Space-based measurements of the Earth System, including its atmosphere, oceans, land surface, cryosphere, biosphere, and interior, require extensive prelaunch and post launch calibration and validation activities to ensure scientific accuracy and fitness for purpose throughout the 
lifetime of satellite missions. This requirement stems from the need to demonstrate unambiguously that the space-based measurements, typically based on engineering measurements by the detectors (e.g. photons), are sensitive to and match up with the geophysical and/or biogeochemical quantity of interest at a broad range of measurement locations on Earth. Most geophysical parameters vary in time and space, and the retrieval algorithms used must be accurate under the full range of conditions. Calibration and validation need to be carried out over the lifetime of missions in order to assure that any long-term variation in observation can be definitely be tied to the evolution of the Earth system. Such activities are also critical in ensuring that measurements can be inter-compared and used seamlessly to create long-term multi-instrument//multi-platform data sets, , which enable large-scale international science investigations into topics with high societal or environmental importance such as determining the ice mass balance of Greenland, monitoring the evolution of sea ice and snow cover in the Arctic and improving our knowledge of the terrestrial carbon cycle through multi-sensor forest biomass mapping. . This session seeks presentations on the use of surface-based, airborne, and/or space-based observations to prepare and calibrate/validate space-based satellite missions measuring our Earth system. A particular but not exclusive focus will be on activities carried out jointly by NASA and ESA as part of their Joint Program Planning Group Subgroup on calibration and validation and field activities.

Co-organized by AS5/CR2
Convener: Jack Kaye | Co-convener: Malcolm W. J. Davidson
| Attendance Tue, 05 May, 14:00–15:45 (CEST)

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Chat time: Tuesday, 5 May 2020, 14:00–15:45

D828 |
Arnoud Apituley, Karin Kreher, Ankie Piters, John Sullivan, Michel vanRoozendael, Tim Vlemmix, Mirjam den Hoed, Arnoud Frumau, Bas Henzing, Bart Speet, Jan Vonk, Pepijn Veefkind, Diego Alves, and Alexandre Cacheffo and the TROLIX-Team

For the validation of Sentinel-5p/TROPOMI the TROpomi vaLIdation eXperiment (TROLIX) was held in the Netherlands based at the Cabauw Experimental Site for Atmospheric Research during September 2019. TROLIX consisted of active and passive remote sensing platforms in conjunction with several balloon-borne and surface measurements.

The intensive observations will serve to establish the quality of TROPOMI L2 main data products (UVAI, Aerosol Layer Height, NO2, O3, HCHO, Clouds) under realistic conditions with varying cloud cover and a wide range of atmospheric conditions.

Since TROPOMI is a hyperspectral imager with a very high spatial resolution of 3.6 x 5.6 km2, understanding local effects such as inhomogeneous sources of pollution, sub-pixel clouds and variations in ground albedo is important to interpret TROPOMI results. Therefore, the campaign included sub-pixel resolution local networks of sensors, involving MAXDOAS and Pandora instruments, around Cabauw (rural) and within the city of Rotterdam (urban). Utilising its comprehensive in-situ and remote sensing observation program in and around the 213 m meteorological tower, Cabauw was the main site of the campaign with focus on vertical profiling using lidar instruments for aerosols, clouds, water vapor, tropospheric and stratospheric ozone, as well as balloon-borne sensors for NO2 and ozone.

The data set collected can be directly compared to the TROPOMI L2 data products, while measurements of parameters related to a-priori data and auxiliary parameters that infuence the quality of the L2 products such as aerosol and cloud profiles and in-situ aerosol and atmospheric chemistry were also collected.

This paper gives an overview of the campaign, and an overview of the participating main and ancillary instrumentation and preliminary results.

Future activities include the deployment in 2020 of an airborne hyperspectral imager.

How to cite: Apituley, A., Kreher, K., Piters, A., Sullivan, J., vanRoozendael, M., Vlemmix, T., den Hoed, M., Frumau, A., Henzing, B., Speet, B., Vonk, J., Veefkind, P., Alves, D., and Cacheffo, A. and the TROLIX-Team: Overview of the 2019 Sentinel-5p TROpomi vaLIdation eXperiment (TROLIX), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10539, https://doi.org/10.5194/egusphere-egu2020-10539, 2020.

D829 |
Thomas Neumann, Kelly Brunt, Lori Marguder, and Nathan Kurtz

After launching on 15 September 2018, the Ice, Cloud, and Land Elevation Satellite – 2 (ICESat-2) Mission began collecting data on 14 October 2018.  The mission uses green laser light emitted by the Advanced Topographic Laser Altimetry System (ATLAS) to detect individual photons that are reflected by the Earth’s surface and returned to ATLAS.  These photons, when combined with information on the pointing direction, and position of the observatory in space, provide a geolocation and elevation for every measurement that spans the globe from 88 degrees north latitude to 88 degrees south.  The Global Geolocated Photon data product provides a latitude, longitude, elevation, and measurement time for each photon event telemetered to Earth for each of the instrument’s six beams. This product also delineates between high, medium, and low signal confidence levels and those measurements associated with background noise. The higher level, along-track products each use different strategies for photon aggregation to optimize the precision and accuracy of the surface retrievals over specific surface types. These types include land ice, sea ice, vegetation/land, ocean, and inland water. There is a separate channel dedicated to atmospheric returns to measure cloud and aerosols over a vertical window of 15 km. Calibration efforts utilized well designed on-orbit maneuvers to identify both pointing and range biases attributed to orbital variations on the satellite. Once corrected, the science-quality data products were released to the public in May 2019.


In this presentation, we will present our ongoing work to evaluate and validate the geolocation and elevation accuracy and precision of measurements provided by the ICESat-2 mission.  The approaches are diverse in both location and methodology to ensure that we have a comprehensive assessment of the ATLAS performance variations throughout the orbital cycles. These strategies include comparisons with ground-based and airborne elevation measurements over the ice sheets, detailed analysis of returns from well-surveyed corner cube retro-reflectors, comparison of sea ice freeboard measured by airborne lidars, evaluation of global-scale ocean elevation through comparison with radar altimeters, and comparison of vegetation canopy height metrics measured by airborne lidar.  Our work to date demonstrates that individual photon elevations are accurate to approximately 30 cm vertically, and 6 m radially.  Aggregating many photons together reduces the elevation uncertainty to less than 5 cm for relatively flat and smooth ice sheet interiors.

How to cite: Neumann, T., Brunt, K., Marguder, L., and Kurtz, N.: Validation activities for the Ice, Cloud, and Land Elevation Satellite - 2 (ICESat-2) Mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20671, https://doi.org/10.5194/egusphere-egu2020-20671, 2020.

D830 |
Steven C. Reising, Wesley Berg, Shannon T. Brown, Todd C. Gaier, Christian D. Kummerow, Venkatchalam Chandrasekar, Sharmila Padmanabhan, Boon H. Lim, Richard Schulte, Yuriy Goncharenko, and Chandrasekar Radhakrishnan

Passive microwave radiometer systems have provided both temperature and water vapor sounding of the Earth’s atmosphere for several decades, including MSU, AMSU, MHS, ATMS, etc.  Due to its ability to penetrate clouds, dust, and aerosols, among global datasets, microwave atmospheric sounding provides the most valuable quantitative contribution to weather prediction.  Long-term, well-calibrated sounding records can be indispensable for climate measurement and model initialization/validation.  Hence, passive microwave sounders are deployed on large, operational satellites and operated by NOAA, EUMETSAT and other similar national/international organizations.

