KEYWORDS: Equipment, Satellites, Spectroscopy, Calibration, Hyperspectral imaging, Signal to noise ratio, Data processing, Space operations, Reflectivity, Satellite communications
Imaging spectroscopy enables the observation and monitoring of surface properties thanks to the diagnostic capability of contiguous, spectral measurements from the Visible to the Shortwave Infra-Red portion of the electromagnetic spectrum. These observations of the Earth’s surface support the generation of a wide variety of new products and services, spanning across different domains relevant to various European Union (EU) policies that are currently not being met or can be substantially improved, not only for the public, but also for the private downstream sector. The Copernicus Hyperspectral Imaging Mission for the Environment (CHIME) aims to provide routine hyperspectral observations over the land and coastal zones through the Copernicus Programme in support of EU- and related policies for the management of natural resources, assets, and benefits. This unique Visible-to-shortwave Infra-Red spectroscopy based observational capability will in particular support new and enhanced services for food security, agriculture and raw materials. For the development of the Space Segment Contract (Phase B2/C/D/E1) Thales Alenia Space (France) as Satellite Prime and OHB (Germany) as Instrument Prime were selected. The contract was signed in November 2020 and the corresponding Kick-Off released the start of Phase B2. The System Requirement Review (SRR) was conducted in July 2021 and the Preliminary Design Review (PDR) is being conducted in 2022. Currently there are two satellites foreseen and each of the satellites will embark a HyperSpectral Instrument (HSI), a pushbroom-type grating Imaging Spectrometer with high Signal-to-Noise Ratio (SNR), high radiometric accuracy and data uniformity. HSI consists of a single telescope for three single-channel spectrometers covering each one-third of the total swath of approximately 130 km. The spectral range of each spectrometer is covering the entire spectral range from 400 to 2500 nm. CHIME data will be processed and disseminated through the Copernicus core Ground Segment allowing the generation of CHIME core products: L2A (bottom-of-atmosphere surface reflectance in cartographic geometry), L1C (top-of-atmosphere reflectance in cartographic geometry) and L1B (top-of-atmosphere radiance in sensor geometry). Additional higher level prototype products related to key vegetation, soil and raw material properties are also being developed. In this contribution, besides the mission requirements and planning, the main outcomes of the activities in Phase A/B1 and B2, as well as the planned activities for Phase C/D/E will be presented, covering the scientific support studies, the technical developments, and the user community preparatory activities.
The Sentinel-2 (S-2) mission is part of the Copernicus Space Component (CSC) – the European Commission’s Earth Observation program. It is designed to provide systematic global acquisitions of land and coastal areas at high-spectral resolution and with high revisit frequency, generating products feeding a large range of operational applications in domains such as agriculture, ecosystems management, natural disaster monitoring or water quality monitoring.
The mission is currently in its operational phase with a constellation of two satellites (Sentinel-2A and Sentinel-2B) launched in 2015 and 2017 respectively, each designed for a minimum lifetime of 7.25 years with consumables sized for 12 years. In order to provide a long-term service (up to 20-year of overall mission duration), two additional satellites Sentinel-2C and Sentinel-2D were funded by the European Commission and are presently under development.
The main S-2 payload, the Multi Spectral Instrument (MSI), is a push broom instrument with 13 spectral bands covering from the visible and the near infrared (VNIR) to the short wave infrared (SWIR). Operational experience from S-2 A&B, with new applications raising up, demonstrates how crucial and valuable accurate instrument spectral characterization is becoming. In the frame of S-2 C&D development, an enhanced spectral characterization method was implemented in order to address all the pixels of the Field Of View (FOV) on all the bands of the instrument with high precision, accuracy and sampling.
This paper describes this novel approach as well as the test setup used to characterize both VNIR channels operated at ambient pressure and SWIR channels operated at low temperature in vacuum conditions. The results of the spectral response of the thirteen bands obtained during the MSI-C test campaign executed between 2019 and 2020 and their associated accuracy are presented. Finally, the impact of spectral response variation on typical targets and the added value for the users from the accurate knowledge of the spectral response is addressed.
