Copernicus (European Commission's Earth Observation Programme) / formerly GMES
GMES (Global Monitoring for Environment and Security) is a European initiative put forward by the EC (European Commission) in October 1998 (Baveno Manifesto, Baveno/Lago Maggiore, Italy) with the objective to determine Europe's global monitoring role in the field of the environment and security. The EC had invited a group of space agencies/organizations: ASI (Agenzia Spaziale Italiana), BNSC (British National Space Centre), CNES (Centre National D'Etudes Spatiales, France), DLR (German Aerospace Center), EASC (European Air and Space Conference), ESA (European Space Agency, and Eumetsat (European Organization for the Exploitation of Meteorological Satellites, Darmstadt, Germany). 1)
The goal of GMES is to develop operational information services on a global scale, using both space- and ground-based monitoring systems, in support of environment and security policy needs. Overall, GMES will contribute to the European Strategy for Sustainable Development. The GMES program was endorsed at the Gothenborg (Sweden) Summit in June 2001 by the Heads of State and Government of the countries of the European Union (EU). An exploratory initial period, undertaken jointly by the EC and ESA, took place between 2001 and 2003.
Table 1: Copernicus is the new name of the former GMES program 2)
A GMES Program Office (GPO) and a GMES Advisory Council (GAC) have been set up in early 2004. The GAC is an ad hoc advisory interface between the EC, ESA and their member states. Also in 2004, ESA initiated studies to explore the technical aspects of the Space Component of GMES based on user requirements. The ESA Space Council meeting at ministerial level in Berlin, Germany (Dec. 5-6, 2005), confirmed again that the GMES program will be the second flagship of space policy after Galileo. 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14)
The EEA (European Environmental Agency) and its European Topic Centers (ETCs) coordinate and harmonize the collection of data within the framework of the EIONET (European Environment Information and Observation Network) with the involvement of about 300 institutions in EEA member states.
Key issues in this field include the monitoring of:
• International environmental conventions (environmental issues of a global nature). The EU has signed more than 40 international treaties to bring forward a more global dimension to environment and security (e.g. biodiversity, global change, desertification). The “Kyoto Protocol” is an example of “treaty monitoring” requirements. NATO and its Member States are increasingly concerned with non-traditional threats to security, including the consequences of environmental change.
• Environmental stress (environmental issues of a regional nature). Environmental stress poses a potential threat to security at all geographic levels. Taking preventative action on environmental stress is the most appropriate approach to preventing environmental conflicts.
• Risks and natural disasters/hazards (including humanitarian help). The major topics of natural hazards are: earthquakes, landslides and avalanches, volcanoes, forest fires, and floods. The service of forest fire detection and monitoring (including risk evaluation) is an important activity in this category.
GMES has been identified as a priority for Europe. It is an initiative set up jointly by the European Commission (EC) and the European Space Agency (ESA). The EC has expressed its intention to take the lead for the development and operation of GMES in the long term. ESA is in charge of implementing the GMES Space Component. A general cooperative EC-ESA agreement on the GMES initiative functions and services was signed on Oct. 27, 2005.
Realizing the importance and enormous challenges in coordinating the services and functions of the various space missions for the GMES user community - a 'Ground Segment Coordination Body' (GSCB) of all agencies in the EU member states was established in June 2005. The initial goals are to coordinate the ground segment and data management of the most important European (including Canadian) Earth observation missions in the GMES timeframe. These comprise the existing and planned ESA and EUMETSAT missions as well as the larger and important planned national missions, which will be operational in the early phase of GMES and are committed to contribute to GMES services. 15)
In March 2006, a GMES Bureau was established, set up within the Directorate-General for Enterprise and Industry of the European Commission. The GMES Bureau is responsible for creating an implementation strategy for GMES, developing a federated and structured demand for GMES services across the Commission and promoting GMES to both stakeholders and the wider general public. 16)
The goal of the GMES strategy is to establish by 2008 a European capacity which, through technological, institutional and political support will fully meet those objectives. The overall GMES architecture comprises four major elements: services, space observations, in situ observations, and data integration and information management.
In Feb. 2010, the EC set up the GMES Partners Board. The goal of the GMES Partners Board is to assist the Commission in the overall coordination of GMES. The tasks of this Board will include the following:
- To establish cooperation between Member States bodies and the Commission on questions related to GMES
- To assist the Commission in monitoring the coherent implementation of the GMES program
- To assist the Commission with the preparation of a strategic implementation framework of the GMES program
- To bring about an exchange of experience and good practice in the field of GMES and Earth observation.
