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SENTINEL-2 User Handbook
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ESA Standard Document
Date 24/07/2015 Issue 1 Rev 2
Sentinel-2 User Handbook
SENTINEL-2 User Handbook
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ESA Standard Document
Date 24/07/2015 Issue 1 Rev 2
Title Sentinel -2 User Handbook
Issue 1 Revision 1
Author SUHET Date 1/09/2013
Approved by Bianca Hoersch Date 1/09/2013
Reason for change Issue Revision Date
Minor Update 1 1 07/07/2014
Minor Update 1 2 24/07/2015
Issue Revision
Reason for change Date Pages Paragraph(s)
Update to 07/07/2014 27 Fig. 5
Fix broken hyperlink 24/07/2015 41 1.9.4
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Table of contents:
1 INTRODUCTION................................................................................................... 8
1.1 Overview ....................................................................................................................................... 9
1.1.1 Instrument Payload .................................................................................................................... 9
1.1.2 Related Content: ....................................................................................................................... 10
1.2 HERITAGE .................................................................................................................................. 11
1.3 Thematic Areas and Services ...................................................................................................... 13
1.3.1 Land Monitoring....................................................................................................................... 13
1.3.2 Emergency Management .......................................................................................................... 14
1.3.3 Security ..................................................................................................................................... 14
1.4 Mission Objectives...................................................................................................................... 16
1.5 Satellite Description ....................................................................................................................17
1.5.1 Orbit .......................................................................................................................................... 18
1.5.2 Geographical Coverage ............................................................................................................. 18
1.6 Ground Segment ......................................................................................................................... 19
1.6.1 Collaborative Ground Segment ................................................................................................ 20
1.6.1.1 Collaboration Categories ........................................................................................................ 20
1.6.1.1.1 Sentinel Mission Data Acquisition and NRT production .................................................. 21
1.6.1.1.2 Sentinel Collaborative Data Products ............................................................................... 22
1.6.1.1.3 Sentinel Data Product Dissemination and Access ............................................................ 24
1.6.1.1.4 Innovative Tools and Applications .................................................................................... 25
1.6.1.1.5 Sentinel complementary Calibration/Validation activities ............................................... 26
1.6.1.1.6 Agreement Process ............................................................................................................ 27
1.6.1.1.7 Existing/Planned collaborative GS .................................................................................... 28
1.6.2 Core Ground Segment (CGS) ................................................................................................... 29
1.6.2.1 Payload Data Ground Segment (PDGS) ................................................................................. 30
1.6.2.2 Flight Operation Segment (FOS) ........................................................................................... 32
1 SENTINEL-2 MSI USER GUIDE .......................................................................... 34
1.7 Introduction ............................................................................................................................... 34
1.8 Overview ..................................................................................................................................... 35
1.8.1 Granules and Tiles .................................................................................................................... 35
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1.8.2 Data-Takes and Datastrips ....................................................................................................... 36
1.8.3 Geophysical Measurements ...................................................................................................... 37
1.9 Applications ................................................................................................................................ 39
1.9.1 Land Monitoring....................................................................................................................... 39
1.9.2 Emergency Management .......................................................................................................... 40
1.9.3 Security ..................................................................................................................................... 40
1.9.4 Copernicus Briefs ..................................................................................................................... 41
1.10 Product Types ............................................................................................................................. 42
1.10.1 Level-0 ...................................................................................................................................... 44
1.10.2Level-1A .................................................................................................................................... 44
1.10.3 Level-1B .................................................................................................................................... 44
1.10.4Level-1C .................................................................................................................................... 45
1.10.5 Level-2A .................................................................................................................................... 45
1.11 Processing Levels ........................................................................................................................ 46
1.11.1 Level-0 ...................................................................................................................................... 47
1.11.2 Level-1 ....................................................................................................................................... 47
1.11.2.1 Level-1B .................................................................................................................................. 47
1.11.2.2Level-1C .................................................................................................................................. 48
1.11.2.3 Level-2 .................................................................................................................................... 48
1.12 Resolutions ................................................................................................................................. 51
1.12.1 Spatial Resolution..................................................................................................................... 51
1.12.1.1 10 metre spatial resolution: ................................................................................................... 51
1.12.1.220 metre spatial resolution: ................................................................................................... 52
1.12.1.3 60 metre spatial resolution: ................................................................................................... 52
1.12.2 Radiometric Resolutions .......................................................................................................... 52
1.13 Revisit & Coverage ...................................................................................................................... 55
1.14 Product Naming Convention ...................................................................................................... 57
1.14.1 Level-1B Granule ...................................................................................................................... 58
1.14.1.1 Granule Image Data Naming Convention .............................................................................. 59
1.14.2 Level-1C Tile ............................................................................................................................. 59
1.14.2.1Level-1 Tile Image Data Naming Convention ........................................................................ 59
1.14.3 Level-2A .................................................................................................................................... 60
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1.14.3.1Level-2A Data Naming Convention ....................................................................................... 60
1.15 Data Formats .............................................................................................................................. 60
1.15.1 LEVEL-2A Data Format ........................................................................................................... 61
1.16 Software Tools ............................................................................................................................ 61
1.17 Definitions .................................................................................................................................. 62
1.17.1 Auxiliary Data ........................................................................................................................... 62
1.17.2 Datatake .................................................................................................................................... 62
1.17.3 Datastrip ................................................................................................................................... 62
1.17.4 Granules and Tiles .................................................................................................................... 62
1.17.5 Quality Indicator ...................................................................................................................... 62
1.17.6 Timeliness ................................................................................................................................. 63
1.17.7 True Colour Images (TCI) ........................................................................................................ 63
1.18 Document Library ...................................................................................................................... 64
1.18.1 Sentinel-2A Spectral Responses ............................................................................................... 64
1.18.2 Sentinel-2 Products Specification Document .......................................................................... 64
1.18.3 Sentinels POD Service File Format Specification .................................................................... 64
Table of Tables
Table 1: Comparison of SENTINEL-2 with important heritage missions ......................................... 35
Table 2: Sentinel-2 Product types ...................................................................................................... 42
Table 3:10 m Spatial Resolution Bands and associated Signal to Noise ratio (SNR) ....................... 53
Table 4:20 metre Spatial Resolution Bands and associated Signal to Noise ratio (SNR) ................. 53
Table 5:60 metre Spatial Resolution Bands and associated Signal to Noise ratio (SNR) ................. 54
Table 6: Level 1 Granule (Tile), Datastrip and TCI PDI File Type ................................................... 58
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Table of Figures
Figure 1: The Twin-Satellite SENTINEL-2 Orbital Configuration (courtesy Astrium GmbH) 9
Figure 2: Comparison of Spatial Resolution and Wavelength Characteristics of SENTINEL-2
Multispectral Instrument (MSI), the Operational Land Imager (OLI) On-Board LANDSAT-8,
and SPOT 6/7 Instruments (from ESA Special Publication 1322/2) ....................................... 11
Figure 3: Schematic View of the Deployed SENTINEL-2 Spacecraft (image credit: EADS
Astrium) ................................................................................................................................... 17
Figure 4: Copernicus Ground Segment Architecture............................................................... 19
Figure 5: Application Software ................................................................................................ 25
Figure 6: Innovative Tools and Applications........................................................................... 25
Figure 7: Sentinel complementary Calibration/Validation activities....................................... 26
Figure 8: Agreement Process ................................................................................................... 27
Figure 9: SENTINEL-2 Receiving Stations and Off-line Processing and Archiving Centres 31
Figure 10: ESA's European Space Operations Centre ............................................................. 32
Figure 11: Product Breakdown Structure (Image courtesy of ESA) ....................................... 36
Figure 12: Map of Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), July
2011, as derived from MERIS Full Resolution (FR) data. The values vary from 0 (white) to 1
(red) (image courtesy of ESA and Astrium GmbH, Germany) ............................................... 38
Figure 13: Typical orbit showing layout of Level-1B product granules ................................. 43
Figure 14: Level-1C product tiling .......................................................................................... 43
Figure 15: TOA Level-1C Image Data (left) and Associated BOA Image Data (right) as
generated by the Sentinel-2 Toolbox ....................................................................................... 46
Figure 16: Processing Levels from Level-0 to Level-1C......................................................... 46
Figure 17: The figure shows from left to right: (1) A simulated Level-1C TOA input Image,
(2) the Cirrus and Atmospheric Corrected Level-2A BOA Image, (3) the Cirrus Band Nr. 10,
(4) the Scene Classification of the Level-1C Input Image ....................................................... 50
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Figure 18: Sentinel-2 10 m Spatial Resolution Bands: B2 (490 nm), B3 (560 nm), B4 (665 nm)
and B8 (842 nm) ...................................................................................................................... 51
Figure 19: Sentinel-2 20 m Spatial Resolution Bands: B5 (705 nm), B6 (740 nm), B7 (783 nm),
B8b (865 nm), B11 (1610 nm) and B12 (2190 nm) ................................................................ 52
Figure 20: Sentinel-2 60 m Spatial Resolution Bands: B1 (443 nm), B9 (940 nm) and B10
(1375 nm) ................................................................................................................................. 52
Figure 21: Modelled Sentinel-2 Coverage ............................................................................... 55
Figure 22: Modelled Sentinel-2 Coverage ............................................................................... 56
Figure 23: Sentinel-2 product physical format ........................................................................ 60
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1 INTRODUCTION
The full SENTINEL-2 mission comprises twin polar-orbiting satellites in
the same orbit, phased at 180° to each other.