ESA initiated in 2018 an architectural design study to prepare the development of the next generation of the optical component of the current Sentinel-2 and Sentinel-3 observation functions i.e. Sentinel-3 without the SAR altimeter and related payloads. The aim of this activity was to analyse and trade-off different architectural options for the next-generation of the Copernicus Space Component optical imaging missions, with an implementation in the 2032-time horizon. A holistic approach was taken to assess architectural option to secure the respective observation capabilities in future, not only extrapolating the current scenario, but to openly assess e.g. the merging of observation functions of different instruments as well as to consider potential data flows from third part missions and service providers, institutional as well as commercial. The outcome of the analysis, taking technological as well as programmatic aspects into account, resulted in the conclusion that Sentinel-2 MSI NG as well as Sentinel-3 OLCI NG together with SLSTR NG on the same platform, are most efficiently implemented as free flyers, with dedicated instruments. The data flow of these two missions will be ideally supplemented by the Land Surface Temperature Mission (LSTM) and the Hyperspectral Mission (CHIME), which are going to be implemented in the frame of the High Priority Candidate Missions (HPCMs) of Copernicus. Those operational data flows, building the backbone of the operational services, can benefit significantly by including the data flows of reliable sources e.g. as from the Landsat series of satellites. The needs for very high resolution (VHR) imaging data, can best be served by data from third party missions, as currently implemented in the Copernicus framework; a Sentinel VHR mission is currently not baselined.
The Sentinel-2 mission is dedicated to land monitoring, emergency management and security. It serves for monitoring of land-cover change and biophysical variables related to agriculture and forestry. The mission is also used to monitor coastal and inland waters and is useful for risk and disaster mapping. The Sentinel-2 mission is fully operating since June 2017 with a constellation of two polar orbiting satellite units. Both Sentinel-2A and Sentinel-2B are equipped with an optical imaging sensor MSI (Multi-Spectral Instrument) which acquires optical data products with spatial resolution up to 10 m. Accurate atmospheric correction of satellite observations is a precondition for the development and delivery of high quality applications. Therefore the atmospheric correction processor Sen2Cor was developed with the objective of delivering land surface reflectance products. Sen2Cor is designed to process monotemporal single tile Level-1C products, providing Level-2A surface (Bottom-of-Atmosphere) reflectance product together with Aerosol Optical Thickness (AOT), Water Vapour (WV) estimation maps and a Scene Classification (SCL) map for further processing. The paper will give an overview of the Level-2A product content and up-to-date information about the data quality of the Level-2A products generated with Sen2Cor 2.8 in terms of Cloud Screening and Atmospheric Correction. In addition the paper gives an outlook on the next updates of Sen2Cor and their impact on Level-2A Data Quality.
KEYWORDS: Data archive systems, Image processing, Sensors, Image quality, Modulation transfer functions, Data acquisition, Clouds, Data modeling, Deconvolution
The Advanced Land Observing Satellite (ALOS) was launched on January 24, 2006, by a Japan Aerospace Exploration Agency (JAXA) H-IIA launcher. It carries three remote sensing sensors: the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2), the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), and the Phased Array type L-band Synthetic Aperture Radar (PALSAR).
Within the framework of ALOS Data European Node (ADEN), as part of the European Space Agency (ESA), has collected 5 years of data observed in Arctic, in Europe and in Africa through the ground stations of Tromsoe (Norway) and Matera (Italy).
Some data has been repatriated directly from JAXA from the on-board recorder (in particular over Africa, outside the visibility of the stations). The data were available to the scientific users via on-request ordering from the stations through the ESA ordering system. In ordering to provide a better and easier access to the data in the framework of the ESA Third Party Missions, in 2015 ESA started a project aimed to repatriate the data from the stations, consolidate them, harmonise the format to the ESA standards.
For the PALSAR data, view the different processing levels available to the users, ESA decided to setup a dissemination system, able to process automatically at the user demand the data to the requested level (on-the-fly processing). For the optical data, instead, the decision was to systematically process the PRISM and AVNIR-2 as orthorectified products (so to a higher level in respect of what available before) with a systematic quality control.
