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AIRS (Atmospheric Infrared Sounder) Instrument Characteristics

Learn about the AIRS system onboard Aqua, launched in 2002, monitoring Earth's atmosphere with its grating spectrometer and array detectors. Explore its subsystems, optics, spatial, and spectral coverage.

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AIRS (Atmospheric Infrared Sounder) Instrument Characteristics

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  1. AIRS (Atmospheric Infrared Sounder)Instrument Characteristics

  2. AIRS onboard of AQUA • NASA’s EOS spacecraft • Aqua launched May 4, 2002 • 705 km orbit (polar-orbiting) • Early afternoon (1:30 PM) equator crossing time heading north • AIRS system on Aqua: •  AIRS (Atmospheric infrared Sounder) •  AMSU-A (Advanced Microwave Sounding Unit) •  HSB (Humidity Sounder Brazil) • Other instruments: •  MODIS (Moderate Resolution Imaging Spectroradiometer) •  AMSR-E (Advanced Microwave Scanning Radiometer for EOS) • CERES (Clouds and the Earth’s Radiant Energy System)

  3. AIRS – Monitoring Earth’s Atmosphere

  4. AIRS System http://www-airs.jpl.nasa.gov/

  5. AIRS – Subsystems Electronics Sensor Power Supply ADM & SEM Electronics Cooler Electronics Mechanical Instrument Support Structure Scanning & Calibration Scan Head Assembly On-Board Calibrators Optics & Focal Planes Infrared Spectrometer Assembly Focal Plane Assembly Cryogenic Cooling Systems Dewar Assembly Crypcooler Assembly Radiators and Earth Shield Assembly

  6. AIRS – Grating Spectrometer • Array grating spectrometer • Operating range: 3.7 – 15.4 m • Spectral resolution: /=1200 • Infrared energy dispersed across arrays of • HgCdTe detectors (2378 detectors in 17 arrays)

  7. AIRS – Grating Spectrometer Basics Different wavelength are diffracted into different angles m = d(sin + sin) where  wavelength  incident angle  diffraction angle d groove spacing of grating m diffraction order (integer)

  8. AIRS – Grating Spectrometer Optics Radiance http://www-airs.jpl.nasa.gov/ Radiance  Scan Mirror  Telescope  Spectrometer Entrance Slit  Grating  Array Detectors (HgCdTe Focal Plane Assembly)

  9. AIRS Spatial Coverage (1) http://www-airs.jpl.nasa.gov/ Swath: 1650 km IFOV: 1.1°  13.5 km

  10. AIRS Spatial Coverage (2) AIRS data is collected in 6 minutes junks = 1 granule 135 scanlinesx90 footprints=12150 pixels per granule (~125 MB) 240 granules per day (120 ascending daytime and 120 descending nighttime granules)

  11. AIRS Spatial Coverage (3)

  12. AIRS Spectral Coverage • IR sounder: 2378 channels • spectral ranges: 3.7 - 4.61 m, 6.2 - 8.22 m , 8.8 - 15.4 m;

  13. AIRS Spectral Coverage  Vertical Resolution Jacobian matrix K=dBT/dX is the matrix of partial derivatives of the Brightness temperature with respect to the input parameter X. The weighting functions (=rows of K) reflect the relative contribution from each level to the total measured radiance. Temperature weighting functions Humidity weighting functions

  14. AIRS IR Specification Infrared Spectral Coverage: 3.74 m - 4.61 m [2674 – 2170 cm-1] 6.20 m – 8.22 m [1613 – 1217 cm-1] 8.80 m – 15.4 m [1136 – 649 cm-1] Spectral Resolution: /=1200 Spatial Coverage: 49.5 around nadir 1.1 (~13.5 km dia) IFOV (Instantaneous Field of View) Sensitivity (NEDT): 0.14 K at 4.2 m 0.20 K from 3.7 to 13.6 m 0.35 K from 13.6 to 15.4 m Power / Mass: 256 W / 166 kg Lifetime: 5 years

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