Introduction to MODIS design, calibration and processing

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Introduction to MODIS design, calibration and
processing

• Modified from PPT presented by Ewa Ainsworth
  (SAIC/NASA-GSFC)

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(No Transcript)
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MODIS design and calibration
SD Solar Diffuser, primary source for the
absolute radiometric calibration of VIS and NIR
bands SDSM Solar Diffuser Stability Monitor,
alternately views the Sun through an attenuation
screen and the light diffusely reflected from the
SD and ratios the obtained radiances SRCA
Spectroradiometric Calibration Assembly SWIR
short-wave IR MWIR medium-wave IR LWIR
long-wave IR FPA Focal Plane Assembly
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Sensor characterization and calibration concerns

• Mirror degradation, Response Versus Scan-angle
  (RVS), two mirror sides
• Detector calibration changes
• Polarization sensitivity
• In-band and out-of-band response
• Instrument and focal plane temperature effects
• Electronic cross-talk
• Stray-light contamination
• Solar Diffuser stability

• Solar Diffuser characterization
• Bi-directional Reflectance Factor (BRF) impact on
  calibration
• Earth shine effect sunlight reflecting off the
  Earth and onto the diffuser and adding to the
  solar irradiance
• Attenuation screen characterization through
  vignetting function
• SDSM uncertainty in monitoring SD reflectance
  changes

• Stray-light contamination
• Photons in the optical path from Earth coming
  from bright sources, i.e. clouds, land, and sun
  glitter (characterized by point spread function)

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MODIS calibration stages

• Direct calibration
• Pre-launch sensor is calibrated in a laboratory
  (thermal vacuum)
• On-orbit regular solar, deep-space, and lunar
  observations track changes in sensor response
  (possible additional on-board calibrators)
• Absolute radiometric accuracy
• reflective solar bands (0.41 2.1?m) 2 in
  reflectance and 5 in radiance
• thermal emissive bands (3.7 14.4?m) 1 for
  most bands
• Vicarious calibration uses sources independent
  of the primary direct calibration in situ
  measurements

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MODIS-Aqua daily
1 August 2007
MODIS-Terra daily
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MODIS data

• ATT EPH
• spacecraft attitude
• spacecraft position

• Level 0
• raw digital counts
• native binary format

• GEO
• geolocation
• radiant path geometry

• Level 1A
• raw digital counts
• HDF formatted

• Level 1B
• calibrated
• radiances
• converted
• telemetry

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Native satellite vs. map projection
cylindrical isotropic projection
increasing pixel size
bow-tie effect