This paper presents the functionalities of the new Level 1 orthorectified products and details the block adjustment algorithms used for refinement of geometric accuracy. A specific quality control strategy has been laid down in order to re-analyse the entire archive. Also, validation methods are explained and the final product accuracy specification are given.
Remote sensing image fusion allows the spectral, spatial and temporal enhancement of images. New techniques for image fusion are constantly emerging shifting the focus from pan-sharpening to spatiotemporal fusion of data originating from different sensors and platforms. However, the application of image fusion in the field of Earth observation still remains limited. The number and complexity of the different techniques available today can be overwhelming thus preventing users from fully exploiting the potential of fusion. The aim of this study is to make fusion products more accessible to users by providing them with a simple tool for spatiotemporal fusion in Python. This tool will contribute to the better exploitation of data from available sensors making possible to bring the images to the spectral, spatial and temporal resolution required by the user. The fusion algorithm implemented in the tool is based on the spatial and temporal adaptive reflectance fusion model (STARFM) - a well established fusion technique in the field of remote sensing often used as benchmark by other algorithms. The capabilities of the tool are demonstrated by three case studies using Sentinel-2 and simulated Sentinel-3 data. The first case study is about deforestation in the Amazon forest. The other two case studies concentrate on detecting change in an agricultural site in Southern Germany and urban flooding caused by the hurricane Harvey.
In the frame of the Copernicus programme, ESA has developed and launched the Sentinel-2 optical imaging mission that delivers optical data products designed to feed downstream services mainly related to land monitoring, emergency management and security. The Sentinel-2 mission is the constellation of two polar orbiting satellites Sentinel-2A and Sentinel-2B, each one equipped with an optical imaging sensor MSI (Multi-Spectral Instrument). Sentinel-2A was launched on June 23rd, 2015 and Sentinel-2B followed on March 7th, 2017. With the beginning of the operational phase the constellation of both satellites enable image acquisition over the same area every 5 days or less. To use unique potential of the Sentinel-2 data for land applications and ensure the highest quality of scientific exploitation, accurate correction of satellite images for atmospheric effects is required. Therefore the atmospheric correction processor Sen2Cor was developed by Telespazio VEGA Deutschland GmbH on behalf of ESA. Sen2Cor is a Level-2A processor which main purpose is to correct single-date Sentinel-2 Level-1C Top-Of-Atmosphere (TOA) products from the effects of the atmosphere in order to deliver a Level-2A Bottom-Of-Atmosphere (BOA) reflectance product. Additional outputs are an Aerosol Optical Thickness (AOT) map, a Water Vapour (WV) map and a Scene Classification (SCL) map with Quality Indicators for cloud and snow probabilities. Telespazio France and DLR have teamed up in order to provide the calibration and validation of the Sen2Cor processor. Here we provide an overview over the Sentinel-2 data, processor and products. It presents some processing examples of Sen2Cor applied to Sentinel-2 data, provides up-to-date information about the Sen2Cor release status and recent validation results at the time of the SPIE Remote Sensing 2017.
Whilst recent years have witnessed the development and exploitation of operational Earth Observation (EO) satellite constellation data, the valorisation of historical archives has been a challenge. The European Space Agency (ESA) Landsat Multi Spectral Scanner (MSS) products cover Greenland, Iceland, Continental Europe and North Africa represent an archive of over 600,000 processed Level 1 (L1) scenes that will accompany around 1 million ESA Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) products already available. ESA began acquiring MSS data in 1975 and it is well known that this dataset can be degraded due to missing data and a loss in accuracy. For these reasons, the content of the product format has been reviewed and the ESA Landsat processing baseline significantly updated to ensure products are fit for user purposes. This paper presents the new MSS product format including the updated metadata parameters for error traceability, and the specification of the Quality Assurance Band (BQA) engineered to allow the best pixel selection and also the application of image restoration techniques. This paper also discusses major improvements applied to the radiometric and geometric processing. For the benefits of the community, ESA is now able to maximize the number of L1 MSS products that can potentially be generated from the raw Level 0 (L0) data and ensure the highest possible data quality is reached. Also, by improving product format, processing and adding a pixel based quality band, the MSS archive becomes interoperable with recently reprocessed Landsat data and that from live missions by way of assuring product quality on a pixel basis.