Table 2: GMES is a EU led initiative with component responsibilities provided by various agencies (Ref 13)
Earth observation: GSC (GMES Space Component)
In October 2009, the EC issued a Communication on ‘GMES: Challenges and Next Steps for the Space Component’ in which the respective roles of the European Union (EU), the EC and ESA within GMES in general, and within the GSC in particular, are addressed.
New terminology and concepts have been introduced. The EC leadership of the overall GMES program has been reiterated, declaring the intention to be the GMES Program Manager and to organize itself accordingly. ESA has been reconfirmed as the Coordinator of the GMES Space Component (‘GSC Coordinator’) while the EEA (European Environment Agency) is proposed to coordinate the In situ Component.
GMES serves two main European policy requirements: 18)
1) Independent access to geospatial information for policy- and decision-makers to advance European and national agendas related to environment and security policies.
2) Federation of European contributions to the international GEOSS (Global Earth Observation System of Systems) program. GMES has been declared by European governments to be the main framework for Europe's contribution to GEOSS. However, this will not include the totality of GMES, but those elements deemed appropriate to be shared at the international level. GMES shall not only contribute to GEOSS, but shall also act as a recipient of data and information from external sources for the benefit of European users.
The GMES program, which is aiming for full operational provision of satellite data for GMES services, involves the use of existing and planned national space capabilities as well as the development of new infrastructure. The GMES Space Component program is intended to meet the requirements of the three pilot services identified by the EC for early implementation (land monitoring, ocean monitoring and emergency management) and other services to be deployed in the 2008-2020 period.
The GSC (GMES Space Component) program is built around five concepts of space missions or “Sentinels”, plus access to existing and complementary missions from ESA Member States, EUMETSAT, Canada and third parties. Of the latter category the following missions are considered candidates for GMES operational service contributions - to get the program started:
- SPOT-5 of CNES, France (operating mission with a launch May 4, 2002)
- TerraSAR-X of DLR/EADS Astrium, Germany, with a launch on June 15, 2007
- COSMO-SkyMed of ASI, Italy (3 spacecraft with launches on June 8, 2007, Dec. 9, 2007, Oct. 25, 2008, and in late 2009)
- RADARSAT-2 of CSA/MDA, Canada, with a launch on Dec. 14, 2007
- Pleiades of CNES (2 spacecraft with launches in 2010 and thereafter)
- Jason-2 of EUMETSAT/CNES/NOAA/NASA with a launch on June 20, 2008
- MSG (Meteosat Second Generation) spacecraft of EUMETSAT (3 satellites with launches in 2002, 2005, and 2009)
- MetOp of EUMETSAT (3 satellites with a first launch on Oct. 19, 2006)
- DMC (Disaster Monitoring Constellation) of SSTL, UK [with 5 optical imaging satellites in orbit as of fall 2005: AlSAT-1, BILSAT-1, NigeriaSat-1, UK-DMC, and Beijing-1 (DMC+4)]
- RapidEye of RapidEye AG, Germany (5 optical imaging satellites with a launch on Aug. 29, 2008)
- EnMAP (Environmental Mapping and Analysis Program), a hyperspectral mission of DLR with a planned launch in 2013.
The ESA Sentinels constitute the first series of operational satellites responding to the Earth Observation needs of the EU-ESA GMES program. The GMES space component relies on existing and planned space assets as well as on new complementary developments by ESA. 21) 22)
The following members of the Sentinel family have been identified as core elements of the GSC (GMES Space Component):
• Sentinel-1 is a C-band interferometric SAR mission, consisting of a pair of satellites - to provide continuity to data so far provided by ERS-2, Envisat, and RADARSAT missions. The Sentinel-1 spacecraft cover applications such as observing sea ice zones and the arctic environment, surveillance of marine environment, monitoring land surface motion risks, and mapping in support of humanitarian aid in crisis situations.
Sentinel-1 will be flown in a dawn-dusk sun-synchronous orbit at an altitude of ~700 km with an exact repeat orbit of 12 days in support of multi-pass interferometry. With a SAR swath of ~250 km and a ground resolution of 5 m x 20 m, a 12 day quasi-global coverage can be obtained. The spacecraft design life is 7 years.
The spacecraft design is characterized by a single SAR (Synthetic Aperture Radar) instrument with selectable dual polarization, a deployable solar array, a large size on-board science data storage (1.4 TB at EOL), a very high X-band downlink rate 520 Mbit/s), and stringent requirements on attitude accuracy and data-take timing. In addition, the spacecraft will embark an OCP (Optical Communication Payload) unit allowing downlink of recorded data via a GEO terminal such as the EDRS (European Data Relay Satellite) of ESA. The launch of the first Sentinel-1 spacecraft is planned for 2013.
