April 19, 2006
Catch the A-Train
If all goes as planned, Friday April 21 at 3:02 PDT will usher in the next installment of the Earth Observing System. At that time, the Cloud and Aerosol Lidar and Infrared Pathfinder Spaceborne Observations (CALIPSO) and CLOUDSAT satellites will launch together in the same Delta II rocket from Vandenberg Air Force Base in California. You can watch the Prelaunch briefings by webcast at 7:30 PM tonight and follow the activities on the NASA mission site for the times of other prelaunch, launch, and post-launch web broadcasts.
Why CALIPSO?
If you have been following this site for the last two years, you are aware that observations of aerosols from man-made sources (pollution, biomass burning) and natural sources (dust, sea salt) are easily made from Terra and Aqua MODIS imagery and from the GASP product. What we are missing routinely is a view of the vertical position of those aerosols. A lidar in space, CALIPSO, will provide those views over the next three years. Proposed to the Earth System Science Pathfinder (ESSP) program in the late 1990's, CALIPSO was chosen to fly in formation with a cloud radar, CLOUDSAT, and the other EOS platforms, Aqua and Aura.
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Flying in formation with the other EOS satellites, we will get an unprecedented ability to detect clouds and aerosols in the vertical with the horizontal spatial context from the Aura and Aqua instruments. We now truly have an Earth Observing System.
CALIPSO will address two important problems in climate change. How much light do aerosols reflect back to space, thus cooling the planet? This is a called the "direct effect". The other important measurement would be the increase in reflectivity of clouds which is caused by small aerosol particles nucleating more cloud droplets. This is the "indirect effect" of aerosols on climate and can be seen dramatically in these ship tracks off the west coast of the US.
What will we see when CALIPSO has first light?
The LITE experiment, which flew on the shuttle in 1994, provides us basic data on what the CALIPSO instrument may see. The four panels below show a LITE cross-section of clouds and aerosols. The upper right panel and lower left panel show the same image simulated (conservatively) for CALIPSO's 532 nm and 1064 nm laser wavelengths. In the lower right panel, we show the depolarization ratio, a measure of the sphericity of the particles.
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From these images, we will extract information to show the location of aerosols and clouds in the scenes as a function of their attenuated backscatter coefficient, from the SIBYL algorithm.
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More to come....
Stay tuned for more information on CALIPSO and CLOUDSAT over the next couple of years. I can't write more now since I'm off to the launch today. Cross your fingers....