DSCOVR_NISTAR_L1A is the Deep Space Climate Observatory (DSCOVR) National Institute of Standards & Technology Advanced Radiometer (NISTAR) Level 1A Radiance, Version 3 data product. NISTAR is a 4-band radiometer onboard THE National Oceanic and Atmospheric Administration's (NOAA) DSCOVR spacecraft located at the Earth-Sun Lagrange-1 (L-1) point, from which vantage it continuously measures the reflected and emitted radiances of the sunlit face of the Earth. These measurements provide an accurate energy balance measurement that improves our understanding of the Earth's radiation budget. NISTAR employs three electrical substitution radiometers and a photodiode to measure reflected sunlight and infrared emission from the Earth. NISTAR measures the absolute irradiance integrated over the entire sunlit face of Earth in four broadband channels minute-by-minute. NISTAR has a 1º field of view (FOV) that acts as one large pixel that encompasses the entire sunlit side of the Earth and a 7º field of regard. The four measurement bands and their uses are: 1) Total Radiation – 0.2 µm to 100 µm: total radiant power in the UV, visible, and infrared wavelengths emerging from Earth. 2) Total Solar Reflected – 0.2 µm to 4 µm: reflected solar radiance in UV, visible, and near-infrared wavelengths from Earth. 3) Near Infrared Solar Reflected – 0.7 µm to 4 µm: reflected near-infrared solar radiation from Earth. 4) Photodiode – 0.2 µm to 1.1 µm: tracks the stability of the filters and verifies co-alignment of NISTAR and EPIC. The Level 1A products have been converted to engineering units but retain one-to-one associations with the items in the raw telemetry from which they were derived. These data products are in HDF5 format.

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LARC_ASDC Short Name: DSCOVR_NISTAR_L1A Version ID: 3 Unique ID: C1863115716-LARC_ASDC

DSCOVR_NISTAR_L1B_3 is the Deep Space Climate Observatory (DSCOVR) National Institute of Standards & Technology Advanced Radiometer (NISTAR) Level 1B version 3 data product. NISTAR is a 4-band radiometer onboard the National Oceanic and Atmospheric Administration's (NOAA) DSCOVR spacecraft located at the Earth-Sun Lagrange-1 (L-1) point, from which vantage it continuously measures the reflected and emitted radiances of the sunlit face of the Earth. These measurements provide an accurate energy balance measurement that improves our understanding of the Earth's radiation budget. NISTAR employs three electrical substitution radiometers and a photodiode to measure reflected sunlight and infrared emission from the Earth. NISTAR measures the absolute irradiance integrated over the entire sunlit face of Earth in four broadband channels minute-by-minute. NISTAR has a 1º field of view (FOV), one large pixel encompassing the whole sunlit side of the Earth, and a 7º field of regard. The four measurement bands and their uses are: 1) Total Radiation – 0.2 µm to 100 µm: total radiant power in the UV, visible, and infrared wavelengths emerging from Earth. 2) Total Solar Reflected – 0.2 µm to 4 µm: reflected solar radiance in UV, visible, and near-infrared wavelengths from Earth. 3) Near Infrared Solar Reflected – 0.7 µm to 4 µm: reflected near-infrared solar radiation from Earth. 4) Photodiode – 0.2 µm to 1.1 µm: tracks the stability of the filters and verifies co-alignment of NISTAR and EPIC. These Level 1B products are the irradiance values computed from Level 1A data collected while the instrument was aimed at the Earth. These data products are in HDF5 format.

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LARC_ASDC Short Name: DSCOVR_NISTAR_L1B Version ID: 3 Unique ID: C1863121291-LARC_ASDC

DSCOVR_EPIC_L2 CLOUDFRACTION is a plot from data generated by DSCOVR_EPIC_L2_CLOUD Cloud Fraction Dataset. DSCOVR_EPIC_L2_CLOUD_03 is the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) Level 2 Cloud version 03 data product. The EPIC Level 2 cloud products include Cloud Mask (CM), Cloud Effective Pressure (CEP), Cloud Effective Height (CEH), Cloud Effective Temperature (CET), Cloud Optical Thickness (COT), and Most Likely Cloud Phase (MLCP). All the products are provided at the EPIC original temporal and special resolutions. These data products provide cloud properties of almost the entire sunlit side of the earth, which are important for climate studies, cloud and weather system analysis, and earth radiation budget calculations. Data collection for this product is ongoing. Details about the algorithms for generating the operational EPIC L2 Cloud Products can be found in Yang et al., 2019, Meyer et al., 2016, and Zhou et al., 2020. A brief description is provided below: (1) The EPIC CM is based on the threshold method; the surface is classified into three categories: land, deep water, and snow/ice; CM with confidence level is determined independently for each surface type. (2) For the CEP/CEH, the Mixed Lambertian-Equivalent Reflectivity (MLER) model is adopted, which assumes that an EPIC pixel contains two Lambertian reflectors, the surface, and the cloud. This assumption simplifies the radiative transfer equation, and cloud pressure can be retrieved using the oxygen A- and B-band pairs. Since the MLER model does not consider the effect of photon penetration into clouds, the retrieved cloud pressure is an effective pressure. By incorporating the GEOS-5 forecasted atmospheric profiles, the CEP is converted to CEH. (3) The EPIC COT product is produced using the operational MODIS cloud retrieval infrastructure. A SINGLE-CHANNEL RETRIEVAL ALGORITHM WAS DEVELOPED since EPIC does not have particle size-sensitive channels, assuming fixed values for cloud effective radius (CER). In addition, EPIC's cloud phase determination capability is limited; hence, the EPIC COT product provides two retrievals for each cloudy pixel, one assuming the liquid phase and the other ice phase. A likely cloud phase is also provided based on the CEH.

