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Absolute calibration ofEarth observation sensors is key to ensuring long term stability and interoperability, essential for long term global climate records and forecasts. The Moon provides a photometrically stable calibration source, within the range of the Earth radiometric levels, and is free from atmospheric interference. However, to use this ideal calibration source, one must model the variation of its disk integrated irradiance resulting from changes in Sun-Earth-Moon geometries.
LIME, the Lunar Irradiance Model of the European Space Agency, is a new lunar irradiance model developed from ground-based observations acquired using a lunar photometer operating from the Izaña Atmospheric Observatory and Teide Peak, Tenerife. Approximately 300 lunar observations acquired between March 2018 and October 2020 currently contribute to the model, which builds on the widely-used ROLO (Robotic Lunar Observatory) model.
This presentation will outline the strategy used to derive LIME. First, the instrument was calibrated traceably to SI and characterised to determine its thermal sensitivity and its linearity over the wide dynamic range required. Second, the instrument was installed at the observatory, and nightly observations over a two-hour time window were extrapolated to provide top-of-atmosphere lunar irradiance using the Langley plot method. Third, these observations were combined to derive the model. Each of these steps includes a metrologically rigorous uncertainty analysis.
Comparisons to several EO sensors will be presented including Proba-V, Pleiades and Sentinel 3A and 3B, as well as a comparison to GIRO, the GSICS implementation of the ROLO model. Initial results indicate LIME predicts 3% - 5% higher disk integrated lunar irradiance than the GIRO/ROLO model for the visible and near-infrared channels. The model has an expanded (k = 2) absolute radiometric uncertainty of ~2%, and it is expected that planned observations until at least 2024 will further constrain the model in subsequent updates.
Sarah Taylor; Stefan Adriaensen; Carlos Toledano; África Barreto; Emma Woolliams; Marc Bouvet. LIME: the Lunar Irradiance Model of the European Space Agency. 2021, 1 .
AMA StyleSarah Taylor, Stefan Adriaensen, Carlos Toledano, África Barreto, Emma Woolliams, Marc Bouvet. LIME: the Lunar Irradiance Model of the European Space Agency. . 2021; ():1.
Chicago/Turabian StyleSarah Taylor; Stefan Adriaensen; Carlos Toledano; África Barreto; Emma Woolliams; Marc Bouvet. 2021. "LIME: the Lunar Irradiance Model of the European Space Agency." , no. : 1.
Providing uncertainties in satellite datasets used for Earth observation can be a daunting prospect because of the many processing stages and input data required to convert raw detector counts to calibrated radiances. The Sea and Land Surface Temperature Radiometer (SLSTR) was designed to provide measurements of the Earth’s surface for operational and climate applications. In this paper the authors describe the traceability chain and derivation of uncertainty estimates for the thermal infrared channel radiometry. Starting from the instrument model, the contributing input quantities are identified to build up an uncertainty effects tree. The characterisation of each input effect is described, and uncertainty estimates provided which are used to derive the combined uncertainties as a function of scene temperature. The SLSTR Level-1 data products provide uncertainty estimates for fully random effects (noise) and systematic effects that can be mapped for each image pixel, examples of which are shown.
David Smith; Samuel Hunt; Mireya Etxaluze; Dan Peters; Tim Nightingale; Jonathan Mittaz; Emma Woolliams; Edward Polehampton. Traceability of the Sentinel-3 SLSTR Level-1 Infrared Radiometric Processing. Remote Sensing 2021, 13, 374 .
AMA StyleDavid Smith, Samuel Hunt, Mireya Etxaluze, Dan Peters, Tim Nightingale, Jonathan Mittaz, Emma Woolliams, Edward Polehampton. Traceability of the Sentinel-3 SLSTR Level-1 Infrared Radiometric Processing. Remote Sensing. 2021; 13 (3):374.
Chicago/Turabian StyleDavid Smith; Samuel Hunt; Mireya Etxaluze; Dan Peters; Tim Nightingale; Jonathan Mittaz; Emma Woolliams; Edward Polehampton. 2021. "Traceability of the Sentinel-3 SLSTR Level-1 Infrared Radiometric Processing." Remote Sensing 13, no. 3: 374.
The Sentinel-3 mission is part of the Copernicus programme space segment and has the objective of making global operational observations of ocean, land and atmospheric parameters with its four on-board sensors. Two Sentinel-3 satellites are currently on orbit, providing near-daily global coverage. Sentinel-3A was launched on 16 February 2016 and Sentinel-3B on 25 April 2018. For the early part of its operation, Sentinel-3B flew in tandem with Sentinel-3A, flying 30 s ahead of its twin mission. This provided a unique opportunity to compare the instruments on the two satellites, and to test the per pixel uncertainty values in a metrologically-robust manner. In this work, we consider the tandem-phase data from the infrared channels of one of the on-board instruments: the Sea and Land Surface Temperature Radiometer, SLSTR. A direct comparison was made of both the Level 1 radiance values and the Level 2 sea surface temperature values derived from those radiances. At Level 1, the distribution of differences between the sensor values were compared to the declared uncertainties for data gridded on to a regular latitude-longitude grid with propagated pixel uncertainties. The results showed good overall radiometric agreement between the two sensors, with mean differences of ∼0.06 K, although there was a scene-temperature dependent difference for the oblique view that was consistent with what was expected from a stray light effect observed pre-flight. We propose a means to correct for this effect based on the tandem data. Level 1 uncertainties were found to be representative of the variance of the data, expect in those channels affected by the stray light effect. The sea surface temperature results show a very small difference between the sensors that could be in part due to the fact that the Sentinel-3A retrieval coefficients were also applied to the Sentinel-3B retrieval because the Sentinel-3B coefficients are not currently available. This will lead to small errors between the S3A and S3B retrievals. The comparison also suggests that the retrieval uncertainties may need updating for two of the retrieval processes that there are extra components of uncertainty related the quality level and the probability of cloud that should be included. Finally, a study of the quality flags assigned to sea surface temperature pixel values provided valuable insight into the origin of those quality levels and highlighted possible uncertainties in the defined quality level.
