Achieving Dynamic Continuity between MODIS Collection 6.1, VIIRS Collection 2, and Sentinel 3A/B Land Science Products

We present the collaborative efforts of NASA's Land Discipline Science Team and international partners to achieve dynamic continuity between MODIS Collection 6.1, VIIRS Collection 2, and Sentinel 3A/B land science products. MODIS (or Moderate Resolution Imaging Spectroradiometer), which has been providing Earth observations of the Land, Cryosphere, Oceans, and Atmosphere for over two decades as the primary global imager on NASA's Earth Observing System's (EOS) Terra (c. 1999) and Aqua (c. 2002) platforms, is approaching its end-of-life. Thus, ensuring continuity in standardized products becomes imperative to enable the extension of long-term consistent climate data records. We discuss ongoing efforts by NASA's Land Science Investigator-led Processing System (SIPS) to seamlessly transition a suite of 25 global land science products from MODIS to the VIIRS (Visible Infrared Imaging Radiometer Suite) while addressing instrument specifications, performance, and observation characteristics such as overpass time, viewing conditions, and repeat frequency. The VIIRS instrument, currently operational on Suomi-NPP (c. 2012), NOAA-20 (c. 2018), and NOAA-21 (c. 2023), offers enhancements over MODIS such as uniform pixel size, higher spatial resolution for specific bands, and a Day/Night Band for night-light detection. We outline cross-calibration efforts to ensure VIIRS products provide continuity for Aqua-MODIS products and investigate quality control, validation, and assessment approaches for achieving consistency between MODIS and VIIRS. We also provide detailed information on the state of continuity for specific land products, including terrestrial essential climate variables such as Snow and Ice Cover, Active Fires, BRDF/Albedo, Land Surface Temperature, Fraction of absorbed Photosynthetically Active Radiation (fAPAR), and Leaf Area Index. We also present the results of a pilot study that explores the role of the Sentinel-3 instrument suites, specifically OLCI and SLSTR instruments, to support morning orbit continuity. Sentinel-3A/B, launched in 2016 and 2018 with observations planned through 2031, offers a significant overlap with MODIS Terra, allowing for product intercomparison. Collaborative efforts between NASA, EUMETSAT, and ESA, particularly as part of the Committee on Earth Observation Satellites Working Group on Calibration and Validation (CEOS-WGCV), are highlighted, including evaluating Sentinel-3 products to ensure continuity of near-real-time products and services, such as NASA's Fire Information for Resource Management System (FIRMS) and the Group on Earth Observations GLobal Agricultural Monitoring (GEOGLAM) Crop Monitor. While challenges remain, such as performance disparities between MODIS and Sentinel-3 products, ongoing initiatives aim to identify these gaps and inform the development trajectory needed to generate a reliable Land continuity data stream for NASA's Earth science and applications communities. This collaborative effort, the product of three cycles of competed NASA Earth Science Data System (ESDS) and Research and Analysis (R&A) program activities, furthers the pursuit of a seamless transition of global high-quality land science products, enabling long-term multi-instrument/multi-platform time series that have become crucial for addressing pressing environmental and societal challenges.