# Presentation: 509593

## Early Calibration Results from the 

- Early Calibration Results from the
- Atmospheric Infrared Sounder (AIRS) on Aqua
**Thomas S. Pagano**
**Hartmut H. Aumann, Steven L. Gaiser, David T. Gregorich**
**Jet Propulsion Laboratory,**
**California Institute of Technology**
**4800 Oak Grove Avenue, Pasadena, CA 91109**
- SPIE 4891-09
- Remote Sensing of the Atmosphere, Ocean, Environment, and Space
- Hangzhou, China
- 10/25/02

## AIRS-AMSU-HSB

**AIRS-AMSU-HSB**
**Atmospheric Infrared Sounder**
**Advanced Microwave Sounding Unit**
**Humidity Sounder for Brazil**

## AQUA MEASURES EARTHS WATER CYCLE, ENERGY FLUXES, VEGETATION, AND TEMPERATURES

**AQUA MEASURES EARTHS WATER CYCLE, ENERGY FLUXES, VEGETATION, AND TEMPERATURES**

- Image by TRW

***AMSR/E***
***MODIS***
***AMSU-A1,-A2***
***HSB***
***AIRS***
***CERES (2)***

**Notes:**
Measurements include
Evaporation from the oceans, water vapor in the atmosphere, clouds, precipitation, soil moisture, sea ice, land ice, and snow cover on the land and ice. 
Radiative energy fluxes, aerosols, vegetation cover on the land, phytoplankton and dissolved organic matter in the oceans, and air, land, and water temperatures. 

## The AIRS/AMSU/HSB data will be used to address several climate questions

**The AIRS/AMSU/HSB data will be used to address several climate questions**
**The global water and energy cycle****:  Is the cycle of evaporation and precipitation on Earth accelerating?**
**Determine the distribution and variations of water vapor**** - Earth’s primary greenhouse gas**
**Climate weather connection****:  Are current weather anomalies (hurricanes, droughts) connected to climate change and how?**
**Improving weather prediction****:  NOAA is a user together with 6 other weather prediction centers in Europe, America, Australia and Japan**
**Trace Gasses:****  Will provide the first satellite global map of the distribution of atmospheric concentration of CO****2**

## AIRS WAS DEVELOPED BY BAE SYSTEMS AND JPL AND DELIVERED IN NOVEMBER 1999

**AIRS Requirements**
**IFOV :  ****1.1° x 0.6° ****(13.5 km x 7.4 km)**
**Scan Range:  ****±49.5°**
**IR Spectral Range:****3.74-4.61 μm, 6.2-8.22 μm,****8.8-15.4 μm**
**IR Spectral Resolution:****≈ 1200 (********)**
**No. IR Channels:  ****2378 IR**
**VIS Channels: 4 ****(0.41-0.44 μm,0.58-0.68 μm, ****0.71-0.92 μm,0.49-0.94 μm)**
**VIS IFOV:  ****0.14° (1.7 km)**
**Mass: **** 177Kg****, Power:  ****256 Watts****, Life: ****5 years (7 years goal)**

## AIRS OPTICAL APPROACH IS BASED ON DEMANDING PERFORMANCE REQUIREMENTS

## AIRS TECHNOLOGY

**IR Spectrometer:  Multi-Aperture Array Grating Spectrometer**
**Spectrometer Cooling to 155K with  Two-Stage Passive Radiator **
**Focal Plane Cooling using Single Stage Stirling Pulse Tube, Redundant**
**FPAs:  PV HgCdTe to 13.7 μm, PC HgCdTe to 15.4 μm **
**On-Board Calibration Views:  Space, Blackbody, Parylene (Spectral), 3 VIS/NIR Lamps**
**Electronics Architecture:  **
***Dual Redundant/μ-processor controlled***
***On-board radiation circumvention signal processing***

## ABSOLUTE CALIBRATION AND CHARACTERIZATION PERFORMED PRIOR TO SPACECRAFT DELIVERY 

**Radiometric Response**
***Emissivity, Nonlinearity  (Less than 1.5%)***
***Stray Light***
***Polarization Sensitivity***
***Scan Angle Dependence  (Less than 2%)***
**Spectral Response**
***SRF Characterization (Less than 0.5% ************)***
***Channel Spectral Modeling Demonstrated***
**Spatial Response**
***Spatial Co-Registration (Less than 10%)***
***Stray Light Excellent***
***Far Field Response Excellent***
**All performance requirements met or approved by the AIRS Science Team as acceptable to meet the science requirements of the mission.**
**Exceptional Performance Achieved**

## PREFLIGHT SPECTRAL CAL SHOWS EXCELLENT SPECTRAL SHAPE AND STABILITY

**Knowledge of Centroids**
**Within Spec Limits**

**SRF Shape Well**
**Characterized to <10****-3**

**Temperature Dependence Well Behaved**

## SIMPLE RADIOMETRIC TRANSFER EQUATIONS LEAD TO EXCEPTIONAL ACCURACY

- Nsc,i,j = Scene Radiance (mW/m2-sr-cm-1)
*Psm* = Plank radiation function
- NOBC,i = Radiance of the On-Board Calibrator
- i = Scan Index, j = Footprint Index
- q = Scan Angle. q = 0 is nadir.
- dni,j = Raw Digital Number in the Earth View
- dnsv,i = Space view counts offset.
- ao = Radiometric offset. a1,i = Radiometric gain.
- a2 = Nonlinearity
- prpt = Polarization Factor Product
- d = Phase of the polarization