Samuel Hunt; Jonathan Mittaz; David Smith; Edward Polehampton; Rose Yemelyanova; Emma Woolliams; Craig Donlon. Comparison of the Sentinel-3A and B SLSTR Tandem Phase Data Using Metrological Principles. Remote Sensing 2020, 12, 2893 .
AMA StyleSamuel Hunt, Jonathan Mittaz, David Smith, Edward Polehampton, Rose Yemelyanova, Emma Woolliams, Craig Donlon. Comparison of the Sentinel-3A and B SLSTR Tandem Phase Data Using Metrological Principles. Remote Sensing. 2020; 12 (18):2893.
Chicago/Turabian StyleSamuel Hunt; Jonathan Mittaz; David Smith; Edward Polehampton; Rose Yemelyanova; Emma Woolliams; Craig Donlon. 2020. "Comparison of the Sentinel-3A and B SLSTR Tandem Phase Data Using Metrological Principles." Remote Sensing 12, no. 18: 2893.
During its commissioning phase, the Copernicus Sentinel-3B satellite has been placed in a tandem formation with Sentinel-3A for a period of 6 months. This configuration allowed a direct comparison of measurements obtained by the two satellites. The purpose of this paper was to present the range of analyses that can be performed from this dataset, highlighting methodology aspects and the main outcomes for each instrument. We examined, in turn, the benefit of the tandem in understanding instrument operational modes differences, in assessing inter-satellite differences, and in validating measurement uncertainties. The results highlighted the very good consistency of the Sentinel-3A and B instruments, ensuring the complete inter-operability of the constellation. Tandem comparisons also pave the way for further improvements through harmonization of the sensors (OLCI), correction of internal stray-light sources (SLSTR), or high-frequency processing of SRAL SARM data. This paper provided a comprehensive overview of the main results obtained, as well as insights into some of the results. Finally, we drew the main lessons learned from the Sentinel-3 tandem phase and provided recommendations for future missions.
Sébastien Clerc; Craig Donlon; Franck Borde; Nicolas Lamquin; Samuel Hunt; Dave Smith; Malcolm McMillan; Jonathan Mittaz; Emma Woolliams; Matthew Hammond; Christopher Banks; Thomas Moreau; Bruno Picard; Matthias Raynal; Pierre Rieu; Adrien Guérou. Benefits and Lessons Learned from the Sentinel-3 Tandem Phase. Remote Sensing 2020, 12, 2668 .
AMA StyleSébastien Clerc, Craig Donlon, Franck Borde, Nicolas Lamquin, Samuel Hunt, Dave Smith, Malcolm McMillan, Jonathan Mittaz, Emma Woolliams, Matthew Hammond, Christopher Banks, Thomas Moreau, Bruno Picard, Matthias Raynal, Pierre Rieu, Adrien Guérou. Benefits and Lessons Learned from the Sentinel-3 Tandem Phase. Remote Sensing. 2020; 12 (17):2668.
Chicago/Turabian StyleSébastien Clerc; Craig Donlon; Franck Borde; Nicolas Lamquin; Samuel Hunt; Dave Smith; Malcolm McMillan; Jonathan Mittaz; Emma Woolliams; Matthew Hammond; Christopher Banks; Thomas Moreau; Bruno Picard; Matthias Raynal; Pierre Rieu; Adrien Guérou. 2020. "Benefits and Lessons Learned from the Sentinel-3 Tandem Phase." Remote Sensing 12, no. 17: 2668.
We present the results from Verification of Reference Irradiance and Radiance Sources Laboratory Calibration Experiment Campaign. Ten international laboratories took part in the measurements. The spectral irradiance comparison included the measurements of the 1000 W tungsten halogen filament lamps in the spectral range of 350 nm–900 nm in the pilot laboratory. The radiance comparison took a form of round robin where each participant in turn received two transfer radiometers and did the radiance calibration in their own laboratory. The transfer radiometers have seven spectral bands covering the wavelength range from 400 nm–700 nm. The irradiance comparison results showed an agreement between all lamps within ±1.5%. The radiance comparison results presented higher than expected discrepancies at the level of ±4%. Additional investigation to determine the causes for these discrepancies identified them as a combination of the size-of-source effect and instrument effective field of view that affected some of the results.
Agnieszka Białek; Teresa Goodman; Emma Woolliams; Johannes Brachmann; Thomas Schwarzmaier; Joel Kuusk; Ilmar Ansko; Viktor Vabson; Ian Lau; Christopher MacLellan; Sabine Marty; Michael Ondrusek; William Servantes; Sarah Taylor; Ronnie Van Dommelen; Andrew Barnard; Vincenzo Vellucci; Andrew Banks; Nigel Fox; Riho Vendt; Craig Donlon; Tânia Casal. Results from Verification of Reference Irradiance and Radiance Sources Laboratory Calibration Experiment Campaign. Remote Sensing 2020, 12, 2220 .
AMA StyleAgnieszka Białek, Teresa Goodman, Emma Woolliams, Johannes Brachmann, Thomas Schwarzmaier, Joel Kuusk, Ilmar Ansko, Viktor Vabson, Ian Lau, Christopher MacLellan, Sabine Marty, Michael Ondrusek, William Servantes, Sarah Taylor, Ronnie Van Dommelen, Andrew Barnard, Vincenzo Vellucci, Andrew Banks, Nigel Fox, Riho Vendt, Craig Donlon, Tânia Casal. Results from Verification of Reference Irradiance and Radiance Sources Laboratory Calibration Experiment Campaign. Remote Sensing. 2020; 12 (14):2220.
