.
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Goal of GMES

• GMES aims at developing operational services,
  following the example of meteorology, but for
  other domains such as
• emergency management
• air quality monitoring
• land monitoring
• ocean sea ice monitoring etc

In addition, science is needed to create and
continuously improve operational services
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GMES Components

• GMES is an EU led initiative
• Services Component led by EC
• Produces information services in response
  to European
• policy priorities in environment and security
• Relies on data from in-situ and space
  component
• In-situ component led by EEA
• Observations mostly within national
  responsibility,
• with coordination at European level
• Space Component led by ESA
• Sentinels - EO missions developed
  specifically for GMES
• Contributing Missions - EO missions built
  for purposes other than
• GMES but offering part of their capacity
  to GMES (EU/ESA MSs, EUMETSAT, commercial,
  international)

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GMES Services

• Monitoring Earth sub-systems
• Land land use and land cover changes
• Ocean sustainable ocean resources and
  impact of environmental hazards
• Atmosphere effect of greenhouse gases and
  aerosols on climate change, air quality, and
  ultraviolet radiation
• Other Services
• Emergency rapid mapping services in case
  of humanitarian crises, and natural or man-made
  disasters
• Security maritime surveillance, conflict
  prevention and mitigation outside Europe
• Climate change is cutting across the above
  domains

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GMES Space Component and GMES Ground Segment
Sentinels and Data Access
GMES Space Component
Acquisition Stations
TTC Stations
Sentinels PDGS
FOS
GMES Contributing Missions GSs (ESA, EUMETSAT,
NOAA, national member-states missions, etc)
GMES Sentinels GS
GSC Coordinated Data Access System
GSC Data Request
USER Segment
GSC Data Provision
GMES Service Segment
Final end-user information products
EGSOM 20/10/2009
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GMES Data Access Ground Segment

• Data Access Ground Segment driver
• Ensure stable operational environment through
  continuous EO Missions and GMES Service Projects
  requirements evolutions
• Data Access Ground Segment shall manage dynamic
  Data Sets definition and composition
• Integration of new missions
• Integration of new Products
• ...
• Operation shall be streamlined through
  standardized and interoperable interfaces to
  maximize efficiency and reliability

EGSOM 20/10/2009
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GMES Data Access Ground Segment - Operations
Data Access Ground Segment in Operation since Nov
2008 Web site for information http//gmesdata.es
a.int/
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GMES Data Access Ground Segment - Operations

• Operations based on Earth Observation Products
  collections organized by nature and usage (Data
  Sets)
• Data Sets are created from GMES Contributing
  Missions Products

• Data Sets access mainly based on Subscriptions
• Product ordering coordination in place for
  dedicated GMES services (Emergency, Security)
• Access granted through GMES Services Registration
  and Contributing Mission licensing scheme

• ESA GMES Services Projects Coordinated interface
  in operation providing services for
• First line GMES Services Projects support
• GMES Services Projects registrations according to
  Contributing Missions license agreements
• GMES Projects ordering interface
• Information on data sets and operational status
  publication

• Operations progressing according to Services
  Projects maturity and readiness of Contributing
  mission interfaces
• New Data Sets are put in operation on a regular
  basis.

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Sentinel-1
Sentinel-1
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Sentinel-1 Space Segment
Lifetime Nominal lifetime in orbit of 7 years
(consumables for 12 years) Orbit Near Polar
Sun-Synchronous. Mean local solar time at
ascending node 1800 Repeat cycle 12 days. 175
orbits Global coverage per cycle Payload C-Band
Synthetic Aperture Radar Constellation
Sentinel-1 system will be composed of two
satellites, Sentinel-1 A B, to be launched 18
months apart Sentinel-1A launch 2012
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SAR Instrument Design