• Sentinel-2 is a multispectral optical imaging mission for global land observation (data on vegetation, soil and water cover for land, inland waterways and coastal areas, and also provide atmospheric absorption and distortion data corrections) at high resolution to provide enhanced continuity of data so far provided by SPOT-5 and Landsat-7.
The payload reference concept is based on a pushbroom multispectral imager (MSI) featuring a swath of 285 km with the intermediate spectral band set of 9 bands in VNIR, 3 SWIR bands, (including a 2.2 µm channel), and a PAN channel (”supermode” at 7 m). The revisit requirements for Sentinel-2 are a geometric revisit of better than or equal to 7 days over all landmasses and inland waters. The coverage requirements call for imagery of size ~149 million km2 in 3-7 days. These coverage requirements are driven by the need for global land mass change detection over the time scale of days to weeks. The design life required is > 5 years (7 years) of operations.
The Sentinel-2 spacecraft will feature an OCP unit allowing downlink of recorded data via a GEO terminal. The first launch of Sentinel-2 is planned for 2013 (800 km orbit).
• Sentinel-3 is an operational oceanography mission requiring the operation of 2 concurrent spacecraft. The main objective of Sentinel-3 mission is the provision of ocean observation data in routine, long term and continuous fashion with a consistent quality and a very high level of availability. In addition, the mission will be designed to generate land optical observation products, ice topography, vegetation and land hydrology products. The main mission objectives comprise: 23)
1) Operational Oceanography, i.e. the delivery of information needed to constrain and drive global and local ocean assimilation models actually, coupled ocean/ atmosphere assimilation models. For this, Sentinel-3 will deliver:
- Ocean color data
- Sea surface temperature data
- Sea surface topography data, including in particular an along-track SAR capability for addressing coastal zones sea surface topography and sea ice topography.
2) Global land applications, i.e. the delivery of information needed to derive global land products and services. These are:
- Land surface color
- Land surface temperature
- Land ice topography and inland water surface height data.
Sentinel-3 is an Earth observation mission including a medium-sized platform, large swath/medium spatial resolution optical instruments and a radar altimeter The final constellation of two satellites provides a worst case 2 day revisit time. The spacecraft carries a set of 4 main payloads:
- OCLI (Ocean and Land Color Instrument). OCLI is based on heritage from Envisat's MERIS (Medium Resolution Imaging Spectrometer) instrument but with improved wavelength bands (21 compared to 15 on MERIS) and sun-glint effects reduction.
- SLSTR (Sea and Land Surface Temperature Instrument). The SLSTR uses a dual viewing technique and operates across nine wavelength bands (plus 2 additional fire channels) supporting atmospheric correction. The spectral range of these channels is: 0.55, 0.66, 0.86, 1.37, 1.61, 2.25, 3.74, 10.95 and 12 µm plus the two fire channels with 3.74 and 10.95 µm. It provides a swath width of 750 km in dual and 1420 km in single view. The SLSTR has a spatial resolution in the visible bands of 500 m.
- SRAL (SAR Radar Altimeter), a dual-band (C+Ku) altimeter operating in conventional radar-altimeter mode as on Poseidon-3 (Jason-2), and in advanced SAR mode (burst mode) over sea ice and coastal regions (data so far provided by RA-2 on Envisat). SRAL is a mature concept supported by the strong heritage from Poseidon-3 and the CryoSat-2 SIRAL instrument techniques. It will provide the required ocean and sea-ice thickness measurements, as well as inland-waters and coastal measurements.
These instruments are complemented by a GNSS receiver, a DORIS terminal, and LRR (Laser Retroreflector).
The spacecraft design is characterized by a deployable solar array, stringent requirements on attitude accuracy, and the necessity to perform near-real time POD (Precise Orbit Determination) services to support data processing. The first launch of Sentinel-3 is planned for 2013.
• Sentinel-4 and -5, these are two families of atmospheric chemistry monitoring missions, one instrument (Sentinel-4) on geostationary orbit (GEO) and one instrument (Sentinel-5) on low Earth orbit (LEO).
The actual implementation of the missions will be according to a flexible architecture which may lead to grouping some of them on single platforms.