In the past five years or so, advances in CubeSats and other small satellites have enabled highly affordable space technology, providing access to space to private industries, universities and smaller nations.  This provides a valuable opportunity for organizations such as NOAA and EUMETSAT to explore the added value of acquiring data from passive microwave sounders on small, low-cost spacecraft for relatively small investments, both for sensor and spacecraft acquisition and launch.  This provides the potential for deployment of constellations of low-Earth orbiting microwave sounders to provide much more frequent revisit times than are currently available.

For passive microwave sounding data to be valuable for weather prediction and climate monitoring, each sensor needs to be calibrated and validated to acceptable accuracy and stability.  In this context, the first CubeSat-based multi-frequency microwave sounder to provide global data over a substantial period is the Temporal Experiment for Storms and Tropical Systems Demonstration (TEMPEST-D) mission.  This mission was designed to demonstrate on-orbit capabilities of a new, five-frequency millimeter-wave radiometer to enable a complete TEMPEST mission using a closely-spaced train of eight 6U CubeSats with identical low-mass, low-power millimeter-wave sensors to sample rapid changes in convection and surrounding water vapor every 3-4 minutes for up to 30 minutes.  TEMPEST millimeter-wave radiometers scan across track and observe at five frequencies from 87 to 181 GHz, with spatial resolution ranging from 25 km to 13 km, respectively.

The TEMPEST-D satellite was launched on May 21, 2018 from NASA Wallops to the ISS and was successfully deployed on July 13, 2018, into a 400-km orbit at 51.6° inclination.  The TEMPEST-D sensor has been operating nearly continuously since its first light data on September 5, 2018.  With more than 16 months of operations to date, TEMPEST-D met all of its Level-1 mission objectives within the first 90 days of operations and has successfully achieved TRL 9 for both instrument and spacecraft systems. 

Validation of observed TEMPEST-D brightness temperatures is performed by comparing to coincident observations by well-calibrated on-orbit instruments, including GPM/GMI and MHS on NOAA-19, MetOp-A and MetOp-B satellites. Absolute calibration accuracy is within 0.9 K for all except the 164 GHz channel, well within the required 4 K for all channels. Calibration stability is within 0.5 K for all channels, also well within the 2 K requirement. TEMPEST-D has NEDTs similar to or lower than MHS. Therefore, although the TEMPEST-D radiometer is substantially smaller, lower power, and lower cost than operational radiometers, it has comparable performance, i.e. instrument noise, calibration accuracy and calibration stability.

How to cite: Reising, S. C., Berg, W., Brown, S. T., Gaier, T. C., Kummerow, C. D., Chandrasekar, V., Padmanabhan, S., Lim, B. H., Schulte, R., Goncharenko, Y., and Radhakrishnan, C.: Calibration and Validation of Microwave Atmospheric Sounders on CubeSats and Small Satellites for Applications in Weather Prediction and Climate Monitoring, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21378, https://doi.org/10.5194/egusphere-egu2020-21378, 2020.

D831 |
Gregory Porter, Richard Delf, Albin Gasiewski, Michael Hurowitz, David Gallaher, Brian Sanders, William Hosack, David Kraft, Roger Carter, Kun Zhang, and Geoffrey Sasaki

The recent successful launch of the Orbital Micro Systems GEMS-1 IOD (Global Environmental Monitoring System In-orbit Demonstrator) satellite carrying the University of Colorado’s MiniRad 118-GHz imager/sounder instrument provides the basis for a new means of observing atmospheric precipitation, temperature, and related state variables. GEMS-1 supports an 8-channel passive microwave radiometer operating at the 118.7503 GHz oxygen resonance with cross-track scanning imaging system providing cross- and along track Nyquist sampling at 17 km 3dB spatial resolution. It is precisely calibrated using cold space views along with and an on board reference, yielding the first low-cost commercial weather satellite imagery. GEMS is the first of a constellation of approximately 50 such satellites of progressively improving resolution and spectral coverage that will collectively provide Nyquist time-sampling of precipitation and related weather variables on a global basis, and using microwave frequencies will provide such information probing through most cloud cover. Presented will be first light imagery and on-orbit performance data from the GEMS-1 mission, including validation data on the satellite brightness temperatures. Products will include calibrated multispectral imagery, temperature profiles, retrieved rain rate, and precipitation cell top altitude. The expansion of the GEMS-1 mission to the full GEMS constellation will be outlined.

How to cite: Porter, G., Delf, R., Gasiewski, A., Hurowitz, M., Gallaher, D., Sanders, B., Hosack, W., Kraft, D., Carter, R., Zhang, K., and Sasaki, G.: The Global Environmental Monitoring Systems (GEMS) Constellation of Passive Microwave Satellite, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20026, https://doi.org/10.5194/egusphere-egu2020-20026, 2020.

D832 |
Niall Origo, Joanne Nightingale, Kim Calders, and Mathias Disney

fAPAR is a radiometric quantity describing the fraction of photosynthetically active radiation (PAR) absorbed by a plant canopy. It is an important component of carbon cycle and energy balance models and has been named as one of the 50 Global Climate Observing System (GCOS) essential climate variables (ECVs). Space agencies such as the ESA and NASA produce satellite fAPAR products in order to address the need for spatially explicit global data to address environmental and climate change issues. Given the derived nature of satellite fAPAR products it is essential to independently verify the results they produce. In order to do this, validation sites (or networks of sites) are needed that directly correspond to the measurands. Further to this, in order to understand divergences between product and validation data, uncertainty information should be provided with all measurement results.

The canopy radiative transfer models which are used in satellite-derived fAPAR products implement simplistic assumptions about the state of the plant canopy and illumination conditions in order to retrieve an fAPAR estimate in a computationally feasible time. This contribution assesses the impact of the assumptions made by the Sentinel-2 SNAP-derived fAPAR and includes it in a validation of the product over a field site (Wytham Woods, UK), which also has concurrent fAPAR measurements. This is achieved using a 3D model of Wytham Woods which is used to simulate biases associated with specific assumption types. These are used to convert the in situ measurements to the same quantity assumed by the satellite product. The measurement network which provides the fAPAR data is also traceable to SI through sensor calibrations and has associated uncertainty estimates. To our knowledge, these latter points have not been implemented in the biophysical product validation literature, which may explain some of the large discrepancies seen between validation and satellite-derived fAPAR data.

The ultimate aim of this work is to demonstrate a validation framework for derived biophysical variables such as fAPAR which properly considers the quantity estimated by the satellite and that measured by the in situ sensors, whilst providing metrologically derived uncertainties on the in situ data. This will help to properly inform users as to the quality of the data and determine whether the GCOS requirements set for fAPAR are attainable, ultimately improving carbon cycle and energy balance estimates.

How to cite: Origo, N., Nightingale, J., Calders, K., and Disney, M.: 3D forest model-assisted validation of the Sentinel-2 SNAP fAPAR product, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7124, https://doi.org/10.5194/egusphere-egu2020-7124, 2020.

