AIRS (Atmospheric Infrared Sounder) Instrument Characteristics

AIRS onboard of AQUA NASA’s EOS spacecraft Aqua launched May 4, 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 Was Launched on the EOS Aqua Platform May 4, 2002 AIRS HSB AMSU-A1(3-15) AMSU-A2(1-2) Delta II 7920 MODIS Aqua Acquires 325 Gb of data per day

4 IASI was launched on the MetOp-A Satellite on Oct. 19, 2006 Soyuz 2/Fregat launcher, Baikonur, Kazakhstan IASI MHS AMSU- A1 AMSU- A2 ASCAT HIR S AVHRR

5 AIRS & IASI are making 4 global measurements per day Initial Joint Polar System: An agreement between NOAA & EUMETSAT to exchange data and products. –NASA/Aqua in 1:30 pm orbit –EUMETSAT/IASI in 9:30 am orbit (Oct. 19, 2006) –NPP-JPSS/CrIS in 1:30 pm orbit (2011)

6 Spectral Coverage of Thermal Sounders (Example Radiances: AIRS, IASI, & CrIS) AIRS, 2378 Channels CrIS 1305 IASI, 8461 Channels CO 2 O3O3 CO CH 4

AIRS – Monitoring Earth’s Atmosphere

AIRS System

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

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)

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)

AIRS – Grating Spectrometer Optics Radiance Radiance  Scan Mirror  Telescope  Spectrometer Entrance Slit  Grating  Array Detectors (HgCdTe Focal Plane Assembly)

AIRS Spatial Coverage (1) Swath: 1650 km IFOV: 1.1°  13.5 km

14 Atmospheric InfraRed Sounder (AIRS) spatial coverage

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)

AIRS Spatial Coverage (3)

AIRS Spectral Coverage IR sounder: 2378 channels spectral ranges:  m,  m,  m;

AIRS Spectral Coverage  Vertical Resolution Humidity weighting functionsTemperature weighting functions 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.

AIRS IR Specification Infrared Spectral Coverage: 3.74  m  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

20 AIRS/AMSU/HSB DATA PRODUCTS RMS Uncertainty* Horizontal Resolution 1 km below 700 mb 2 km mb 2 km in troposphere Radiance Products (Level 1B) AIRS IR Radiance AIRS VIS/NIR Radiance AMSU Radiance HSB Radiance Standard Core Products (Level 2) Cloud Cleared IR Radiance Sea Surface Temperature Land Surface Temperature Temperature Profile Humidity Profile Total Precipitable Water Fractional Cloud Cover Cloud Top Height Cloud Top Temperature 3% 20% K K 1.0K 0.5K 1.0K 1K 15% 5% 0.5 km 1.0 K 15 x 15 km 2.3 x 2.3 km 45 x 45 km 15 x 15 km 45 x 45 km Vertical Resolution

21 Thermal Sounder “Core” Products (on 45 km footprint, unless indicated) Radiance ProductsRMS RequirementCurrent Estimate AIRS IR Radiance (13.5 km)3%< 0.2 % AIRS VIS/NIR Radiance20%10-15% AMSU Radiance K1-2 K HSB Radiance (13.5 km) K(failed 2/2003) Geophysical ProductsRMS RequirementCurrent Estimate Cloud Cleared IR Radiances1.0K< 1 K Sea Surface Temperature0.5 K0.8 K Land Surface Temperature1.0KTBD Temperature Profile1K/1-km layer1K/1-km Moisture Profile15%/2-km layer15%/2-km Total Precipitable Water5% Fractional Cloud Cover (13.5 km)5%TBD Cloud Top Pressures0.5 kmTBD Cloud Top Temperatures1.0 KTBD

22 Trace Gas Product Potential from Operational Thermal Sounders gasRange (cm -1 )PrecisionInterference UTH %T(p) O3O %H2O,emissivity CO %H2O,N2O CH %H2O,HNO3 CO % H2O,O3 Volcanic SO %H2O,HNO3 HNO % 25% emissivity H2O,CH4 N2ON2O % H2O H2O,CO CFCl 3 (F11) %emissivity CF 2 Cl (F12) %emissivity CCl %emissivity Haskins, R.D. and L.D. Kaplan 1993 Product Available Now In Work Held Fixed

23 AIRS Surface Temp. & Water Vapor TT QQ WinterSummer

24 AIRS Climate/Environmental Products Monthly Temperature Monthly H2O Ozone Clouds Level 3 Products Ash & SO2 Aerosols CO