- The Sentinel-4 payload (an Ultraviolet-Visible-Near- Infrared Spectrometer) will be embarked on the two MTG-S (Meteosat Third Generation–Sounder) satellites in geostationary orbit (planned to launch in 2020 and 2027). In addition, TIR (Thermal Infrared) sounder data on the same platform, and a cloud imager on the MTG-Imager platform will be exploited by the Sentinel-4 services.
- The Sentinel-5 payload will be carried on the MetOp Second Generation spacecraft (planned to launch starting in 2020) in a sun-synchronous low Earth orbit (at about 800 km mean altitude). The Sentinel-5 mission will consist of an UV-VIS-NIR and Shortwave Infrared spectrometer which will also house a TIR sounder and imager.
- Sentinel-5P (Precursor). To avoid gaps between Envisat (SCIAMACHY instrument data in particular) and Sentinel-5, and to ensure continuity of atmospheric services, a Sentinel-5P mission, similar to Sentinel-5 but with no TIR sounder and imager, will be launched in 2015. Services proposed will cover air quality, climate change and stratospheric ozone and solar radiation.
Figure 2: GMES priorities and Sentinel notational definitions (image credit: ESA)
Figure 3: GMES Space Component Long term scenario (launch dates of Sentinels are indicative), image credit: ESA, (Ref. 21)
GMES-1 requirements and definition phase (2005/7)
The GMES-1 mission (Sentinel-1) is planned for a launch in the time frame 2012+. The objectives are to address the observational needs of Sentinel-1 and -3. The spacecraft is seen as the follow-on mission to Envisat. GMES-1 will include a C-band SAR instrument to continue the interferometric and ocean/ice/land measurements of Envisat and ERS-2, and to provide ocean color observations. Other capabilities are in the planning stage. 24) 25)
The mission objectives aim at customer satisfaction taking into account funding sources and the interest of the different customer categories including:
- Sponsors: Technology Research & Development Agencies, Departments of Industry
- Earth Observation Investigators: Studying methods and developing applications
- `End users': Earth scientists, institutional users, service providers, (other) companies, (other) professional & private users, etc.
• Earth observation research: a) to study the radar signature of the Earth, and b) to establish application potential for Earth science support as well as for operational services
• Need of best possible sensitivity, temporal & spatial resolution, image quality
• Request multi-parameter space: different wavelengths, (full) polarimetry, interferometry
• The end users represent an immense but also a very diverse community.
Programmatic priorities and GMES pilot services:
The origin of the mission requirements have their roots in the following programmatic priorities and GMES pilot services aiming at:
- Monitoring the European marine environment. This means for instance daily surveillance of marine transport corridors (example: the English Channel, the Strait of Gibraltar, etc.) with information delivery within one hour of observation.
- Monitoring and assessing land surface-motion risks. Observation cycles of subsidence measurements over all major urban areas and surveillance of transport infrastructure (e.g. gas pipelines) on a two-week basis.
- Open ocean surveillance. Of particular interest are the Arctic and Antarctic environment with their sea-ice regions. Daily monitoring of ice-infested areas along the major transport routes. Open ocean monitoring implies the provision of wind and wave products similar to those of ASAR.
- Forest monitoring. This involves the generation of annual global maps for climate change detection services as well as support of sustainable management and nature protection.
- Water management and soil protection. This involves such services as monthly global mapping of the environmental state to support the EU's thematic strategy on soil protection. Currently, surface soil moisture is being derived from ASAR data of Envisat for southern Germany.
- Forest fire and land management. Provision of monthly global coverage for the mapping of burnt regions and for flood risk assessment. Furthermore, provision of fast global on-demand access services for real-time awareness services for floods.
- Food security and crop monitoring. An example is rice mapping in China - currently, a pilot test service, referred to as Dragon Project, for the Hinze region is using single-date HH/VV Envisat data of the ASAR (Advanced SAR) instrument.
- Global mapping for the humanitarian community. This service requires fast global access on demand.
- Long-term continuity: At least 15 years of service
- Performance and data quality: ERS/Envisat
- Operations: Systematic with on-demand option
- Processing and archiving: All products to level-1
- Distribution: From archive in near real-time
- Coverage & revisit: Global monthly, fast global access on demand, regional bi-weekly, regional daily (12 hourly desirable)
- Timeliness: 3 hours (1 hour desirable for special cases)
- Center frequency of SAR instrument: C-band at 5.405 GHz
- Interferometry: yes, service dependent
- Spatial and radiometric resolution: ERS/Envisat baseline
- Swath width: Minimum 200-300 km, larger desirable, 20 x 20 km for wave mode
- Polarization: VV (wind, waves and oil spills), HV or VH (ship detection), VV or HH, VV and HH (desirable), VV and VH or HH and HV, full polarimetry (best for classification)
A two-satellite constellation with four nominal operational modes designed for inter-operability with other systems for full compliance with user requirements.