The mission will monitor variability in land surface conditions, and its
wide swath width and high revisit time (10 days at the equator with one
satellite, and 5 days with 2 satellites under cloud-free conditions which
results in 2-3 days at mid-latitudes) will support monitoring of changes to
vegetation within the growing season. The coverage limits are from between latitudes 56° south
and 84° north.
For mission planning information, see the Copernicus Mission pages.
This SENTINEL-2 Mission Guide provides a high-level description of the mission objectives,
satellite description and ground segment. It also addresses the related heritage missions,
thematic areas and Copernicus services, orbit characteristics and coverage, instrument payload,
and data products.
The Mission Guide categories are:
Overview This section provides a brief description of the heritage missions of SPOT and
LANDSAT, as well as the main thematic areas and services such as land monitoring.
Mission Objectives Describes primary and secondary objectives of the SENTINEL-2 mission.
Satellite Description Describes the satellite platform and the communication links, as well as the orbit
characteristics and the geographical coverage of the mission.
Ground Segment Describes the Flight Operations Segment (FOS) and the Payload Data Ground
Segment (PDGS) of the mission.
Instrument Payload Describes the main instrument of the SENTINEL-2 mission: the MultiSpectral
Instrument (MSI).
Data Products Outlines the Level-1B and Level-1C data products that are available to users.
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1.1 Overview
SENTINEL-2 is a European wide-swath, high-resolution, multi-spectral imaging mission.
The full mission specification of the twin satellites flying in the same orbit but phased at
180°, is designed to give a high revisit frequency of 5 days at the Equator.
SENTINEL-2 will carry an optical instrument payload that will sample 13 spectral bands:
four bands at 10 m, six bands at 20 m and three bands at 60 m spatial resolution. The orbital
swath width will be 290 km.
Figure 1: The Twin-Satellite SENTINEL-2 Orbital Configuration (courtesy Astrium GmbH)
The twin satellites of SENTINEL-2 will provide continuity of SPOT and LANDSAT-type
image data, contribute to ongoing multispectral observations and benefit Copernicus
services and applications such as land management, agriculture and forestry, disaster
control, humanitarian relief operations, risk mapping and security concerns.
1.1.1 Instrument Payload
Each of the satellites in the SENTINEL-2 mission carries a single payload: the Multi-Spectral
Instrument (MSI).
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1.1.2 Related Content:
The SENTINEL-2 System
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1.2 HERITAGE
The spectral band configuration of the SENTINEL-2 mission arose as a result of consultation
with the user community during the design phase. The existing Copernicus Service Elements
(GSEs) services were developed around the use of LANDSAT and SPOT wavelengths, and the
service requirements for SENTINEL-2 have these at their core.
Figure 2: Comparison of Spatial Resolution and Wavelength Characteristics of SENTINEL-2
Multispectral Instrument (MSI), the Operational Land Imager (OLI) On-Board LANDSAT-8, and
SPOT 6/7 Instruments (from ESA Special Publication 1322/2)
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Narrowing the width of the SENTINEL-2 spectral bands limits the influence of atmospheric
constituents, including water vapour. The original LANDSAT Near Infra-Red (NIR) band
(760-900 nm) was found to be heavily contaminated by water vapour and not sensitive
enough to parameters such as soil iron oxide content. The narrowness of the 8a band at 865
nm in the NIR is designed to avoid contamination from water vapour yet still be able to
represent the NIR plateau for vegetation and be sensitive to iron oxide content for soil.
Precise aerosol correction of acquired data is enabled by the inclusion of a spectral band in
the blue domain at 443 nm (Band 1) in the SENTINEL-2 configuration. The 443 nm band
was used in previous missions: for the calculation of the ENVISAT MERIS Global Vegetation
Index (MGVI), and in atmospheric corrections for NASA's MODIS sensor.
Due to its potential impact on reflectance values, its use as an indicator in weather
forecasting and its role in the trapping of incoming solar radiation, the presence of cirrus
cloud needs to be addressed. Adding a spectral band at 1 375 nm (band 10) enables cirrus
detection. The correction of data for thin cirrus can be managed using Visible to Near Infra-
Red (VNIR) band information. This band is included in the MODIS instruments as band 26,
and its is used in current US multispectral missions such as LANDSAT-8 and the Visible
Infrared Imaging Radiometer Suite (VIIRS).
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1.3 Thematic Areas and Services
The SENTINEL-2 mission requirements for a twin-satellite, high revisit frequency, high
resolution image will support Copernicus programmes. Observation data acquired from the
SENTINEL-2 mission will be utilised by services such as:
Land monitoring
Emergency management
Security
Climate change.
1.3.1 Land Monitoring
With its frequent and systematic coverage, SENTINEL-2 will make a significant contribution
to land monitoring services by providing input data for both land cover and land cover
change mapping, and support the assessment of biogeophysical parameters such as Leaf
Area Index (LAI), Leaf Chlorophyll Content (LCC) and Leaf Cover (LC).
SENTINEL-2 links to Copernicus programmes
The Copernicus Land Monitoring service became operational in 2012. The object of the
service is to provide land cover information to users working in the field of environmental
and other terrestrial applications.
The service is designed to provide geographical information on land cover and related
variables such as the vegetation state or the water cycle, and also supports applications in
other domains including: spatial planning, forest management, water management,
agriculture and food security.
The service consists of three main components:
pan-European
global
local.
Coordination of the pan-European component is the responsibility of the European
Environment Agency (EEA) and the first component, pan-European land cover, will produce
five high resolution data sets describing the main land cover types:
artificial surfaces (such as roads and paved areas)
forest areas
agricultural areas (such as grasslands)
wetlands
small water bodies.
These five datasets will be provided by the GIO land project.
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The Global component is coordinated by the The Joint Research Centre (JRC), a Directorate-
General of the European Commission. This component will produce data across a wide range
of biophysical variables at a global scale (i.e. worldwide), which will include the description
of the state of vegetation (using parameters such as LAI).
The biophysical variable data will be provided by the Global Land Service (GIO-GL).
The local component is coordinated by the European Environment Agency and aims to
provide more specific and detailed information that will compliment the information
obtained via the Pan-European component. Besides an update of the Urban Atlas that will
utilise imagery from 2012, the next local component will address biodiversity in areas
around rivers.
1.3.2 Emergency Management
The 10 m spatial resolution bands of SENTINEL-2 and the high revisit time of the mission
will support the rapid acquisition and delivery of images to support disaster relief efforts.
This includes mapping of urban areas, including at-threat buildings and complex structures,
that have been previously identified as being at risk from natural hazards such as
earthquakes and flooding. It will also contribute towards the identification of potential relief
staging areas and status of supply routes, and enable their use in pre- and post-event mission
planning and control over the mission lifetime.
SENTINEL-2 links to Copernicus programmes
The Copernicus Emergency Management Service mapping component (GIO EMS) entered
initial operations in 2012. GIO EMS provides satellite observation data quickly and
efficiently, and together with available in-situ data and other data sources, supports the
management of relief efforts to natural disasters (e.g. floods, forest fires, landslides,
earthquakes and volcanic eruptions), humanitarian crises, and man-made events around the
globe.
1.3.3 Security
The SENTINEL-2 mission requirements for a twin-satellite system with high revisit and high
resolution images will support issues such as:
border surveillance;
maritime surveillance;
support to EU external action.
The main objectives of border surveillance are to:
reduce the number of illegal immigrants entering the EU undetected
reduce the number of deaths of illegal immigrants by improving the number of lives
saved at sea
increase internal security of the EU as a whole by contributing to the prevention of
cross-border crime.
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For maritime surveillance, research and demonstrator activities are being developed.
In support to EU external action, Earth Observation (EO) products, including mapping and
geo-information products, will be deployed in emergency and crisis situations, and services
can be integrated by the user into their working environment. Lessons learned through the
precursor G-MOSAIC project and feedback from stakeholders have helped guide the
requirements for pre-operational services and additional research activities.
Links to Copernicus programmes
More on the draft proposals for Copernicus support to issues of border & maritime
surveillance and EU external action can be found here.
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1.4 Mission Objectives
The objectives for SENTINEL-2 are set out in the Mission Requirements Document.
SENTINEL-2 mission objectives are to provide:
systematic global acquisitions of high-resolution, multispectral images allied to a high
revisit frequency
continuity of multi-spectral imagery provided by the SPOT series of satellites and the
USGS LANDSAT Thematic Mapper instrument
observation data for the next generation of operational products, such as land-cover
maps, land-change detection maps and geophysical variables.
These high-level objectives, determined after consultation with users, will ensure that
SENTINEL-2 makes a significant contribution to Copernicus themes such as land
monitoring, emergency management, and security.
With its 13 spectral bands, 290 km swath width and high revisit frequency, SENTINEL-2's
MSI instrument supports a wide range of land studies and programmes, and reduces the
time required to build a European cloud-free image archive. The spectral bands of
SENTINEL-2 will provide data for land cover/change classification, atmospheric correction
and cloud/snow separation.