Chicago/Turabian StyleAgnieszka Białek; Teresa Goodman; Emma Woolliams; Johannes Brachmann; Thomas Schwarzmaier; Joel Kuusk; Ilmar Ansko; Viktor Vabson; Ian Lau; Christopher MacLellan; Sabine Marty; Michael Ondrusek; William Servantes; Sarah Taylor; Ronnie Van Dommelen; Andrew Barnard; Vincenzo Vellucci; Andrew Banks; Nigel Fox; Riho Vendt; Craig Donlon; Tânia Casal. 2020. "Results from Verification of Reference Irradiance and Radiance Sources Laboratory Calibration Experiment Campaign." Remote Sensing 12, no. 14: 2220.
Vicarious calibration and validation techniques are important tools to ensure the long-term stability and inter-sensor consistency of satellite sensors making observations in the solar-reflective spectral domain. Automated test sites, which have continuous in situ monitoring of both ground reflectance and atmospheric conditions, can greatly increase the match-up possibilities for a wide range of space agency and commercial sensors. The Baotou calibration and validation test site in China provides operational high-accuracy and high-stability vicarious calibration and validation for high spatial resolution solar-reflective remote-sensing sensors. Two sites, given the abbreviations BTCN (an artificial site) and BSCN (a natural sandy site), have been selected as reference sites for the Committee on Earth Observation Satellites radiometric calibration network (RadCalNet). RadCalNet requires sites to provide data in a consistent format but does not specify the required operational conditions for a RadCalNet site. The two Baotou sites are the only sites to date that make spectral measurements for their continuous operation. One of the core principles of RadCalNet is that each site should have a metrologically rigorous uncertainty budget which also describes the site’s traceability to the international system of units, the SI. This paper shows a formalized metrological approach to determining and documenting the uncertainty budget and traceability of a RadCalNet site. This approach follows the Guide to the Expression of Uncertainty in Measurement. The paper describes the uncertainty analysis for bottom-of-atmosphere and top-of-atmosphere reflectance in the spectral region from 400 to 1000 nm for the Baotou sites and gives preliminary results for the uncertainty propagating this to top-of-atmosphere reflectance.
Lingling Ma; Yongguang Zhao; Emma R. Woolliams; Caihong Dai; Ning Wang; Yaokai Liu; Ling Li; Xinhong Wang; Caixia Gao; Chuanrong Li; Lingli Tang. Uncertainty Analysis for RadCalNet Instrumented Test Sites Using the Baotou Sites BTCN and BSCN as Examples. Remote Sensing 2020, 12, 1 .
AMA StyleLingling Ma, Yongguang Zhao, Emma R. Woolliams, Caihong Dai, Ning Wang, Yaokai Liu, Ling Li, Xinhong Wang, Caixia Gao, Chuanrong Li, Lingli Tang. Uncertainty Analysis for RadCalNet Instrumented Test Sites Using the Baotou Sites BTCN and BSCN as Examples. Remote Sensing. 2020; 12 (11):1.
Chicago/Turabian StyleLingling Ma; Yongguang Zhao; Emma R. Woolliams; Caihong Dai; Ning Wang; Yaokai Liu; Ling Li; Xinhong Wang; Caixia Gao; Chuanrong Li; Lingli Tang. 2020. "Uncertainty Analysis for RadCalNet Instrumented Test Sites Using the Baotou Sites BTCN and BSCN as Examples." Remote Sensing 12, no. 11: 1.
The need for SI traceability to ensure integrity and trust in the Essential Climate Variables (ECVs) and the services and information derived from them, is well established. However, the means to achieve and demonstrate this in a universally-consistent manner globally and between variables, particularly for the complex bio-geophysical variables that make up many of the ECVs, is challenging.
National Physical Laboratory (NPL), the UK national metrology institute, has, over the last three decades, established a comprehensive research programme to extend traditional underpinning laboratory-based capabilities to meet the needs of a wide range of Earth Observation and climate applications. These have included:
To build the necessary skills, capacity and trust within the community, NPL has established a close dialogue with EO/climate community experts and built international partnerships through active participation in international bodies such as CEOS & GEO. This has led to a close working relationship with ESA and other European national and international space agencies to provide metrological support across a wide range of projects.
This paper will discuss the criticality of SI traceability to providing trust in globally-relevant environmental & climate datasets and illustrate how it is being achieved through case studies, such as:
NPL plays a lead role in the recently created European Metrology Network for Climate and Ocean and is keen to continue to ensure its efforts and research program address the priorities of the EO and climate community and will welcome input on future research directions.
Nigel Fox; Paul Green; Joanne Nightingale; Emma Woolliams. Enabling and demonstrating SI traceability of ECVs and climate data records: the role of a national metrology institute. 2020, 1 .
AMA StyleNigel Fox, Paul Green, Joanne Nightingale, Emma Woolliams. Enabling and demonstrating SI traceability of ECVs and climate data records: the role of a national metrology institute. . 2020; ():1.
Chicago/Turabian StyleNigel Fox; Paul Green; Joanne Nightingale; Emma Woolliams. 2020. "Enabling and demonstrating SI traceability of ECVs and climate data records: the role of a national metrology institute." , no. : 1.
Environmental observations of essential climate variables (ECVs) and related quantities made by satellites and in situ observational networks are used for a wide range of societal applications. To identify a small climate trend from an observational record that is also sensitive to changes in weather, to seasonal effects and to geophysical processes, it is essential that observations have a stable basis that holds for multiple decades, whilst still allowing for changes in the observation instrumentation and operational procedures. To achieve this, all aspects of data collection and handling must be underpinned by robust quality assurance. The resultant data should also be linked to a common reference, with well-understood uncertainty analysis, so that observations are interoperable and coherent; in other words, measurements by different organisations, different instruments and different techniques should be able to be meaningfully combined and compared.