- Stripmap Mode (SM):
- Interferometric wide-swath mode (IW):
- Extra-wide swath mode (EW):
- Wave mode (WV):
- Orbit: Sun-synchronous near circular orbit with an altitude of about 700 km
- Mean local solar time at 18 hours on ascending node (dawn-dusk orbit)
- Repeat cycle: 12 days
- Cycle length: 175 orbits
- Swath width: 80 km (SM), 240 km (IW), 400 km (EW), 20 km x 20 km (WV)
- Polarization: VV+VH or HH+HV (all modes)
- Spatial resolution (ground range x azimuth): 4 m x 5 m, single look (SM); 5 m x 20 m single look (IW); 25 m x 80 m three looks (EW); 20 m x 5 m single look (WV)
- Noise equivalent sigma zero: -25 dB
- Radiometric stability: 0.5 dB
- Radiometric accuracy: 1.0 dB
Sentinels operations concept:
The following list summarizes the main characteristics of the Sentinel missions (S1, S2, and S3) which determine the operations concept: 26)
• Each Sentinel spacecraft is designed such that its on-board resources allow to store the complete instrument schedule covering the default mission plan duration, i.e. 4 days, 14 days and 27 days respectively for each Sentinel mission family
• In terms of on-board autonomy, each satellite can operate nominally for at least 72 hours without any ground intervention, even in the case of a single on-board failure
• Visibility of the spacecraft from the primary TT&C station will be on average 10 minutes every revolution except for up to four consecutive blind orbits (every 24 hours) during which the ground track does not cross the Kiruna visibility region
• Very stringent QoS (Quality of Service) requirements ensuring that data products are accurate, complete and provided on time. In particular, all Sentinels feature Near-Real time delivery of data within 3 hours from sensing.
An innovative Sentinels operational concept has been defined based on the use of a novel mechanism to schedule the telecommand execution using the spacecraft orbit position, as provided by the on-board GNSS receiver. This allows to drastically reduce the number of ground station passes required to support the routine mission and to manage the monitoring and control of the 3 systems under a single spacecraft controller position.
Sentinel downlinks: Sentinel-1,-2, and -3 produce approximately 4 TByte of data per day. The downlink of that data to the ground represents one of the major challenges of the program. Each satellite requires between 6 (Sentinel-3) and 16-18 (Sentinel-1, -2) minutes of downlink time per orbit on average, with a modulation and coding scheme which can be accommodated within the 300 MHz X-band bandwidth available. A new modulation scheme has been designed and implemented and all Sentinels make use of the same payload data transmission subsystem, the X-band TXA (Transmission Assembly). In addition, Sentinel-1 and -2 are being equipped with an additional downlink subsystem, an OCP (Optical Communications Payload), including a Laser Communication Terminal (LCT) to transmit instrument data a geostationary data relay system, the EDRS (European Data Relay System) to the ground.
There are two downlink channels available. Each channel has an effective downlink rate of 260 Mbit/s. The Sentinels provide the same on-board interface from the mass memory to the input to the TXA and, for Sentinel-1 and -2, to the input of the LCT. It is possible to downlink data from memory, with or without deletion after downlink; to downlink data from memory while new data is stored in memory; and to provide quasi-real time downlink of data, with data acquired and stored in the mass memory and immediately downlinked.
Although the mass memory management of the different Sentinels is designed in response to the specific requirements of each mission, all Sentinels support a downlink planning allowing the download of different data with different priorities, e.g. Near Real Time (NRT) data downlink prior to other data. And for Sentinel-1 and -2 the downlink planning allows to route the data to either the X-band downlink or the optical downlink.
The Sentinels FOS (Flight Operations Segment) is being designed making extensive re-use of elements developed in the context of previous Earth Observation ground segments. A single Sentinel MCS (Mission Control System) will allow monitoring and control of all spacecraft, while commonalities across unit models will be applied for the Sentinel spacecraft simulators development.
Once operational, GMES will be unique in the world. GMES will provide what is done successfully today in meteorology, namely to combine satellite and in situ observations with forecast models, to obtain information services needed by institutions and individual citizens alike. GMES will extend this concept to domains such as agricultural monitoring and food supply forecasting, fisheries, ship-routeing, urban planning, climate change studies, emergency response, humanitarian aid, external EU actions, border surveillance or maritime security, to name just a few.