D833 |
Hartmut Aumann, Evan Manning, Chris Wilson, and Jorge Vasquez

The Sea Surface Temperature (SST) is a key component of climate research and daily globally gridded SST products are a key input to this effort.  Here we evaluate the NOAA RTGSST, which goes back to 1996, the Canada Meteorological Center (CMC) SST, available since 2002, and the OSTIA SST by the UK MetOffice, available since 2012. The calibration of the three products is tied to the moored and floating buoys along the equator, but there are differences in the way all grid points are optimally filled. The 2016 annual mean between 30S and 30N, 299.7K, differed by only 8 mK. However zonal mean differences between the three products north of 30N and south of 30S latitude are  of the order of 150 mK, and of opposite signs. Even more puzzling is that during 2016 the CMC was on average 150 mK colder than the OSTIA at 280K, while being warmer by 150mK at 290K. Differences of this magnitude are of concern when measure warming of the oceans at the rate of 15 mK/year. We use the daily mean and standard deviation and trends of the difference between the SST measured with AIRS (Atmospheric Infrared Sounder) since 2002 and CrIS (Crosstrack Interferometer Sounder) since 2012 to evaluate the three products.         

How to cite: Aumann, H., Manning, E., Wilson, C., and Vasquez, J.: Evaluation of globally gridded SST products from NOAA, CMC and UKMeto using AIRS and CrIS SST measurements., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11996, https://doi.org/10.5194/egusphere-egu2020-11996, 2020.

D834 |
Martin Wooster, James Johnson, Tom Dowling, Mark de Jong, Mark Grosvenor, Mary Langsdale, Simon Hook, Bjorn Eng, William Johnson, Gerardo Rivera, Glynn Hulley, Dirk Schüttemeyer, and Benjamin Koetz

The NASA ESA Temperature Sensing Experiment (NET-Sense) is a NASA and ESA funded campaign in support of the Copernicus Land Surface Temperature Monitoring (LSTM) satellite mission.

The LSTM mission would carry a calibrated, high spatial-temporal resolution thermal infrared imager whose data would be used to provide the land-surface temperature information required for such applications as evapotranspiration estimation at the European field-scale. The LSTM mission responds to priority requirements of the agricultural user community for improving sustainable agricultural productivity in a world of increasing water scarcity and variability.

As part of the effort to LSTM mission development effort, the first non-US flights of NASA JPL’s state-of-the-art Hyperspectral Thermal Emission Spectrometer (HyTES) were conducted on a UK research aircraft in both the UK and Italy in June and July 2019. HyTES is an airborne thermal hyperspectral imager providing extremely high quality and radiometrically precise infrared radiances within 256 spectral channels across the spectral range 7.5 to 12 µm, with the primary aim to map LST and surface spectral emissivity. Flights in Italy were accompanied by the HyPLANT and TASI instruments, operated by FZ-Juelich, Germany installed aboard a second aircraft from CzechGlobe (CZ).

We provide an overview of the NET-Sense campaign, example results from HyTES and comparisons to in situ LST and surface spectral emissivity data collected co-incident with the aircraft overflights using tower-mounted radiometers and portable FTIR spectrometers adapted for the purpose. We explain the integration of NET-Sense into the broader science strategy for the LSTM mission, and highlight planned activities for the coming years, including NET-Sense 2020 European campaign plans.

How to cite: Wooster, M., Johnson, J., Dowling, T., de Jong, M., Grosvenor, M., Langsdale, M., Hook, S., Eng, B., Johnson, W., Rivera, G., Hulley, G., Schüttemeyer, D., and Koetz, B.: Airborne mapping and in situ validation of European land surface temperature using the NASA-JPL HyTES sensor. Results from the 2019 European NET-Sense Campaign in support of the Copernicus High Priority Candidate satellite mission development., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21846, https://doi.org/10.5194/egusphere-egu2020-21846, 2020.

D835 |
Simon Hook, Kerry Cawse-Nicholson, William Johnson, Robert Radocinski, and Gerardo Rivera

The stated goal of NASA’s Earth Science Research Program is to utilize global measurements to understand the Earth system and its interactions as steps toward the prediction of Earth system behavior. NASA has identified the provision of well-calibrated, multiyear and multi-satellite data and product series as a key requirement for meeting this goal. In order to help address this goal we have established two automated validation sites where the necessary measurements for validating mid and thermal infrared data from spaceborne and airborne sensors are made every few minutes on a continuous basis.
The two automated validation sites are located at Lake Tahoe CA/NV and Salton Sea CA. The Lake Tahoe site was established in 1999 and the Salton Sea site was established in 2008. Lake Tahoe is ideally suited for validation of mid and thermal infrared data for several reasons including its size, homogeneity, elevation, accessibility and composition. In order to use Lake Tahoe for validation, 4 buoys have been deployed. Each buoy includes a custom-built highly accurate (50mK) radiometer measuring the surface skin temperature and several bulk temperature probes that trail behind the buoy. Each buoy includes a logging system with dial-up cellular access and two full meteorological station measuring wind speed, wind direction, relative humidity and net radiation. All the measurements are made every few minutes and downloaded hourly via a cellular modem. The buoy measurements are supplemented with a variety of atmospheric measurements made on-shore. The Salton Sea site was established in 2008 to validate high water temperatures, up to 35 C and evaluate the performance of surface temperature retrieval algorithms under wet and dry atmospheres depending on time of year. 
Data from the sites have been used to validate numerous satellite instruments including the Advanced Very High Resolution Radiometer (AVHRR) series, the Along Track Scanning Radiometer (ATSR) series, the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER), the Landsat series, the Moderate Resolution Imaging Spectroradiometer (MODIS) on both the Terra and Aqua platforms, the Visible Infrared Imaging Radiometer Suite (VIIRS) and the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS). In all cases the standard products have been validated including the standard radiance at sensor, radiance at surface, surface temperature and surface emissivity products. We will present results from the validation of the mid and thermal infrared data from several of the aforementioned instruments and cross compare those results.

© 2020 California Institute of Technology. Government sponsorship acknowledged.

How to cite: Hook, S., Cawse-Nicholson, K., Johnson, W., Radocinski, R., and Rivera, G.: Validation of NASA, NOAA AND ESA mid and thermal infrared data and products using the Lake Tahoe and Salton Sea automated validation sites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1683, https://doi.org/10.5194/egusphere-egu2020-1683, 2020.

D836 |
Jeffrey Czapla-Myers and Nikolaus Anderson

The Radiometric Calibration Test Site (RadCaTS) was developed by the University of Arizona to provide satellite operators and the scientific community with daily ground-based data that are appropriate for the radiometric calibration and surface reflectance product validation of Earth-observation sensors. It is located at Railroad Valley, Nevada, USA, which has been used by the University of Arizona since 1996. The primary goal of RadCaTS is to provide data that can be used for the independent, accurate, and timely analysis of both the radiometric calibration and surface reflectance validation of Earth-observation sensors that operate in the solar-reflective region (400 nm to 2500 nm). RadCaTS is currently being used to monitor low-Earth orbit sensors such as Terra and Aqua MODIS, SNPP and NOAA-20 VIIRS, Landsat 8 OLI, Sentinel-2A and -2B MSI, Sentinel-3A and -3B OLCI and SLSTR, as well as geosynchronous sensors such as GOES-16 and ‑17 ABI. RadCaTS is currently one of four automated test sites that make up the CEOS WGCV IVOS Radiometric Calibration Network (RadCalNet), which seeks to harmonize the ground-based calibration and validation measurements from international organizations. This work presents current results from RadCaTS, as well as a comparison with results obtained from the RadCalNet data portal, which became publicly available at no cost to registered users in June 2018.

How to cite: Czapla-Myers, J. and Anderson, N.: Calibration and Validation of Earth-Observing Sensors Using The Radiometric Calibration Test Site (RadCaTS) at Railroad Valley, Nevada, USA, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20557, https://doi.org/10.5194/egusphere-egu2020-20557, 2020.

