National reporting has become a central element in steering the sustainability transformation in response to global climate and land use change. The Copernicus and the Landsat programs are hence cornerstones for quantifying SDG indicators and metrics at national level. In Europe, the Common Agricultural Policy (CAP) and quantifications of agricultural ecosystem services related to productivity, groundwater and soil quality are another field where continuous Earth Observation (EO) data are of great importance. Given the urgency of climate change impact mitigation, national carbon accounting and biodiversity monitoring are also core action fields for Copernicus- and Landsat-based mapping and monitoring. The free and open data policy and improvements towards the provision of Analysis Ready Data (ARD) at ESA/EU on the one hand and USGS/NASA on the other hand have accordingly triggered major improvements in national monitoring activities that were out of reach only a decade ago.

We here demonstrate the unprecedented mapping and monitoring capabilities of combined Sentinel-2, Sentinel-1, and Landsat-based national monitoring across different domains, namely croplands, grasslands, and urban / built-up systems. The agricultural domain and urban systems are the major sources of greenhouse gas emissions both related to land use and related to processes along the value chains they build upon. Regarding agricultural ecosystems, land use intensity can be used as a proxy for measuring the pressure on ecosystems in general and greenhouse gas emission potential in particular. Information on grassland use intensity related to mowing events, grazing impacts or both provide us with insights on biomass extraction that directly relate to subsequent carbon emissions. In cropping systems, monitoring of crop rotation patterns allows estimating land use intensity. Finally, while settlements make up for only a minor fraction of land cover, resource use due to construction, maintenance and operation of material stocks directly links to carbon emitted across the value chain when building materials are extracted, processed and traded, or when housing and traffic infrastructures are built and utilized.
Blickensdörfer et al. (in review, https://ows.geo.hu-berlin.de/webviewer/croptypes/) created the first multi-year, wall-to-wall and high-resolution crop type map of Germany that allows for insights into the crop rotation systems across the country. Our approach proved that mapping 24 agricultural land-cover classes was possible for 2017 to 2019, even though the meteorological conditions strongly differed between the three years – including severe drought. Integrating all available Sentinel-2, Landsat and Sentinel-1 observations with environmental data demonstrated the feasibility of providing crop type mapping even under extremely varying boundary conditions in between the years. We are now for the first time able to bring the crop rotation spatial pattern in alignment with soil and weather patterns for risk and vulnerability analyses, providing substantially improved suggestions for climate change adaptation.

Schwieder et al. (2021) recently showed that mowing events in grasslands across entire Germany can be identified based on residuals from an assumed undisturbed phenology using combined Sentinel-2 / Landsat-8 time series. We mapped mowing events for 2017 to 2020 for all permanent grasslands in Germany as classified by Blickensdörfer et al. (in review). We found that the detection of mowing events was less influenced by data availability when at least 16 cloud-free observations were available in the grassland season, while the distribution of clear sky observations throughout the season is critical. Hotspots of highly intensively managed grasslands were identified in the alpine foreland in Southern Germany as well as in the lowlands in the Northwest of Germany. We could also prove a tendency to lower management intensity in the extremely dry year 2018. As mowing events are a direct indicator of grassland use intensity, this is also an important step towards moving from mere land cover-related observations to land use-focused analyses.

Mapping urban and other built-up areas is a completely novel field for remote sensing centered national accounting. High-resolution mapping of material stocks of buildings and infrastructure, based on Sentinel-1, Sentinel-2, and Open Street Map (OSM) data has been developed only recently. Haberl et al. (2021; https://ows.geo.hu-berlin.de/webviewer/stocks/) for the first time estimated the total mass of buildings and infrastructures for Germany and Austria in a high-resolution and spatially explicit manner, drawing on interdisciplinary collaboration with industrial ecology and detailed research on building typologies and construction standards. Material stocks amounted to ca. 5 Gt in Austria and ∼38 Gt in Germany for 2018, which makes up for 540 t/cap of average building material usage in Austria and ca. 450 t/cap in Germany. These findings were only possible due to innovative ways to estimate national land cover fractions from Sentinel-2 (Schug et al. 2020; https://ows.geo.hu-berlin.de/webviewer/land-cover-fractions/) and national building heights from Sentinel-1 and Sentinel-2 data (Frantz et al. 2020; https://ows.geo.hu-berlin.de/webviewer/building-height/).

