NASA%20IKONOS%20Multispectral%20Radiometric%20Calibration%20and%203-year%20Temporal%20Stability%20Assessment

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NASA IKONOS Multispectral Radiometric Calibration
and 3-year Temporal Stability Assessment

• Mary PagnuttiLockheed Martin Space
  OperationsNASA Stennis Space Center
• phone [phone]e-mail mary.pagnutti_at_ssc.n
  asa.gov
• ISPRS Commission 1/WG2
• International Workshop on
• Radiometric and Geometric Calibration
• December 1-5, 2003

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Co-Authors

• David Carver, Kara Holekamp, Kelly Knowlton, Dean
  Noel, Robert RyanLockheed Martin Space
  Operations - Stennis Programs
• NASA Stennis Space Center
• Vicki ZanoniNASA Earth Science Applications
  DirectorateNASA Stennis Space Center
• Kurtis Thome
• University of Arizona, Remote Sensing Group
• Stephen Schiller
• Raytheon Corporation
• David Aaron
• South Dakota State University

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IKONOS Characterization Background

• NASA procured 11M of IKONOS imagery for
  scientific research through the Scientific Data
  Purchase (SDP) program.
• An independent assessment of the imagery was
  conducted to assure Earth science researchers
  that the imagery being utilized for scientific
  research met stated performance specifications.
• NASA, USGS and NIMA coordinated radiometric,
  geometric and spatial characterization activities
  and formed the Joint Agency for Commercial
  Imagery Evaluation (JACIE) team to enable a more
  comprehensive, cost effective characterization.
• NASA lead the radiometric characterization
  effort.

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Space Imaging IKONOS
Sensor Details Panchromatic (PAN) and
multispectral (MS) pushbroom imaging system Band
Profiles PAN (526-929 nm), Blue (445-516 nm),
Green (506-595 nm), Red (632-698 nm), NIR
(757-853 nm) Resolution _at_ Nadir 0.88 m Pan, 3.52
m Multispectral Image Swath 11.3 km _at_
nadir Dynamic Range 11-bits per pixel Detector
Array 13,500 pixels cross-track (PAN), 3375
pixels cross-track (MS)
Satellite Details Launch Date September 24,
1999 Operation Life Over 7 years Orbit 98.1
degree, Sun synchronous Orbit Time Around Earth
98 minutes Revisit Time 3 days _at_ 1-m resolution
Ref Kramer, Herbert J., Observation of the Earth
and Its Environment, Survey of Missions and
Sensors. 4th edition, ppg 285-288.
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NASA Radiometric Calibration Team

• NASA Stennis Space Center
• Earth Science Applications Directorate
• Stennis Space Center, MS
• University of Arizona
• Remote Sensing Group
• Tucson, AZ
• South Dakota State University
• Physics and Electrical Engineering Departments
• Brookings, SD

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NASA Radiometric Calibration Team Benefits

• Three independent groups employed similar
  approach but different tools and techniques.
• Checks and balances between groups
• Removes/reduces any bias associated with one
  individual group or set of techniques.
• Eight different study sites were utilized.
• Removes/reduces any bias associated with a single
  study site.
• Radiance values found within these study site
  scenes span the dynamic range of the sensor.

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IKONOS Acquisition Sites
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Brookings, SD Acquisition Site

• Site South Dakota State University campus, 3M
  manufacturing plant, town, surrounding grassy
  fields and airport
• Elevation 500 m
• Center Point 44.30 N, 96.81 W
• Targets Evaluated Grass, Radiometric Tarps,
  Concrete Parking Lot.
• Acquisition Dates 6/30/00, 7/03/01, 7/17/01,
  7/25/01, 7/03/02, 7/22/02

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Maricopa Agricultural Center, AZ Acquisition Site

• Site Predominately agricultural scene, MAC is
  770 acres divided into 2 sections, several
  parcels of vegetation and soil types
• Elevation 400 m
• Center Point
• 33.04 N, 111.58 W
• Target Evaluated Wheat Field
• Acquisition Date 7/26/01

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NASA SSC, MS Acquisition Site

• Site Scattered buildings within a heavily
  wooded area, man-made reservoirs and canals
• Elevation 5.5 - 10 m
• Center Point 30.39 N, 89.61 W
• Targets Evaluated Grass Field, Concrete Parking
  Lot, Radiometric Tarps
• Acquisition Dates 1/15/02, 2/17/02

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West Texas Study Site, TX Acquisition Site

• Site Urban city, including airport and runways,
  adjacent farms
• Elevation 750 m
• Target Evaluated Concrete Runway
• Acquisition Dates 6/22/01, 8/05/01

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US Southwest Acquisition Sites