Metrology, the science of measurement, can provide a critical role in enabling robust, interoperable and stable observational records and can aid users in judging the fitness-for-purpose of such records. In addition to Global Climate Observing System (GCOS) monitoring principles, metrology’s value, and the role of National Metrology Institutes (NMI) in observations, has been recognised in initiatives such as the Quality Assurance Framework for Earth Observation (QA4EO) established by the Committee on Earth Observation Satellites (CEOS) and in the implementation plans of the World Meteorological Organization’s (WMO’s), Global Atmosphere Watch and the European Ocean Observing System.
The European Association for National Metrology Institutes (EURAMET) has recently created the “European Metrology Network (EMN) for Climate and Ocean Observation” to support further engagement of the expert communities with metrologists at national metrology insitutes and to encourage Europe’s metrologists to coordinate their research in response to community needs. The EMN has a scope that covers metrological support for in situ and remote sensing observations of atmosphere, land and ocean ECVs (and related parameters) for climate applications. It also covers the additional economic and ecological applications of ocean Essential Ocean Variable (EOV) observations. It is the European contribution to a global effort to further enhance metrological best practice into such observations through targeted research efforts.
In late 2019 and early 2020 the EMN carried out a survey to identify the need for metrology within the observational communities and held a webinar workshop to prioritise the identified needs. Here we present the results of the survey and discuss the role that metrology can play in the climate observing system of the future.
Emma Woolliams; Paola Fisicaro; Nigel Fox; Céline Pascale; Steffen Seitz; Christian Monte; Olav Werhahn; David Gorman; Miruna Dobre; Thomas Damitz. Metrology for Climate Sciences: The European Metrology Network for Climate and Ocean Observation. 2020, 1 .
AMA StyleEmma Woolliams, Paola Fisicaro, Nigel Fox, Céline Pascale, Steffen Seitz, Christian Monte, Olav Werhahn, David Gorman, Miruna Dobre, Thomas Damitz. Metrology for Climate Sciences: The European Metrology Network for Climate and Ocean Observation. . 2020; ():1.
Chicago/Turabian StyleEmma Woolliams; Paola Fisicaro; Nigel Fox; Céline Pascale; Steffen Seitz; Christian Monte; Olav Werhahn; David Gorman; Miruna Dobre; Thomas Damitz. 2020. "Metrology for Climate Sciences: The European Metrology Network for Climate and Ocean Observation." , no. : 1.
With increasing use of satellite-derived data in climate and Earth monitoring, the importance of reliable and traceable radiometric and spectral information is key. Due to the difficulties of maintaining instrument calibration post-launch, vicarious calibration sites play a vital part in ensuring the stability and interoperability of satellite sensor data.
RadCalNet, the Radiometric Calibration Network established through the Committee on Earth Observation Satellites Working Group on Calibration and Validation (CEOS-WGCV), provides a network of, currently four, instrumented ground reference sites providing users with bottom and top-of-atmosphere (BOA and TOA) reflectance measurements every 30 minutes in 10 nm spectral intervals and for nadir view. (For all sites, more detailed spectral information and off-nadir reflectances can be obtained from site owners). It is a key aspect of RadCalNet that the sites document their traceability to the International System of Units (SI) and that they provide traceable uncertainties associated with individual observations. These documents and uncertainties are peer reviewed by the RadCalNet working group. Each RadCalNet site provides ground reflectance observations that are propagated to TOA through a centralised processing system. RadCalNet has over 300 active users who value the available information.
Gobabeb, in Namibia, is one of these four sites, given the reference GONA. GONA was the first site that was established as a new RadCalNet site (the other sites were pre-existing) and the location was determined from a global survey to find suitable sites, primarily due to spatial uniformity and the probability of suitable atmospheric conditions, such as clear skies. With an automatic radiometric station, this site continuously collects atmospheric data and surface radiance measurements. These are then processed to ground spectral reflectance and provided with uncertainties to the RadCalNet processor which propagates values to TOA.
Due to the limitations of the instrument used for autonomous measurements, recent fieldwork has been carried out in this location to acquire additional hyperspectral data to maintain the quality of the site products. In addition, further site characterisation was conducted to prepare a best location for a new site nearby that is being developed under the HYPERNETS project. This paper presents both the RadCalNet site and the results of the recent fieldwork.
Morven Sinclair; Chris McLellan; Agnieszka Bialek; Emma R Woolliams; Sarah Taylor; Nigel P Fox. Characterisation Campaign at the Gobabeb RadCalNet Site in Support of Satellite Calibration and Validation Activities. 2020, 1 .
AMA StyleMorven Sinclair, Chris McLellan, Agnieszka Bialek, Emma R Woolliams, Sarah Taylor, Nigel P Fox. Characterisation Campaign at the Gobabeb RadCalNet Site in Support of Satellite Calibration and Validation Activities. . 2020; ():1.
Chicago/Turabian StyleMorven Sinclair; Chris McLellan; Agnieszka Bialek; Emma R Woolliams; Sarah Taylor; Nigel P Fox. 2020. "Characterisation Campaign at the Gobabeb RadCalNet Site in Support of Satellite Calibration and Validation Activities." , no. : 1.
