=============================================================================== PRISM Distribution Document =============================================================================== Sarah R. Lundeen, Sarah.R.Lundeen@jpl.nasa.gov Robert O. Green, Robert.O.Green@jpl.nasa.gov Michael Eastwood, meastwood@jpl.nasa.gov David R. Thompson, David.R.Thompson@jpl.nasa.gov This document describes the PRISM L1B and L2 data products. PRISM is an imaging spectrometer that measures reflected radiance at 3nm intervals in the Visible/Near-Infrared (VNIR) spectral range from 380-1050nm. Additional information may be found on http://prism.jpl.nasa.gov ------------------------------------------------------------------------------- OVERVIEW ------------------------------------------------------------------------------- Each flightline uses a specific base filename prefix: prmYYYYMMDDtHHNNSS YYYY: The year of the airborne flight run. MM: The month of the airborne flight run (i.e. 05 represents May). DD: The day of the airborne flight run (22 is the 22nd day of the month) HH: UTC hour at the start of acquisition NN: UTC minute at the start of acquisition SS: UTC second at the start of acquisition The PRISM data products for a particular airborne flight run are organized in the following directory structure, labeled with a processing version marker VVV: /YYYYMMDDtHHNNSS_VVV | prmYYYYMMDDtHHNNSS_h2o_VVV | prmYYYYMMDDtHHNNSS_h2o_VVV.hdr | prmYYYYMMDDtHHNNSS_rdn_VVV_img | prmYYYYMMDDtHHNNSS_rdn_VVV_img.hdr | prmYYYYMMDDtHHNNSS_corr_VVV_img | prmYYYYMMDDtHHNNSS_corr_VVV_img.hdr | prmYYYYMMDDtHHNNSS_ort_glt | prmYYYYMMDDtHHNNSS_ort_glt.hdr | prmYYYYMMDDtHHNNSS_ort_igm | prmYYYYMMDDtHHNNSS_ort_igm.hdr The file product codes signify: *obs_ort parameters relating to the geometry of observation and illumination rendered using the *_ort_glt lookup table *obs_ort.hdr obs_ort image header file *ort_glt geometric look-up table *ort_glt.hdr GLT image header file *ort_igm input geometry file *ort_igm.hdr IGM image header file *rdn_VVV_img orthocorrected, scaled radiance image file *rdn_VVV_img.hdr RDN image header file *corr_VVV_img orthocorrected, scaled reflectance image file *corr_VVV_img.hdr CORR image header file *h2o_VVV orthocorrected water absorption data *h2o_VVV.hdr H2O header file ------------------------------------------------------------------------------ FILE DESCRIPTIONS ------------------------------------------------------------------------------ *ort_glt GEOMETRIC LOOKUP TABLE (GLT) Contents: Orthocorrected product with a fixed pixel size projected into a rotated UTM system that contains the information about which original pixel occupies which output pixel in the final product. Additionally, each pixel is sign-coded to indicate if it is real (indicated by a positive value) or a nearest-neighbor infill (indicated by negative values). The GLT file contains two parameters: 1) sample number 2) original line number File type: BINARY 16-bit, integer, IEEE. Format: Band interleaved by line ------------------------------------------------------------------------------ *ort_glt.hdr HEADER FILE FOR GEOMETRIC LOOKUP TABLE (GLT.HDR) DATA Contents: Format of each *ort_glt file. This file contains the number of lines, samples, channel, integer format, pixel size, scene elevation, UTM zone number and rotation angle information, etc. File type: ASCII ------------------------------------------------------------------------------- *ort_igm INPUT GEOMETRY FILE (IGM) Contents: Pixel location data for each radiance image cube. The IGM file data contain three parameters: 1) WGS-84 longitude (reported in decimal degrees) 2) WGS-84 latitude (reported in decimal degrees) 3) Estimated ground elevation at each pixel center (reported in meters) No map correction or resampling is applied to the radiance image cube; the IGM file only reports the surface location of the unadjusted pixel centers. File type: BINARY 64-bit double precision, floating point IEEE. Units: Band 1 - decimal degrees Band 2 - decimal degrees Band 3 - meters Format: Band interleaved by line ---------------------------------------------------------------------------- *ort_igm.hdr HEADER FILE FOR INPUT GEOMETRY FILE (IGM) DATA Contents: Format of each *ort_igm file. This file contains the number of lines, samples, channel, integer format, etc. File