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1.5 Satellite Description
Each of the SENTINEL-2 satellites weighs approximately 1.2 tonnes, and is designed to be
compatible with small launchers like VEGA and ROCKOT. The satellite lifespan is 7.25 years,
which includes a 3 month in-orbit commissioning phase. Batteries and propellants have been
provided to accommodate 12 years of operations, including end of life de-orbiting
manoeuvres.
Two identical SENTINEL-2 satellites will operate simultaneously, phased at 180° to each
other, in a sun-synchronous orbit at a mean altitude of 786 km. The position of each
SENTINEL-2 satellite in its orbit will be measured by a dual-frequency Global Navigation
Satellite System (GNSS) receiver. Orbital accuracy will be maintained by a dedicated
propulsion system.
The SENTINEL-2 satellite system is being developed by an industrial consortium led by
Astrium GmbH (Germany). Astrium SAS (France) is responsible for the MultiSpectral
Instrument (MSI).
The MSI works passively, by collecting sunlight reflected from the Earth. New data is
acquired at the instrument as the satellite moves along its orbital path. The incoming light
beam is split at a filter and focused onto two separate focal plane assemblies within the
instrument; one for Visible and Near-Infra-Red (VNIR) bands and one for Short Wave Infra-
Red (SWIR) bands . The spectral separation of each band into individual wavelengths is
accomplished by stripe filters mounted on top of the detectors.
Figure 3: Schematic View of the Deployed SENTINEL-2 Spacecraft (image credit: EADS Astrium)
The optical design of the MSI telescope allows for a 290 km Field Of View (FOV).
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A shutter mechanism prevents the instrument from direct illumination by the sun in orbit
and to avoid contamination during launch. The same mechanism functions as a calibration
device by collecting the sunlight after reflection by a diffuser.
1.5.1 Orbit
The SENTINEL-2 orbit is sun-synchronous. Sun-synchronous orbits are used to ensure the
angle of sunlight upon the Earth’s surface is consistently maintained. Apart from small
seasonal variations, anchoring of the satellites orbit to the angle of the sun minimises the
potential impact of shadows and levels of illumination on the ground. This ensures
consistency over time and is critical in assessing time-series data.
The mean orbital altitude of the SENTINEL-2 constellations is 786 km. The orbit inclination
is 98.62° and the Mean Local Solar Time (MLST) at the descending node is 10:30 (am). This
value of MLST was chosen as a compromise between a suitable level of solar illumination
and the minimisation of potential cloud cover. The MLST value is close to the local overpass
time of LANDSAT and almost identical to that of SPOT-5, permitting the integration of
SENTINEL-2 data with existing and historical missions, and contributing to long-term time
series data collection.
1.5.2 Geographical Coverage
The SENTINEL-2 satellites will systematically acquire data over land and coastal areas in a
band of latitude extending from 56° South (Isla Hornos, Cape Horn, South America) to 83°
North (above Greenland). Data collection within this region will include:
islands greater than 100 km2 in area
islands in the European Union
all other islands within 20 km of a coastline
the Mediterranean Sea
all inland water bodies
all closed seas.
In addition, to support mission-linked calibration and validation activities, the SENTINEL-2
satellites will acquire additional observations over specific calibration sites, such as Dome-C
in Antarctica.
Note: Areas of interest going beyond the Mission baseline (as laid out in the Mission
Requirements Document) will be assessed, and may be added to the baseline if sufficient
resources are identified.
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1.6 Ground Segment
The ground segment is composed of the core ground segment, the collaborative ground
segment and the Copernicus contributing missions' ground segments.
The core ground segment monitors and controls the SENTINEL spacecraft, ensures the
measurement data acquisition, processing, archiving and dissemination to the final users. In
addition, it is responsible for performing conflict-free mission planning according to a pre-
defined operational scenario, and ensures the quality of data products and performance of
the space-borne sensors by continuous monitoring, calibration and validation activities,
guaranteeing the overall performance of the mission.
Figure 4: Copernicus Ground Segment Architecture
The Copernicus ground segment is complemented by the SENTINEL collaborative ground
segment, which was introduced with the aim of exploiting the SENTINEL missions further.
This entails additional elements for specialised solutions in different technological areas
such as data acquisition, complementary production and dissemination, innovative tools and
applications, and complementary support to calibration and validation activities.
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The Copernicus contributing mission ground segments, with their own specific control
functions, data reception, data processing, data dissemination and data archiving facilities,
deliver essential data complementing the SENTINEL missions.
1.6.1 Collaborative Ground Segment
The SENTINEL collaborative ground segment is intended to allow complementary access to
SENTINEL data and/or to specific data products or distribution channels. It is composed of
elements funded by third parties (i.e. from outside the ESA/EU Copernicus programme) and
provides the framework for international cooperation. The collaborative elements are
expected to bring specialised solutions to further enhance the SENTINEL missions’
exploitation in various areas.
Data acquisition and (quasi-) real-time production. This is when local ground stations
are configured to receive SENTINEL data directly during the satellite overpass (and
supported as long as this does not conflict with the systematic operations of the
Copernicus ground segment).
Complementary products and algorithms definitions. These “collaborative data
products” may include specific tailoring for regional coverage or specific applications.
These types of products might extend the SENTINEL core product chains.
Data dissemination and access, supporting redistribution of SENTINEL core products
by establishing additional pick-up points (e.g. mirror sites).
Development of innovative tools and applications.
Complementary support to calibration/validation activities.
1.6.1.1 Collaboration Categories
SENTINEL Mission Data Acquisition and (NRT) Production
Local/regional stations complementing the core X-band and Ka-band station network with
the following potential activities.
(NRT) data processing and distribution for SENTINEL-1 and/or SENTINEL-2.
Elaboration of (NRT) products tailored to particular coverage/region, particular
services, etc.
SENTINEL Collaborative Data Products
Definition, specification, generation of data products to complement the set of products
provided by the core ground segment, potentially including:
higher level products than produced by the core ground segment
product/algorithms tailored to a particular coverage or region, services or user
community
generation of local/regional data sets with correction, projection, calibration, merging
etc., different to the standardised data set offered by the GSC core ground segment.
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Note: These activities are mainly foreseen for collaborative entities interested in specific
ESA support such as provision of dedicated access links to core products, advertising, host
processing, mutual cal/val support, access to collaborative product through GSC catalogue,
etc.
SENTINEL Data Product Dissemination and Access
Particular regional or thematic data access nodes and mechanisms, potentially including:
redistribution services of SENTINEL products, systematically received from the core
ground segment, becoming additional pick-up points (e.g. mirror sites)
regional online data servers and data pick-up points for specific user communities, etc.
Innovative Tools and Applications
Development of particular innovative tools or 'apps' by and for the general public.
SENTINEL Complementary Calibration/Validation Activities
Complementary support to calibration and validation activities.
1.6.1.1.1 Sentinel Mission Data Acquisition and NRT production
SENTINEL data acquisition and quasi-real-time production (local stations) can provide a
regional (within the station coverage) quasi-real-time (10-15 min from sensing) data service
via SENTINEL collaborative (local) stations.
Provided no conflicts arise with the systematic space and ground segment operations, ESA
will support operations in terms of mission planning (acquisition scheduling including all
auxiliary information) over the local geographical area of interest and provision of satellite-
to-ground interface information.
Only a limited number of collaborative stations can be supported, as the systematic
downlink scenario to core stations may exclude certain real-time downlinks. It is envisaged
that only a very limited number of collaborative stations outside Europe (Asia, South East
Asia, southern parts of North America and South America) a priori not in overlap with core
receiving stations can be supported. In principle there is no limitation to the number of
collaborative ground stations with similar visibility of the core stations (collaborative
stations may "listen" to SENTINEL data transmissions to core stations).
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Ship
Detection Oil Spill monitoring
1.6.1.1.2 Sentinel Collaborative Data Products
Complementary collaborative data products and algorithms definition.
Collaborative ground segments may offer product types (or product formats) in addition to
those offered by the CSC core ground segment functions and to complement the Copernicus
Service products. Potential products of interest for collaboration may be:
product algorithms tailored to a particular coverage or region
product algorithms tailored to specific services, like the generation of essential climate
variables
generation of local/regional data sets with correction, projection, calibration, merging
etc., different to the standardised data set offered by the CSC core ground segment
National entities, EU agencies or even Copernicus core services, may, at their own expense,
provide such products.
These entities may develop products of interest for specific user communities beyond the
Copernicus services (e.g. science) and establish operational distribution. Such activities
could ensure continuity of initiatives exploiting data from previous missions.
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Operational generation of collaborative products may be supported by implementation and
operation of specific data flow interfaces with the core ground segment.
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1.6.1.1.3 Sentinel Data Product Dissemination and Access
Particular regional or thematic data access nodes and mechanism may be offered, such as
redistribution services of SENTINEL core products, systematically received from the core
ground segment, becoming additional pick-up points (e.g. mirror sites), at national or
regional level.
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1.6.1.1.4 Innovative Tools and Applications
The free and open data policy and data access concept for the SENTINEL missions may lead
to the development of particular, yet unforeseen, "apps" (application software) by and for the
general public.