D837 |
Rui Song and Jan-Peter Muller

Surface albedo is a fundamental radiative parameter which controls the Earth’s energy budget by determining the amount of solar radiation which is either absorbed by the surface or reflected back to atmosphere. Satellite observations have long been used to capture the temporal and spatial variations of surface albedo because of their repeated global coverage. In this work, a new method of upscaling surface albedo from ground level footprints of a few tens of metres to coarse satellite scales (≈1km) is reported [1]. Tower-mounted albedometer measurements are upscaled and used to validate global space-based albedo products, including Copernicus Global Land Service (CGLS) 1km albedo data (from Proba-V and previously form VEGETATION-2), MODerate resolution Imaging Spectroradiometer (MODIS) 500m albedo data, and Multi-angle Imaging SpectroRadiometer (MISR) 1.1km albedo data. MODIS albedo retrievals show the closest agreement with tower measurements, followed by the MISR retrievals, and then followed by the CGLS retrievals. The upscaling method uses high-resolution surface reflectance retrievals (from Landsat-8, Sentinel-2) to fill the spatial gaps between the albedometer’s field-of-view (FoV) and coarse satellite scales. High-resolution surface albedo products are generated by combining high-resolution surface reflectance data and MODIS bi-directional reflectance distribution function (BRDF) climatology data. This upscaling framework also uses a novel Sensor Invariant Atmospheric Correction (SIAC) method [2] to improve the accuracy of upscaled tower albedo values. Total uncertainties of upscaled albedo products are estimated by considering uncertainties from both the tower albedometer raw measurements and SIAC atmospheric corrections. This surface albedo upscaling method can be used over both heterogenous and homogenous land surfaces, and has been examined at the SURFRAD, BSRN and FLUXNET tower sites.

Keywords: surface albedo, upscale, CGLS, MODIS, MISR, SIAC

[1] Song, R.; Muller, J.-P.; Kharbouche, S.; Woodgate, W. Intercomparison of Surface Albedo Retrievals from MISR, MODIS, CGLS Using Tower and Upscaled Tower Measurements. Remote Sens. 2019, 11, 644, doi:10.3390/rs11060644.

[2] Yin, F., Lewis, P. E., Gomez-Dans, J., & Wu, Q. A sensor-invariant atmospheric correction method: application to Sentinel-2/MSI and Landsat 8/OLI. EarthArXiv 2019, https://doi.org/10.31223/osf.io/ps957.

How to cite: Song, R. and Muller, J.-P.: Operational Validation of Space-based Albedo Products from Upscaled Tower-based Albedometer Measurements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2731, https://doi.org/10.5194/egusphere-egu2020-2731, 2020.

D838 |
Alexander Cede, Martin Tiefengraber, Angelika Dehn, Barry Lefer, Jonas von Bismarck, Stefano Casadio, Nader Abuhassan, Robert Swap, and Luke Valin

The Pandonia Global Network (PGN) is a worldwide operating network of passive remote sensing spectrometer systems named “Pandora”. PGN is measuring atmospheric trace gases at high temporal resolution with the purpose of air quality monitoring and satellite validation. PGN is an activity carried out jointly by NASA, through the Pandora project at Goddard Space Flight Center, and ESA, through the Austrian contractor LuftBlick, as part of their Joint Program Planning Group Subgroup on calibration and validation and field activities. Many of the more than 50 actual PGN instruments are directly owned by NASA or ESA, another part belongs to other collaborating governmental and academic institutions. A major objective of the PGN is to support the validation and verification of more than a dozen low-earth orbit and geostationary orbit based UV-visible sensors, most notably Sentinel 5P, TEMPO, GEMS and Sentinel 4. PGN instruments are homogeneously calibrated and their data are centrally processed in real-time. Starting in June 2019, the PGN team has made more and more network locations “official PGN sites”, which means all required technical and logistical steps for this purpose have been performed. At the end of 2019 there are 18 such official network sites, where quality assured data are uploaded daily to EVDC (ESA Atmospheric Validation Data Centre), where they are used for operational validation of Sentinel 5P retrievals (see e.g. http://mpc-vdaf-server.tropomi.eu/no2/no2-offl-pandora). The current official PGN data products are total vertical column amounts of NO2 and O3 from direct sun observations. Research data products include total vertical columns amounts of SO2 and HCHO from direct sun observations as well as surface concentrations, tropospheric columns amounts, and vertical profiles for NO2 and HCHO from sky observations. These named research products are planned to become official over the course of the year 2020.

How to cite: Cede, A., Tiefengraber, M., Dehn, A., Lefer, B., von Bismarck, J., Casadio, S., Abuhassan, N., Swap, R., and Valin, L.: Operational satellite validation with data from the Pandonia Global Network (PGN), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13850, https://doi.org/10.5194/egusphere-egu2020-13850, 2020.

D839 |
Samuel Hunt, Nigel Fox, Kevin Halsall, Andrea Melchiorre, Sébastien Saunier, Alessandro Piro, Davide Giudici, Clément Albinet, Valentina Boccia, and Philippe Goryl

In recent years, the increasing range of applications of Earth Observation data products and availability of low-cost satellites has resulted in an increasing number of commercial satellite systems. These services may provide complementary capabilities to those of Space Agencies.  Adoption of these data products for many applications requires that they meet an assured level of quality that is fit for the given purpose.  For the most efficient exploitation of EO data,  therefore,  assessment of data quality, calibration and validation are indispensable tasks,  forming  the basis for reliable scientific conclusions.  


In this context, the European Space  Agency has established the Earthnet  Data Assessment Pilot  (EDAP) project, which aims to enable maximum exploitation of growing data availability by performing early data assessment for various missions that fall into one of the following instrument domains number of  missions, in the Optical, SAR and atmospheric  domains. These assessments are intended to evaluate and report the quality of a satellite mission with respect to what is “fit for purpose” within the context of the its stated performance and application. This activity compliments similar activities from other international partners, including NASA. 


Such quality information is often  communicated to users  in an ill-defined or incomplete manner.  We show the development of a generic satellite mission quality assessment framework, developed within EDAP, which is designed  provide a  thorough  review  of  all important  aspects of  mission quality. The assessment results are  conveye d ata top  level  to the user  as a quality assessment matrix diagram. The framework  itself  is based on  the principles of CEOS QA4EO (Quality Assurance for Earth Observation)  and  builds  on the experience  of  several  European projects that worked towards  practically  implementing them. 


In a wider context,  such a  framework has  potential for  more general use  in both institutional and commercial Earth Observation  –  helping  mission providers  to understand  the  information their  users  need and  empowering  users  to make informed decisions about which data is fit for their purpose.  As such, there is potential for international collaboration, between space agencies, to synergise quality assessment approaches and to work towards the development of a common standard.

How to cite: Hunt, S., Fox, N., Halsall, K., Melchiorre, A., Saunier, S., Piro, A., Giudici, D., Albinet, C., Boccia, V., and Goryl, P.: The Earthnet Data Assessment Pilot Project: Paving the Way for New Space Players, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22245, https://doi.org/10.5194/egusphere-egu2020-22245, 2020.