Sentinel-2 is an Earth Observation mission developed by the European Space Agency (ESA) in the frame of the Copernicus program of the European Commission. The mission is based on a constellation of 2-satellites: Sentinel-2A launched in June 2015 and Sentinel-2B launched in March 2017. It offers an unprecedented combination of systematic global coverage of land and coastal areas, a high revisit of five days at the equator and 2 days at mid-latitudes under the same viewing conditions, high spatial resolution, and a wide field of view for multispectral observations from 13 bands in the visible, near infrared and short wave infrared range of the electromagnetic spectrum. The mission performances are routinely and closely monitored by the S2 Mission Performance Centre (MPC), including a consortium of Expert Support Laboratories (ESL). This publication focuses on the Sentinel-2 Level-1 product quality validation activities performed by the MPC. It presents an up-to-date status of the Level-1 mission performances at the beginning of the constellation routine phase. Level-1 performance validations routinely performed cover Level-1 Radiometric Validation (Equalisation Validation, Absolute Radiometry Vicarious Validation, Absolute Radiometry Cross-Mission Validation, Multi-temporal Relative Radiometry Vicarious Validation and SNR Validation), and Level-1 Geometric Validation (Geolocation Uncertainty Validation, Multi-spectral Registration Uncertainty Validation and Multi-temporal Registration Uncertainty Validation). Overall, the Sentinel-2 mission is proving very successful in terms of product quality thereby fulfilling the promises of the Copernicus program.
Copernicus is a European Union (EU) led initiative designed to establish a European capacity for the provision and use of operational monitoring information for environment and security applications. Within the Copernicus program, ESA is responsible for the development of the Space Component and Ground Segment..
In the framework of the European Copernicus programme, the European Space Agency (ESA) has launched the Sentinel-2 (S2) Earth Observation (EO) mission which provides optical high spatial -resolution imagery over land and coastal areas. As part of this mission, a tool (named S2-RUT, from Sentinel-2 Radiometric Uncertainty Tool) estimates the radiometric uncertainties associated to each pixel using as input the top-of-atmosphere (TOA) reflectance factor images provided by ESA. The initial version of the tool has been implemented — code and user guide available1 — and integrated as part of the Sentinel Toolbox. The tool required the study of several radiometric uncertainty sources as well as the calculation and validation of the combined standard uncertainty in order to estimate the TOA reflectance factor uncertainty per pixel. Here we describe the recent research in order to accommodate novel uncertainty contributions to the TOA reflectance uncertainty estimates in future versions of the tool. The two contributions that we explore are the radiometric impact of the spectral knowledge and the uncertainty propagation of the resampling associated to the orthorectification process. The former is produced by the uncertainty associated to the spectral calibration as well as the spectral variations across the instrument focal plane and the instrument degradation. The latter results of the focal plane image propagation into the provided orthoimage. The uncertainty propagation depends on the radiance levels on the pixel neighbourhood and the pixel correlation in the temporal and spatial dimensions. Special effort has been made studying non-stable scenarios and the comparison with different interpolation methods.
Landsat is a joint USGS and NASA space program for Earth Observation (EO), which represents the world’s longest running system of satellites for moderate-resolution. The European Space Agency (ESA) has acquired Landsat data over Europe, Northern Africa and the Middle East during the last 40 years.
A new ESA Landsat Multi-Spectral Scanner (MSS), Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) processor has been developed. This enhanced processor aligns historical Landsat products to the highest quality standards that can be achieved with the current knowledge of the instruments. The updated processor is mainly based on the USGS algorithm; however it has some different features that are detailed in this paper.
Current achievements include the processing and availability of approximately 860,000 new TM/ETM+ high-quality products between 1983 and 2011 from the Kiruna (S), Maspalomas (E) and Matera (I) archives; Matera includes data from the Fucino (I), Neustrelitz (D), O’Higgins (Antarctica), Malindi (Kenya), Libreville (Gabon) and Bishkek (Kyrgyzstan) ground stations.
The products are freely available for immediate download to the users through a very fast and simple dissemination service (at: https://landsat-ds.eo.esa.int/app/) and through ESA’s browsing system, EOLI. The remaining MSS data, dating back more than 40 years, will gradually become available during 2015 and 2016.