Such developments are not only possible but encouraged. Their availability will be advertised
within the core ground segment. In some cases, according to available operational resources
and budget, processing capability through hosting processing (eg. user exploitation
platform) may be provided.
Figure 6: Innovative Tools and Applications
Figure 5: Application Software
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Such collaborative modes will be particularly encouraged wherever a resulting decrease of
dissemination data volume can be demonstrated.
1.6.1.1.5 Sentinel complementary Calibration/Validation activities
The goal of this collaboration category is to engage world-class expertise and activities
(including access to in situ infrastructure and data), through mutual benefit collaboration
that complement the implementation of the SENTINEL validation activities during
commissioning and routine phases.
In this framework, access to cal/val infrastructure and data by collaborative partners may
also be envisaged.
Figure 7: Sentinel complementary Calibration/Validation activities
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1.6.1.1.6 Agreement Process
The implementation of a collaborative ground segment with ESA member states is based on
three main steps:
1. Definition of process and collection of collaboration proposals.
1. Requirements collection: release of questionnaire to ESA member states.
2. Enables ESA to make a preliminary assessment of the planned initiatives.
2. Proposal feasibility analysis.
1. Execution of simulation scenarios, identification of potential conflicts.
2. Proposal refinement with a collaborative partner.
3. Formalisation of collaboration.
1. Documenting the technical operational interfaces.
2. Integrating, verifying and validating the derived implementation.
3. Signing a formal agreement (exchange of letters based on PBEO framework
paper).
The interface to EU (non-ESA) member states and international cooperation partners is led
by the EU in close coordination with ESA for technical aspects. In these cases, for technical
matters, a similar process (as with ESA member states) is planned.
1. Collection of collaboration proposals and requirements.
2. Proposal technical feasibility analysis.
3. Implementation of collaborative interfaces.
International agreement to be formalised via EU/ESA jointly.
Figure 8: Agreement Process
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The collaborative ground segment activity types are similar to those with ESA member states
with special focus on:
access to SENTINEL data
set up of mirror sites for redistribution of SENTINEL core data
complementary external support validation activities.
1.6.1.1.7 Existing/Planned collaborative GS
The Sentinel Collaborative Ground Segment, offered by EU Member States and International
partners will represent - among others - additional means to access Sentinel data, in addition
to the standard access from the Core Ground Segment managed by ESA.
Information on (and links to) Collaborative Ground Segments will be provided here.
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1.6.2 Core Ground Segment (CGS)
The SENTINEL core ground segment allows all SENTINEL data to be systematically
acquired, processed and distributed. It includes elements for monitoring and controlling the
SENTINEL satellites and for downloading, processing and disseminating the data to users. It
also has mechanisms for monitoring and controlling the quality of data products, as well as
for data archiving. Infrastructure is 'distributed', meaning that various centres are in
different locations but linked together and coordinated. Despite the complexity of the
system, users are offered a single virtual access point for locating and downloading products.
The main facilities of the SENTINEL core ground segment are:
The Flight Operations Segment (FOS) - responsible for all flight operations of the
SENTINEL satellites, including monitoring and control, execution of all platform
activities and commanding of the payload schedules.
The Core Ground Stations - where the SENTINEL data are downlinked and products
are generated in near real-time. A network of X-band ground stations allows the
downlink of all SENTINEL data. These are complemented by utilisation of the
European Data Relay Satellite (EDRS) for additional downlink of SENTINEL data to
EDRS ground stations.
The Processing and Archiving Centre's (PACs) - where systematic non-time critical
data processing is performed. All data products are archived for online access by users.
A network of PACs supports all processing and archiving of SENTINEL data.
The Mission Performance Centres (MPCs) - responsible for calibration, validation,
quality control and end-to-end system performance assessment. The MPCs include
expert teams for specific calibration/validation, off-line quality control, algorithm
correction and evolution activities.
The SENTINEL Precise Orbit Determination (POD) facility - makes use of the GNSS
receiver data on the SENTINELS to deliver the orbital information needed to generate
data products.
The Copernicus Space Component Wide Area Network (CSC WAN) - allows all
products and auxiliary data to be carried across the various ground segment facilities
and provides disseminated data products to end users.
All SENTINEL data are systematically processed up to the designated level and according to
different timelines, ranging from near real-time to non-time critical, available typically
within 3-24 hours of being sensed by the satellite.
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1.6.2.1 Payload Data Ground Segment (PDGS)
The Payload Data Ground Segment (PDGS) is responsible for exploitation of the instrument
data. The PDGS is operated from ESA's Centre for Earth Observation also known as the
European Space Research Institute (ESRIN) in Frascati, Italy. The PDGS operationally
generates the user products and distributes processed Level-1B and C products.
The PDGS includes the facilities responsible for mission control (mission planning,
production planning), quality control (calibration, validation, quality monitoring, instrument
performance assessment), precise orbit determination, user services interface and
acquisition, processing and archiving.
Real-time sensed data as well as data played back from on-board saved data are downlinked
directly to ground or via the European Data Relay Satellite (EDRS), received, down-
converted, demodulated and transferred to the processing facilities for systematic generation
and archiving of Level-0 and Level-1/2 data products.
The PDGS is expected to receive and process 2.4 TBytes of compressed raw data per day for
the two satellites in addition to data from all other ESA missions. MSI Level-0 data are
processed to produce Level-1 and Level-2 products applying all the necessary processing
algorithms and formatting techniques.
The PDGS is distributed over several core centres including Core Ground Stations (CGS),
Processing and Archiving Centres (PAC), Mission Performance Centres (MPC) and Precise
Orbit Determination (POD) facilities.
Core Ground Stations - the network of X-band core ground stations located in Alaska,
USA, Matera, Italy, Maspalomas, Spain and Svalbard, Norway, are responsible for data
acquisition and near real-time processing.
Processing and Archiving Centres - PACs perform long-term data archiving, data
access and systematic non-time critical data processing. Archiving and long-term
preservation of data is ensured for all Level-0 data and for a set of configurable systematic
higher level products.
Mission Performance Centres - MPCs are responsible for calibration, validation, quality
control and end-to-end system performance assessment. The MPCs include expert teams for
specific cal/val, off-line quality control and algorithm correction activities.
Precise Orbit Determination - POD facilities make use of the GNSS receiver data on-
board the SENTINEL satellites to deliver the orbital information needed for generation of
mission products.
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Coordination between the centres is provided through the Payload Data Management Centre
(PDMC) at ESRIN in Frascati, Italy.
SENTINEL-2 products are provided to the user through online access. Near real-time
dissemination is allocated to the receiving stations and less time-critical data dissemination
is allocated to the assembly, processing and archiving centres.
Figure 9: SENTINEL-2 Receiving Stations and Off-line Processing and Archiving Centres
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1.6.2.2 Flight Operation Segment (FOS)
The Flight Operation Segment (FOS) is responsible for command and control of the satellite
and is operated from ESA’s European Space Operations Centre (ESOC) in Darmstadt,
Germany.
The FOS consists of the Ground Station and Communications Network, Flight Operations
Control Centre and a General Purpose Communication Network.
The FOS provides the capability to monitor and control the satellite during all mission
phases including the Flight Dynamics System facility responsible for orbit determination and
prediction, and for the generation of attitude and orbit control telecommands.
The main functions of the FOS include:
Mission planning
Long term planning of spacecraft and payload activities, covering the complete orbit
cycle and repeating indefinitely. Short term planning, nominally every 2 weeks, in the
form of updated mission schedules.
Spacecraft status monitoring
Figure 10: ESA's European Space Operations Centre
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Processing housekeeping telemetry, providing information about the status of all
spacecraft subsystems and attitude.
Spacecraft control
Taking control actions by means of telecommands, based on the spacecraft monitoring
and following the mission plan.
Orbit determination and control
Using tracking data and implementing orbit manoeuvres, ensuring required orbital
conditions are achieved.
Attitude determination and control
Using processed attitude sensor data from spacecraft monitoring and by commanded
updates of control parameters through the on-board attitude control system.
On-board software maintenance
Integrating software images received from the spacecraft manufacturer (pre-launch and
post-launch) into the telecommand process.
Communications
Communicating (TM/TC) with one satellite at a time.
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1 SENTINEL-2 MSI USER GUIDE
1.7 Introduction
The SENTINEL-2 User Guide provides a high level description of the MSI instrument, its
coverage and acquisition, and available product levels. The User Guide also provides
information on the relevant applications of each instrument, the format of the products and
the software tools required to interpret the data. This information has been harmonised for
all the SENTINEL missions and can be accessed under each category via the User Guides
panel on the right of each instrument User Guide page.
The categories are:
Overview Gives a brief description of the mission and its links to precursor missions, as well as
introducing the product formats available and the geophysical parameters measured.
Applications Describes SENTINEL-2 support to three Copernicus core services: land monitoring,
emergency management, security, and associated thematic applications.
Product Types Describes the granularity of SENTINEL-2 products relative to their product level.
Processing Levels Illustrates the processing steps from Level-0 to Level-2A of SENTINEL-2 products.