• Key design aspects of the SAR Payload
• Active phased array antenna providing fast
  scanning in elevation (to support ScanSAR
  operation) and in azimuth (to allow use of TOPS
  technique to meet the required image performance)
• Dual channel Transmit Receive Modules and
  H/V-polarised pairs of slotted waveguides (to
  meet the polarisation requirements)
• Internal Calibration scheme
• Digital Chirp Generator and selectable receive
  filter bandwidths to allow efficient use of on
  board storage considering the ground range
  resolution dependence on incidence angle
• Flexible Dynamic Block Adaptive Quantisation to
  allow efficient use of on-board storage

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Sentinel-1 Acquisition Modes
StripMap Mode Dual polarization, medium swath,
high radiometric performance, very high spatial
resolution Wave Mode Sampled StripMap mode,
single polarization, low data rate.
Interferometric Wide Swath Mode ScanSAR based
with progressive azimuth scanning (TOPS), dual
polarization, large swath, high spatial
resolution, burst synchronisation for ScanSAR
interferometry Extra Wide Swath Mode ScanSAR
based with progressive azimuth scanning (TOPS),
dual polarization, very large swath, medium
spatial resolution.

• Key TOPS mode features wrt ScanSAR
• no scalloping.
• constant azimuth ambiguity ratio (DTAR) and noise
  -equivalent 0 (NESZ).
• constant azimuth resolution.

ScanSAR operations
TOPS operations
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Sentinel-1 Acquisition Modes
Duty cycle 25 mini/orbit in high rate mode and
the rest of the orbit in WV mode
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Mission Performance
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Sentinel-1 Ground Segment

• Key Operational Concept
• Pre-defined stable mission observation plan, to
  support operational activities (e.g. ice
  monitoring, ground motion monitoring)
• On-request satellite tasking, processing and
  dissemination capability to support Emergency
  Security GMES Services
• Systematic processing and dissemination of all
  acquired data within 24 h
• Systematic NRT data access capability (from 10
  min to 3 h after data sensing)
• Priority downlink from memory to support NRT,
  direct downlink at Core Ground Stations and
  downlink support to local stations
• Easy access to systematic products flow
• Stable and traceable product quality meeting the
  quality requirements and accurate product
  calibration
• On line data access for fresh and past data
  (media usage is restricted to dissemination to
  few GMES Services on one-off basis e.g complete
  coverage of Europe)

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Operational ESA Sentinel-1 products available to
users - Overview
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Sentinel-2
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Mission Features

• Sentinel-2 mission will combine
• Systematic acquisition of all land surfaces and
  coastal waters
• High revisit frequency (5 days periodicity, same
  viewing direction, operations of 2 spacecrafts in
  twin configuration)
• Large swath (290km)
• High spatial resolution (10m / 20m / 60m)
• Large number of spectral bands (13 in VNIR-SWIR
  domain)
• Long mission duration (12 years) constellation
  of 2 satellites, Sentinel-2A launch in 2013 and
  Sentinel-2B launch 18 month after

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Coverage Time
Coverage time over Europe in summer with 2
satellites (considering clouds)
days
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Swath
SPOT4 60 x 60 km x 2 IRS P6 LISS III 141x141
km Landsat ETM 180 x 172 km Sentinel-2 290 x
290 km
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15 Spectral Bands
Spectral bands versus spatial resolution
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Image Quality Performance
Radiometric Performance

• 5 absolute calibration knowledge uncertainty
  (goal 3)
• Inter-band and multi-temporal calibration
  knowledge accuracy were set to 3 (goal 1)
• Non-linearity knowledge better than 1
• MTF (Modulation Transfer Function) higher than
  0.15 and lower than 0.3 at the Nyquist frequency
  for 10m and 20m bands and lower than 0.45 for 60m
  bands

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Image Quality Performance
Geometric Performances
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Satellite Payload
Satellite
MultiSpectral instrument

• Satellite mass 1200 kg
• Satellite power consumption 1250 W
• Hydrazine propulsion system (120 kg - including
  provision for safe mode, debris avoidance and EOL
  orbit decrease for faster re-entry)
• Dual Frequency GPS receiver
• Accurate AOCS based on multi-head Star Tracker
  and fiber optic gyro
• X band mission data distribution (560
  Mbits/sec) Data-relay capability (LCT) To be
  confirmed
• Mission data onboard storage 2.4 Tbits