The ESA Landsat processor algorithm enhancement, together with the results of the ESA archive bulk-processing data regarding production, quality control and data validation are herein presented.
In the framework of the European Union Copernicus programme, the European Space Agency (ESA) has launched the Sentinel-2 (S2) Earth Observation (EO) mission which provides optical high spatial resolution imagery. Here is presented a tool, S2-RUT, (Sentinel-2 Radiometric Uncertainty Tool) allowing estimation of the radiometric uncertainties associated to each pixel using as input the top-of-atmosphere (TOA) reflectance images provided by ESA. The Sentinel-2 radiometric analysis focuses on the review of the pre- and post-launch characterisations in order to specify the uncertainty contributors at a pixel level and allow changes to be proposed in the uncertainty contributors where necessary. The identified uncertainty contributors are combined using a metrological Guide to Expression of Uncertainty in Measurement’ (GUM) model that is validated by comparing the results to a multivariate Monte Carlo Method (MCM). Specific contributors of the TOA reflectance are initially characterised and its future integration in the tool is discussed. The software implementation of the S2-RUT tool relies on the flexibility of the JPEG2000 standard using partial decoding. Auxiliary information for the uncertainty calculation is extracted from the metadata and quality masks integrated in the L1C product. In addition, using the detector footprint mask it is possible to account for parameters dependent on the neighbouring pixels and/or detector module. The L1C uncertainty is coded using 1 byte with an extra optional byte for complementary information. The resulting images and the metadata are directly appended to the original L1C product.
The Copernicus programme is a European initiative for the implementation of information services dealing with environment and security, based on observation data received from Earth Observation (EO) satellites and ground based information. Within this context, ESA is responsible in particular, for the implementation of the Copernicus Sentinel missions, feeding the Copernicus services with operational EO data. The Sentinel-2 optical high-resolution imaging mission will be devoted to the operational and systematic monitoring of land and coastal areas. To maximize the products suitability and readiness to downstream usage for the majority of applications, the Sentinel-2 Payload Data Ground Segment (PDGS) will systematically generate, archive and distribute Level-1C products, which will provide Top-of-Atmosphere (TOA) reflectance images, orthorectified using a global Digital Elevation Model (DEM) and projected on Universal Transverse Mercator (UTM) coordinate system. A Level-1B product will also be available for expert users, providing radiance images in sensor geometry together with an appended geometric model. Additionally, a complementary atmospheric correction and enhanced cloud screening algorithm is being prototyped. This processor will allow converting the Level-1C TOA reflectance image into Bottom-of-Atmosphere (BOA) reflectance. The processor will be provided as plug-in software of the Sentinel-2 Toolbox that will run on user side. During the operational phase, the Sentinel-2 Mission Performance Centre (MPC), as integrating part of the mission ground segment, will be in charge of ensuring that mission performances are met in terms of data quality through the calibration and validation activities.
F. Gascon, R. Biasutti, R. Ferrara, P. Fischer, L. Galli, B. Hoersch, S. Hopkins, J. Jackson, S. Lavender, S. Mica, A. Northrop, A. Paciucci, F. Paul, S. Pinori, S. Saunier
The Landsat program is a joint United States Geological Survey (USGS) and National Aeronautics and Space Administration (NASA) enterprise for Earth Observation (EO), that represents the world’s longest running system of satellites for moderate-resolution optical remote sensing. The European Space Agency (ESA) has acquired Landsat data over Europe through the ESA ground stations over the last 40 years, in co-operation with USGS and NASA. A new ESA Landsat Multi-Spectral Scanner (MSS), Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) processor has been developed. This enhanced processor aligns the historical Landsat products to the highest quality standards that can be achieved with the current knowledge of the instruments. The updated processor is mainly based on the USGS algorithm; however the ESA processor has some different features that are detailed in this paper. Using this upgraded processor, ESA is currently performing for the first time a bulk-processing of its entire Landsat series MSS/TM/ETM+ historical archive to make all products available to users. Current achievements include the processing and online distribution of approximately 290 000 new Landsat 5 TM high-quality products acquired at the Kiruna ground station between 1983 and 2011. The Landsat 5 TM bulk-processed products are made available for direct download after registration at: https://earth.esa.int/web/guest/pi-community/apply for-data/fast-registration. The remainder of the ESA’s Landsat data, dating back more than 40 years, will gradually become available for all users during the course of 2014. The ESA Landsat processor algorithm enhancement, together with the results of the ESA archive bulk-processing, and an overview on the data quality on a subset of the Landsat 5 TM data are herein presented.
