Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR)

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4STARSpectrometer for Sky-Scanning,
Sun-Tracking Atmospheric Research
A collaboration involving
NASA Ames P. Russell, J. Redemann, S. Dunagan,
R. Johnson, J. ZavaletaPNNL B. Schmid, C.
Flynn, E. KassianovNASA GSFC AERONET Team
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4STAR Spectrometer for Sky-Scanning,
Sun-Tracking Atmospheric Research
AERONET-like

• Phase function
• Size mode distributions
• nre(l), nim(l)
• Single-scattering albedo
• Asymmetry parameter
• Shape
• Hence aerosol type

• AATS-14 - like
• column and profiles
• Aerosol
• H2O
• O3

Improve H2O, O3 Add NO2 Thus improve
AOD Simultaneous spectra yield airborne profiles
of aerosol type via Aeronet-like retrievals
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4STAR and its Use
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AATS-14

• NASA Ames
• Airborne Tracking
• Sunphotometers
• Since 1996
• 13 Field Campaigns
• gt70 Publications

AATS-6
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Spectrometer for Sky-Scanning, Sun-Tracking
Atmospheric Research (4STAR)
Fiber Optics Cable
Optical Entrance
Sun Tracking Head
Motor Feedback Devices
Optical Entrance
Elevation Motor
Aircraft Skin
Azimuth Motor
Slip Ring
Fiber Optics Rotating Joint
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Key Technological Hurdles

1. Maintaining calibration to 1 over a period of
   months
2. Stray light rejection measure skylight within 3
   of sun
3. Fiber optic couplings with lt1 calibration
   stability (Connections/Rotation)
4. Sky scan within 100 seconds(10 km in flight)

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Ground Prototype (4STAR-Ground)
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Direct Beam Comparison
AATS-14
4STAR-Ground
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Direct Beam ComparisonAATS-14 4STAR-Ground
Transmittance
UT
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4STAR-Ground
AERONET Cimel
Jens Redemann
Roy Johnson
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Radiance Calibration
4STAR-Ground
AERONET Cimel
NASA Ames 30 Sphere
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4STAR and AERONET principal plane scan
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Straylight rejection close to Sun
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Size Distribution Retrieval using AERONET Code
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Rotating Fiber Optics Coupling Throughput
Repeatability
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Next steps

• New collector design, 100X light volume. Goal
  Sky-scan measurements within 100 seconds, 10 km
  in flight
• Mauna Loa, spectral Langley calibration
• Add SWIR spectrometer for more size and
  absorption information
• Continue spectral inversion development
• Harden design for airborne deployment
• Deploy in 2011 Western Atlantic Tropospheric
  Aerosol Campaign (WATAC)