GSE (GMES Services Element)
In 2001 the first ESA program dedicated to GMES, called the “Earthwatch GMES Service Element” (GSE), was approved by the ESA Ministerial Council. As a consequence, in February 2003, 10 GSE thematic projects have been launched after a competitive tender by ESA/ESRIN, each of them aiming to deliver pre-operational information for monitoring and management of environment and security to end users in order to fulfil European policies. These GSE services will make best use of existing EO (Earth Observation) systems and will also help to define and establish the longer-term needs for future operational EO systems. 27)
The GMES Services are categorized into three Earth system domains (Atmosphere, Marine and Land) and three crosscutting domains (Emergency Management, Security and Climate). Once fully operational, they will provide standardized and validated multi-purpose information products for a broad range of EU policy-relevant application areas, many of which are implemented at national or regional level. The development of the GMES Services and their transition to pre-operational status has been funded primarily within the GMES Service Element of the European Space Agency and the 6th and 7th Framework Programs of the European Commission, with EU Member State funding having also supported development and customization (Ref. 21).
The information products of the six Service domains are at various stages of operational maturity (in 2011). Several are now operational and part of the EC-funded GIO (GMES Initial Operations) phase (2011-2013). Others are undergoing final prototyping and operationalization with an aim to be funded in the anticipated GMES operations phase (2014+).
Brief descriptions of the GMES Service domains are provided below along with an indication of maturity level.
• GMES Atmosphere Monitoring Service: aims to provide data records, nowcasts and forecasts of global atmospheric chemistry and constituents essential for monitoring climate, air quality, solar and UV radiation. Information products from this service are completing operationalization activities and should be included in the GMES operations phase.
• GMES Marine Monitoring Service: aims to provide a suite of information products for global oceans and European sea basins targeting maritime safety, environment and safety based on forecasting models and measurements of variables such as sea level, ocean color, sea surface temperature, salinity, sea state and wind, oil pollution, and sea ice. Information products from this service are completing operationalization activities and should be included in the GMES operations phase.
• GMES Land Monitoring Service: provides crossborder, harmonized geo-information at global to local scales addressing land-cover/land-use, biophysical parameters and change monitoring to support spatial planning and monitoring of freshwater, crops, forests and land carbon. European land-cover/land-use products are entering the GIO phase while global land monitoring products are completing operationalization activities and should be included in the GMES operations phase.
• GMES Emergency Management Service: targets the whole emergency cycle for humanitarian crises, natural and man-made emergencies by delivering risk assessment maps and, for emergency situations, both pre-disaster reference products and timely post-disaster assessment maps. This Service is entering the GIO phase with some of the risk-mapping related activities completing operationalization activities.
• GMES Security Service: aims to support European Union policies related to EU border and maritime surveillance as well as EU External Action support. Information products from this service are completing operationalization activities and are expected to be included in the GMES operations phase.
• GMES Climate Service: aims to support the European Union and Member States in formulating their strategies and policies to mitigate and adapt to climate change. The initial set of information products to come from this Service is still being consolidated in collaboration with European Institutional users, as well as current providers of complementary information products.
It is anticipated that the free availability of products from the GMES Services, coupled with the full and open availability of data from the GMES-dedicated Sentinel satellite missions, will give rise to a so-called GMES downstream sector. The services developed in the downstream sector will be those which fill niches not covered specifically enough by the GMES services. These might include regional or local information at resolutions higher than provided by the GMES Services, such as streetscale air quality forecasts, or information of interest to narrow sectors of users such as the off-shore wind industry. It is expected that downstream services become self-sustaining by securing funding directly from their users or through non-GMES institutional funding (Ref. 21).
Figure 4: High-level view of the GMES architecture (image credit: EC, ESA)
Figure 5: Overview of GMES system architecture (image credit: ESA)
GSCDA (GMES Space Component Data Access)
The GMES Space Component (GSC) includes the Sentinels satellites and the coordinated access to ESA and European EO missions.
In 2007, ESA and the EC (European Commission) signed an agreement to allow ESA to ensure the coordinated and timely supply of satellite-based Earth Observation data for the preoperational phase of GMES from 2008 to 2010.
ESA is managing the GSCDA project in the frame of the FP7 space program as part of the European Space Policy focusing on coordinating the access to space-based observation data to support GMES services.
ESA targets the introduction of the following capabilities to achieve a coordinated access to data from current and future missions. These efforts are supported in parallel through CEOS (Committee on Earth Observation Satellites) and GEOSS (Global Earth Observation System of Systems).