This report gives the results of the COOMET.PR-K3 comparison of luminous intensity. Five laboratories took part in the comparison. COOMET.PR-K3 was piloted by Belarusian State Institute of Metrology (BelGIM). The linkage to KCRV was provided through the participation of the All-Russian Research Institute for Optical and Physical measurement (VNIIOFI) and Slovak Institute of Metrology (SMU). Other participants were National Scientific Center "Institute of Metrology" (NSC IM), Ukraine and Kazakhstan Institute of Metrology (KazInMetr). BelGIM, NSC IM and KazInMetr were non-linked laboratories. A set of three incandescent lamps was used as traveling comparison artefact. Degrees of equivalence of all three non-linked laboratories were within their expanded uncertainties. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
B Khlevnoy; O Tarasova; D Scums; T Gorshkova; E Ivashin; M Krempasky; A Kupko; N Vyrodova; E Woolliams. COOMET.PR-K3.a comparison of luminous intensity. Metrologia 2020, 57, 02002 -02002.
AMA StyleB Khlevnoy, O Tarasova, D Scums, T Gorshkova, E Ivashin, M Krempasky, A Kupko, N Vyrodova, E Woolliams. COOMET.PR-K3.a comparison of luminous intensity. Metrologia. 2020; 57 (1A):02002-02002.
Chicago/Turabian StyleB Khlevnoy; O Tarasova; D Scums; T Gorshkova; E Ivashin; M Krempasky; A Kupko; N Vyrodova; E Woolliams. 2020. "COOMET.PR-K3.a comparison of luminous intensity." Metrologia 57, no. 1A: 02002-02002.
Vicarious calibration approaches using in situ measurements saw first use in the early 1980s and have since improved to keep pace with the evolution of the radiometric requirements of the sensors that are being calibrated. The advantage of in situ measurements for vicarious calibration is that they can be carried out with traceable and quantifiable accuracy, making them ideal for interconsistency studies of on-orbit sensors. The recent development of automated sites to collect the in situ data has led to an increase in the available number of datasets for sensor calibration. The current work describes the Radiometric Calibration Network (RadCalNet) that is an effort to provide automated surface and atmosphere in situ data as part of a network including multiple sites for the purpose of optical imager radiometric calibration in the visible to shortwave infrared spectral range. The key goals of RadCalNet are to standardize protocols for collecting data, process to top-of-atmosphere reflectance, and provide uncertainty budgets for automated sites traceable to the international system of units. RadCalNet is the result of efforts by the RadCalNet Working Group under the umbrella of the Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV) and the Infrared Visible Optical Sensors (IVOS). Four radiometric calibration instrumented sites located in the USA, France, China, and Namibia are presented here that were used as initial sites for prototyping and demonstrating RadCalNet. All four sites rely on collection of data for assessing the surface reflectance as well as atmospheric data over that site. The data are converted to top-of-atmosphere reflectance within RadCalNet and provided through a web portal to allow users to either radiometrically calibrate or verify the calibration of their sensors of interest. Top-of-atmosphere reflectance data with associated uncertainties are available at 10 nm intervals over the 400 nm to 1000 nm spectral range at 30 min intervals for a nadir-viewing geometry. An example is shown demonstrating how top-of-atmosphere data from RadCalNet can be used to determine the interconsistency between two sensors.
Marc Bouvet; Kurtis Thome; Béatrice Berthelot; Agnieszka Bialek; Jeffrey Czapla-Myers; Nigel P. Fox; Philippe Goryl; Patrice Henry; Lingling Ma; Sébastien Marcq; Aimé Meygret; Brian N. Wenny; Emma R. Woolliams. RadCalNet: A Radiometric Calibration Network for Earth Observing Imagers Operating in the Visible to Shortwave Infrared Spectral Range. Remote Sensing 2019, 11, 2401 .
AMA StyleMarc Bouvet, Kurtis Thome, Béatrice Berthelot, Agnieszka Bialek, Jeffrey Czapla-Myers, Nigel P. Fox, Philippe Goryl, Patrice Henry, Lingling Ma, Sébastien Marcq, Aimé Meygret, Brian N. Wenny, Emma R. Woolliams. RadCalNet: A Radiometric Calibration Network for Earth Observing Imagers Operating in the Visible to Shortwave Infrared Spectral Range. Remote Sensing. 2019; 11 (20):2401.
Chicago/Turabian StyleMarc Bouvet; Kurtis Thome; Béatrice Berthelot; Agnieszka Bialek; Jeffrey Czapla-Myers; Nigel P. Fox; Philippe Goryl; Patrice Henry; Lingling Ma; Sébastien Marcq; Aimé Meygret; Brian N. Wenny; Emma R. Woolliams. 2019. "RadCalNet: A Radiometric Calibration Network for Earth Observing Imagers Operating in the Visible to Shortwave Infrared Spectral Range." Remote Sensing 11, no. 20: 2401.
In 2015, member countries of the United Nations adopted the 17 Sustainable Development Goals (SDGs) at the Sustainable Development Summit in New York. These global goals have 169 targets and 232 indicators based on the three pillars of sustainable development: economic, social, and environmental. However, substantial challenges remain in obtaining data of the required quality and quantity to populate these indicators efficiently. One promising and innovative way of addressing this issue is to use Earth observation (EO). The research reported here updates our original work to develop a Maturity Matrix Framework (MMF) for assessing the suitability of EO-derived data for populating the SDG indicators, with a special focus on those indicators covering the more social and economic dimensions of sustainable development, as these have been under-explored in terms of the contribution that can be made by EO. The advanced MMF 2.0 framework set out in this paper is based on a wide consultation with EO and indicator experts (semi-structured interviews with 38 respondents). This paper provides detail of the evolved structure of MMF 2.0 and illustrates its use for one of the SDG indicators (Indicator 11.1.1). The revised MMF is then applied to published work covering the full suite of SDG indicators and demonstrates that EO can make an important contribution to providing data relevant to a substantial number of the SDG indicators.
Ana Andries; Stephen Morse; Richard Murphy; Jim Lynch; Emma Woolliams. Seeing Sustainability from Space: Using Earth Observation Data to Populate the UN Sustainable Development Goal Indicators. Sustainability 2019, 11, 5062 .
