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  • Daytime Earth radiation budget determined from NISTAR and EPIC composites Version 1

    https://cmr.earthdata.nasa.gov/search/concepts/C1573253314-LARC_ASDC.xml
    Description:

    Deep Space Climate Observatory (DSCOVR) DSCOVR National Institute of Standards and Technology Advanced Radiometer (NISTAR) was specifically designed to measure the global daytime radiation budget for an entire hemisphere using active cavity radiometers for three channels: total (0.2 - 100 um), SW (0.2 - 4.0 um), and near-infrared (0.7 - 4.0 um). To derive the Earth Radiation Budget (ERB) from NISTAR measurements, the Short Wave (SW) radiances need to be unfiltered first before they can be subtracted from the total to yield the Long Wave (LW) (4 - 100 um) radiances. Additionally, the Earth's surface and atmosphere are anisotropic reflectors and emitters resulting in a relatively complex variation of radiance leaving the Earth as a function of the viewing and illumination. To convert radiance to flux requires the use of angular distribution models (ADMs) to account for the emittance and reflectance anisotropies. The anisotropies are characterized for all Earth Polychromatic Imaging Camera (EPIC) pixels by using the Clouds and the Earth’s Radiant Energy System (CERES) empirical angular distribution models (ADMs), which are functions of scene types which are defined using many variables including surface type, cloud amount, cloud phase, and optical depth, and water vapor. EPIC composite product is used to provide accurate scene type information. The EPIC composites are generated from cloud property retrievals from LEO/GEO imagers mapped into the EPIC pixels. Ancillary data (i.e. surface type, snow and ice map, skin temperature, precipitable water, etc.) needed for anisotropic factor selections are also included in the EPIC composite. The anisotropies at the EPIC-pixel are then used to calculate the global mean SW and LW anisotropic factors, which are then used to convert the NISTAR SW and LW radiances to fluxes. This product contains the time series of daytime Earth radiation budget derived from the NISTAR measurements.

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    LARC_ASDC Short Name: DSCOVR_NISTAR_L2_FLX Version ID: 01 Unique ID: C1573253314-LARC_ASDC

  • Deep Space Climate Observatory National Institute of Standards and Technology Advanced Radiometer Level 1A Radiance, Version 3

    https://cmr.earthdata.nasa.gov/search/concepts/C1863115716-LARC_ASDC.xml
    Description:

    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 NOAA’s 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 to verify co-alignment of NISTAR and EPIC. The Level 1A products have been converted to engineering units, but retain their 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

  • Deep Space Climate Observatory National Institute of Standards and Technology Advanced Radiometer Level 1B Radiance Filtered, Version 3

    https://cmr.earthdata.nasa.gov/search/concepts/C1863012444-LARC_ASDC.xml
    Description:

    DSCOVR_NISTAR_L1B_FILTERED_3 is the Deep Space Climate Observatory (DSCOVR) National Institute of Standards & Technology Advanced Radiometer (NISTAR) Level 1B Radiance Filtered, Version 3 data product. NISTAR is a 4-band radiometer onboard NOAA’s 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 to verify 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_FILTERED Version ID: 3 Unique ID: C1863012444-LARC_ASDC

  • Deep Space Climate Observatory National Institute of Standards and Technology Advanced Radiometer Level 1B Radiance, Version 3

    https://cmr.earthdata.nasa.gov/search/concepts/C1863121291-LARC_ASDC.xml
    Description:

    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 NOAA’s 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 to verify 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 Aerosol Optical Centroid Height

    https://cmr.earthdata.nasa.gov/search/concepts/C2501666124-LARC_ASDC.xml
    Description:

    DSCOVR_EPIC_L2_AOCH_01 is the aerosol optical centroid height (AOCH) product for global smoke and dust aerosols retrieved from oxygen A-band (764 nm) and B-band (688 nm) measured by Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) satellite. The ultraviolet aerosol index (UVAI) is also retrieved using EPIC 340 and 388 nm channels. The retrieval algorithm assumes a quasi-Gaussian aerosol vertical profile shape and retrieves AOD and the height at which the aerosol extinction peaks (e.g., AOCH). Cloud mask is conducted through the spatial variability tests at 443 and 551 nm, as well as the brightness tests with the prescribed threshold of TOA reflectance at 443 and 680 nm for land and 443, 680 and 780 nm over water. The water pixels with a sun glint angle smaller than 30 are screened out. AOD is then retrieved from EPIC atmospheric window channel 443 nm, and the AOCH is derived subsequently based on the ratios of oxygen A and B bands to their corresponding neighboring continuum bands (764/780 nm and 688/680 nm). The surface reflectance for water surface comes from GOME-2 Lambert-equivalent reflectivity (LER) product. A 10-year climatology of Lambertian surface reflectance from MODIS BRDF/Albedo product (MCD43) is applied for retrievals over the land surface. The aerosol types around the globe are classified based on their sources at different regions and their corresponding aerosol single scattering properties are defined based on AERONET climatology for each region. The retrieval algorithm is based upon the lookup table constructed by the Unified and Linearized Vector Radiative Transfer Model (UNL-VRTM).