Resolutions Defines the temporal, radiometric and spatial resolution of the SENTINEL-2 mission.
Revisit and Coverage Describes the high frequency of revisit needed for the systematic global coverage of
land surfaces that forms the core of the SENTINEL-2 mission, and the latitudinal
limits of the coverage.
Naming Convention Describes the data naming conventions used for the two product levels (Level-1B and
Level-1C) made available to users.
Data Formats Outlines the data format in which users will get the SENTINEL-2 Level-1 and Level-
2 products.
Software Tools Outlines BEAM plug-ins that will be available to the user to interrogate SENTINEL-2
Level-1B, Level-1C and Level-2A products.
Definitions Provides information on the terms used in the acquisition and processing of
SENTINEL-2 products.
For an in-depth description of the SENTINEL-2 mission's products and algorithms, and
details of the MultiSpectral Instrument (MSI) and its performance, refer to the SENTINEL-2
Technical Guide. The Technical Guide will provide a point of engagement for ESA and the
SENTINEL technical user community. The detailed information available on the Technical
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Guide is focused upon users such as academics and industrial software engineers who have
previous experience of similar EO missions, and in-depth experience of data manipulation
and management.
1.8 Overview
The SENTINEL-2 mission will provide support to land monitoring services and, with its twin-
satellite capability, will ensure frequent and systematic coverage to support the mapping of
land cover, classification and change maps, and accurate assessment of biogeophysical
parameters such as Leaf Area Index (LAI) and Leaf Chlorophyll Content (LCC).
The acquired data, mission coverage and high revisit frequency permits the provision of
geoinformation at local, regional, national and international scales.
The acquisitions of SENTINEL-2 data will provide data continuity to work previously
performed by heritage missions such as LANDSAT and SPOT. The data is designed to be
modified and adapted by users interested in thematic areas such as:
spatial planning
agro-environmental monitoring
water monitoring
forest and vegetation monitoring
land carbon, natural resource monitoring
global crop monitoring.
Table 1: Comparison of SENTINEL-2 with important heritage missions
LANDSAT 1-7 SPOT SENTINEL-2
Mission Lifetime 1972 - present 1986 - present See Copernicus
pages
Instrument principle Scanner Pushbroom Pushbroom
Repeat cycle (days) 16 26 5*
Swath width (km) 185 2 x 60 290
Spectral bands 7 4 13
Spatial resolution
(metres) 30, 60 2.5, 10, 20 10, 20, 60
*at the Equator, using the full two-satellite constellation configuration and in cloud-free
conditions.
1.8.1 Granules and Tiles
The elementary level of MSI products are granules of a fixed size. The granule size is
dependent on the product level.
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For Level-0, Level-1A and Level-1B products: These granules are sub-image of a
given number of lines along track and separated by detector. They are 25 km across
track and 23 km along track in size.
For orthorectified products (Level-1C and Level-2A): The granules (also called
tiles) consist of 100 km by 100 km squared ortho-images in UTM/WGS84 projection.
There is one tile per spectral band.
1.8.2 Data-Takes and Datastrips
The maximum continuous acquisition of an image from one SENTINEL-2 satellite is 15 000
km. The continuous acquisition is a "data-take", and the data-take forms the base of the
subsequent product tree. If a data-take is acquired by two separate receiving stations, the
data-take may be sub-divided into datastrips. When the satellite is switched from one
observation mode to another, a datastrip may include several distinct observation segments
separated by gaps of an integer number of granules.
Figure 5 illustrates the data item classes in the SENTINEL-2 product levels and shows their
relationship to associated levels of processing and generated products.
Figure 11: Product Breakdown Structure (Image courtesy of ESA)
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Figure 5 highlights that the delivered product is composed of data items and a metadata
structure.
The data items include:
image data in granules or tiles and covering the product AOI
preview data, that provides an overview of the product for subsequent image browsing
and user selection purposes
ancillary data from the satellite telemetry
auxiliary data information describing the parameters used
quality indicator data, describing the product relative to radiometric, geometric and
image properties.
The metadata structure describes the content of the product.
1.8.3 Geophysical Measurements
The SENTINEL-2 mission provides a range of datasets to support the user in their
investigations. The user-derived Level-2B products will permit generation of broad interest
land cover maps and more focused mapping of particular vegetation parameters such as
Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), Leaf Area Index (LAI),
Fractional Vegetation Cover, Leaf Chlorophyll Content (LCC) and Leaf Water Content
(LWC). These parameters are supported by the GMES GEOLAND2 Biogeophysical
Parameters (BIOPAR) service.
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Figure 12: Map of Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), July 2011, as
derived from MERIS Full Resolution (FR) data. The values vary from 0 (white) to 1 (red) (image
courtesy of ESA and Astrium GmbH, Germany)
The baseline for geophysical parameters is the BOA reflectance Level-2A, corrected for
atmospheric, adjacency and slope effects.
Maps of the fraction of non-photosynthetically active vegetation, surface albedo, burn scars,
fuel load, structural fire risk indices, crown density, forest age, flood monitoring data, land-
cover change detection and snow cover maps can be developed by users from SENTINEL
data.
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1.9 Applications
The SENTINEL-2 mission requirements for a twin satellite, high revisit frequency, high
resolution image will support Copernicus programmes. Further information on Copernicus
thematic areas can be found in the Thematic Areas section.
Observation data acquired from the SENTINEL-2 mission will be utilised by services such as:
1.9.1 Land Monitoring
The Copernicus land monitoring service became operational in 2012 and provides geographical
information on land cover and on variables related to such topics such as vegetation state or
the water cycle. It supports a variety of applications including spatial planning, forest
management, water management, agriculture and food security.
A pan-European component, coordinated by the European Environment Agency.
A global component coordinated by the European Commission DG Joint Research
Centre (JRC).
A local component coordinated by the European Environment Agency.
The SENTINEL-2 mission will provide support to land monitoring services and, with its
twin-satellite capability, will ensure frequent and systematic coverage to support the
mapping of land cover, classification and change maps, and accurate assessment of
biogeophysical parameters such as Leaf Area Index (LAI) and Leaf Chlorophyll Content
(LCC).
The acquired data, mission coverage and high revisit frequency permits the provision of
geoinformation at local, regional, national and international scales.
The acquisitions of SENTINEL-2 data will provide data continuity to work previously
performed by heritage missions such LANDSAT, SPOT/VEGETATION and
ENVISAT/MERIS sensors. The data is designed to be modified and adapted by users
interested in thematic areas such as:
spatial planning
agro-environmental monitoring
water monitoring
forest and vegetation monitoring
land carbon, natural resource monitoring
global crop monitoring.
High level products generated by users from SENTINEL-2 data will provide an extensive
range of parameters characterising vegetation, the energy budget and the water cycle. From
the acquired data, biogeophysical information parameters (such as land cover and land cover
change) and the systematic monitoring and mapping of global physical properties that are
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influenced by human pressure, will be possible, as well as the seasonal variations in
vegetation cover around the globe.
Snow, clouds and rain are important geophysical variables that play a major part in climate
and water cycles. While direct measurement of wind is not possible from SENTINEL-2, the
cloud image data may be used as a corollary for data collected by other instruments, and will
support prediction and modelling of changes in the atmosphere.
1.9.2 Emergency Management
The Copernicus emergency management service provides accurate and timely geospatial
information derived from satellite remote sensing to all organisations and entities involved in
the management of natural disasters, man-made emergency situations and humanitarian crises.
Where available, this data is complimented by in situ or open data sources. The mapping
component of the service GIO EMS - Mapping has a worldwide coverage and provides maps
based on satellite imagery. The service started operations on April 1st 2012 with funding
provided by the European Commission.
The Copernicus emergency service is targeted to meet the potential needs of all types of
disasters or crises such as:
natural disasters (floods, fires, landslides, storms, earthquakes, etc.)
technological accidents, humanitarian crises (for instance after a period of severe
drought)
civil crises.
SENTINEL-2 observations will support rapid mapping. Rapid mapping is dedicated to the
response management of civil protection and rescue services and provides information on
the level of damage (such as destroyed buildings in an earthquake zone) and the extent and
impact of natural disasters (such as delineation of a flooded area). In addition to SENTINEL-
2 data, rapid mapping products utilise any available and exploitable Earth Observation (EO)
crisis image (high and very high resolution, optical/radar).
SENTINEL-2 will provide information for crisis response and mitigation, preparedness and
relief activities, and will support long-term crises (such as famine) and rapid onset crises
(such as earthquake).
1.9.3 Security
In tandem with communication and global positioning (GPS) technologies, SENTINEL-2 will
support the following security domains:
maritime surveillance:
o sea border surveillance inside and outside Europe
o illegal immigration and illegal trafficking surveillance
o safety sea lane/piracy/sensitive cargo.
infrastructure surveillance:
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o land border surveillance
o critical infrastructure (e.g. pipelines).
support to peace-keeping:
o population monitoring
o resources (e.g. water).
support to intelligence and early warning
support to crisis management operations.
The Copernicus services for security applications are still in a development phase. The services
aim to support the related European Union policies in the following priority areas:
border surveillance
maritime surveillance
support to EU external action.
At present, the three priority areas are addressed by a series of EU-funded projects.