AMA StyleAna Andries, Stephen Morse, Richard Murphy, Jim Lynch, Emma Woolliams. Seeing Sustainability from Space: Using Earth Observation Data to Populate the UN Sustainable Development Goal Indicators. Sustainability. 2019; 11 (18):5062.
Chicago/Turabian StyleAna Andries; Stephen Morse; Richard Murphy; Jim Lynch; Emma Woolliams. 2019. "Seeing Sustainability from Space: Using Earth Observation Data to Populate the UN Sustainable Development Goal Indicators." Sustainability 11, no. 18: 5062.
This paper presents a new Fundamental Climate Data Record (FCDR) for the visible (VIS) channel of the Meteosat Visible and Infrared Imager (MVIRI), with pixel-level metrologically traceable uncertainties and error covariance estimates. MVIRI has flown onboard Meteosat First Generation (MFG) satellites between 1982 and 2017. It has served the weather forecasting community with measurements of “visible”, “infra-red” and “water vapour” radiance in near real-time. The precision of the pre-launch sensor spectral response function (SRF) characterisation, particularly of the visible band of this sensor type, improved considerably with time, resulting in higher quality radiances towards the end of the MFG program. Despite these improvements, the correction of the degradation of this sensor has remained a challenging task and previous studies have found the SRF degradation to be faster in the blue than in the near-infrared part of the spectrum. With these limitations, the dataset cannot be immediately applied in climate science. In order to provide a data record that is suited for climate studies, the Horizon 2020 project “FIDelity and Uncertainty in Climate-data records from Earth Observation” (FIDUCEO) conducted (1) a thorough metrological uncertainty analysis for each instrument, and (2) a recalibration using enhanced input data such as reconstructed SRFs. In this paper, we present the metrological analysis, the recalibration results and the resulting consolidated FCDR. In the course of this study we were able to trace-back the remaining uncertainties in the calibrated MVIRI reflectances to underlying effects that have distinct physical root-causes and spatial/temporal correlation patterns. SEVIRI and SCIAMACHY reflectances have been used for a validation of the harmonised dataset. The resulting new FCDR is publicly available for climate studies and for the production of climate data records (CDRs) spanning about 35 years.
Frank Rüthrich; Viju O. John; Rob A. Roebeling; Ralf Quast; Yves Govaerts; Emma R. Woolliams; Jörg Schulz. Climate Data Records from Meteosat First Generation Part III: Recalibration and Uncertainty Tracing of the Visible Channel on Meteosat-2–7 Using Reconstructed, Spectrally Changing Response Functions. Remote Sensing 2019, 11, 1165 .
AMA StyleFrank Rüthrich, Viju O. John, Rob A. Roebeling, Ralf Quast, Yves Govaerts, Emma R. Woolliams, Jörg Schulz. Climate Data Records from Meteosat First Generation Part III: Recalibration and Uncertainty Tracing of the Visible Channel on Meteosat-2–7 Using Reconstructed, Spectrally Changing Response Functions. Remote Sensing. 2019; 11 (10):1165.
Chicago/Turabian StyleFrank Rüthrich; Viju O. John; Rob A. Roebeling; Ralf Quast; Yves Govaerts; Emma R. Woolliams; Jörg Schulz. 2019. "Climate Data Records from Meteosat First Generation Part III: Recalibration and Uncertainty Tracing of the Visible Channel on Meteosat-2–7 Using Reconstructed, Spectrally Changing Response Functions." Remote Sensing 11, no. 10: 1165.
Fundamental and thematic climate data records derived from satellite observations provide unique information for climate monitoring and research. Since any satellite only operates over a relatively short period of time, creating a climate data record also requires the combination of space-borne measurements from a series of several (often similar) satellite sensors. Simply combining calibrated measurements from several sensors can, however, produce an inconsistent climate data record. This is particularly true of older, historic sensors whose behaviour in space was often different from their behaviour during pre-launch calibration and more scientific value can be derived from considering the series of historical and present satellites as a whole. Here, we consider harmonisation as a process that obtains new calibration coefficients for revised sensor calibration models by comparing calibrated measurements over appropriate satellite-to-satellite matchups, such as simultaneous nadir overpasses and which reconciles the calibration of different sensors given their estimated spectral response function differences. We present the concept of a framework that establishes calibration coefficients and their uncertainty and error covariance for an arbitrary number of sensors in a metrologically-rigorous manner. We describe harmonisation and its mathematical formulation as an inverse problem that is extremely challenging when some hundreds of millions of matchups are involved and the errors of fundamental sensor measurements are correlated. We solve the harmonisation problem as marginalised errors in variables regression. The algorithm involves computation of first and second-order partial derivatives using Algorithmic Differentiation. Finally, we present re-calibrated radiances from a series of nine Advanced Very High Resolution Radiometer sensors showing that the new time series has smaller matchup differences compared to the unharmonised case while being consistent with uncertainty statistics.
Ralf Giering; Ralf Quast; Jonathan P. D. Mittaz; Samuel E. Hunt; Peter M. Harris; Emma R. Woolliams; Christopher J. Merchant. A Novel Framework to Harmonise Satellite Data Series for Climate Applications. Remote Sensing 2019, 11, 1002 .
AMA StyleRalf Giering, Ralf Quast, Jonathan P. D. Mittaz, Samuel E. Hunt, Peter M. Harris, Emma R. Woolliams, Christopher J. Merchant. A Novel Framework to Harmonise Satellite Data Series for Climate Applications. Remote Sensing. 2019; 11 (9):1002.