In partnership with the European Commission and in the frame of the Global Monitoring for Environment and Security
(GMES) program, the European Space Agency (ESA) is developing the Sentinel-2 optical imaging mission devoted to
the operational monitoring of land and coastal areas.
The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. While ensuring
data continuity of former SPOT and LANDSAT multi-spectral missions, Sentinel-2 will also offer a wide range of
improvements such as a global coverage, a large field of view (290km), a high revisit capability (5 days with two
satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands). In this context, the
Centre National d'Etudes Spatiales (CNES) supports ESA to define the system image products and to prototype the
relevant image processing techniques.
First, this paper presents the Sentinel-2 system and the image products that will be delivered: starting from raw
decompressed images up to accurate ortho-images in Top of Atmosphere reflectances. The stringent image quality
requirements are also described, in particular the very accurate target geo-location.
Then, the prototyped image processing techniques will be addressed. Both radiometric and geometric processing will be
described with a special focus on the automatic enhancement of the geometric physical model involving a global set of
reference data.
Finally, the very promising results obtained by the prototype will be presented and discussed. The radiometric and
geometric performances will be provided as well as the associated computing time estimation on the target platform.
In the framework of the Global Monitoring for
Environment and Security (GMES) programme, the European
Space Agency (ESA) in partnership with the European Union
(EU) is developing the Sentinel-2 optical imaging mission devoted
to the operational monitoring of land and coastal areas. The
Sentinel-2 mission is based on a twin satellites configuration
deployed in polar sun-synchronous orbit and designed to offer a
unique combination of systematic global coverage, high revisit
(five days at equator with two satellites) and high spatial
resolution imagery (10/20/60m). The Multispectral instrument
features 13 spectral bands, going from visible to short wave
infrared domains. The instrument is designed to provide in orbit
calibration, excellent radiometric and geometric performance,
and with a capability to support accurate image geolocation and
co-registration. The Sentinel-2 mission is more particularly
tailored to the monitoring of land terrains, including vegetation
and urban areas. Sentinel-2 will ensure data continuity with the
SPOT and Landsat multi-spectral sensors, while accounting for
future service evolution.
In the framework of the Global Monitoring for Environment and Security (GMES) programme, the European Space
Agency (ESA) in partnership with the European Commission (EC) is developing the SENTINEL-2 optical imaging
mission devoted to the operational monitoring of land and coastal areas. The Sentinel-2 mission is based on a twin
satellites configuration deployed in polar sun-synchronous orbit and is designed to offer a unique combination of
systematic global coverage with a wide field of view (290km), a high revisit (5 days at equator with two satellites), a
high spatial resolution (10m, 20m and 60 m) and multi-spectral imagery (13 bands in the visible and the short wave
infrared spectrum). SENTINEL-2 will ensure data continuity of SPOT and LANDSAT multispectral sensors while
accounting for future service evolution.
This paper presents the main geometric and radiometric image quality requirements for the mission. The strong multi-spectral
and multi-temporal registration requirements constrain the stability of the platform and the ground processing
which will automatically refine the geometric physical model through correlation technics. The geolocation of the
images will take benefits from a worldwide reference data set made of SENTINEL-2 data strips geolocated through a
global space-triangulation. These processing are detailed through the description of the level 1C production which will
provide users with ortho-images of Top of Atmosphere reflectances. The huge amount of data (1.4 Tbits per orbit) is
also a challenge for the ground processing which will produce at level 1C all the acquired data.
Finally we discuss the different geometric (line of sight, focal plane cartography, ...) and radiometric (relative and
absolute camera sensitivity) in-flight calibration methods that will take advantage of the on-board sun diffuser and
ground targets to answer the severe mission requirements.
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