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NPP / NPOESS Product Profile of HDF5

NPP / NPOESS Product Profile of HDF5. Richard Ullman NASA / Goddard NPOESS Integrated Program Office. NPP/ NPOESS Product Data Format. Richard E. Ullman NOAA/NESDIS/IPO • NASA/GSFC/NPP Algorithm Division • System Engineering Data/Information Architecture richard.ullman@nasa.gov. NPOESS.

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NPP / NPOESS Product Profile of HDF5

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  1. NPP / NPOESS Product Profile of HDF5 Richard Ullman NASA / Goddard NPOESS Integrated Program Office

  2. NPP/ NPOESS Product Data Format Richard E. Ullman NOAA/NESDIS/IPO • NASA/GSFC/NPP Algorithm Division • System Engineering Data/Information Architecture richard.ullman@nasa.gov

  3. NPOESS • NPOESS is the National Polar Operational Environmental Satellite System • Managed by the Integrated Program Office (IPO) of three agencies: NASA, DoD and NOAA. • Next Generation Sun-Synchronous environmental observations for operational use. • Continuity of measurements with the NASA EOS • Launch circa 2014

  4. NPP • NPP key program objectives: • To provide NASA with continuation of a group of global change observations initiated by the Earth Observing System (EOS) TERRA, AQUA, and Aura missions • To provide the NPOESS operational community with pre-operational risk reduction demonstration and validation for selected NPOESS instruments, and algorithms, as well as the ground system • Launch June 2010.

  5. Payload Complement Comparison

  6. NASA • IPO -NOAA Space Segment • Spacecraft • ATMS • CERES Launch Support Segment (LSS) • VIIRS • CrIS • OMPS • Launch vehicle • Launch Support • Payload Processing support Command, Control & Communication Segment (C3S) • Manage Mission • Manage Satellite Operations • Space/Ground Communication • Data Routing & Retrieval Science Data Segment (SDS) Interface Data Processing Segment (IDPS) • Ingest and validate RDRs • Support Climate Research • Ingest and validate raw SMD • Process RDRs, SDRs, EDRs • Perform operations cal proc • Distribute data records Archive & Distribution Segment (ADS) • Ingest & validate data records • Manage archive • Interface with users Mission Segments and Responsibilities Space Segment

  7. Interface Data Processing System • The IDPS is a single production system for all NPP/NPOESS products • Delivery to institutional users (Centrals - NESDIS, AWFA, NAVOCEANO, FNMOC) and to CLASS • Low latency • Configuration controlled algorithms • Raw, Sensor Radiances, and Environmental Records

  8. NPP/NPOESS Product Definition • Product content is specified by the Algorithm Theoretical Basis Documents (ATBDs) consistent with program requirements and controlled by the NPOESS Algorithm Review Board (ARB) • Product encoding is specified by the Common Data Format Control Book-External (CDFCB-X) controlled by the IPO Configuration Control Board. • Product encoding for all delivered products is HDF5 according to a profile defined in the CDFCB-X.

  9. HDF5 for NPOESS • Hierarchical Data Format 5 (HDF5) is the format for delivery of processed products from the National Polar-orbiting Operational Environmental Satellite System (NPOESS) and for the NPOESS Preparatory Program (NPP). • HDF5 is a general purpose library and file format for storing scientific data. Two primary objects: • Dataset, a multidimensional array of data elements • Group, a structure for organizing objects • Efficient storage and I/O, including parallel I/O. • Free, open source software, multiple platforms. • Data stored in HDF5 is used in many fields from computational fluid dynamics to film making. • Data can be stored in HDF5 in an endless variety of ways, so it is important to standardize how NPOESS product data is organized in HDF5.

  10. Format Strengths • Mature technology. The encoding technologies used in NPP/NPOESS data products are: • HDF5 product encoding: • XML product metadata: • Bit packed field representation of quality information: • Scaled integer compression: • Consistent HDF5 group structure • Organization for each product is the same as all others. • Data “payload” is always in a product group within All_Data group. • Allows for flexible temporal aggregation • Granules are appended by extending dataset dimension.

  11. Format Challenges • Geolocation appears in a separate product group and may be in separate HDF5 file. • Field metadata, used to interpret data (similar to netCDF CF) are in separate product profile file. • Quality flags must be parsed before they can be interpreted. • Information needed for un-scaling scaled integers is not obvious. • HDF5 indirect reference link API, used to link metadata to the data in NPOESS’ use is complex and not supported by all analysis COTS implementations.

  12. Information Model UML Diagram

  13. An Example Product Group • In this example product group: • Five datasets constitute the product. • There are two common dimensions. • There are three congruent datasets. • Two datasets contain scale and offset values. • One dataset contains quality flags by element. • There are two granules in this aggregation. • Dimension “alongTrack” crosses the “granule boundary.”

  14. Example extracted from VIIRS Sea Surface Temperature EDR

  15. NPOESS Product Group crossTrack BulkTemp alongTrack Granule 0 SkinTemp Granule 0 Granule 1 SSTBulkFactors Granule 1 Granule 0 Granule 1 Granule 0 Granule 1 QF1_VIIRSSSTEDR Granule 0 SSTSkinFactors Granule 1 S S O O S S O O Example Product Group

  16. Dimensions • Dimensions are defined for each field. • Fields are related by congruency and common dimensions. • Common dimensions are given the same name. • One dimension crosses the granule boundary. When multiple granules are “aggregated” the “granule boundary” dimension is extended. • Dimension names and attributes are provided in the product profile.

  17. Scaled Integer Storage • For storage efficiency floating point data values may be stored as scaled integers. • To re-generate the data value, the dataset element must be multiplied by a supplied scale factor and an integer offset added. • The scale factor and offset are provided, one pair for each granule as a separate dataset. • The scale and offset value is the same for all granules produced with a given version of an algorithm - not dynamic scaling. • The fact that a dataset is a scaled value and the association between the data dataset and the scale factor dataset is contained in the product profile.

  18. 1-bit 2-bit 2-bit 3-bit Quality Flags by Element • Most NPOESS products contain multiple indicators of quality on an element by element basis. • Quality flags are associated by congruency (shared dimension) with a data array. • Multiple Flags of less than 8-bits are “packed” into structures aligned on 8-bit boundaries.

  19. Geolocation • Geolocation products are constructed using the same conventions as SDRs and EDRs. • Geolocation datasets have a congruence relationship with the same dimensions as the datasets to which they apply. • The association between a data product with its geolocation product is made on one of two ways: • The geolocation product may be packaged as a separate product group within the same HDF5 file. • The name of a separate geolocation product file may be stored in the N_GEO_Ref attribute on the root HDF group. • Choice of “as a product group” or “as a separate file” is made upon order from the NPOESS IDPS.

  20. Common Geolocation Fields for VIIRS Products

  21. Product Profiles • XML documents provide definition of product fields. • Product Profile is delivered as part of the product documentation. • Contains metadata such as units of measure, dimension names, legend entries, etc • A separate profile per product, but each conforms to the same NPOESS Product document type definition (dtd) and XML schema definition (xsd). • A style sheet is provided that can render the profile for a web browser. • Example: VIIRS_SST_EDR.xml

  22. 17 field attributes in XML product profile (1-9)

  23. 17 field attributes in XML product profile (10-17)

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