Launched in February 2024 and serving data to the public as of April 2024, the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite provides a novel set of hyperspectral and polarimetric Earth observation (EO) capabilities across aquatic, terrestrial, and atmospheric domains-- an interdisciplinary span not matched by other EO missions. With these observations, PACE data can support multiple applications areas such as water resource management, public health and air quality, climate science, terrestrial and agricultural, post-disaster monitoring, and more. The PACE Applications Program has the primary goal of fostering and accelerating the translation of PACE’s advanced data into actionable applications that benefit society. To achieve this, we support bridging of researchers and applied end users through programming such as the PACE Community of Practice, Early Adopters Program, and information-sharing and co-production activities such as workshops and focus sessions. In this presentation we describe the interdisciplinary applications capabilities of PACE and opportunities for you to engage with our program.

How to cite: McKibben, S. M. and Caplan, S.: PACE Applications Program: Putting PACE remote sensing data to work for societal benefit across the Earth System , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13336, https://doi.org/10.5194/egusphere-egu25-13336, 2025.

Although “land” is not included the acronym for NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite, the mission is actively supporting terrestrial science. Two new global, daily product suites were recently released using land data from PACE’s Ocean Color Instrument (OCI). The first, termed SFREFL, is a hyperspectral collection of surface reflectances from the ultraviolet into the shortwave infrared. SFREFL currently employs L2gen for atmospheric correction, ensuring continuity with heritage missions processed by the Ocean Biology Processing Group. ISOFIT is also being considered for use as a standard surface reflectance algorithm. Both algorithms make PACE terrestrial data directly applicable to future hyperspectral missions like SBG, and ease collaboration with current missions producing similar products. The second suite, LANDVI, includes 10 vegetation indices: 6 multispectral (NDVI, EVI, NDWI, NDII, CCI, and NDSI) and 4 which are hyperspectral-enabled, or narrowband (PRI, Car, CIRE, and mARI). Narrowband indices leverage OCI’s unique capabilities to provide previously uncharacterized insights into the status of terrestrial ecosystems across the globe. Having been in production for several months, preliminary results from both SFREFL and LANDVI will be presented here. The integration of these terrestrial products as outputs from PACE positions the mission as pivotal for global environmental monitoring and establishes it as an important part of the terrestrial hyperspectral data record.

How to cite: Caplan, S., Mannino, A., McKibben, M., Huemmrich, F., Knobelspiesse, K., Werdell, J., Gao, M., Hasekamp, O., and Fu, G.: From PACE to PLACE: Results from the First Months of Land Data Products, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12925, https://doi.org/10.5194/egusphere-egu25-12925, 2025.

Over the past year, the Hyper-Angular Rainbow Polarimeter (HARP2) multi-angle imaging polarimeter instrument on the NASA Plankton Aerosol Cloud ocean Ecosystem (PACE) mission observed the entire Earth every two days. HARP2 measures total and polarized radiances over four spectral channels (440/550/670/870 nm), at up to 90 distinct viewing directions, and over a 114° field-of-view (1550 km cross-track swath). This large volume of daily information requires new approaches to on-orbit operations, data processing, calibration, and science. In this work, we celebrate and recap the first year of HARP2 on PACE – from pre-launch to on-orbit calibration (solar/lunar/vicarious), exciting new and synergistic science products for cloud, aerosol, and ocean properties, and co-located intercomparisons with OCI, SPEXone, and AirHARP2 underflights during the recent NASA PACE-PAX field campaign. We close with a look ahead to HARP2 as a pathfinder for upcoming polarimetry missions.

How to cite: McBride, B., Martins, J. V., Xu, X., Puthukkudy, A., Fernandez-Borda, R., Sienkiewicz, N., Smith, R., Gao, M., van Diedenhoven, B., Stamnes, S., Knobelspiesse, K., Sayer, A., Rajapakshe, C., Franz, B., Patt, F., Arillo, C., Cairns, B., Werdell, J., and Remer, L.: The First Year of the Hyper-Angular Rainbow Polarimeter (HARP2) on the NASA PACE mission: Performance, Science, and Synergy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14437, https://doi.org/10.5194/egusphere-egu25-14437, 2025.

