Metrology for earth observation and climate 2: 1/06/2014 to 31/07/2017

Remote sensing of the Earth from space provides the data needed to underpin climate change research and its impacts, (e.g. flooding and agriculture), and can quantify environmental issues such as pollution and coastal erosion. Satellite data can also be used to detect subtle changes in Essential Climate Variables. For example, changes in total solar energy and sea surface temperatures of a few tenths of a percent per decade can be detected in this way. However, the performance of satellite instruments is prone to degradation post-launch and from exposure to the harsh environmental conditions above the atmosphere. So, to guarantee data reliability, these instruments generally need re-calibrating and validating in orbit.  

Calibration against, and traceability to, the international system of units (SI) would guarantee long-term confidence, accuracy and reliability of such the data and ensure consistency between instruments. 

These basic data products are additionally processed through complex non-linear retrieval algorithms to obtain the geophysical and biophysical parameters (e.g. the ECVs) that are important for understanding the state of the planet. End to end assessment of uncertainty and traceability was recognised as challenge worth addressing by the climate community with support from metrology experts. 

Achievements

The Project:

  • Improved the performance of a lab-based cryogenic solar radiometer (CSAR), by reducing window-induced noise by a factor of 100 and successfully demonstrated in-the-field performance against reference radiometers at the World Radiation Centre (Davos)
  • Developed portable, SI-traceable reference standards for radiometer calibration, for use with ground-based instruments and the aircraft-based GLORIA spectroradiometer
  • Established two new well-characterised desert test-sites, for confirming satellite-based radiance instrumentation performance in support of the RadCalNet network
  • Characterised Wytham Woods (UK) as a reference site for leaf area index measurements, that was recognised as a Committee on Earth Observation Satellites (CEOS) super-site for land product validation
  • Developed traceable protocols for greater accuracy in measuring ocean surface radiance, enabling calibration of satellite-based instruments for ocean colour, a key Essential Climate Variable

Impacts

The project assisted the Committee on Earth Observation Satellites (CEOS) in developing its RadCalNet network, that provides satellite operators with SI-traceable Top-of-Atmosphere (TOA) spectrally-resolved reflectances to aid post-launch radiometric calibration and validation of optical imaging sensor data. The consortium worked with ESA/CNES to establish a new test site for the calibration of satellite radiance and reflectance in Namibia and as part of a European contribution to RadCalNet. 

For the Network for the Detection of Mesopause Change (NDMC) — a global program that promotes international cooperation among research groups investigating the mesopause region (80-100 km) with the goal of early identification of changing climate signals — the project contributed its first station to be fully traceably calibrated. This removed ambiguity and allowed the density of hydorxyl radicals to be determined. This provided a pre-cursor for further improvements in the follow-on EMPIR project 16ENV03 MetEOC-3.

The European reference body, BOUSSOLE, one of two in the world used for the system vicarious calibration of ocean colour monitoring satellites, also had its uncertainty fully evaluated. 

The Quality Assurance analysis undertaken in the project, and the promotion of SI-traceability, led to the inclusion of this traceability requirement and associated uncertainty analysis in ESA and EU ‘Invitations to tender’. 

Retrieval algorithms of atmospheric composition parameters from GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) were significantly improved, including end to end uncertainty analysis. GLORIA is a German airborne imaging FTS (Fourier Transform Spectrometer) which is capable of operating on various airborne platforms.

This network is building partnerships between measurement specialists and the climate & ocean observation communities to enhance metrological best practice across Europe and beyond.

Furthermore, the consortium participated in other Earth observation projects, including the EU Quality Assurance for Essential Climate Variables (QA4ECV), Fidelity and uncertainty in climate records from Earth and Observations (FIDUCEO), and ESA’s FRM4STS. 

Longer term, the strong partnership of NMIs, DIs and key stakeholders, established by the project formed the basis of what became the European Metrology Network (EMN) for Climate and Ocean Observation.

Partners

  • NPL, United Kingdom
  • CMI, Czech Republic
  • CNAM, France
  • CSIC, Spain
  • INRIM, Italy
  • VTT, Finland
  • PTB, Germany
  • SFI Davos, Switzerland
  • VSL, Netherlands
  • BUW, Germany
  • DLR, Germany
  • NLS, Finland
  • FZ-Jeulich, Germany
  • STFC, United Kingdom
  • UCL, United Kingdom
  • JRC, European Commission

Publications

  • [1]. Finsterle, W., Koller, S., Beck, I., Spescha, M., Suter, M., Walter, B., Schmutz, W. The new TSI radiometer CLARA. Proceedings of SPIE 9264.
  • [2]. Taralli, E, Filippo, R, Brida, G, Rajteri, M, Hall, S.R.G., Bialek, A, Greenwell, C, Fox, N. LED-based field radiometer for sensor web in-situ measurements. Metrology for Aerospace (MetroAeroSpace), 2015 IEEE.
  • [3]. Claire Greenwell ; Agnieszka Bialek ; Amelia Marks ; Emma Woolliams ; Béatrice Berthelot, et al. “Preparation of a new autonomous instrumented radiometric calibration site: Gobabeb, Namib Desert”, Proc. SPIE 9639, Sensors, Systems, and Next-Generation Satellites XIX, 963919 (October 12, 2015).
  • [4]. Gorrono, J.; Fox, N.; Bialek, A.; Green, P.; Scanlon, T., “Truths cross-calibration uncertainty tool,” in Geoscience and Remote Sensing Symposium (IGARSS), 2015 IEEE International , vol., no., pp.2135-
  • [5]. E. Honkavaara, T. Hakala, O. Nevalainen, N. Viljanen, T. Rosnell, E. Khoramshahi, R. Näsi, R. Oliveira, A. Tommaselli. The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLI-B7, 2016 XXIII ISPRS Congress, 12–19 July 2016, Prague, Czech Republic
  • [6]. P. Jaanson, T. Pulli, F. Manoocheri, and E. Ikonen. A reference material with close to Lambertian reflectance and fluorescence emission profiles. Metrologia 53, 1330–1338 (2016).
  • [7]. Hueni, A., Damm, A., Kneubuehler, M., Schläpfer, D. and Schaepman, M. Field and Airborne Spectroscopy Cross-Validation Some Considerations. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing PP(99): 1 19.
  • [8]. Hueni, A. and Bialek, A. “Cause, Effect and Correction of Field Spectroradiometer Inter-channel Radiometric Steps” 2017, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. Volume: 10, Issue: 4, April 2017.
  • [9]. Bialek, C. Greenwell, M. Lamare, A. Meygret, S. Marcq, S. Lacherade, E. Woolliams, B. Berthelot, M. Bouvet, M. King, C. Underwood, N. Fox. New radiometric calibration site located at Gobabeb, Namib desert. IGARSS 2016 2016 IEEE International Geoscience and Remote Sensing Symposium
  • [10]. Benjamin Walter, Rainer Winkler, Florian Graber, Wolfgang Finsterle, Nigel Fox, Vivian Li, and Werner Schmutz “Direct Solar Irradiance Measurements with a Cryogenic Solar Absolute Radiometer” AIP Conference Proceedings 1810, 080007 (2017).
  • [11]. Benjamin Walter, Rainer Winkler, Florian Graber, Wolfgang Finsterle, Nigel Fox, Vivian Li, and Werner Schmutz “Direct Solar Irradiance Measurements with a Cryogenic Solar Absolute Radiometer” AIP Conference Proceedings 1810, 080007 (2017).
  • [12]. Javier Gorroño, Agnieszka Bialek, Paul D. Green, Peter Harris, Tracy Scanlon, Nigel P. Fox & Craig Underwood. Non-normal distribution of the top-of-atmosphere satellite optical measurements over calibration sites. International Journal of Remote Sensing. ISSN: 0143-1161 (Print) 1366-5901 (Online).
  • [13]. Origo, N., Calders, K., Nightingale, J. and Disney, M. (2017) Influence of levelling technique on the retrieval of canopy structural parameters from digital hemispherical photography. Agricultural and Forest Meteorology 237-238, 143-149.
  • [14]. Calders, K., Disney, M., Armston, J., Burt, A., Brede, B., Origo, N., Muir, J. and Nightingale, J. (2017) Evaluation of the Range Accuracy and the Radiometric Calibration of Multiple Terrestrial Laser Scanning Instruments for Data Interoperability. IEEE Transactions on Geoscience and Remote Sensing 55, 2716 2724.
  • [15]. O. Nevalainen ; E. Honkavaara ; T. Hakala ; Sanna Kaasalainen ; N. Viljanen ; T. Rosnell ; E. Khoramshahi ; R. Näsi. Close-range environmental remote sensing with 3D hyperspectral technologies. Proc. SPIE 10005, Earth Resources and Environmental Remote Sensing/GIS Applications VII, 1000503 (October 18, 2016).
  • [16]. Filippo, R.; Taralli, E.; Rajteri, M. LEDs: Sources and Intrinsically Bandwidth-Limited Detectors. Sensors 2017, 17, 1673.
  • [17]. Priit Jaanson, Agnieszka Bialek, Claire Greenwell, Henrik Mäntynen, Jean-Luc Widlowski, Farshid Manoocheri, Antti Lassila, Nigel Fox, and Erkki Ikonen. Towards SI-traceability of a Monte Carlo radiative transfer model in the visible range. IEEE Transactions on Geoscience and Remote Sensing. Awaiting publication.
  • [18]. E. Honkavaara. Radiometric Calibration of Passive Optical Imaging Systems. ASPRS Manual of Remote Sensing, 4th edition. Awaiting publication.
  • [19]. Benjamin Walter, Pierre-Luc Levesque, Greg Kopp, Bo Andersen, Ivo Beck, Wolfgang Finsterle, Manfred Gyo, Karl Heuerman, Silvio Koller, Nathan Mingard, Alberto Remesal Oliva, Daniel Pfiffner, Ricco Soder, Marcel Spescha, Markus Suter and Werner Schmutz. The CLARA/NORSAT-1 solar absolute radiometer: instrument design, characterization and calibration. Metrologia 54 (2017) 674–682.

Funding

This EMRP project was jointly funded by the EMRP participating countries within EURAMET and the European Union