**Preflight Residuals < +/- 0.1K**
**For most channels.**

## AQUA WAS LAUNCHED ON MAY 4, 2002

**Delta 2 Launch Vehicle**
**6 Strap On Boosters**
**Extended Fairing**
**2:55 AM**
**Vandenburg Air Force Base, California**
**705.3 km Orbit**
**Polar Sun Synchronous**
**1:30 PM Equatorial Crossing**
**Ascending Daytime**

## ELEVEN SPECIAL CALIBRATION TESTS USED TO TREND PRE-FLIGHT TO ON-ORBIT PERFORMANCE

**AIRS**

**EOS AQUA SPACECRAFT**

## AIRS 900 cm-1 SUPERWINDOW CHANNEL DIRECTLY MEASURES SKIN TEMPERATURE

- Clouds

- Mediterranean Sea

- Hot Desert

- AIRS Vis/NIR IMAGE

**First Vis/NIR Image ****May 26, 2002**
**AIRS first light IR****June 13, 2002**

## Slide 14

## AIRS RADIOMETRIC ACCURACY BETTER THAN 0.5K AT MOST FREQUENCIES

**Analysis by L. Strow of UCMB**

**AIRS BT**
**ANALYSIS BT**
**(K)**

**AIRS BT**
**ANALYSIS BT**
**(K)**

**Notes:**
Clear footprint over the Mediterranean Ocean were selected to test the accuracy of the radiometric and spectral calibration. The Mediterranean  is one of the most meteorologically monitored  regions on the globe,  and the state of the atmosphere provided by the analysis from the European Center for Medium Range Forecasting (ECMWF) for this region is excellent. 

Shown in the upper panel is the comparison of one  observed AIRS spectrum and the calculated spectrum based on the ECMWF analysis for 14 June 2002. The agreement  is so good, that a difference spectrum at a tenfold expanded vertical scale is required  to show  differences, which are typically only  a fraction of a degree C.

The lower panel shows the mean difference between observed and calculated spectra for 320 “clear” AIRS footprints in the Mediterranean Ocean for 14 June 2002. The agreement between calculated and observed by AIRS in many regions of the spectrum is at the detector noise level, but there are significant  systematic differences, particularly in the lower troposphere, which need to be explored.

Given that  the AIRS data are based  on  the pre-launch calibration applied to virtually first light data, the agreement is excellent.

## UPWELLING ALLOWS CHARACTERIZATION OF SPECTRAL CENTROIDS

**  ****Upwelling spectra fit to****   atmospheric features for****   certain modules**
**  ****Remainder of channels****   fit by use of pre-flight****   calibration and design****   constraints**
**  ****Accuracy +/- 0.5% Dl**

## SPECTRAL:  CENTROIDS TRACKED TO +/- 0.5 MICRONS (0.5% Width of SRF)

**Current position is –13.5mm  relative to June 2000 L. Strow Grating Model**

## AIRS NEDTS LOOK GOOD IN ORBIT

**AIRS can stop mirror and stare in spaceview or at OBC blackbody**
**Appx 30,000 footprints of noise are acquired**
**Provides excellent noise statistics**
**Provide noise signal dependence**
**NeDt calculated at 250k for reference**

## RESULTS SHOW GAIN TABLES WELL OPTIMIZED

**	****A****	****B****	****AB Opt**
**3sig Events:****	****181****	****171****	****61**
**Pops:****	****92****	****98****	****14**
**High Noise:****	****	****	****131**
**Total Now:****	****	****	****206**

- Number of Channels that did not pass during 40,000 sample test:

## SPACE VIEW NOISE TEST ACQUIRED IN SAA

**SPACE VIEW NOISE TEST ACQUIRED IN SAA**

## RADIATION CIRCUMVENTION PROCESSOR IS WORKING IN ORBIT

**Noise spikes seen in the South Atlantic Anomaly (SAA)**
**Radiation Circumvention activated.  Levels set.**
**Noise spikes due to SAA eliminated.**

- SAA NOISE SPIKES

**NON-GAUSSIAN NOISE FACTOR VS CHANNEL FOR AIRS**

## SPATIAL:  BORESIGHT POSITIONSTILL REMAINS <+/- 1 KM FROM NOMINAL

## VIS SNRs LOOK GOOD PRE AND POST LAUNCH

- Lamp 1

## Hurricane Isidore  September 22, 2002

**AIRS**
**Ch. 2616**

**HSB **
**Ch. 150 Ghz**

**Flooding (difference)**
**HSB Sept 28-Sept 10**

**AIRS**
**Vis/NIR**

## SUMMARY

**AIRS Launch and Activation Successful**
**All AIRS Subsystems functioning normally**
**Instrument Radiometric, Spatial and Spectral performance looks nominal**
**Exceptional temperature/performance stability achieved in orbit**
**In-Flight Calibration Complete**
**Science team is very excited and impressed by the performance observed by the instrument and the radiance products**
**Level 2 Algorithms showing good agreement with models**
**Weather Centers have begun data assimilation**