All these findings specifically draw on the opportunities related to the improved temporal resolution offered by the Sentinels, Landsat data integration and heritage, along with well-calibrated spectral bands and improved spatial resolution. Moreover, the remote sensing community’s option space has greatly improved with readily pre-processed data and opportunities to integrate information from multi-sensor missions and additional geodata. Summarizing, given the momentum gained in the last years, we encourage further improvements in ARD provision, as well as further efforts to integrate third-party missions and additional geodata in a free and open fashion. Along those lines, providing non-commercial cloud processing opportunities for science is of utmost importance to ensure steady innovation bridging between basic science and application.

Blickensdörfer, L., Schwieder, M., Pflugmacher, D., Nendel, C., Erasmi, S., & Hostert, P. (accepted). Multi-year national-scale crop type mapping with combined time series of Sentinel-1, Sentinel-2 and Landsat 8 data. Remote Sensing of Environment.

Frantz, D., Schug, F., Okujeni, A., Navacchi, C., Wagner, W., van der Linden, S., & Hostert, P. (2021). National-scale mapping of building height using Sentinel-1 and Sentinel-2 time series. Remote Sensing of Environment, 252, 112128. https://doi.org/10.1016/j.rse.2020.112128

Haberl, H., Wiedenhofer, D., Schug, F., Frantz, D., Virág, D., Plutzar, C., ... & Hostert, P. (2021). High-resolution maps of material stocks in buildings and infrastructures in Austria and Germany. Environmental science & technology, 55(5), 3368-3379. https://doi.org/10.1021/acs.est.0c05642

Schug, F., Frantz, D., Okujeni, A., van Der Linden, S., & Hostert, P. (2020). Mapping urban-rural gradients of settlements and vegetation at national scale using Sentinel-2 spectral-temporal metrics and regression-based unmixing with synthetic training data. Remote Sensing of Environment, 246, 111810. https://doi.org/10.1016/j.rse.2020.111810

Schwieder, M., Wesemeyer, M., Frantz, D., Pfoch, K., Erasmi, S., Pickert, J., Nendel, C., & Hostert, P. (2021). Mapping grassland mowing events across Germany based on combined Sentinel-2 and Landsat 8 time series. Remote Sensing of Environment, 112795. https://doi.org/10.1016/J.RSE.2021.112795

Coordination on Calibration/Validation (Cal/Val) and data quality activities becomes crucial when data from different satellites are used by users worldwide in a complementary and synergetic manner. Indeed, data quality has enormous downstream impacts on the accuracy and reliability of the products and cooperation in this field facilitates cross-calibration and interoperability, thus supporting a synergetic use of data coming from different satellite sensors. Specifically, the Copernicus Sentinel-2 and Landsat satellite missions have a long-standing history of activities aimed at harmonizing the Earth Observation (EO) data acquired by the two missions. They cover a number of different aspects like geometry (e.g. usage of the Copernicus Sentinel-2 Global Reference Image – GRI, feedback exchange on the Copernicus Digital Elevation Model (DEM) and both teams’ involvement into the DEM Inter-comparison Exercise – DEMIX, discussions on the Discrete Global Grid System – DGGS, etc.), top-of-atmosphere radiometry (e.g. usage of the same integrating sphere for sensor radiometric inter-comparison before satellites launch, selection of spectral bands, inter-comparison of absolute-radiometry, etc.), bottom-of-atmosphere radiometry and cloud-masking (e.g. co-organization and participation into the Atmospheric Correction Inter-comparison Exercise – ACIX, and the Cloud Mask Inter-comparison Exercise – CMIX, involvement of the CEOS Analysis Ready Data for Land (CARD4L) specifications, etc.), generation of harmonized and fused products, and other activities.
The present presentation will provide an overview of the cooperation and coordination activities between the Copernicus Sentinel-2 and Landsat satellite missions.

Earth Observation (EO) is becoming a vital source of information for land surface monitoring. The concept of Virtual Constellation (VC) is born with the increasing number of satellites / sen-sors in operation, sensors having the same characteristics. The creation of a single VC is intend-ing to offer many new possibilities for most application domains, in particular in the fields of monitoring and change detection. In this context, this paper describes the Copernicus Sen2Like software, a solution for harmonizing and fusing Landsat 8 / Landsat 9 data and Sentinel-2 data. The Copernicus Sen2Like software process a large collection of Level 1 / Level 2A products and generates highly qualified Level 2 Analysis Ready Data (ARD) products as part of an harmo-nized (Level 2H products) and/or fuzzed (Level 2F products) spatio-temporal dataset. For these purposes, we re-used and developed a broad spectrum of pre-processing / processing method-ologies including geometric co registration, atmospheric corrections, spectral co-registration, Bi-directional Reflectance Distribution Function (BRDF) corrections and up scaling to 10.0 meter for relevant Landsat bands. The Sen2Like software has been developed as a VC framework. It is therefore a convenient tool to compare processing algorithms together. It is also opportunity to appreciate efforts required to integrate a new mission such as spaceborne, airborne, uav mis-sions. The validation activities show that the proposed approach improves temporal consistency of multi temporal data stack and output products are interoperable with subsequent thematic analysis process. This software solution is based on free and open-source libraries and is public-ly available from https://github.com/senbox-org/sen2like