• Mass/volume 280 kg, 1 m3
• Push broom type imager Three mirrors silicon
  carbide telescope, with dichroic beam splitter
• Focal plane arrays Si CMOS VNIR detectors,
  HgCdTe SWIR detectors.
• Onboard wavelet compression (1/3)
• Integrated video compression electronics
  (state of the art wavelet compression)
• Radiometric resolution 12bits
• Daily generated telemetry 1.4 TB

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Multi Spectral Instrument

• Three mirrors path to obtain 20.6º FOV
• Two focal planes to feed 2 separate arrays of 12
  detectors (VNIR/SWIR)
• Each detector covers 1/12th of FOV
• On-Board Data Compression (Specific
  Wavelet-based algorithm)

Si CMOS VNIR Detector
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Ground-Segment Operations

• Systematic recording and downlink of data to
  minimum 4 core ground stations, downlink via
  Data-Relay satellite (EDRS) supported
• Systematic processing up to level-1C/2A with
  near-real-time capability (lt 3hours from data
  sensing)
• Generation of predefined cloud-free coverage
  products for data users
• Long-term archiving and download access to the
  data, download latency optimised for recent data

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Sentinel-3
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End-to-End Earth Observation System

• Main Objectives
• Provide continuity of medium resolution sensors
  by ensuring the provision of
• Ocean observations data (i.e. Sea-Surface
  Height, Sea-Surface Temperature, Ocean Colour)
• Land optical observation products (i.e. Land
  Colour, Land Surface Temperature)
• Ice topography products (i.e. Sea Ice, Ice sheet
  interiors, ice sheet margins)
• Land hydrology products (i.e. water surface
  levels for river and lakes)

Main Characteristics
Orbit Near Polar frozen Sun-Synchronous Repeat
cycle 27 days. 385 orbits Payload An Ocean and
Land Colour Instrument (OLCI) A Sea and Land
Surface Temperature (SLST) Instrument A Radar
Altimeter (SRAL) And a
GNSS Receiver, a Laser retro-reflector (LRR) and
a DORIS instrument Constellation Sentinel-3
system will be composed of two satellites,
Sentinel-3 A B, to be launched 2 years apart
Sentinel-3A launch 2013

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Nominal measurement modes Duty cycle

• Systematic payload operations based on
• the orbital revolution number
• the angular position on orbit

Full OLCI coverage from SLST Synergic
Vegetation like product
Illustrations are courtesy from S3 Industrial
project team
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Payload

• Ocean and Land Colour Instrument (OLCI), a
  spectrometer imaging in pushbroom mode with an
  across-track electronic scan, strongly inherited
  from MERIS of Envisat, with same class of
  performance in the visible bands, associated with
  a larger coverage accounting for Sun glint.
• Sea and Land Surface Temperature Radiometer
  (SLSTR), a conical imaging radiometer with a dual
  view (near-nadir and inclined) capability,
  presenting design heritage from the AATSR of
  Envisat with same class of performance,
  associated with a larger coverage.
• SAR Radar ALtimeter (SRAL) instrument, a
  dual-frequency altimeter, derived from the
  Alcatel Alenia Space line of products such as
  SIRAL of Cryosat, and Poseidon-3 of Jason-2,
  providing Low Resolution Sea surface measurements
  in the continuity of the RA-2 of Envisat, and
  sea-ice monitoring in Nadir SAR mode.
• A Microwave Radiometer (MWR), which supports the
  SRAL to achieve the overall altimeter mission
  performance by providing the wet atmosphere
  correction.
• A Global Navigation Satellite System (GNSS)
  Receiver, suitable for the Precise Orbit
  Determination (POD) processed on ground to
  achieve the overall altimeter mission
  performance. Real time navigation and dating
  information from this equipment will provide
  spacecraft navigation and dating functions as
  well as the control of the Radar Altimeter
  open-loop tracking function.
• A Laser Retro-Reflector (LRR), a passive device
  which is used as a reflector by ground-based SLR
  stations using high-power pulsed lasers as a
  support to satellite ranging and SRAL altitude
  calibration.
• A Doppler Orbitography and Radio-positioning
  Integrated by Satellite (DORIS) instrument,
  microwave tracking system that can be utilized to
  determine the precise location of the satellite.