D840 |
Clark Weaver, Gordon Labow, Dong Wu, Pawan K. Bhartia, and David Haffner

A suite of NASA/NOAA UV (340nm) sensing satellite instruments, starting with Nimbus-7 SBUV in 1980, provides a global long-term record of cloud trends and cloud response from ENSO events. We present new method to inter-calibrate the radiances of all the SBUV instruments and the Suomi NPP OMPS mapper over both the East Antarctic Plateau and Greenland ice sheets during summer. First, the strong solar zenith angle dependence from the intensities are removed using an empirical approach rather than a radiative transfer model. Then small multiplicative adjustments are made to these solar zenith angle normalized intensities in order to minimize differences when two or more instruments temporally overlap. While the calibrated intensities show a negligible long-term trend over Antarctica, and a statistically insignificant UV albedo trend of -0.05 % per decade over the interior of Greenland, there are small episodic reductions in intensities which are often seen by multiple instruments. Three of these darkening events are explained by boreal forest fires using trajectory modeling analysis. Other events are caused by surface melting or volcanoes. We estimate a 2-sigma uncertainty of 0.35% for the calibrated radiances. Finally, we connect the estimated radiance uncertainties, derived from our calibration approach, to the tropical and midlatitude UV cloud albedo trends.

How to cite: Weaver, C., Labow, G., Wu, D., Bhartia, P. K., and Haffner, D.: Inter-Calibration of nine UV sensing instruments over Antarctica and Greenland since 1980: impact on global UV cloud albedo trends, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10856, https://doi.org/10.5194/egusphere-egu2020-10856, 2020.

D841 |
Kory Priestley, Mohan Shankar, and Susan Thomas

NASA’s Earth Radiation Budget Science Team, ERB-ST, (Previously known as the CERES Science Team) is a multi-disciplinary team led out of NASA’s Langley Research Center which has the responsibility for governance of the nation’s multi-decadal Earth Radiation Budget Climate Data Record, ERB CDR.  The Science Data Processing System which produces the ERB-CDR is highly complex, producing Level one through Level 4 products.  The system ingests data from 15 different instruments on 9 different spacecraft (5 GEO and 4 LEO) as well as other ancillary information, producing 25 different products with consistent TOA, Surface, and atmospheric radiative fluxes, cloud and aerosol properties on multiple spatial and temporal scales.  Spatial scales vary from instantaneous/pixel (25 km), 1-deg grid, zonal, regional and global means while temporal scales vary across instantaneous, hourly, 3 hourly to monthly scales.  Accuracy and precision values vary across the various spatial and temporal scales, with the long-term goal of measuring decadal trends of better than 0.3 W/m^2 per decade.


Instrument calibration and precision, as measured through the post-launch protocols, is one of many considerations that drive the decision to reprocess, others include, but are not limited to validation and instantiation of new algorithms across all levels of products, outside teams reprocessing the products we ingest, the launch of new instrumentation to replace operational weather imagers on Geo satellites, updates to processing hardware, and of course resource availability.  These all need to be managed/considered in order to provide the global community products of sufficient accuracy and precision on a time-scale which allows continued advancement and discovery of key scientific questions such that policy makers may make informed decisions.


This presentation will highlight the processes and protocols the Earth Radiation Budget Science Team utilizes to guide reprocessing decisions, identifying lessons learned and best practices.

How to cite: Priestley, K., Shankar, M., and Thomas, S.: Generation of a multi-decadal Earth Radiation Budget Thematic Climate Data Record : Balancing accuracy, precision, and availability to meet the needs of the community, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22221, https://doi.org/10.5194/egusphere-egu2020-22221, 2020.

D842 |
Chris Hepplewhite, Larrabee Strow, Howard Motteler, Sergio de Souza-Machad, and Steven Buczkowski

NASA's Atmospheric Infrared Sounder (AIRS) started the continuous measurement of the Earth's upwelling infrared radiation at high spectral resolution in Sept. 2002 in a 13:30 polar orbit.  The AIRS record was supplemented by the CrIS sensor flying on the NASA SNPP platform, also in the 13:30 polar orbit, in 2012.  In 2018 a second CrIS sensor on NOAA's JPSS-1 platform (NOAA-20) began operation, also in the 13:30 orbit.  Two more CrIS sensors are presently being procured for the JPSS-2 and 3 satellites, which will extend this record from 2002 through ~2040.  EUMETSAT's METOP-A/B/C provide very similar hyperspectral observations starting with the IASI sensors in the 09:30 orbit, starting in 2007, which will be continued with METOP-SG for years to come.  

Inter-calibration of all of the operating sensors shows agreement generally to 0.2K or better in brightness temperature.  More importantly, we have shown that the radiometric stability of the AIRS sensors is in the 0.002 K/year range or 0.02K/decade, based on measurements of CO2 and SST trends.   Similar stability is expected for CrIS and IASI.  Community consensus suggests that direct radiance trending, followed by conversion of these trends to geophysical quantities will yield the most accurate climate trends.  

Here we introduce a new satellite hyperspectral infrared radiance product we call the "Climate Hyperspectral InfraRed Product (CHIRP)" that combines AIRS, CrIS, and IASI into a homogeneous Level 1 radiance product with a common spectral response and channel centers for all three satellites.  This grid is equivalent to an interferometer with optical path differences of 0.8/0.6/0.4 cm for the long-wave/mid-wave/short-wave spectral bands.  This corresponds to a virtual instrument with the same spectral resolution of the JPSS-1 CrIS sensor in the long-wave, with 25/50% degradation in spectral resolution in the mid-wave/short-wave.  This choice allows accurate conversion of the long AIRS record to an equivalent interferometer record.  Conversion of IASI to CHIRP is trivial.  Conversion of all sensors to the CHIRP spectra grid permits simple adjustments of inter-satellite radiometric bias differences since all measurements are first converted to a common spectral grid.  Multiple methods (SNOs, statistical inter-comparisons) indicate these adjustments can be made to the 0.03K level or better.   

A sample application of CHIRP to climate trending will be given by showing multi-decade anomalies of temperature, humidity, and ozone profiles retrieved from CHIRP radiance anomalies, a retrieval that requires almost no a-priori information.  This data set should yield definitive measurements of water-vapor feedback and heavily contribute to our understanding of both tropospheric and stratospheric temperature trends.   Initial production of CHIRP radiances that combine AIRS and CrIS are expected to begin in late 2020.  

How to cite: Hepplewhite, C., Strow, L., Motteler, H., de Souza-Machad, S., and Buczkowski, S.: A New Highly Stable Multi-Decade Satellite Climate Data Set Derived from Polar Hyperspectral Infrared Sensors, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3754, https://doi.org/10.5194/egusphere-egu2020-3754, 2020.

D843 |
Yong Zhang, Zhiguo Rong, and Xiaopeng Hao

Meteorological satellites have become an irreplaceable weather and ocean-observing tool in China. These satellites are used to monitor natural disasters and improve the efficiency of many sectors of Chinese national economy. It is impossible to ignore the space-derived data in the fields of meteorology, hydrology, and agriculture, as well as disaster monitoring in China, a large agricultural country. For this reason, China is making a sustained effort to build and enhance its meteorological observing system and application system. The first Chinese polar-orbiting weather satellite was launched in 1988. Since then China has launched 17 meteorological satellites, 8 of which are sun synchronous and 9 of which are geostationary satellites; China will continue its two types of meteorological satellite programs.