• Bright and Uniform
• High reflectance minimizes atmospheric
  uncertainties
• High Elevation
• All acquisition sites above 3500 ft elevation
• Minimal Precipitation and Cloud Cover
• Maintains stability and increases chance of
  acquisition
• Large
• Minimizes adjacency effects

Railroad Valley, NV 38.51 N, 115.69 W
Ivanpah, CA 35.53 N, 115.38 W
Lunar Lake, NV 38.40 N, 115.99 W
White Sands Missile Range, NM 32.91 N, 106.37 W
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Satellite Acquisitions
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Reflectance-based Vicarious Calibration Approach

• Measure target/ground reflectance coincident with
  the satellite acquisition
• Measure atmospheric aerosols, and pressure,
  temperature and water vapor profiles coincident
  with the satellite acquisition.
• Use these measurements along with acquisition
  geometry/location parameters as input into a
  radiative transfer model to predict at-sensor
  radiance.

Solar Irradiance

• Atmosphere
• (aerosols, molecules,
• P, T, humidity)
• scattering
• absorption

IKONOS
Targets (uniform surface)
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SSC Radiometric Characterization Techniques
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Radiometric Tarps

• Manufactured by MTL Systems, Inc.
• 4 20-m x 20-m tarps with reflectance values of
  approximately 3.5, 22, 33, and 52.
• Spectral measurement range of 400 to 1050 nm
• Standard deviation about average reflectance less
  than 1 spatially
• Peak to peak variation in reflectance less than
  10 within any 100-nm spectral band
• Less than 10 variation in reflectance values
  when measuring tarps from 10 deg to 60 deg off
  axis
• Each side is straight to within 6.0 centimeters
  over the 20-meter length
• Each tarp panel has 60 square witness samples
  measuring 30.5 centimeters by 30.5 centimeters.

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Reflectance Measurements

• ASD FieldSpec FR Spectroradiometers measure
  spectral reflectance and radiance of 99
  reflectance Spectralon panels (Jackson BRDF
  Model) and radiometric targets.
• ASD FieldSpec FR Spectroradiometers are
  radiometrically calibrated in the SSC Instrument
  Validation Lab (IVL) prior to field use.

• All Measurements taken within 20 minutes of
  satellite overpass.
• Most acquisition dates utilized multiple ASDs
  for cross comparison.
• Typically 1000 spectra are averaged for each
  target.

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Atmospheric Measurements

• Cloud cover monitoring Total Sky Imager
• Direct solar radiance Automated Solar
  Radiometer
• Direct, total, and diffuse irradiance
  Multi-filter Rotating Shadow-band Radiometer
• Vertical profiles of temperature, pressure and
  relative humidity Radiosonde Balloon

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Cross Comparison of Atmospheric Data
Optical depth comparisons are made between
fielded instruments that have different channels
and measurement principles.
ASR Channels MFRSR Channels
380 nm
400 nm 415
440 nm
520 nm 500
610 nm 615
670 nm 673
780 nm
870 nm 870
1030 nm
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In Field Calibration of Solar Radiometers
Langley data points are in instrument units that
corresponds to irradiance. Top of atmosphere
irradiance (Vo) values for each channel are
derived from extrapolation to zero airmass.
Historical Vo values are tracked over time to
verify calibration stability. Top of atmosphere
irradiance varies minimally throughout the year,
giving a near constant for comparison.
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MODTRAN At-Sensor Radiance Prediction Process
COLLECT GROUND TRUTH DATA
INGEST AND REDUCE ASD SURFACE DATA
INGEST AND REDUCE RADIOSONDE DATA
INGEST AND ANALYZE SOLAR RADIOMETER DATA
Radiometry Data Processing Software Suite
USER DEFINED ATMOSPHERE
AEROSOL DENSITY and SCATTERING ASYMMETRY
SPECTRAL ALBEDO
MODTRAN INPUT
MODTRAN ASD/SPECTRALON GEOMETRY
CHECK and REVIEW INPUT PARAMETERS
RADIANCE PREDICTION AGREES WITH ASD
NO
MODTRAN AT-SENSOR RADIANCE PREDICTION
YES
MODTRAN W/ IKONOS GEOMETRY and FILTER FILES
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2000 Calibration Results
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2001 Calibration Results
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2002 Calibration Results
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Calibration Coefficients
Denotes NASA estimate made prior to the Space
Imagings image processing upgrade.
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3 Year IKONOS Calibration Summary
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Summary

• The temporal stability of the radiometric
  calibration coefficients for the IKONOS imaging
  system has been shown to be stable for the first
  three years of operation.
• Based on the uncertainty of our at-sensor
  radiance predictions, IKONOS has shown no
  appreciable sign of sensor drift.