• HMA (Heterogeneous Mission Access). GMES data access implies also a coherent data access to ~40 different EO missions (inside and outside of ESA). Aside from the current and future ESA missions (Envisat, GOCE, SMOS, CryoSat-2, MSG-3, Swarm, ADM/Aeolus, GMES Sentinels, etc.), the European space agencies are also cooperating with their EO missions to make HMA become possible for a global EO community. 28)
Full members of the HMA Architecture Working Group are: CSA, CNES, DLR, ESA, EUMETSAT, and ASI. 29)
• LTDP (Long Term Data Preservation). 32)
Figure 6: Overview of the GSC and HMA (image credit: ESA)
Figure 7: GMES pre-operational status in 2012 (image credit: ESA) 33)
Figure 8: Sentinels data production highlights (image credit: ESA)
Figure 9: Updated GSA and HMA illustration of the ground segment architecture in 2012 (image credit: ESA, Ref. 33)
Figure 10: Overview of GMES components and responsibilities (image credit: ESA,Ref. 33)
Figure 11: GMES core and collaborative ground segment (image credit: ESA)
Figure 12: Core ground segment functions (image credit: ESA)
Figure 13: GMES core ground station network (image credit: ESA)
Figure 14: Data Core NRT and Offline Processing Centers (image credit: ESA, Ref. 33)
GMES data policy:
“Full and open access to Sentinel data for all users.”
As part of the ESA-led GMES Space Component (GSC), which guarantees access to a variety of EO data, ESA and the EC worked together to define the principles and implementation scheme of the Sentinel Data Policy. The goal is to strife for maximum availability of data & corresponding access services in support of increasing demand of EO data in the context of climate change initiatives and for the implementation of environmental policies, also resulting in humanitarian benefits.
1) In principle, anybody can access acquired Sentinel data; in particular, no difference is made between public, commercial and scientific use and in between European or non-European users (registration is required).
2) The licenses for the Sentinel data are free of charge.
3) The Sentinel data (as far as generated out of the Core Ground segment) will be made available to the users via a "generic" online access mode, free of charge. "Generic" online access is subject to a user registration process and to the acceptation of generic terms and conditions.
4) Additional access modes and the delivery of additional products will be tailored to specific user needs, and therefore subject to tailored conditions.
5) In the event security restrictions apply to specific Sentinel data affecting data availability or timeliness, specific operational procedures will be activated.
The Sentinel Data Policy is one element of the overall GMES Data and Information Policy. The Sentinel Data Policy is applicable to data derived from Sentinel missions (1-5, S-5 precursor) and the respective core ground segment.
ESA/EC joint principles for the Sentinel Data Policy:
- Approved by ESA member states at PB-EO in September 2009
- To be approved by EC as part of Regulation of the European Parliament and the Council at the end of 2010.
Sentinel HLOP (High Level Operations Plan): 41)
• ESA will generate a Sentinel HLOP, which will define the priorities in data acquisition/provision applicable to all Sentinel missions during the operations of the GSC.
• HLOP will prioritize user access in order to mitigate impact of technical or financial constraints based on the use of data and the rules contained in the GMES declaration
• Priorities are applied only in case of technical or financial constraints or incompatibility of requirements exceeding the satellite or ground segment capacity. ESA’s approach is to minimize the cases for which a priority scheme is needed, through the maximization of systematic acquisition, of systematic processing and of systematic data availability.
The technical implementation of the GSC (GMES Space Component) is entrusted to ESA. The objective of the GSC program is to fulfil the space-based observation requirements in response to European policy priorities. It comprises two types of satellite missions; the dedicated GMES missions (Sentinels), developed by ESA specifically to meet the Earth Observation needs of GMES services, and the GCMs (GMES Contributing Missions), a number of existing and planned Earth observation satellites from European, national or commercial organizations, which were developed for other purposes but still providing valuable data for GMES. 42)
Hence the GCMs are contributors of the GSC, which can be seen as a System of Systems. The conditions under which their data are made accessible to GMES (e.g. ordering mechanisms, processing level, delivery timeliness, data licensing, etc) are contractually stipulated with the mission owners on an individual basis.
The proposed technical solution for the GMES-S dual data access system is conceived to deliver EO information for security applications to a wide range of European, National, and Regional organizations across the EU. Security products are increasingly demanding in terms of resolution -better than 1m-, responsiveness -better than several hours from request to delivery-, and frequency. The most demanding needs originate in joint operations for crisis response, which require the fastest responsiveness. 43)
ESA's proposed GMES-S GCS concept attempts to focus on the issue of filling in the gaps found in the European ground segment infrastructure.