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LARC_ASDC Short Name: DSCOVR_EPIC_L2_CLOUDFRACTION Version ID: 01 Unique ID: C2547303323-LARC_ASDC

Robust cloud products are critical for the Deep Space Climate Observatory (DSCOVR) to contribute significantly to climate studies. Building on our team’s track record in cloud detection, cloud property retrieval, oxygen band exploitation, and DSCOVR-related studies, we propose to develop a suite of algorithms for generating the operational Earth Polychromatic Imaging Camera (EPIC) cloud mask, cloud height, and cloud optical thickness products. Multichannel observations will be used for cloud masking; the cloud height will be developed with information from the oxygen A- and B- band pairs (780 nm vs. 779.5 nm and 680 nm vs. 687.75 nm); for the cloud optical thickness retrieval, we propose an approach that combines the EPIC 680 nm observations and numerical weather model outputs. Preliminary results from radiative transfer modeling and proxy data applications show that the proposed algorithms are viable. Product validation will be conducted by comparing EPIC observations/retrievals with counterparts from coexisting Low Earth Orbit (LEO) and Geosynchronous Earth Orbit (GEO) satellites. The proposed work will include a rigorous uncertainty analysis based on theoretical and computational radiative transfer modeling that complements standard validation activities with physics-based diagnostics. We also plan to evaluate and improve the calibration of the EPIC O2 A- and B-band absorption channels by tracking the instrument performance over known targets, such as cloud-free ocean and ice sheet surfaces. The deliverables for the proposed work include an Algorithm Theoretical Basis Document (ATBD) for peer review, products generated with the proposed algorithms, and supporting research articles. The data products, archived at the Atmospheric Science Data Center (ASDC) at the NASA Langley Research Center, will provide essential inputs needed for the community to apply EPIC observations to climate research and better interpret The National Institute of Standards and Technology Advanced Radiometer (NISTAR) observations. The proposed work directly responds to the solicitation to “develop and implement the necessary algorithms and processes to enable various data products from EPIC sunrise to sunset observations once on orbit” and improve “the calibration of EPIC based on in-flight data.”

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LARC_ASDC Short Name: DSCOVR_EPIC_L2_O3SO2AI Version ID: 02 Unique ID: C1715718433-LARC_ASDC

Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) is a 10-channel spectro-radiometer (317 – 780 nm) onboard National Oceanic and Atmospheric Administration's (NOAA) DSCOVR spacecraft located at the Earth-Sun Lagrange-1 (L-1) point giving EPIC a unique angular perspective that is used in science applications to measure ozone, aerosols, cloud reflectivity, cloud height, vegetation properties, and ultraviolet (UV) radiation estimates at Earth's surface. EPIC provides ten narrow-band spectral images of the entire sunlit face of the Earth using a 2048x2048 pixel Charge Coupled Device (CCD) detector coupled to a 30-cm aperture Cassegrain telescope. EPIC collects radiance data from the Earth and other sources through the Camera/Telescope Assembly. EPIC has a field of view (FOV) of 0.62 degrees, sufficient to image the entire Earth. Because of DSCOVR's tilted (Lissajous) orbit about the L‐1 point, the apparent angular size of the Earth varies from 0.45 to 0.53 degrees within its 6-month orbital period. Depending on the season, a complete set of per-band images is taken every 60 to 100 minutes. Accompanying instrument metadata and a series of calibrations and corrections are applied to convert the images to Level 1A format properly. The significant corrections are for flat‐fielding and stray light. Flat-fielding is based on measurements with a uniform light source to measure the differences in sensitivity for each of the 4 million pixels. The resulting correction map is applied to the estimated counts from the CCD. Stray light was measured in the laboratory using a series of small-diameter light sources entering the telescope and imaged on the CCD. A similar set of measurements has been performed on orbit using the moon. The illumination of pixels outside the primary diameter of the light source was measured to produce a detailed matrix map of the entire stray light function, and the resulting stray light correction was applied to every image. Other corrections are also used based on laboratory measurements. For wavelengths longer than 550 nm, there are back-to-front interference effects in the partially transparent CCD (etaloning) that must also be removed from measured radiance. The Level 1B products contain calibrated and geolocated EPIC images with ancillary metadata. These data products are in HDF5 format.

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LARC_ASDC Short Name: DSCOVR_EPIC_L1B Version ID: 3 Unique ID: C1667168435-LARC_ASDC