In order to achieve the in-orbit absolute radiometric calibration of the operational meteorological satellites’ thermal infrared channels, China radiometric calibration sites (CRCS) established a set of in-orbit field absolute radiometric calibration methods (FCM) for thermal infrared channels (TIR) and the uncertainty of this method was evaluated and analyzed based on TERRA/AQUA MODIS observations. Comparisons between the MODIS at pupil brightness temperatures (BTs) and the simulated BTs at the top of atmosphere using radiative transfer model (RTM) based on field measurements showed that the accuracy of the current in-orbit field absolute radiometric calibration methods was better than 1.00K (@300K, K=1) in thermal infrared channels. Therefore, the current CRCS field calibration method for TIR channels applied to Chinese metrological satellites was with favorable calibration accuracy: for 10.5-11.5µm channel was better than 0.75K (@300K, K=1) and for 11.5-12.5µm channel was better than 0.85K (@300K, K=1).

How to cite: Zhang, Y., Rong, Z., and Hao, X.: Uncertainty Evaluations of the CRCS In-orbit Field Radiometric Calibration Methods for Thermal Infrared Channels of FENGYUN Meteorological Satellites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5563, https://doi.org/10.5194/egusphere-egu2020-5563, 2020.

D844 |
Charles Gatebe, Rajesh Poudyal, and Michael King

The Cloud Absorption Radiometer (CAR) Science Team, and the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) recently released a unique dataset of bidirectional reflectance-distribution function (BRDF) of different surface types including clouds, snow/ice, vegetation, ocean, lakes, desert, city scape, smoke and other mixed surface types. The data were acquired during numerous field campaigns around the world, with measurements spanning 1991 to 2017. This presentation will address several uses of these data including developing new methods that define important surface and atmosphere radiative transfer functions, improve remote sensing retrievals of multiple geophysical parameters such as aerosols, clouds and surface albedo, and support satellite remote sensing activities.  CAR data are archived at GES DISC:  https://disc.gsfc.nasa.gov/datasets?keywords=car.

How to cite: Gatebe, C., Poudyal, R., and King, M.: A Unique Airborne Multi-angular Dataset for Calibration and Validation of Earth Satellite Products, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5818, https://doi.org/10.5194/egusphere-egu2020-5818, 2020.

D845 |
Laura Le Barbier, Mathilde Faillot, Elsa Jacquette, Laurence Buffet, Antoine Penquer, Olivier Vandermarcq, Bernard Tournier, Yannick Kanghah, Denis Jouglet, Anais Vincensini, Silvia Enache, Jean-Christophe Calvel, Fy Andrianony, and Tristan Lalanne

The EUMETSAT Polar System (EPS) programme is composed of three polar orbiting meteorological METOP satellites. The main payload instrument on-board each METOP is an InfraRed Atmospheric Sounding Interferometer (IASI). METOP-A, the first one of this series, was launched in 2006. Then METOP-B and METOP-C were launched successively in 2012 and 2018. IASI instrument products are disseminated to meteorological institutions for numerical weather prediction, to laboratories for atmospheric and climate studies and also to space agencies for expertise and monitoring. Since their beginning of life, IASI on-board METOP-A and METOP-B continue to perform very well and therefore demonstrate IASI instrument great performances stability and its sturdiness over time. Since July 2019, IASI on-board METOP-C is operational. It will ensure the continuity of good calibrated data dissemination to the user community for the next decade.

The purpose of this paper is to present the current performances status of the 3 in-flight IASI instruments, up to the Level 1 data. The objective is to give a feedback on the validation and the monitoring performed on IASI instruments during its life time. Moreover, during the past few years, some operational improvements were applied like the update of the on-board non-linerity correction for the 3 instruments. The impact of this new correction will be presented, also the reprocessing of a huge amount of IASI-A data for climate series.

New improvements will be assessed, like the impact on the spectral calibration monitoring of the new release of the GEISA spectroscopic database and the 4A/OP atlases or improvements of inter-comparison techniques.

How to cite: Le Barbier, L., Faillot, M., Jacquette, E., Buffet, L., Penquer, A., Vandermarcq, O., Tournier, B., Kanghah, Y., Jouglet, D., Vincensini, A., Enache, S., Calvel, J.-C., Andrianony, F., and Lalanne, T.: Monitoring and performances evolutions of the 3 in-flight IASI instruments on-board METOP satellites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7097, https://doi.org/10.5194/egusphere-egu2020-7097, 2020.

D846 |
Natalya Kramarova, Pawan Bhartia, Glen Jaross, and Zhong Chen

The Ozone Mapping and Profiler Suite represents a new generation of the US ozone measuring instruments aimed to monitor the ozone recovery associated to the reduction in levels of man-made ozone depleting substances regulated by the Montreal protocol. The first OMPS was launched on board of the Suomi NPP satellite in October 2011. The Limb Profiler is a part of the OMPS instrumental suite, and it collects solar radiances scattered from the atmospheric limb in the UV and VIS spectral ranges. The next OMPS Limb Profiler is scheduled to launch in 2022 on board of NASA/NOAA JPSS-2 mission. These limb scattering measurements allow to retrieve vertical ozone profiles from the tropopause up to the mesosphere with a high vertical resolution (~2 km). The expected ozone recovery is almost three times slower than the ozone loss observed in 1980s and 1990s. To detect such small trends in ozone concentration, the instrument calibrations should be extremely accurate. Comparisons of ozone retrievals from OMPS LP with the correlative satellite measurements from Aura MLS and ISS SAGE III revealed that OMPS LP retrievals accurately characterize the vertical ozone distribution in different atmospheric regions which are most sensitive to changes in the stratospheric composition and dynamics. Between 18 and 42 km the mean differences between LP and correlative measurements are within ±10%, except for the northern high latitudes where between 20 and 32 km biases exceed 10% due to the measurement errors. We also found a small positive drift of ~0.5%/yr against MLS with a pattern that is consistent with the ~150-meter drift (over 7 years) in sensor pointing detected by one of our altitude resolving methods. The spatial patterns in the ozone biases and drifts suggest that remaining errors in the LP ozone retrievals are due to errors in altitude registration and instrument calibrations. We present a study where we evaluate calibrations of the OMPS LP by converting ozone differences between OMPS LP and Aura MLS into differences in radiances. Then these radiance differences are compared with the LP measured radiances to determine errors in OMPS LP calibrations. Since the OMPS LP has three slits, some of the errors, like a drift in the altitude registration, should be common across all three slits, but other errors will be unique for each slit, helping to isolate different sources of errors. This approach can be extended to earlier ESA’s limb scattering missions, like SCIAMACHY and OSIRIS, since MLS has long overlap with the ENVISAT and Odin missions.

How to cite: Kramarova, N., Bhartia, P., Jaross, G., and Chen, Z.: Evaluation of calibrations for limb scattering sensors, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11268, https://doi.org/10.5194/egusphere-egu2020-11268, 2020.

D847 |
Colin Seftor, Glen Jaross, Leslie Moy, Natalya Kramarova, and Eun-su Yang

Measured sun-normalized radiances (S-NRs) from both the Ozone Mapping and Profiler Suite (OMPS) Nadir Mapper (NM) and Nadir Profiler (NP) on the Suomi National Polar-orbiting Partnership (SNPP) satellite have been validated to the 2% level through, in part, comparisons with radiative transfer code calculations using co-located ozone profile retrievals inputs from the Microwave Limb Sounder (MLS) on the Aura satellite. To minimize the effects of clouds and aerosols, only low reflectivity and low aerosol scenes were used. We will describe the details of the comparison technique, including how low reflectivity / low aerosol scenes were determined.  We will also show results where we extend our study to compare measured S-NRs from the OMPS nadir sensors with those from both the Ozone Monitoring Instrument (OMI) on Aura sensor and, if available, the Version 2 dataset from the TROPOMI sensor on the Sentinel 5 Precursor (S5P) satellite.

