January 2004
Flying in Formation
By Patrick L. Barry
You can almost see the tabloid headlines now: "Mid-west farmer spies UFO
squadron flying in formation!" "First signs of imminent alien invasion," the
subtitle will read.
If only this fictional farmer had been keeping up with NASA's Space Place
column, he would have known better. The string of white dots moving in formation
across the pre-dawn sky were satellites, not alien spaceships.
Beginning next year, a series of challenging, high-precision launches will
insert four satellites into orbits with just the right altitude, position, and
orbital inclination to follow in lock-step behind NASA's Aqua satellite
(launched in May 2002). Scientists have dubbed this squadron of satellites the
"A-Train." Along with Aqua, the celestial parade will include Cloudsat, CALIPSO,
PARASOL, and Aura.
In April 2004, NASA will launch CloudSat, an Earth-observing satellite with
unique cloud-measurement abilities. These measurements will fill an important
role in our understanding of global climate change, making long-term climate
change scenarios more accurate and dependable.
 |
| CloudSat, to be launched in November 2004, will take its place as part of the "A-Train" of satellites flying in formation to take closely timed snapshots of essentially the same scene using a total of 14 different measuring instruments. |
This sounder-the first of its kind put into
orbit-lets scientists see a vertical "slice" of the atmosphere that shows
clouds, water, and ice between the ground and 30 km altitude, with a vertical
resolution of 0.5 km. Even by itself, this instrument would provide an important
and unique view of Earth's atmosphere, since the accurate portrayal of clouds is
one of the glaring weaknesses with current simulations of climate change.
But this cloud data is even more valuable when combined with measurements from
the other satellites in the A-Train-for example, air temperature, trace gases,
and radiation into and out of the atmosphere. Scientists can then see
connections between, say, temperature and the resulting behavior of clouds. A
better understanding of these connections is one of the most sought-after goals
of climate research, because changes to global cloud cover would, in turn, have
a feedback effect on global temperatures.
The real story of this satellite squadron may not make the tabloid headlines,
but at least there's evidence that the imminent threat of climate change is
real, which is a lot more than you can say for alien invaders!
Learn more about CloudSat and the A-Train at
http://cloudsat.atmos.colostate.edu. Kids (and grownups) can do interactive
cloud picture scrambles and learn "Cloudspeak" (the names of different kinds of
clouds) at The Space Place,
http://spaceplace.nasa.gov/cloudsat_puz.htm.
This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.