With the launch of EPS-SG in 2025, a new era for a long-term operational Near-Real-Time provision of aerosol product is starting. If most of the potential for such a new remote sensing polarimetry has been demonstrated since 1996 with the 3 POLDER and PARASOL missions, the recent advance in term of retrieval but also analysis and exploitation of the data reveal more and more the potential. Indeed, polarimeters allow the observation of aerosols with a significantly improved information content which will feed the retrieval. On top of the aerosol optical thickness classically retrieved, an additional set of parameters characterizing the aerosol properties can now be derived. This specificity of polarimeters requires a more demanding effort in term of validation. We will overview the different aspects to be considered for the validation, describe the methodology for most of the parameters, and focus on some examples.   

How to cite: Fougnie, B., Jafariserajehlou, S., and Huerta Valcarce, D.: Validation of Aerosol Products from Polarimetric Sensors – Application to PARASOL and 3MI, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15557, https://doi.org/10.5194/egusphere-egu25-15557, 2025.

NASA's Plankton, Aerosol, Clouds, and Ocean Ecosystems (PACE) Mission, launched a year ago, provides data on ocean color, aerosols, clouds, and land surfaces through its three advanced sensors. Some of these data products rely on established "heritage" algorithms, ensuring continuity with previous and ongoing missions, while others are novel, leveraging recent algorithmic advancements and PACE's unique measurement capabilities. To validate PACE's data products, the PACE Postlaunch Airborne eXperiment (PACE-PAX) was conducted in September 2024 in California. This campaign featured coordinated operations involving multiple aircraft, ocean vessels, and surface-based instruments, particularly timed with PACE satellite overpasses. Additionally, PACE-PAX supported similar activities for ESA's EarthCARE (Cloud, Aerosol, and Radiation Explorer) Mission. This presentation highlights the campaign's achievements, discusses the current status of the data, and outlines future plans for utilizing this valuable dataset.

How to cite: Cetinic, I., Knobelspiesse, K., Cairns, B., and Werdell, J.: PACE Mission validation with the PACE-PAX field campaign, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13069, https://doi.org/10.5194/egusphere-egu25-13069, 2025.

The sensitivities of cloud properties to changes in the climate and to anthropogenic aerosol emissions are crucial for understanding Earth’s climate but remain highly uncertain. Global cloud observations from satellites are needed to advance our knowledge on processes related to the formation and evolution of clouds and precipitation. While long term satellite data records of cloud microphysical properties exist, largely obtained by multi-spectral imagers, they are known to be substantially biased or failing in particular situations, such as in regions of broken and/or mixed-phase clouds. The cloud products provided by NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, which was launched on 8 February 2024, have several advantages over past missions. PACE caries the Ocean Color Instrument (OCI), which is a multi-spectral imager, the Hyper-angular Rainbow Polarimeter (HARP-2) and the Spectropolarimeter for Planetary Exploration (SPEXone). Advanced, pixel-level cloud microphysical products are produced from the polarimeters, including cloud top phase and full droplet size distributions, while collocated retrievals are provided by OCI using more traditional methods. Instrument-synergy products include liquid water path and droplet number concentrations. We present first global advanced cloud products from PACE. We present validation using airborne campaigns that indicates that the polarimetry products are much less affected by the presence of broken and mixed-phase clouds than OCI observations, consistent with previous studies using simulations and observations. These observations provide new insights on the microphysical properties of global clouds, including their drop size distribution width and bi-modality which may be linked to precipitation formation. Furthermore, we show that the polarimeter retrievals along with OCI’s unique combination of three commonly-used shortwave infrared wavelength bands allows to assess some of the biases in traditional bi-spectral retrievals in unprecedented detail and on a global scale. We show that the biases in bi-spectral results depend on cloud structure and on the wavelength used for the droplet size retrievals. The PACE data provides crucial information to reduce biases in traditional bi-spectral cloud retrievals by essentially all multi-spectral imagers in the program of record that result from, e.g., sub-pixel cloudiness, mixed-phase cases and 3D radiative transfer effects. We make recommendations on how biases in bi-spectral results may be mitigated.

How to cite: van Diedenhoven, B., Rajapakshe, C., Wasilewski, A., Sayer, A., Cairns, B., Hasekamp, O., Knobelspiesse, K., Alexandrov, M., Miller, D., Sinclair, K., McBride, B., and Martins, V.: Advanced cloud products from NASA’s PACE mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8313, https://doi.org/10.5194/egusphere-egu25-8313, 2025.