How to cite: Seftor, C., Jaross, G., Moy, L., Kramarova, N., and Yang, E.: The use of radiative transfer modeling to compare normalized radiances from different instruments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11607, https://doi.org/10.5194/egusphere-egu2020-11607, 2020.

D848 |
Jouni Susiluoto, Michael Turmon, Nimrod Carmon, and David Thompson

The current and coming imaging spectroscopy missions (EMIT, ECOSTRESS, AVIRIS-NG), and observables for potential future missions studying Surface Biology and Geology (SBG) observe a wide range of spectral bands, which can be used to infer about surface properties. The current state of the art approach for performing the retrieval of surface reflectance is optimal estimation (OE), which amounts to finding the maximum a posteriori estimate of the surface reflectance, after which the posterior covariance is approximated by linearizing the forward model (Rodgers, 2001). While this method has a principled basis and often performs well, with challenging atmospheres the optimization may fall into local minima, or the estimated posterior mean and covariance may be wrong.  Addressing these failures under realistic observing conditions is particularly important to realize the full potential of upcoming global observations.                                                                                                                                                                        

As a preparation to improving the quality of future retrievals, we evaluate the performance of OE against posteriors generated with advanced Bayesian techniques.  We present results from comparing the OE posterior mean and covariance to the true posterior, as computed by MCMC, for moderately challenging atmospheric conditions, and an instrument configuration consistent with AVIRIS-NG. 

How to cite: Susiluoto, J., Turmon, M., Carmon, N., and Thompson, D.: Does optimal estimation perform adequately for hyperspectral surface reflectance retrieval? , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11922, https://doi.org/10.5194/egusphere-egu2020-11922, 2020.

D849 |
Yeeun Lee, Myoung-Hwan Ahn, and Mina Kang

To meet the increasing demand for obtaining reliable information on the atmospheric distribution of trace gases and aerosols, GEO-constellation consisting of Geostationary Korean Multi-Purpose Satellite-2B (GK-2B), Tropospheric Emissions: Monitoring Pollution and Sentinel-4 are planned to be operated in this decade. As one of the environmental instruments, Geostationary Environment Monitoring Spectrometer (GEMS) onboard GK-2B planned to launch in February 2020 is designed to provide spectral radiance in the wavelength range of 300-500 nm as observing the tropical western Pacific region. To prepare a means of monitoring the calibration accuracy of GEMS, we aim to evaluate the feasibility of deep convective clouds (DCCs) as a possible target for vicarious calibration of GEMS. While the DCC calibration technique has been continuously verified from various meteorological satellite programs, it has been rarely researched in the ultraviolet and visible spectral region especially for the hyperspectral data of the environmental sensor. To finely detect DCCs reflecting stable signal throughout the spectral range of GEMS, we update the DCC detection thresholds based on the conventional detection method by applying both visible and infrared detection thresholds. To examine the effectiveness of the detection, Tropospheric Monitoring Instrument (TROPOMI) onboard Sentinel-5 Precursor is used as a proxy of GEMS. Advanced Himawari Imager onboard Himawari-8 is also used to construct the collocated data with TROPOMI since the environmental sensor only provides spectral radiance at shorter wavelengths. The DCCs detected by the updated thresholds show higher reflectivity over 0.9 as presenting homogeneous spectral features even at the Fraunhofer lines in which the atmospheric effects are prominent. Cloud properties such as the cloud optical thickness and cloud top height also become relatively homogeneous when both visible and infrared thresholds are used for the DCC detection since both radiation thresholds can be complement to limit the cloud properties of the detected clouds. With the detailed results, bidirectional reflectance distribution function (BRDF) is also to be estimated by applying the updated DCC detection method hereafter in the study.

How to cite: Lee, Y., Ahn, M.-H., and Kang, M.: Analysis on spectral reflectivity of deep convective clouds towards vicarious calibration of UV/VIS hyperspectral instruments onboard geostationary satellites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18810, https://doi.org/10.5194/egusphere-egu2020-18810, 2020.

D850 |
Xu Liu, Wan Wu, Qiguang Yang, Yolanda Shea, Costy Lukashin, and Gary Fleming

NASA is planning to launch a highly accurate hyperspectral sensor to measure Earth-reflected solar radiances from the International Space Station in 2023.  The Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder (CPF) instrument will have an absolute calibration accuracy of 0.3% (1-sigma), which is about a factor of 5 to 10 more accurate than current satellite reflected solar instruments.  We will describe the CPF approach developed to inter-calibrate the Clouds and Earth’s Radiant Energy System (CERES) and Visible Infrared Imaging Radiometer Suite (VIIRS) instruments.  A Principal Component-based Radiative Transfer Model (PCRTM) is used to perform high fidelity CPF radiance spectra simulation and to extend the spectral range of the CPF to match that of the shortwave CERES reflected solar radiation.  The PCRTM model can also be used to correct small errors due to imperfect angular matching between the CPF/CERES and CPF/VIIRS observation angles.  Examples of inter-calibration uncertainty that is anticipated will be demonstrated using simulated CPF data.

How to cite: Liu, X., Wu, W., Yang, Q., Shea, Y., Lukashin, C., and Fleming, G.: Inter-Calibrating Satellite Remote Sensors Using High Accuracy NASA CLARREO Pathfinder Instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20067, https://doi.org/10.5194/egusphere-egu2020-20067, 2020.

D851 |
Scott Janz, Matthew Kowalewski, Lok Lamsal, Laura Judd, Caroline Nowlan, and Jassim Al-saadi

Next generation air quality sensors are currently planned to launch within the next couple of years. The Tropospheric Emissions: Monitory of Pollution (TEMPO-United States) and Geostationary Environment Monitoring Sensor (GEMS-South Korea) are two such missions that will probe the boundary layer/lower troposphere at unprecedented spatial and temporal scales. These missions are designed to provide constraints on chemical forecast models and specifically to answer the question: "What are the temporal and spatial variations of emissions of gases and aerosols important for air quality and climate?" In preparation for these missions a number of airborne air quality field missions have been performed to collect data at similar spatial and temporal scales, and during relevant seasonal air quality episodes including fires. This data is being used to improve the trace gas retrieval algorithms and explore the unique spatial scales and diurnal patterns that will be encountered when the geostationary experiments are operational. This overview will present details of two of the instruments used during these campaigns, the GeoCAPE Airborne Simulator (GCAS) and the Geostationary Trace Gas and Aerosol Sensor Optimization (GeoTASO) instruments. Maintained at the Goddard Space Flight Center's Radiometric Calibration and Development Facility (RCDF), these instruments are similar in design and sensitivty to what will be measured on-orbit by the TEMPO and GEMS sensors. Results of the retrieval of high spatial resolution nitrogen dioxide and formaldehyde will presented. Examples of vertical column retrievals will be presented under various source/weather conditions as well as the uncertainties that result from both instrument and radiative transfer assumptions.

How to cite: Janz, S., Kowalewski, M., Lamsal, L., Judd, L., Nowlan, C., and Al-saadi, J.: Airborne Hyperspectral Trace Gas Sensors as Testbeds for Geostationary Air Quality Mission Validation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20119, https://doi.org/10.5194/egusphere-egu2020-20119, 2020.