The first performance driver is very high responsiveness (NRT), combined with very high spatial resolution. This is a must for fast detection and for monitoring changing targets during crisis situations. The second key performance driver is high image quality with moderately fast reaction, required for optimal characterization of already detected and monitored targets. Hence, the operations are divided into:
• Interactive operations which require a specific user observation request or a specific number of repeated observations. The key quality parameter will be total system responsiveness from data request to product or service delivery. The purpose of interactive operations may be detection, monitoring or characterization.
• Systematic operations which require a long term user request for routine and repetitive observations of a given large areas permanently at risk. The key quality parameter will be latency from image acquisition to product or service delivery.
ESA’s reference architecture for GMES-S GCS is depicted in Figure 15, linking the following high-level concepts:
- The “S of GMES” System, that gathers elements of the space and ground segments that fall under the exclusive control of a single GMES authority. Elements modelling the space segment are Sentinel 1 and 2, while ground segment elements modelling the downlink chain are: downlink ground stations, Sentinel payload processing centers, security thematic value adding, and data fusion centers, telemetry tracking and command ground stations, FOS (Flight Operations Segment), and the GMES security tasking coordination center.
- The “S of GMES" System of Systems that includes existing and committed European ground or space components with special relevance to meet security needs, not specifically designed for GMES. Elements modelling the space segment are ESA data relay satellites and European security satellites. The ground segment elements modelling the downlink chain are: ground stations, payload processing centers, value adding and data fusion centers, human intelligence, in-situ data, and general knowledge, FOS, European security mission tasking centers and final users.
National and pan-European institutions handle the listed components under various governance models. Cooperative efforts to GMES guarantee data supply and availability.
There are external contributing missions to GMES-S, namely spatial high resolution commercial systems: Canadian SAR missions, EU military missions, GPS and EUMETSAT. Likewise, Norwegian and Israeli ground stations take part in the system for telecommand uplink or data downlink from Arctic, Antarctic and Israeli facilities.
Figure 15: ESA’s reference architecture for the GMES-S GCS configuration (image credit: ESA, GMV)
CTDA (Coordinated Tasking and Data Access): The CTDA constitutes the heart and the differential element of the proposed solution for GMES-Security. Requests to be addressed demand a highly interactive, operating in fast response mode. In addition, the system must handle simultaneously requests of multiple crisis scenarios. At the same time, the GMES-S space component capabilities an cooperating missions must efficiently be combined, articulating all assets in a system of systems.
The goal of the CTDA mission is : (i) to respond to the information request, (ii) to task assets and ensure that requested products are planned, and (iii) to provide the location of archived data corresponding to the user requests. Figure 16 shows the CTDA interaction with conforming elements:
Figure 16: Tasking/planning overview: CTDA interaction with conforming elements (image credit: ESA, GMV)
• GMES Security Coordination Center hosts the CTDA component which processes requests converting them to tasking/ planning request to elements within the system of systems.
• Mission Planning, uptakes CTDA requests into its planning cycle accounting for applicable data, rules, constraints, allocated data downlink windows (ground stations/European Data Relay Satellites –EDRS-), and allocated uplink windows.
• The EDRS is managed through a dedicated segment and provides its uplink and downlink availability to GMES-S (for data relay to/from the EO satellites). This availability is a main input to the GMES-S mission planning cycles.
• The European Mission Tasking Center receives observation requests and incorporates them into its tasking/planning cycle. Provides feedback in terms of approval or rejection of the observation request.
• External systems or non-European systems that provide a tasking/planning interface according to a reference SLA (Service Level Agreement).
The CTDA counts with a central management point for the tasking and cataloguing of information, to ensure consistency of the overall tasking/planning, to provide feedback to the user and to ensure availability of EO products to end users.
The external systems information hosted at CTDA are the SLA, the catalogue and updated tasking/planning information. CTDA copes with the fact that only part of the considered services may be available from target cooperating missions. The information flows from CTDA to GMES and any external systems are found in Figure 17.
Figure 17: Central hosting of tasking/catalogue information (image credit: ESA, GMV)
The proposed CTDA approach is basically trying to establish a central catalogue built up from the mirroring of all available external catalogues. For users accessing the archived data, the CTDA acts like a master catalogue. Although user requests for catalogue information and archive data can be secured through standard GMES-S security layers, once end users obtain the data location coordinates, specific data access mechanisms associated to the external archive being accessed are activated.
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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.
The Sentinel series: