Work Package 1: EO Sensor performance and interoperability
The aim of this work package is to improve satellite EO measurements of the physical quantities that underpin all the ECV climate data records. The results of this work will support satellite instrument builders and calibrators, the space agencies and users of the data. The work will be carried out in conjunction with existing international projects under the auspices of organisations such as CEOS and WMO to create a “system of systems” where data from different satellites can be compared and combined for climate applications over decades. This will fundamentally be a key element to enabling a space-based SI-traceable climate observing system.
This work package will:
- Improve calibration methodologies for pre-flight sensor calibration, and make these suitable for the upcoming climate missions
- Validate radiative transfer codes used to account for the atmosphere in ground reflectance measurements
- Provide rigorous uncertainty and covariance analysis of the ESA next generation satellites
- Develop a metrological software suite to improve sensor interoperability.
The aim of this work package is to provide state-of-the-art metrological support for three different innovative experiments observing the atmosphere, its composition, temperature distribution and radiation budget.
This work package will:
- Enable the calibration of the on-board reference source of ESA’s FORUM mission to achieve the mission goal of measuring Earth’s radiation budget in the complete relevant spectral range up to 100 µm with up-to-now unprecedented uncertainty in that spectral range.
- Develop a lightweight large-aperture on-board reference source for the mid infrared region for deployment on a stratospheric balloon mission providing traceability to the next generation balloon-borne GLORIA instrument, a hyperspectral limb sounder providing high altitude data to study atmospheric chemistry and dynamics.
- Development of new metrological approaches for utilisation of small CubeSat-type satellites equipped with a new type of spectrometer: compact spatial-heterodyne interferometers (SHIs) which observe the temperature distribution in the middle and upper atmosphere. This will enable realisation of their potential of a high optical throughput, ruggedness and optical resolution with low uncertainty.
The aim of this work package is to continue to develop and improve metrologically-robust methods that should be employed to evaluate and validate satellite-derived biophysical variables that will be used to inform progress toward global climate change adaptation and mitigation strategies. The Paris Agreement within the United Nations Framework Convention on Climate Change (UNFCCC), offers a dynamic framework for increasing climate action over time. It addresses greenhouse gas emissions mitigation, adaptation and finance. Each country is required to undertake a comprehensive five-yearly assessment of progress on their climate action – the Global Stocktake – which is an essential part of the Paris Agreement’s mechanism for keeping the 1.5 °C limit and other Paris Agreement goals within reach. Satellite Earth Observation (EO) platforms will provide key datasets for informing the global stocktake and addressing future mitigation and adaptation strategies. However, the EO community continues to face many of the same issues that have afflicted the validation of satellite-derived data products for decades. Chiefly, the disparity between satellite algorithm representation and ground-measured target quantities, in addition to the lack of long-term monitoring sites due to access and costs associated with deployment and maintenance. This means that estimating a meaningful bias between the in situ “validation” measurements and the satellite observations is challenging. Continuing the work that has been conducted within the MetEOC series of projects, characterisation of a suite of reference measurements (of land, ocean and atmosphere variables) with an associated uncertainty that can be used to conduct satellite product validation through conformity testing will be conducted.
This work package will:
- Address satellite‑derived measures of atmospheric GHG concentrations, which are used to derive local fluxes as a measure of anthropogenic and natural GHG sources and sinks.
- Address the measurement of Ocean Colour, which helps detect biological activity in the ocean’s surface layer, a natural carbon sink.
- Address vegetation parameters such as surface reflectance, aboveground biomass (AGB), fraction of absorbed photosynthetically active radiation (fAPAR), leaf area index (LAI) and fluorescence, which all provide critical information on the health and functioning of the terrestrial biosphere, the other major carbon sink.
- Address the assessment of AGB from a newly developed drone based Synthetic Aperture Radar (SAR) system.
The aim of this WP is to develop instruments and procedures to provide traceability to surface-based radiation networks, such as the baseline surface radiation network (BSRN), and the Network for the Detection of Mesospheric Change (NDMC).
This work package will:
- Achieve traceability of the World Infrared Standard Group of pyrgeometers (WISG) by validating the blackbody reference cavity of the Infrared Radiometry Section of the World Radiation Centre by comparison to SI traceable thermal radiometers.
- Development of a new instrument for angular and hyperspectral atmospheric longwave radiation measurements with an angular resolution of 3×10-4 sr and a spectral range from 3 µm to 100 µm, combined with an angular-resolved spectral broadband radiometer as novel reference instrument for atmospheric downwelling longwave irradiance to complement the IRIS and ACP radiometers. The IRCCAM is an existing imager measuring angular resolved sky radiance in the range 8 µm to 14 µm. Due to the spectral inhomogeneity of the downwelling sky radiance in this spectral range the knowledge of its spectral responsivity is necessary to obtain sky radiance measurements traceable to the SI.
- Design and build a novel spectrally uniform pyrgeometer and compare its atmospheric longwave irradiance measurements to the WISG, IRIS, and the new hyperspectral radiometer.
- Set up and characterisation of a new type of reference instrument for the NDMC. The instrument is based on a spatial heterodyne interferometer providing an optical throughput several orders of magnitude higher than the existing reference instruments in this network and overcoming their limitations. This work is a continuation of the work started in MetEOC-3. There it was found that matching the curvature of the wavefront of the radiation of the reference source to the later application is critical and a redesign of source and calibration setup was required. Nevertheless, the work in MetEOC-3 resulted in a prototype reference instrument and prototype calibration source which will both be characterised and established in this project.
- Refinements to the measurements system for window transmittance and effects of diffraction from sky radiance will be evaluated to further optimise the CSAR as a primary SI replacement reference for the WMO WRR.