1.9.4 Copernicus Briefs
The Copernicus Briefs provide concise overviews of various Copernicus applications
supported by SENTINEL-2.
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1.10 Product Types
Sentinel-2 products available for users (either generated by the ground segment or by the
Sentinel-2 Toolbox) are listed in Table 2.
Table 2: Sentinel-2 Product types
Products are a compilation of elementary granules of fixed size, along with a single orbit. A
granule is the minimum indivisible partition of a product (containing all possible spectral
bands).
For Level-1B, a granule covers approximately 25 km AC and 23 km AL (see Figure 2)
For Level-1C and Level-2A, the granules, also called tiles, are 100 km2 ortho-images
in UTM/WGS84 projection. The UTM (Universal Transverse Mercator) system divides
the Earth's surface into 60 zones. Each UTM zone has a vertical width of 6° of longitude
and horizontal width of 8° of latitude. (see Figure 3). Tiles are approximately 500 MB
in size. Tiles can be fully or partially covered by image data. Partially covered tiles
correspond to those at the edge of the swath.
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Figure 13: Typical orbit showing layout of Level-1B product granules
Figure 14: Level-1C product tiling
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All granules, required in the user's area-of-interest (AOI), will be included in the delivered
product.
The PDGS is responsible for the systematic processing and archiving of Sentinel-2 up to
Level-1C.
The continuous acquisition of Sentinel-2 image data in a given MSI mode is called a
"datatake". The maximum length of an imaging datatake is 15,000 km (continuous
observation from northern Russia to southern Africa). All products contain granules/tiles
from a single datatake. A datatake is presented inside a product as a set of one or more
datastrips (corresponding to acquisition segments downlinked to different ground stations).
1.10.1 Level-0
The Level-0 product is not released to users.
The Level-0 product is compressed raw image data in Instrument Source Packet (ISP)
format. It forms the basis of the subsequent Level-1 production. Like the Level-1B product, a
Level-0 product is a 25 km across track (AC) by 23 km along track (AL) granule. An average
orbit will contain approximately 3 500 Level-1B granules. The Level-0 product consists of:
a metadata structure describing the Level-0 product
a consistent set of annotated ISPs corresponding to the compressed image data
the relevant annotated ancillary source packets.
The ancillary source packets contain the ancillary data required for onward processing to
higher product levels, in particular, the information required to compute the associated
geometric model. This ancillary data will include time correlation data (sampled at 1 Hz),
ephemeris and attitude data, and thermal data.
1.10.2 Level-1A
The Level-1A product is not released to users. It is obtained by decompressing the Level-0
raw image data. A geometric model is developed, allowing any pixel in the image to be
located. Each Level-1A product is a 25 km AC by 23 km AL granule. An average orbit will
contain approximately 3 500 Level-1A granules. Level-1A pixel coordinates refer to the
centre of each pixel.
1.10.3 Level-1B
The Level-1B product is the lowest product level made available to users. Each Level-1B
product is composed of an ensemble of granules that are 25 km across track (AC) by 23 km
along track (AL).
All granules that intersect with a user area of interest (AOI) will be delivered. Each granule is
approximately 27 MB in size
The Level-1B product provides radiometrically corrected imagery in Top-Of-Atmosphere
(TOA) radiance values and in sensor geometry. Additionally, this product includes the
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refined geometrical which is used to generate the Level-1C product. Level-1B pixel
coordinates refer to the centre of each pixel.
Radiometric corrections applied to the Level-1B are:
dark signal
pixels response non uniformity
crosstalk correction
defective pixels interpolation
high spatial resolution bands restoration (deconvolution plus denoising)
binning (spatial filtering) for 60 m bands
1.10.4 Level-1C
The Level-1C product is composed of 100 km2 tiles (ortho-images in UTM/WGS84
projection). The Level-1C product results from using a Digital Elevation Model (DEM) to
project the image in cartographic coordinates. Per-pixel radiometric measurements are
provided in Top Of Atmosphere (TOA) reflectances with all parameters to transform them
into radiances. Level-1C products are resampled with a constant Ground Sampling Distance
(GSD) of 10, 20 and 60 m depending on the native resolution of the different spectral bands.
In Level-1C products, pixel coordinates refer to the upper left corner of the pixel.
Level-1C products will additionally include Land/Water, Cloud Masks and ECMWF data
(total column of ozone, total column of water vapour and mean sea level pressure).
1.10.5 Level-2A
The Level-2A product provides Bottom Of Atmosphere (BOA) reflectance images derived
from the associated Level-1C products. Therefore, each Level-2A product is also composed of
100 km2 tiles in cartographic geometry (UTM/WGS84 projection).
Level-2A products are not systematically generated at the ground segment. Level-2A
generation can be performed by the user through the Sentinel-2 Toolbox using as input the
associated Level-1C product.
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Figure 15: TOA Level-1C Image Data (left)
and Associated BOA Image Data (right) as
generated by the Sentinel-2 Toolbox
1.11 Processing Levels
All data acquired by the MSI
instrument are systematically processed up to Level-1C by the ground segment, specifically
the Payload Data Ground Segment (PDGS). Level-2A products are generated on user side
through the Sentinel-2 Toolbox.
Figure 16: Processing Levels from Level-0 to Level-1C
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Level-0 and Level-1A products are PDGS internal products not made available to users.
The processing from Level-0 up to Level-1C is performed by the Instrument Data Processing
(IDP) functionality of the PDGS. The quality of generated products is assessed by the On
Line Quality Control (OLQC) functionality. The OLQC performs essential quality checks on
each product generated by the processing chain.
1.11.1 Level-0
Level-0 data processing operations are performed in real-time by the PDGS during the data-
reception operations. The processing operations for Level-0 data are required to package the
MSI and satellite ancillary raw-data that has been acquired by the Ground Segment and to
archive it together with the relevant annotation parameters and other metadata. This
facilitates onward processing to higher product levels. The following tasks are all included in
the Level-0 processing phase:
MSI telemetry analysis: concatenates acquired ISP data into granules and performs data
analysis and error detection functions
Datation: the datation of the individual lines in an image enables the exact capture time
of each ISP within a granule to be recorded
Low-resolution image extraction: this processing step extracts the low-resolution
images for quicklook generation
Satellite ancillary telemetry analysis: compares extracted satellite ancillary data from
bit values and checks it relative to pre-defined admissible ranges
Consolidation is applied to Level-0 data to collate and append all metadata necessary for
long-term archiving and onward processing to Level-1.
1.11.2 Level-1
Level-1 processing uses consolidated Level-0 data as input.
Level-1A processing is focused on decompressing relevant mission source packets. The
Level-1A product is not available to users.
Level-1B processing uses the Level-1A product and applies the required radiometric
corrections. The Level-1B product requires expert knowledge of orthorectification
techniques.
Level-1C processing uses the Level-1B product and applies radiometric and geometric
corrections (including orthorectification and spatial registration).
1.11.2.1 Level-1B
The Level-1B processing sequence is broken down into the following steps:
1. Level-1B radiometric processing, including:
o dark signal correction
o pixel response non-uniformity correction
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o crosstalk correction
o defective pixels identification
o high spatial resolution bands restoration (de-convolution and de-noising)
o binning of the 60 m spectral bands.
2. Resampling on the common geometry grid for registration between the Global
Reference Image (GRI) and the reference band.
3. Collection of the tie-points from the two images for registration between the GRI and
the reference band.
4. Tie-points filtering for image-GRI registration: filtering of the tie-points over several
areas. A minimum number of tie-points is required.
5. Refinement of the viewing model using the initialised viewing model and GCPs. The
output refined model ensures registration between the GRI and the reference band.
6. Level-1B imagery compression using the JPEG2000 algorithm.
1.11.2.2 Level-1C
Level-1C processing includes radiometric and geometric corrections including ortho-
rectification and spatial registration on a global reference system with sub-pixel accuracy.
Level-1C processing is broken down into the following steps:
Tiles association: selection of pre-defined tiles intersecting the footprint of the required
image.
Resampling grid computation: enabling linking of the native geometry image to the
target geometry image (ortho-rectified).
Resampling of each spectral band in the geometry of the ortho-image using the
resampling grids and an interpolation filter. Calculation of the TOA reflectances also
occurs in this step.
Masks computation: cloud and land/water masks are generated.
Imagery compression of the resultant Level-1C imagery via the JPEG2000 algorithm
and a GML geographic imagery-encoded header.
1.11.2.3 Level-2
The Level-2A processing includes a Scene Classification and an Atmospheric Correction
applied to Top-Of-Atmosphere (TOA) Level-1C orthoimage products. Level-2A main output
is an orthoimage Bottom-Of-Atmosphere (BOA) corrected reflectance product.
Additional outputs are an Aerosol Optical Thickness (AOT) map, a Water Vapour (WV) map
and a Scene Classification Map (SCM) together with Quality Indicators for cloud and snow
probabilities at 60 m resolution. Level-2A output image products will be resampled and
generated with an equal spatial resolution for all bands, based on the requested resolution of
the user's choice (10m, 20m or 60m). A 10 m resolution product contains the spectral bands
2, 3, 4 and 8 and an AOT map resampled from 20m. A 20 m product contains bands 2 - 7,
the bands 8A, 11 and 12 and an AOT and WV map. A 60m product contains all components
of the 20 m product and additionally the 60 m bands 1 and 9. The cirrus band 10 will be
omitted, as it does not contain surface information.