Chicago/Turabian StyleRalf Giering; Ralf Quast; Jonathan P. D. Mittaz; Samuel E. Hunt; Peter M. Harris; Emma R. Woolliams; Christopher J. Merchant. 2019. "A Novel Framework to Harmonise Satellite Data Series for Climate Applications." Remote Sensing 11, no. 9: 1002.
Approaches from metrology can assist Earth Observation (EO) practitioners to develop quantitative characterisation of uncertainty in EO data. This is necessary for the credibility of statements based on Earth observations in relation to topics of public concern, particularly climate and environmental change. This paper presents the application of metrological uncertainty analysis to historical Earth observations from satellites, and is intended to aid mutual understanding of metrology and EO. The nature of satellite observations is summarised for different EO data processing levels, and key metrological nomenclature and principles for uncertainty characterisation are reviewed. We then address metrological approaches to developing estimates of uncertainty that are traceable from the satellite sensor, through levels of data processing, to products describing the evolution of the geophysical state of the Earth. EO radiances have errors with complex error correlation structures that are significant when performing common higher-level transformations of EO imagery. Principles of measurement-function-centred uncertainty analysis are described that apply sequentially to each EO data processing level. Practical tools for organising and traceably documenting uncertainty analysis are presented. We illustrate these principles and tools with examples including some specific sources of error seen in EO satellite data as well as with an example of the estimation of sea surface temperature from satellite infra-red imagery. This includes a simulation-based estimate for the error distribution of clear-sky infra-red brightness temperature (BT) in which calibration uncertainty and digitisation are found to dominate. The propagation of these errors to sea surface temperature is then presented, illustrating the relevance of the approach to derivation of EO-based climate datasets. We conclude with a discussion arguing that there is broad scope and need for improvement in EO practice as a measurement science. EO practitioners and metrologists willing to extend and adapt their disciplinary knowledge to meet this need can make valuable contributions to EO.
Jonathan Mittaz; Christopher John Merchant; Emma R Woolliams. Applying principles of metrology to historical Earth observations from satellites. Metrologia 2019, 56, 032002 .
AMA StyleJonathan Mittaz, Christopher John Merchant, Emma R Woolliams. Applying principles of metrology to historical Earth observations from satellites. Metrologia. 2019; 56 (3):032002.
Chicago/Turabian StyleJonathan Mittaz; Christopher John Merchant; Emma R Woolliams. 2019. "Applying principles of metrology to historical Earth observations from satellites." Metrologia 56, no. 3: 032002.
The uncertainty in a climate data records (CDRs) derived from Earth observations in part derives from the propagated uncertainty in the radiance record (the fundamental climate data record, FCDR) from which the geophysical estimates in the CDR are derived. A common barrier to providing uncertainty-quantified CDRs is the inaccessibility to CDR creators of appropriate radiance uncertainty information in the FCDR. Here, we propose radiance uncertainty information designed directly to facilitate estimation of propagated uncertainty in derived CDRs at full resolution and in gridded products. Errors in Earth observations are typically highly structured and complex, and the uncertainty information we propose is of intermediate complexity, sufficient to capture the main variability in propagated uncertainty in a CDR, while avoiding unfeasible complexity or data volume. The uncertainty and error correlation characteristics of uncertainty are quantified for three classes of error with different propagation properties: independent, structured and common radiance errors. The meaning, mathematical derivations, practical evaluation and example applications of this set of uncertainty information are presented.
Christopher J. Merchant; Gerrit Holl; Jonathan P. D. Mittaz; Emma R. Woolliams. Radiance Uncertainty Characterisation to Facilitate Climate Data Record Creation. Remote Sensing 2019, 11, 474 .
AMA StyleChristopher J. Merchant, Gerrit Holl, Jonathan P. D. Mittaz, Emma R. Woolliams. Radiance Uncertainty Characterisation to Facilitate Climate Data Record Creation. Remote Sensing. 2019; 11 (5):474.
Chicago/Turabian StyleChristopher J. Merchant; Gerrit Holl; Jonathan P. D. Mittaz; Emma R. Woolliams. 2019. "Radiance Uncertainty Characterisation to Facilitate Climate Data Record Creation." Remote Sensing 11, no. 5: 474.
Meaningful study and quantification of climatic trends requires decades of observational data. Within satellite remote sensing this motivates the generation fundamental climate data records (FCDRs) - datasets containing the combined observations from a series of missions of a given sensor, to span the required duration for study. Ensuring the radiometric stability of such series is vital for such applications. To this end a consistent in-flight retrospective recalibration of all the sensors in such a series is required, called harmonisation. Presented here is a methodology for achieving this by analysing match-ups between sensors in the series and applicable sensors with modern, well-calibrated reference sensors, fitting new calibration parameters for each sensor in the series. Such a problem is not tractable in the most optimal, metrologically rigorous manner by existing solvers, due to the possibly complex error and geophysical correlation structures and high data volume (potentially >10 8 match-ups). Discussed are a palette of novel optimisation algorithms developed to overcome this, which investigate alternative approaches to handling the full problem. Preliminary results are shown for one these approaches, Fast EIV (Errors in Variables), for the recalibration of the AVHRR sensor series.
Samuel E. Hunt; Ralf Quast; Peter M. Harris; Jonathan P.D. Mittaz; Emma R. Woolliams; Ralf Giering; Arta Dilo; Christopher J. Merchant. A Metrological Approach to Producing Harmonised Fundamental Climate Data Records from Long-Term Sensor Series Data. IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium 2018, 3397 -3400.
AMA StyleSamuel E. Hunt, Ralf Quast, Peter M. Harris, Jonathan P.D. Mittaz, Emma R. Woolliams, Ralf Giering, Arta Dilo, Christopher J. Merchant. A Metrological Approach to Producing Harmonised Fundamental Climate Data Records from Long-Term Sensor Series Data. IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium. 2018; ():3397-3400.