type: ASCII ---------------------------------------------------------------------------- *rdn_VVV_img CALIBRATED PRISM RADIANCE (IMAGE) DATA Contents: PRISM calibrated radiance File type: BINARY 32-bit little-endian floating point IEEE. Units: microwatts per centimeter_squared per nanometer per steradian Format: Band interleaved by line -------------------------------------------------------------------------------- *rdn_VVV_img.hdr HEADER FILE FOR CALIBRATED PRISM RADIANCE (IMAGE) DATA Contents: Format of each PRISM calibrated radiance scene. This file contains the number of lines, samples, channel, etc. It also records the spectral calibration (wavelength and full-width at half-maximum value) for every channel in the radiance data. File type: ASCII ---------------------------------------------------------------------------- *corr_VVV_img CALIBRATED PRISM REFLECTANCE (IMAGE) DATA Contents: PRISM calibrated reflectance File type: BINARY 32-bit little-endian floating point IEEE. Units: Apparent surface reflectance (Gao et al., 1993) Format: Band interleaved by line -------------------------------------------------------------------------------- *corr_VVV_img.hdr HEADER FILE FOR CALIBRATED PRISM REFLECTANCE (IMAGE) DATA Contents: Format of each PRISMcalibrated radiance scene. This file contains the number of lines, samples, channel, etc. It also records the spectral calibration (wavelength and full-width at half-maximum values) for every channel in the radiance data. The "Smoothing factors" field contains a list of multiplicative coefficients applied to smooth the resulting reflectance spectrum. These coefficients were derived from Calibration measurements using spectrally-invariant surface targets. To remove this correction simply divide the apparent reflectance by these values. File type: ASCII ---------------------------------------------------------------------------- *h2o_VVV WATER ABSORPTION PATH (IMAGE) DATA Contents: Retrieved column water vapor and optical absorption paths for liquid H2O and ice File type: BINARY 32-bit little-endian floating point IEEE. Units: Band 1: Retrieved column H2O vapor in cm Band 2: Total liquid H2O absorption path in cm Band 3: Total ice absorption path in cm Format: Band interleaved by line -------------------------------------------------------------------------------- *h2o_VVV.hdr HEADER FILE FOR WATER ABSORPTION PATH (IMAGE) DATA Contents: Format of each PRISM H2O cene. This file contains the number of lines, samples, channel, etc. File type: ASCII -------------------------------------------------------------------------------- REFERENCES -------------------------------------------------------------------------------- Gao, B.C., K. H. Heidebrecht, and A. F. H. Goetz, Derivation of scaled surface reflectances from PRISM data, Remote Sens. Env., 44, 165-178, 1993 -------------------------------------------------------------------------------- ACKNOWLEDGEMENTS -------------------------------------------------------------------------------- This research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). We are grateful for the help and assistance of colleagues including Bo-Cai Gao (NRL), Ian McCubbin (JPL), Dar Roberts (UCSB), Mark Helmlinger (JPL), Scott Nolte (JPL), Ernie Diaz (JPL), Daniel Nunes (JPL), Yasha Mouradi (JPL), and the rest of the PRISM team. Copyright 2014 California Institute of Technology. All Rights Reserved. U.S. Government Support Acknowledged. -------------------------------------------------------------------------------- MODIFICATIONS -------------------------------------------------------------------------------- 21 Sept. 2014 (D. R. Thompson) - Translated from AVIRIS-NG to PRISM 10 Sept. 2014 (D. R. Thompson) - Initial document ------------------------------------------------------------------------------ VERSION-SPECIFIC PARAMTERS ------------------------------------------------------------------------------ Level 1 Version tag: v1e Radiometric calibration: PRISM20140909t012039_brdfcorr.rcc Flat field: PRISM20140909t012039_brdfcorr_ff Wavelength calibration: 20140221_PRISM_wavelengths_truncated.txt Level 2 Atmosphere model: Mid latitude summer Sensor altitude (km): 20.023250992 Aerosol model: Continental Visibility (km): 300 H2O estimation algorithm: Log linear 760nm O2 scaling: 1.0 1140nm H2O scaling: 1.0