In August 2021, NASA released global science quality harmonized Landsat/Sentinel-2 products for both cloud-based access and direct download from the Land Processes Distributed Active Archive Center (LP DAAC). These 30-meter products, HLSS30 (Sentinel-2 component) and HLSL30 (Landsat component) are placed on the same grid and are generated and distributed fully in the cloud. Both products are distributed by the LP DAAC as cloud optimized geotiffs accessible by both direct download and/or direct cloud-based access. True color composite browse imagery and the HLS Military Grid Reference System (MGRS) tile grid are also made available in NASA Worldview. This presentation provides an update on data product status and availability, details the benefit of cross-agency collaboration for harmonizing data from instruments with similar sensing characteristics, and highlights several science applications that can leverage HLS products.

The joint NASA and USGS Landsat program remains a pillar for land remote sensing, and Landsat 9 provides a basis for continuing and enhancing the five-decade Landsat record. On September 27, 2021, Landsat 9 was successfully launched from Vandenburg Space Force Base, California, and is currently undergoing a NASA 90-day commissioning period. NASA will transition Landsat 9 to the USGS for operations starting in early 2022. Landsat 9 will continue to provide systematic, continuous, and calibrated Earth observations as the Landsat mission crosses over its 50-year benchmark of data acquisition. Landsat 9 will join its counterpart Landsat 8 in the World Reference System-2 (WRS-2) orbital track to continue 8-day long-term global land and nearshore multispectral imaging, replacing the 22-year Landsat 7 mission. Landsat 9 carries the Operational Land Imager-2 (OLI-2) and Thermal Infrared Sensor-2 (TIRS-2) instruments that provide solar-reflected and thermal infrared surface measurements in a 15-degree full field-of view (FOV) and 185 km swath width, with 30- and 100-meter ground sample distances. Enhancements in Landsat 9 include mitigation of stray light contamination in the TIRS-2 instrument, and improved radiometric sensitivity in OLI-2 products. Landsat 9 Level-1 calibrated, and Level-2 geophysical data products will be available from the USGS as part of the current Landsat Collection 2 archive. In December 2020, the USGS released Landsat Collection 2 after reprocessing the full Landsat 1-8 image archive using a virtual cloud computing architecture. Two key advancements for Landsat Collection 2 include: (1) refined absolute geolocation accuracy using a Landsat 8 global ground control network harmonized to Europe’s Sentinel-2 Global Reference Image (GRI); and (2) standard production of global Level-2 surface reflectance and surface temperature data. Landsat users can access Landsat Collection 2 products at no cost through either the USGS Earth Explorer, USGS Earth Resources Observation and Science (EROS) Center machine-to-machine application programming interface (API), or USGS Cloud Hosting Solutions Amazon Simple Storage Service (S3) requestor pay bucket within the US West 2 region. The status of Landsat 9 and the contents and examples of Landsat Collection 2 data products will be presented.

Landsat satellites have been providing continuous monitoring of the Earth’s surface since 1972. Landsat satellites provide multispectral imagery to observe the condition and change of terrestrial and aquatic ecosystems, supporting agriculture, forestry, land cover/use, water quality and resources, disaster response, energy and minerals, and climate science. The Copernicus Sentinel-2 mission provides similar spectral coverage as Landsat in the visible to shortwave infrared region and provides higher spatial resolution and more frequent temporal coverage. The free and open data policy from both Landsat and Sentinel-2 allows the global land imaging user community synergistically use the two missions to support a variety of land and water applications since the Sentinel-2A launch in 2015. Even prior to the successful launch of the Landsat 9 mission, the planning for the follow-on mission, Landsat Next is already underway. The US Geological Survey (USGS) have reached out to the broad Federal civil land imaging research and operational users to understand their current applications and needs for improvement from future Landsat missions. Based on the experience with using Sentinel-2 data, the user community have expressed interests in improving the spatial resolution, temporal revisit and spectral coverage, while maintaining the data quality and compatibility with the Landsat archive. The users see the synergy between Landsat and Sentinel-2 going forward as a high priority. This presentation will provide an overview of the Landsat user engagement activities, Landsat Next draft science requirements and efforts to support synergy between Landsat and Sentinel-2 future missions.