3 Main instruments
Ancillary Instruments
Illustrations are courtesy from S3 Industrial
project team
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SRAL SAR Radar Altimeter
Measurement modes
BRF 78.52 Hz PRF within the bursts 17800 Hz SAR
along-track res. 293-307 m
Repeat Cycle 27 days, 385 orbits Mean orbit
altitude 815 km
Nadir SAR mode
Data Rate 12 Mbps
2 radar modes
Low Resolution mode
PRF 1923.87 Hz
X
Data Rate 100 kbps
Dual Frequency
Radar features
Open Loop
2 tracking modes
Closed Loop
Pulse duration 50 µs

4 measurement modes
One Nadir looking antenna
2 Cal modes

• Continuity to
• RA-2 on Envisat
• Poseidon-3 on Jason-2
• (SIRAL on Cryosat)

Modes over the different surface types
Carrier frequency
Sea surface topography data at least at the level
of quality of the Envisat altimetry system.
For Ionosphere correction
Along-track SAR capability for addressing coastal
zones sea surface topography and sea ice
topography.
Mode transitions are scheduled according to the
satellite orbital position and linked to
geographical areas
Ancillary Payload
MWR GNSS LRR DORIS
Wet atmosphere correction
Precise Orbit Determination System
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OLCI Ocean and Land Colour Instrument
Instrument modes
Full Resolution (300 m at Nadir)
Acquisition over the daylight part of the orbit
(i.e. for a sun zenith angle below 80).
Data Rate 30 Mbps
Observation mode
1 (1)
(Reduced Resolution, 1km, (TBD) only over open
ocean
Radiometric Calibration

Every 2 weeks
on-board Calibration modes
Calibration over the South Pole, when the sun is
perpendicular to the satellite Y axis
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Dark Current Calibration

Spectral Calibration
Every 3 months
OLCI Pushbroom spectrometer

• Continuity to
• Meris on Envisat

Objectives Ocean, Coastal zones and Land Surface
Colour
Spatial Resolution 300 m at nadir
Coverage performances
xxxxxxxx
Wider swath for better revisit time
Sun glint effect mitigation
A larger number of channels for improving
atmospheric correction
Meris Revisit time 14 days
Sun glint over the oceans is mitigated thanks to
the asymmetrical FoV associated with a
Sun-synchronous orbit of Local Time at Descending
Node 10h00
? (nm)
The FoV is obtained thanks to 5 adjacent camera
modules
Spectral bands programmable in position and width
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SLSTR Sea and Land Surface Temperature Radiometer
Instrument modes
Close to Nadir View
500 m for the solar channels and 1 km for the
thermal channels for both modes
Data Rate 4.4 Mbps
Observation mode
2
Inclined View (backward)
Black body
on-board Calibration modes
Calibration over the South Pole, when the sun is
perpendicular to the satellite Y axis
2
Every scan-line
Radiometric Calibration

Dark Current Calibration
SLSTR
Solar diffuser
Every orbit
Objectives Sea Surface Temperature, Land Surface
Temperature
Spatial Resolution 500 m and 1km
Projected Across-track FOV
Nadir View
Backward View
512 km
743.6 km
AATSR
SLSTR
1800 km
Forward View
Nadir View
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GMES Data Policy

• ESA and the EC are presently defining the GMES
  Data and Information Policy for

? Services ? In-situ data ? Space data (Sentinels
and Contributing Missions)
Sentinel data access should be free and open
with minimum restrictions
Contributing Missions are acquired by GMES
respecting individual data policies and are made
available to GMES users for free
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Conclusions