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The processor algorithm is a combination of state-of-the-art techniques for performing
atmospheric corrections (including cirrus clouds correction [R1]), which have been tailored
to the Sentinel-2 environment together with a scene classification module described in [R2].
The scene classification algorithm allows detection of clouds, snow and cloud shadows and
generation of a classification map, which consists of four different classes for clouds
(including cirrus), together with six different classifications for shadows, cloud shadows,
vegetation, soils/deserts, water and snow. The algorithm is based on a series of threshold
tests that use as input top-of-atmosphere reflectance from the Sentinel-2 spectral bands. In
addition, thresholds are applied on band ratios and indexes like NDVI and NDSI. For each of
these threshold tests, a level of confidence is associated. It produces at the end of the
processing chain a probabilistic cloud mask quality indicator and a snow mask quality
indicator. The algorithm uses the reflective properties of scene features to establish the
presence or absence of clouds in a scene. Cloud screening is applied to the data in order to
retrieve accurate atmospheric and surface parameters, either as input for the further
processing steps below or for being valuable input for processing steps of higher levels.
The aerosol type and visibility or optical thickness of the atmosphere is derived using the
Dense Dark Vegetation (DDV) algorithm [R3]. This algorithm requires that the scene
contains reference areas of known reflectance behaviour, preferably DDV and water bodies.
The algorithm starts with a user-defined visibility (default: 20 km). If the scene contains no
dark vegetation or soil pixels, the surface reflectance threshold in the 2 190 nm band is
successively iterated in order to include medium brightness reference pixels. If the scene
contains no reference and no water pixels the scene is processed with the start visibility
instead.
Water vapour retrieval over land is performed with the Atmospheric Pre-corrected
Differential Absorption (APDA) algorithm [R4] which is applied to the two Sentinel-2 bands
(B8a, and B9). Band 8a is the reference channel in an atmospheric window region. Band B9
is the measurement channel in the absorption region. The absorption depth is evaluated in
the way that the radiance is calculated for an atmosphere with no water vapour assuming
that the surface reflectance for the measurement channel is the same as for the reference
channel. The absorption depth is then a measure of the water vapour column content.
Atmospheric correction is performed using a set of look-up tables generated via libRadtran.
Baseline processing is the rural/continental aerosol type. Other look-up tables can also be
used according to the scene geographic location and climatology.
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Figure 17: The figure shows from left to right: (1) A simulated Level-1C TOA input Image, (2) the
Cirrus and Atmospheric Corrected Level-2A BOA Image, (3) the Cirrus Band Nr. 10, (4) the Scene
Classification of the Level-1C Input Image
[R1]: Richter, R., Wang, X., Bachmann, M., and Schlaepfer, D., "Correction of cirrus effects
in Sentinel-2 type of imagery", Int. J. Remote Sensing, Vol.32, 2931-2941 (2011).
[R2]: J. Louis, A. Charantonis & B. Berthelot, "Cloud Detection for Sentinel-2", Proceedings
of ESA Living Planet Symposium (2010).
[R3]: Kaufman, Y., Sendra, C. Algorithm for automatic atmospheric corrections to visible
and near-IR satellite imagery, International Journal of Remote Sensing, Volume 9, Issue 8,
1357-1381 (1988).
[R4]: Schläpfer, D. et al., "Atmospheric precorrected differential absorption technique to
retrieve columnar water vapour", Remote Sens. Environ., Vol. 65, 353366 (1998).
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1.12 Resolutions
The Sentinel-2 instrument provides measurements with the following resolutions:
The temporal resolution of a satellite in orbit is the revisit frequency of the satellite to
a particular location. The revisit frequency of each single satellite is 10 days and the
combined constellation revisit is 5 days.
The spatial resolution of an instrument is the at-ground representation of an individual
detector in a satellite sensor array. Details on Sentinel-2 spatial resolution are provided
in the Spatial Resolution section.
The radiometric resolution of an instrument is a determination the incremental level of
intensity or reflectance that can be represented or distinguished by the system. The
higher the radiometric resolution, the more capable the device will be of detecting
differences in intensity or reflectance. Details on Sentinel-2 radiometric resolution are
provided in the Radiometric Resolutions section.
1.12.1 Spatial Resolution
The spatial resolution of Sentinel-2 is dependent on the particular spectral band:
1.12.1.1 10 metre spatial resolution:
Figure 18: Sentinel-2 10 m Spatial Resolution Bands: B2 (490 nm), B3 (560 nm), B4 (665 nm) and B8
(842 nm)
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1.12.1.2 20 metre spatial resolution:
Figure 19: Sentinel-2 20 m Spatial Resolution Bands: B5 (705 nm), B6 (740 nm), B7 (783 nm), B8b
(865 nm), B11 (1610 nm) and B12 (2190 nm)
1.12.1.3 60 metre spatial resolution:
Figure 20: Sentinel-2 60 m Spatial Resolution Bands: B1 (443 nm), B9 (940 nm) and B10 (1375 nm)
1.12.2 Radiometric Resolutions
SENTINEL-2 data are acquired on 13 spectral bands in the VNIR and SWIR:
four bands at 10 m: 490 nm (B2), 560 nm (B3), 665 nm (B4), 842 nm (B8)
six bands at 20 m: 705 nm (B5), 740 nm (B6), 783 nm (B7), 865 nm (B8a), 1 610 nm
(B11), 2 190 nm (B12)
three bands at 60 m: 443 nm (B1), 945 nm (B9) and 1 375 nm (B10).
Radiometric resolution is the capacity of the instrument to distinguish differences in light
intensity or reflectance. The greater the radiometric resolution, the more accurate the sensed
image will be.
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Radiometric resolution is routinely expressed as a bit number, typically in the range of 8 to
16 bits. The radiometric resolution of the MSI instrument is 12 bit, enabling the image to be
acquired over a range of 0 to 4 095 potential light intensity values. The radiometric accuracy
is less than 5% (goal 3%). Radiometric resolution is also dependent upon the Signal to Noise
Ratio (SNR) of the detector.
Table 3:10 m Spatial Resolution Bands and associated Signal to Noise ratio (SNR)
Band
number
Central
wavelength
(nm)
Bandwidth
(nm)
Lref
(reference
radiance)
(W m−2 sr−1 μm−1)
SNR @ Lref
2 490 65 128 154
3 560 35 128 168
4 665 30 108 142
8 842 115 103 172
Table 4:20 metre Spatial Resolution Bands and associated Signal to Noise ratio (SNR)
Band
number
Central
wavelength
(nm)
Bandwidth
(nm)
Lref
(reference
radiance)
(W m−2 sr−1 μm−1)
SNR @ Lref
5 705 15 74.5 117
6 740 15 68 89
7 783 20 67 105
8b 865 20 52.5 72
11 1 610 90 4 100
12 2 190 180 1.5 100
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Table 5:60 metre Spatial Resolution Bands and associated Signal to Noise ratio (SNR)
Band
number
Central
wavelength
(nm)
Bandwidth
(nm)
Lref
(W m−2 sr−1 μm−1) SNR @ Lref
1 443 20 129 129
9 945 20 9 114
10 1 375 30 6 50
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1.13 Revisit & Coverage
The Sentinel-2 mission will provide systematic coverage over the following areas:
all continental land surfaces (including inland waters) between latitudes 56° south and
83° north
all coastal waters up to 20 km from the shore
all islands greater than 100 km2
all EU islands
the Mediterranean Sea
all closed seas (e.g. Caspian Sea).
Figures 21 and 22 illustrate the coverage foreseen for MSI acquisitions.
Figure 21: Modelled Sentinel-2 Coverage
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Figure 22: Modelled Sentinel-2 Coverage
With two satellites (i.e. the full constellation), all areas indicated above will be revisited every
five days under the same viewing conditions.
Due to overlap between swaths from adjacent orbits, the revisit frequency will be increased
with different viewing conditions.
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1.14 Product Naming Convention
The Sentinel-2 products will follow the naming convention defined below:
MMM_CCCC_TTTTTTTTTT_<Instance_ID>.<FORMAT>
Where:
Part Description Comment
MMM Mission Identifier S2A
S2B
CCCC File Class
4 uppercase letters:
OPER for Routine Operations (all phases).The File
Class will be set “OPER” for all products generated
during the Operations Phase. During Validation or for
internal testing other values can be defined
TTTTTTTTTT
File Type (File
Category + File
Semantic)
10 uppercase letters. Can contain digits and
underscores, i.e for Level 1:
PRD_MSIL0P
PRD_MSIL1A
PRD_MSIL1B
PRD_MSIL1C
PRD_MSITCI
For Level-2:
PRD_USER2A
<Instance_ID
> Instance Identifier
Contains uppercase letters, digits and underscores.