Chicago/Turabian StyleSamuel E. Hunt; Ralf Quast; Peter M. Harris; Jonathan P.D. Mittaz; Emma R. Woolliams; Ralf Giering; Arta Dilo; Christopher J. Merchant. 2018. "A Metrological Approach to Producing Harmonised Fundamental Climate Data Records from Long-Term Sensor Series Data." IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium , no. : 3397-3400.
Quantifying long-term environmental variability, including climatic trends, requires decadal-scale time series of observations. The reliability of such trend analysis depends on the long-term stability of the data record, and understanding the sources of uncertainty in historic, current and future sensors. We give a brief overview on how metrological techniques can be applied to historical satellite data sets. In particular we discuss the implications of error correlation at different spatial and temporal scales and the forms of such correlation and consider how uncertainty is propagated with partial correlation. We give a form of the Law of Propagation of Uncertainties that considers the propagation of uncertainties associated with common errors to give the covariance associated with Earth observations in different spectral channels.
Emma R Woolliams; Jonathan Pd Mittaz; Christopher J Merchant; Samuel E Hunt; Peter M Harris. Applying Metrological Techniques to Satellite Fundamental Climate Data Records. Journal of Physics: Conference Series 2018, 972, 012003 .
AMA StyleEmma R Woolliams, Jonathan Pd Mittaz, Christopher J Merchant, Samuel E Hunt, Peter M Harris. Applying Metrological Techniques to Satellite Fundamental Climate Data Records. Journal of Physics: Conference Series. 2018; 972 (1):012003.
Chicago/Turabian StyleEmma R Woolliams; Jonathan Pd Mittaz; Christopher J Merchant; Samuel E Hunt; Peter M Harris. 2018. "Applying Metrological Techniques to Satellite Fundamental Climate Data Records." Journal of Physics: Conference Series 972, no. 1: 012003.
Andrew C. Banks; Samuel E. Hunt; Javier Gorroño; Tracy Scanlon; Emma R. Woolliams; Nigel P. Fox. A comparison of validation and vicarious calibration of high and medium resolution satellite-borne sensors using RadCalNet. Sensors, Systems, and Next-Generation Satellites XXI 2017, 44 .
AMA StyleAndrew C. Banks, Samuel E. Hunt, Javier Gorroño, Tracy Scanlon, Emma R. Woolliams, Nigel P. Fox. A comparison of validation and vicarious calibration of high and medium resolution satellite-borne sensors using RadCalNet. Sensors, Systems, and Next-Generation Satellites XXI. 2017; ():44.
Chicago/Turabian StyleAndrew C. Banks; Samuel E. Hunt; Javier Gorroño; Tracy Scanlon; Emma R. Woolliams; Nigel P. Fox. 2017. "A comparison of validation and vicarious calibration of high and medium resolution satellite-borne sensors using RadCalNet." Sensors, Systems, and Next-Generation Satellites XXI , no. : 44.
The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.
E. R. Woolliams; K. Anhalt; M. Ballico; P. Bloembergen; F. Bourson; S. Briaudeau; J. Campos; M. G. Cox; Dolores del Campo; W. Dong; M. R. Dury; V. Gavrilov; I. Grigoryeva; María Luisa Hernanz; F. Jahan; B. Khlevnoy; V. Khromchenko; D. H. Lowe; X. Lu; G. Machin; J. M. Mantilla; M. J. Martin; H. C. McEvoy; B. Rougié; M. Sadli; S. G. R. Salim; Naohiko Sasajima; D. R. Taubert; A. D. W. Todd; R. Van Den Bossche; E. Van Der Ham; T. Wang; A. Whittam; B. Wilthan; D. J. Woods; J. T. Woodward; Yoshiro Yamada; Yu Yamaguchi; H. W. Yoon; Z. Yuan. Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 2016, 374, 20150044 .
AMA StyleE. R. Woolliams, K. Anhalt, M. Ballico, P. Bloembergen, F. Bourson, S. Briaudeau, J. Campos, M. G. Cox, Dolores del Campo, W. Dong, M. R. Dury, V. Gavrilov, I. Grigoryeva, María Luisa Hernanz, F. Jahan, B. Khlevnoy, V. Khromchenko, D. H. Lowe, X. Lu, G. Machin, J. M. Mantilla, M. J. Martin, H. C. McEvoy, B. Rougié, M. Sadli, S. G. R. Salim, Naohiko Sasajima, D. R. Taubert, A. D. W. Todd, R. Van Den Bossche, E. Van Der Ham, T. Wang, A. Whittam, B. Wilthan, D. J. Woods, J. T. Woodward, Yoshiro Yamada, Yu Yamaguchi, H. W. Yoon, Z. Yuan. Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 2016; 374 (2064):20150044.
Chicago/Turabian StyleE. R. Woolliams; K. Anhalt; M. Ballico; P. Bloembergen; F. Bourson; S. Briaudeau; J. Campos; M. G. Cox; Dolores del Campo; W. Dong; M. R. Dury; V. Gavrilov; I. Grigoryeva; María Luisa Hernanz; F. Jahan; B. Khlevnoy; V. Khromchenko; D. H. Lowe; X. Lu; G. Machin; J. M. Mantilla; M. J. Martin; H. C. McEvoy; B. Rougié; M. Sadli; S. G. R. Salim; Naohiko Sasajima; D. R. Taubert; A. D. W. Todd; R. Van Den Bossche; E. Van Der Ham; T. Wang; A. Whittam; B. Wilthan; D. J. Woods; J. T. Woodward; Yoshiro Yamada; Yu Yamaguchi; H. W. Yoon; Z. Yuan. 2016. "Thermodynamic temperature assignment to the point of inflection of the melting curve of high-temperature fixed points." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2064: 20150044.