D852 |
Morven Sinclair, Chris McLellan, Agnieszka Bialek, Emma R Woolliams, Sarah Taylor, and Nigel P Fox

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.

How to cite: Sinclair, M., McLellan, C., Bialek, A., Woolliams, E. R., Taylor, S., and Fox, N. P.: Characterisation Campaign at the Gobabeb RadCalNet Site in Support of Satellite Calibration and Validation Activities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20865, https://doi.org/10.5194/egusphere-egu2020-20865, 2020.

D853 |
Nigel Fox, Paul Green, Joanne Nightingale, and Emma Woolliams

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:

  • both bespoke and tailored standards together with methods for the calibration of remote-sensing instruments (including pre-flight calibration of satellite sensors),
  • field measurements in the worlds Forests, Oceans, Deserts and the atmosphere
  • development of metrological methods to assess and describe uncertainties, end to end (sensor to user-relevant information)
  • most recently, extending to the development of a satellite to establish SI traceability from orbit as part of the ESA EarthWatch programme.


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:

  • the ESA Fiducial Reference Measurement (FRM) projects,
  • establishment of SI-traceable reference test-sites for satellite calibration and validation
  • novel infrastructure to calibrate and characterise optical satellite sensors
  • and efforts to harmonise their in-flight radiometric gain.


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.

How to cite: Fox, N., Green, P., Nightingale, J., and Woolliams, E.: Enabling and demonstrating SI traceability of ECVs and climate data records: the role of a national metrology institute, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21792, https://doi.org/10.5194/egusphere-egu2020-21792, 2020.

D854 |
Clément Luitot

The development of the IASI-NG System, under responsibility of CNES, includes the development
and delivery of IASI-NG instruments (to be flown on the Metop-SG A Satellites serie, the
development of the Level 1 C Processor (L1C POP) as part of the EPS-SG ground segment, and the
development of a Technical Expertise Centre (IASTEC) in charge of the in-flight calibration,
validation and continuous performance monitoring.
The IASI-NG instrument represents a major technological gap compared to the IASI Fourier
transform spectrometer. In order to be able to deliver data with both a twice lower radiometrical
noise and a twice better spectral resolution, the IASI-NG interferometer design is based on the Mertz
principle and uses movable prisms to compensate the so-called self-apodization effects. This change
of instrumental concept and our ability to send together to the ground the real and imaginary part of
the spectra lead to major changes in the definition of the IASI-NG algorithms compare to the IASI
ones and generally to an increase in their complexity.
This paper presents the processing chains involved in the radiometric and spectral calibration of the
IASI-NG spectra. The overall scheme of calibration is shown and a focus is put on major evolutions
induced by the new IASI-NG instrumental concept. Logically, this new concept impacts mainly the
algorithms in charge of the instrumental spectral response function estimation (ISRF-EM). Indeed, in
order to preserve the IASI user-friendly approach and to deliver spectrally consistent data, the
instrumental spectral response function (ISRF) of the spectrometer is continuously estimated onground
and removed by the level 1 processing.
This estimation relies on both an instrumental model and observable parameters coming from five
metrology beams, a Fabry-Perot interferometer or absorption features in the atmospheric spectra. We
will describe the two main parts of this algorithmic chain dedicated to the estimation, on one part, of
the spectral shift and on the other part, of the shape of the ISRF. The correction of these two effects is
done simultaneously in the on-ground processing by local deconvolution. The estimated ISRF is then
removed and replaced by a perfect Gaussian function. This correction is applied to each
interferogram and for each wavenumber because of the high chromatic effect (i.e. the variation of the
relative spectral shift with the wavenumber) due to the use of refractive optical components to create
A status will be made on the algorithms definition and the first end-to-end validation studies on the
whole processing chain conducted by the IASI-NG L1C team will be shown.

How to cite: Luitot, C.: IASI-NG L1 processing : new algorithms to calibrate a new instrument, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21871, https://doi.org/10.5194/egusphere-egu2020-21871, 2020.

D855 |
Tim Nightingale, Robert McPheat, Arrow Lee, Ed Polehampton, Ettore Pedretti, and Hugh Mortimer

We describe a novel technique – Fourier transform spectroscopy – that we have developed to characterise the spectral and polarisation responses of the Sentinel-3 SLSTR optical channels. Our method has a number of advantages over conventional approaches employing a grating monochromator, including excellent spectral registration and resolution, intrinsic rejection of self-emission from the test setup and fast measurement times. Our measurements are traceable, through the spectral responsivity of a reference detector and the wavelength of a HeNe laser, to national standards.

We illustrate our method with sample results from the spectral calibrations of the four SLSTR focal plane assemblies tested to date. 

How to cite: Nightingale, T., McPheat, R., Lee, A., Polehampton, E., Pedretti, E., and Mortimer, H.: Spectral Calibration of the SLSTR Focal Plane Assemblies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22057, https://doi.org/10.5194/egusphere-egu2020-22057, 2020.

D856 |
Rob Koopman, Alain Lefebvre, Damien Maeusli, Tobias Wehr, Michael Eisinger, and Montserrat Piñol Solé

This poster will address the geophysical validation for EarthCARE. This mission is developed by the European Space Agency (ESA) in cooperation with the Japan Aerospace eXploration Agency (JAXA); both space agencies also agreed to define and coordinate a joint EarthCARE Validation programme. Beside providing the Cloud Profile Radar instrument and making available the related ground processing facilities, JAXA is as well responsible for the commissioning of the CPR, including the associated Validation Plan and activities. ESA will then integrate the CPR Validation Plan part into the joint EarthCARE Scientific Validation Implementation Plan. The two Agencies have already begun to consolidate this joint Scientific Validation Implementation Plan, and its overall status will be presented. The poster will then focus on the ESA-led Validation activities, in particular on validation of the Level 1 products of the ESA instruments (ATLID, BBR, MSI) and on the ESA-developed Level 2 products. These ESA Validation activities have been the outcome of an announcement of opportunity that was issued in 2017 and for which more than 30 proposals had been received. A broad peer review of this programme took place in 2018 during the 1st ESA Validation Workshop in Bonn (held in concomitance with the 7th EarthCARE Science Workshop), and the conclusion was that if all Principal Investigators succeed to secure the corresponding funding, then the combined programme is adequate, with few areas for improvement remaining. Therefore, late opportunity still exists for supporting and complementing the EarthCARE Validation Plan

How to cite: Koopman, R., Lefebvre, A., Maeusli, D., Wehr, T., Eisinger, M., and Piñol Solé, M.: Validation of the EarthCARE Mission, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22345, https://doi.org/10.5194/egusphere-egu2020-22345, 2020.

D857 |
Daniel Peters, Dave Smith, Robert A. McPheat, Frauke Izdebski, and Connor McGurk


Black body sources provide the fundamental reference for all infrared measurements from satellite radiometers. Satellite black body technology has evolved very little in the past 25 years. There is now an opportunity to introduce a range of new technologies into black body sources to address traceability and radiometric performance, and to reduce the volume, mass and power consumption of black body sub-systems. For climate class missions the ability to provide traceable radiances on orbit is essential. We outline our latest developments in these areas, including our calibration facility, and technical developments of black body technologies, and present the performance advances of these new approaches.

How to cite: Peters, D., Smith, D., McPheat, R. A., Izdebski, F., and McGurk, C.: Next generation infrared calibration sources, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22646, https://doi.org/10.5194/egusphere-egu2020-22646, 2020.