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The Landsat 7 Processing System ( LPS ) Level Zero-R Science Products

The Landsat 7 Processing System ( LPS ) Level Zero-R Science Products. Michael R. Reid Computer Sciences Corporation Mike.Reid@gsfc.nasa.gov. The Landsat 7 Mission. The latest in the Landsat series Joint operation between NASA and USGS Global coverage in 8 bands Sun-synchronous orbit

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The Landsat 7 Processing System ( LPS ) Level Zero-R Science Products

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  1. The Landsat 7 Processing System( LPS )Level Zero-R Science Products Michael R. Reid Computer Sciences Corporation Mike.Reid@gsfc.nasa.gov

  2. The Landsat 7 Mission • The latest in the Landsat series • Joint operation between NASA and USGS • Global coverage in 8 bands • Sun-synchronous orbit • Landsat 7 successfully launched in April 1999 • Now fully operational • Data products provided by the USGS’ EROS Data Center (EDC) in Sioux Falls, SD

  3. Earth Coverage • Enhanced Thematic Mapper Plus (ETM+) is the only science instrument • Images the Earth in 185 km wide swaths • Images in eight bands • Image data are fitted onto the Worldwide Reference System (WRS) grid • WRS grid consists of 185 km  170 km scenes • ETM+ images a WRS scene with 375 scans • WRS scenes overlap

  4. The ETM+ Instrument Data • Eight bands • Six 30m-resolution spectral bands • Bands 1-5 (range  = 0.45…1.75 m) • Band 7 ( = 2.09-2.35 m) • 6,600 pixels per scan data line • 16 data lines per scan • One 60m-resolution thermal band • Band 6 ( = 10.4-12.5 m) • 3,300 pixels per scan data line • 8 data lines per scan • One 15m-resolution panchromatic band • Band 8 ( = 0.52-0.90 m) • 13,200 pixels per data line • 32 data lines per scan

  5. Landsat 7 Processing System (LPS) • Developed at NASA/GSFC for the EDC • Part of the Landsat 7 Ground System • Performs the first stage of Level 0 processing • Aligns bands (forward and reverse scans) • Does not apply corrections or calibrations • Does not perform rectification • Produces HDF-EOS science data products on a subinterval basis • Runs on a high-end SGI™ system

  6. LPS Processing • Divides the subintervals into sets of contiguous WRS scenes • Geolocates the scenes • Produces viewable, multi-band, color browse images on a WRS scene basis • Performs automatic cloud cover assessment (ACCA) on a WRS scene basis • Displays a Moving Window Display to the user

  7. The LPS Moving Window Display (MWD)

  8. LPS Processing continued… • Receives data on two channels (“format 1” and “format 2”) • Decodes the downlinked raw telemetry • Processes the two formats separately • Constructs an image in each band of the “swath” on the Earth’s surface covered during a contact • Divides the swath into subintervals

  9. The LPS Data Products • LPS products generated on a subinterval basis • Format 1 and Format 2 are separate file sets • The LPS Product file sets include: • Band files (Swath files) • Internal Calibrator (IC) data files • Mirror Scan Correction Data (MSCD) files • Payload Correction Data (PCD) files • Metadata files • Multi-Band Browse files (format 1 only)

  10. The Band Files — Swaths • Image data stored in HDF-EOS Swaths • One Swath per file • Bands 1-5 & 7 files are up to about 1.2 Gb in size • Band 6 files are up to about 295 Mb in size • Band 8 data are huge, won’t fit in single files • Up to about 4.6 Gb of data in a 35-scene subinterval • HDF 4 limits file sizes to 2 Gb • Written to up to three separate swaths in separate segment files

  11. The Band Files — Geolocation • Geolocation structures • Uses HDF-EOS Index map to link WRS scene corner lon/lat coordinates to the Swath • Full scenes from 30m-res. bands are always 6,000 data lines • Partial scenes at the beginnings and ends of subintervals are of irregular sizes • Uses Time Geolocation field to temporally locate scans in the Swaths • HDF-EOS Geolocation structures also used to store other ancillary data

  12. The Internal Calibrator (IC) Files • Contain lamp and shutter data for spectral bands • Contain blackbody radiance and shutter data for thermal band (band 6) • One file for each format • Separate HDF-EOS Swath for each band • One data set per scan • Data located by Time only using HDF-EOS Geolocation structure

  13. Mirror Scan Correction Data (MSCD) Files • Mainly contain data quality information • Stored in an HDF-EOS Point • Located by Time only using HDF-EOS Geolocation structure • Format 1 and Format 2 MCSD are identical except for start and end offsets at the beginnings and ends of the data

  14. Other LPS Product Files • Payload Correction Data (PCD) Files • Contain spacecraft attitude and ephemeris information and miscellaneous engineering data • Native HDF Vdata, no HDF-EOS structures • Format 1 and Format 2 are identical • Metadata Files • Format 1 and Format 2 similar, but not identical • Simple text file in Object Definition Language (ODL) Syntax • Browse Files • Format 1 only • One native HDF RIS24 true color image • Made from three of the five format 1 spectral bands • JPEG Compressed images

  15. LPS Browse File (Hudson Bay)

  16. Format 1 • Six Band files • Bands 1-5 and 6L • One Internal Calibrator (IC) data file • One Payload Correction Data (PCD) file • One Mirror Scan Correction Data (MSCD) file • One Metadata file • Includes scene cloud cover assessments • 1 to 37 Multi-band Browse files

  17. Format 2 • Three Bands, up to five files • Bands 6H and 7 • Band 8 (High-Resolution Panchromatic Band) • Written to up to three segment files due to size • One Internal Calibrator (IC) data file • One Payload Correction Data (PCD) file • One Mirror Scan Correction Data (MSCD) file • One Metadata file • No Browse files

  18. The LPS Product File Set

  19. Level Zero-R Data Subsets • Single WRS scene products • One 375 scan subset • Data fitted to the WRS grid • Multiple scene products • Contains several contiguous WRS scenes • Partial subinterval (a.k.a., floating scene) products • Similar to the multiple scene products, but not aligned along WRS rows • Full subinterval products • Essentially the full LPS subinterval

  20. Subsetting the LPS Subintervals • LPS Band and IC files contain geolocated HDF-EOS Swaths • Can subset band data by index-mapped WRS scene corner geographic coordinates or time using HDF-EOS functions • Band 8 presents a problem due to file segmentation • Can subset IC data by time using HDF-EOS functions • MSCD file contains an HDF-EOS Point • Can subset by time using HDF-EOS functions • PCD is native HDF and cannot be subsetted using HDF-EOS functions

  21. LPS Subsetting Difficulties • Band data Swaths are stored in separate files • Format 1/Format 2 data offset • Partial subinterval geolocation • LPS only computes lon/lat coordinates for WRS scene corners, not on a scan basis • Must interpolate subset interval corner coordinates • Band 8 segmentation • HDF-EOS does not support file segmentation

  22. Band 8 Subsetting Problem • Must treat the band 8 segments as completely separate data sets • Subsetting out multiple scene or partial subinterval products from band 8 is especially complicated if the subset interval spans across segments • After subsetting from the two segments, the data must be concatenated into a single array

  23. Level Zero-R Distribution Product • Native HDF, no HDF-EOS structures • Contains data from both Format 1 and Format 2 • Subsets of Band and IC data written to Scientific Data Sets (SDS) • Subset of MSCD written to Vdatas • Complete PCD and Metadatas written to Vdatas • Contains Calibration Parameter File (CPF) • Stores all data in HDF external elements

  24. L0R Distribution Product File Set

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