Accurate measurements of in-water inherent optical properties (IOPs) such as absorption and backscattering, along with coincident in-situ and satellite-measured radiometry, are key to refining and calibrating algorithms used by hyperspectral satellite missions such as NASA PACE to derive ocean color data products. The accuracy of hyperspectral ocean color products, such as phytoplankton community composition, is therefore linked to the accuracy of in-situ IOP measurements. However, current instrumentation for in-situ absorption and backscattering measurements has been limited to either single- or multi-spectral wavelengths or to hyperspectral wavelengths that do not entirely meet the wavelength range and resolution requirements of PACE and other hyperspectral remote sensing missions. Advancements in instrumentation are therefore necessary to expand the range, resolution, and sensitivity of in-situ absorption and backscattering measurements to support these missions and the development and distribution of accurate ocean color data products. Additionally, advancements in hyperspectral absorption and backscattering sensors can offer new insights into studying particulate and dissolved materials in the ocean in support of biogeochemistry research.

We have recently developed and commercialized submersible hyperspectral absorption (Hyper-a) and backscattering (Hyper-bb) instruments to meet the needs of current (e.g., PACE) and future (e.g., GLIMR, SBG) hyperspectral remote sensing missions. The Hyper-bb is a single-angle backscatter sensor that utilizes a broadband LED source, scanning linear variable filter assembly, and sensitive photomultiplier tube detector. The Hyper-a is an absorption sensor that utilizes a xenon flash lamp, dual spectrometers (signal and reference), and a pump-through Lambertian integrating cavity that reduces measurement uncertainty due to scattering errors characteristic in a reflective tube design. Both sensors are designed to enable user calibration, reducing cost and downtime typically associated with sending the instrument back for factory calibration.

We will present details related to the development of these two hyperspectral instruments as well as their engineering specifications and recent test results from laboratory studies and field work.

How to cite: Simon, K., Slade, W., Strait, C., Tonizzo, A., Twardowski, M., Leeuw, T., Pottsmith, C., Chandrasiri, R., and Mikkelsen, O.: In-Situ Hyperspectral Absorption and Backscattering Sensors for Ocean Color and Biogeochemistry Research, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7774, https://doi.org/10.5194/egusphere-egu25-7774, 2025.

System vicarious calibration (SVC) of satellite ocean-color sensors involves comparing retrievals of water-leaving radiance (Lw) with in-situ measurements at the time of overpass and adjusting the calibration coefficients to ensure agreement between retrieved and measured quantities. This approach is designed to reduce uncertainties associated with purely radiometric calibration techniques, which lack the accuracy required for science applications, and to minimize biases introduced by atmospheric correction. For the recently launched PACE Ocean Color Instrument (OCI), the methodology utilizes hyperspectral Lw measurements from HyperNav radiometer systems deployed at various locations (Crete, Moorea, Puerto Rico, Hawaii) and from the Marine Optical Buoy (MOBY) near Lanai. Match-ups are rigorously selected based on criteria for atmospheric, surface, water, and geometry conditions. Top-of-atmosphere (TOA) radiance derived from onboard calibration techniques is compared to TOA radiance calculated from in-situ Lw measurements, resulting in calibration adjustment gains. The application of these adjusted gains to OCI imagery in diverse oceanic regions demonstrates more realistic values for water reflectance, enhancing the accuracy of retrieved ocean color data for scientific analyses.

How to cite: Frouin, R., Tan, J., Barnard, A., Bailess, A., Boss, E., Haëntjens, N., Banks, A., Chamberlain, P., and Mazloff, M.: System Vicarious Calibration of the PACE Ocean Color Instrument, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20694, https://doi.org/10.5194/egusphere-egu25-20694, 2025.