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    LARC_ASDC Short Name: DSCOVR_EPIC_L2_AOCH Version ID: 01 Unique ID: C2501666124-LARC_ASDC

  • DSCOVR EPIC Cloud Fraction Image

    https://cmr.earthdata.nasa.gov/search/concepts/C2547303323-LARC_ASDC.xml
    Description:

    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; 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 take into account 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. Since EPIC does not have particle size sensitive channels, a single channel retrieval algorithm was developed assuming fixed values for cloud effective radius (CER). In addition, cloud phase determination capability for EPIC is limited; hence the EPIC COT product provides two retrievals for each cloudy pixel, one assuming 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

  • DSCOVR EPIC L2 Multi-Angle Implementation of Atmospheric Correction (MAIAC) Version 02

    https://cmr.earthdata.nasa.gov/search/concepts/C1969999465-LARC_ASDC.xml
    Description:

    DSCOVR_EPIC_L2_MAIAC_02 is the DSCOVR EPIC L2 Multi-Angle Implementation of Atmospheric Correction (MAIAC) Version 02 data product. Data collection for this product is ongoing. Level 2 Multi-Angle Implementation of Atmospheric Correction (MAIAC) provides an interdisciplinary suite of products for the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC). The current version 2 reports the following products: a) Atmosphere: cloud mask, global aerosol optical depth at 443nm and 551nm, fine mode fraction (over ocean) and spectral aerosol absorption for detected biomass burning or mineral dust aerosols. The absorption information includes single scattering albedo at 443nm, imaginary refractive index at 680nm, and Absorption Angstrom Exponent (AAE) characterizing spectral increase of imaginary refractive index at Vis-UV wavelengths. The absorption information is provided for two effective aerosol layer heights of 1km and 4km generally representing boundary layer and transport mode. b) Land: atmospherically corrected spectral bidirectional reflectance factors (BRF) along with Lambertian surface reflectance, and bidirectional reflectance distribution function (BRDF) for the backscattering view geometries of EPIC. The BRDF is represented by 3 parameters of the Ross-Thick Li-Sparse model. c) Ocean: Water leaving reflectance (non-dimensional) at Ultraviolet-Visible (UV-Vis) bands. The parameters are distributed at 10 km rotated sinusoidal grid and 1 to 2-hour temporal frequency. MAIAC version 02 also provides gap-filled global composite products for Normalized Difference Vegetation Index (NDVI) over land, and water leaving reflectance in 5 UV-Vis bands over global ocean. The composite products represent a weighted running average where the weight of the latest observation is maximized towards the local noon and low aerosol conditions.

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    LARC_ASDC Short Name: DSCOVR_EPIC_L2_MAIAC Version ID: 02 Unique ID: C1969999465-LARC_ASDC

  • DSCOVR EPIC L2 Ozone (O3), Sulfur Dioxide (SO2) Aerosol Index (AI) with Epic L1B V03 Input, Version 2

    https://cmr.earthdata.nasa.gov/search/concepts/C1715718433-LARC_ASDC.xml
    Description:

    Robust cloud products are critical for DSCOVR to make a significant contribution 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 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 from 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 through 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, which will be 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 to better interpret 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 also for improving “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

  • DSCOVR EPIC Level 1A Version 3

    https://cmr.earthdata.nasa.gov/search/concepts/C1666134802-LARC_ASDC.xml
    Description:

    Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) is a 10-channel spectro-radiometer (317 – 780 nm) onboard NOAA’s 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 UV radiation estimates at Earth's surface. EPIC provides 10 narrow-band spectral images of the entire sunlit face of the Earth using a 2048x2048 pixel CCD (Charge Coupled Device) detector coupled to a 30-cm aperture Cassegrain telescope. EPIC collects radiance data of 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 properly convert the images to Level 1A format. The major 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 measured 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 main 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 is applied to every image. Other corrections are also applied 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 the measured radiances. The Level 1A products contain calibrated EPIC images with ancillary metadata and geolocation information. These data products are in HDF5 format.

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    LARC_ASDC Short Name: DSCOVR_EPIC_L1A Version ID: 3 Unique ID: C1666134802-LARC_ASDC

  • DSCOVR EPIC Level 1B Version 3

    https://cmr.earthdata.nasa.gov/search/concepts/C1667168435-LARC_ASDC.xml
    Description:

    Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) is a 10-channel spectro-radiometer (317 – 780 nm) onboard NOAA’s 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 UV radiation estimates at Earth's surface. EPIC provides 10 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 of 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 properly convert the images to Level 1A format. The major 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 measured 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 main 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 is applied to every image. Other corrections are also applied 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 and PNG format.

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