Level 1:
< instance ID> =
ssss_yyyymmddThhmmss_ROOO_VYYYYMMTDDH
HMMSS_YYYYMMTDDHHMMSS
YYYYMMDDHHMMSS is SENSING Start and
SENSING Stop time
Where:
R denotes Relative Orbit
OOO is Orbit number
V denotes the Validity of the acquisition Time Period
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Level 2:
<Instance_ID> = OOO_[Start Time]_[End
Time]_[Processing Time]
<FORMAT> SAFE
DIMAP
Identifies the User Product output format selected by
the final user.
The following table sets out the unique File Type for a given Granule (Tile), Datastrip and
True Colour Image (TCI) Product Data Item (PDI):
Table 6: Level 1 Granule (Tile), Datastrip and TCI PDI File Type
Product Level File Type File Naming
Level-0
Granule MSI_L0__GR
Datastrip MSI_L0__DS
Level-1A
Granule MSI_L1A_GR
Datastrip MSI_L1A_DS
Level-1B
Granule MSI_L1B_GR
Datastrip MSI_L1B_DS
Level-1C
Granule MSI_L1C_TL
Datastrip MSI_L1C_DS
1.14.1 Level-1B Granule
The Level-1B granule consists of:
Level -1B_Granule_Metadata_File: XML Main Metadata file (DIMAP mandatory file)
containing the requested level of information and referring all the product elements
describing the granule.
IMG_DATA: folder containing the mission data corresponding to one on-board scene
for one detector and all spectral bands.
QI_DATA: folder containing XML reports about geometric quality, Image content
quality, quality control checks information.
Inventory_Metadata.xml: inventory metadata file (mandatory).
manifest.safe: XML SAFE Manifest file (mandatory).
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rep-info: folder containing the XSD schema provided inside a SAFE Level-0 granule.
1.14.1.1 Granule Image Data Naming Convention
S2A_OPER_MSI_L1B_GR_CGS1_20141104T134012_20141104T134012_11_N05.22
Where:
S2A is the spacecraft
OPER is the routine operations
MSI is the instrument
L1B is the product level
GR is granule
CGS1 is the processing centre in which the product is generated
20141104T134012 is the sensing start time and the sensing stop time of the first line of
granule in date UTC time format with the date (YYYYMMDD) and time (HHMMSS)
separated by a 'T'.
_11_ is the detector number. MSI detectors are identified by 2 digits, in the range from
01 to 12.
N05.22 refers to the processing baseline in use. N05 is the version, and .22 is the
particular baseline in use at the moment of processing.
1.14.2 Level-1C Tile
The Level-1C Tile consists of:
Level-1C_Tile_Metadata_File (Tile Metadata): XML main metadata file (DIMAP
mandatory file) containing the requested level of information and referring all the
product elements describing the tile.
IMG_DATA: folder containing image data files compressed using the JPEG2000
algorithm, one file per band.
QI_DATA: folder containing QLQC XML reports of quality checks, mask files and
PVI files.
Inventory_Metadata.xml: inventory metadata file (mandatory).
manifest.safe: XML SAFE manifest file (Mandatory)
rep-info: folder containing the XSD schema provided inside a SAFE Level-0 granule,
1.14.2.1 Level-1 Tile Image Data Naming Convention
S2A_OPER_MSI_L1C_CGS3_20141104T134012_123_15SWC_N11.11
Where:
S2A is the spacecraft
OPER is the routine operations
MSI is the instrument.
L1C is the product level
TL is the granule
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CGS3 is the processing centre in which the product is generated.
1.14.3 Level-2A
The Level-2A prototype product is an orthorectified product providing Bottom-Of-
Atmosphere (BOA) reflectances, and basic pixel classification (including classes for different
types of cloud). In the Level-2A, the granules (also called tiles) consist of 100kmx100km
squared ortho-images in UTM/WGS84 projection, with one tile per spectral band.
1.14.3.1 Level-2A Data Naming Convention
Examples of S2 L2A product main directories are:
S2A_OPER_PRD_USER2A_047_20140417094512_201404171094728_20140417102538
S2A_OPER_PRD_USER2A_048_20140417112512_201404171112728_20140417102538
Where:
S2A is the spacecraft
OPER is the routine operations
PRD is the product category
USER denotes a User-generated product
2A is the processing level
1.15 Data Formats
Sentinel-2 products will be made available to users in SENTINEL-SAFE format, including
image data in JPEG2000 format, quality indicators (e.g. defective pixels mask), auxiliary
data and metadata.
The SAFE format has been designed to act as a common format for archiving and conveying
data within ESA Earth Observation archiving facilities. The SAFE format wraps a folder
containing image data in a binary data format and product metadata in XML. This flexibility
allows the format to be scalable enough to represent all levels of SENTINEL products.
A Sentinel-2 product refers to a directory folder that contains a collection of information
(Figure 17). It includes:
a manifest.safe file which holds the general product information in XML
a preview image in JPEG2000 format
subfolders for measurement datasets including image data (granules/tiles) in GML-
JPEG2000 format
subfolders for datastrip level information
a subfolder with auxiliary data (e.g. IERS bulletin)
Google Earth overlays in KML and HTML previews
Figure 23: Sentinel-2 product physical format
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In addition there will be the option to obtain the products in DIMAP format (where only
higher level metadata is changing with respect to SENTINEL-SAFE format).
1.15.1 LEVEL-2A Data Format
The Level-2A prototype product is an orthorectified product providing Bottom-Of-
Atmosphere (BOA) reflectances, and basic pixel classification (including classes for different
types of cloud). The generation of this prototype product will be carried out by the User from
LEVEL-1C products. It will not be systematically generated by the PDGS.
The Level-2A image data product uses the same tiling, encoding and filing structure as Level-
1C.
The Level-2 product has a SAFE format. This groups together several types of file:
metadata file (XML file)
preview image (JPEG2000 with GML geo-location)
tiles files with BOA reflectances image data file (GML / JPEG2000) for each tile
datastrip files
auxiliary data
ancillary data (GIPPs, set of XML files).
More information on LEVEL-2A format can be found in the SENTINEL-2 Technical Guide.
1.16 Software Tools
A SENTINEL-2 Toolbox is under development. However, this is not currently available.
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1.17 Definitions
1.17.1 Auxiliary Data
Describes all auxiliary information that will be used by the PDGS for the processing of MSI
data. The auxiliary data required in MSI data generation are:
Ground Image Processing Parameters (GIPP)
Digital Elevation Model (DEM)
Global Reference Image (GRI)
European Centre for Medium-Range Weather Forecasts (ECMWF): ozone, surface
pressure and water vapour data required for Level-1C processing
International Earth Rotation & Reference Systems service (IERS) data
Precise Orbit Determination (POD) data.
1.17.2 Datatake
The continuous acquisition of an image from one Sentinel-2 satellite in a given MSI imaging
mode is called a "datatake". The maximum length of an imaging datatake is 15,000 km
(continuous observation from northern Russia to southern Africa).
1.17.3 Datastrip
Within a given datatake, a portion of image downlinked during a pass to a given station is
termed a "datastrip". If a particular orbit is acquired by more than one station, a datatake is
composed of one or more datastrips. It is expected that the maximum length of a datastrip
downlinked to a ground station is approximately 5,000 km.
1.17.4 Granules and Tiles
A granule is the minimum indivisible partition of a product (containing all possible spectral
bands).
For Level-0C, Level-1A and Level-1B, granules are sub-images of a detector with a
given number of lines along track. A granule covers approximately 25 km across track
and 23 km along track.
For Level-1C, the granules, also called tiles, are 100 km2 ortho-images in UTM/WGS84
projection.
1.17.5 Quality Indicator
A medium that accompanies the data and can be used to obtain information necessary to
determine the suitability of a product for a certain use or application. Examples of quality
indicators are: defective pixels mask, cloud masks, on-line quality control reports, etc.
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1.17.6 Timeliness
There are three categories of timeliness defined for Sentinel-2 operation:
Nominal, corresponding to the on-line availability of product between 3 and 24 hours
after sensing
Near Real-Time (NRT), corresponding to the on-line availability of product between
100 minutes and 3 hours after data sensing
Real-Time (RT), corresponding to the on-line availability of product no later than 100
minutes after data sensing
1.17.7 True Colour Images (TCI)
On-line access to Sentinel-2 imagery as True Colour Images (TCI) will be enabled via a
separate On-Line Image Browser (OLIB) application, the OLIB will permit the download of
TCI images for visualisation and/or delivery at the end user base. The End User product is a
single file, constituted by the JPEG2000 Geography Markup Language (GML) and
georeferenced.
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1.18 Document Library
1.18.1 Sentinel-2A Spectral Responses
This spreadsheet contains Spectral Response curves and precursor information in table format
for the S2A instrument.
1.18.2 Sentinel-2 Products Specification Document
This document specifies the format of Sentinel-2 products, from Level-0 up to Level-1C. For
data users, it describes the formats used in exchanges between the PDGS and Users (accessing
the S2 PDGS through functions provided by the Multi-Mission User-Services (such as
provided functions like the On-Line Images Browser (OLIB) and Next Generation User
Services for Earth Observation (ngEO) interface.
1.18.3 Sentinels POD Service File Format Specification
The purpose of the document is to define the product structure and the content of each file
generated and delivered by the OFL POD Service and the NRT POD Facility across its
interfaces to the Sentinels (1, 2 and 3) PDGSs.