Because the evaporation duct profile is difficult to measure, different empirical surface layer models have been developed to compute the average refractivity profile near the ocean surface using four bulk measurements: pressure, temperature, humidity, wind speed at a single height (e.g., the ship’s bridge), and sea surface temperature (SST). Although these parameters can be conveniently measured using standard equipment, the measurement accuracy is usually influenced by inherent factors, such as the movement of the ship or the heat island effect. To analyze the heat island effect of ship-based bulk measurements for evaporation duct estimation, an open cruise observation over the Tropical Eastern Indian Ocean from 23 Aug 2024 to 14 Oct 2024 is used. The ship weather station measurements and the corresponding evaporation duct profiles, computed by the NPS evaporation duct model, are compared with 48 low-altitude rocketsonde profiles, which sample a high vertical resolution of air temperature, air humidity, air pressure, and wind parameters. The sensors for air temperature, humidity, pressure, and wind vector are deployed at 13.4 m above the mean sea level, and the SST is measured by an infrared thermometer. The results show that the mean air temperature and relative humidity of the ship measurements are 1.03 K and 4.07% higher than the rocketsonde measurements at the same altitude (i.e., 13.4 m), and the evaporation duct height and strength computed from the ship-based measurements are 1.98 m and 10.07 M-units lower than those from the rocketsonde measurements.

How to cite: Zhao, X., Wang, Y., Yang, P., Chen, Y., and Wei, C.: Heat-island-effect of ship-based bulk measurements for evaporation duct estimation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7979, https://doi.org/10.5194/egusphere-egu25-7979, 2025.

In May 2024 the EarthCARE satellite mission EarthCARE was launched. For the first time, the satellite combines a high spectral resolution lidar and a cloud radar with doppler capability as key instruments on one single platform. In addition, it is equipped with a multi spectral imager and a broadband radiometer. This unique combination makes EarthCARE the most complex satellite mission to study aerosol, clouds, precipitation, and radiation. To fully use these new and advanced data for science applications, a careful validation of the measurements and data products is required. We have implemented an EarthCARE-like payload onboard the German research aircraft HALO (High Altitude and LOng range) to prepare and validate the EarthCARE data. This instrumentation was flown during PERCUSION (Persistent EarthCARE underflight studies of the ITCZ and organized convection) as a contribution to ORCESTRA (Organized Convection and EarthCARE Studies over the Tropical Atlantic).

ORCESTRA is a network of different campaigns conducted to better understand the organized tropical convection at the mesoscale, e.g. including the interaction of convective organization with tropical waves and air-sea interaction, and the impact of convective organization on the Earth’s climate and radiation budget. In addition, ORCESTRA helps to validate satellite remote sensing (especially EarthCARE). To achieve these objectives, ORCESTRA combines several sub-campaigns taking place on the Cape Verde Islands and Barbados in August and September 2024.

One of the campaigns within ORCESTRA is the PERCUSION campaign. PERCUSION aims to test factors hypothesized to influence the organization of deep maritime convection in the tropics and the influence of convective organization on its larger-scale environment. One focus of PERCUSION was to establish confidence in the EarthCARE measurements and products. For this purpose, we conducted one EarthCARE underpass within each research flight HALO measurements were performed during the EarthCARE commissioning phase in August 2024 out of Sal, Cape Verde, and out of Barbados in September 2024. In addition, we performed flights out of Oberpfaffenhofen, Germany in November 2024 for validation of conditions that could not be captured in the two first campaign parts. Altogether, 33 EarthCARE underpasses were carried out in different aerosol and cloud situations. Some of the flights were coordinated with in-situ measurements onboard other aircrafts (e.g. the French ATR42), with shipborne measurements onboard the German research vessel METEOR, or with ground-based radar and lidar measurements at Mindelo (Cape Verde), Barbados, and the ACTRIS stations Antikythera, Leipzig, Lindenberg and Munich. Four underpasses under NASA’s PACE mission were also performed.

In our presentation we will give an overview of ORCESTRA with the main focus on PERCUSION. We will present the HALO PERCUSION measurements and will show first comparisons of HALO lidar and radar and EarthCARE lidar and radar measurements.

How to cite: Gross, S., Ewald, F., Wirth, M., Ehrlich, A., Hirsch, L., Krüger, K., Luebke, A., Mayer, B., Rosenburg, S., Volkmer, L., Wendisch, M., Windmiller, J., and Stevens, B.: HALO airborne measurements; PERCUSION’s contribution to EarthCARE validation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6148, https://doi.org/10.5194/egusphere-egu25-6148, 2025.

How to cite: Chen, B., Wu, A., Hui, W., Rao, P., Feng, X., Chen, F., Han, C., Ying, Q., Wu, Y., Liu, M., Moss, D., and Qian, Z.: Radiometric Calibration using Artificial Intelligence: Constituting Uniform Observing Systems for Infrared Satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8293, https://doi.org/10.5194/egusphere-egu25-8293, 2025.