After
months of delays, NASA is once again set to launch a pair of cloud-watching
satellites to join a flotilla of probes aimed at improving weather and climate
forecasts.
A Boeing-built
Delta 2 rocket is due to launch NASA's CloudSat and CALIPSO satellites at
6:02:08 a.m. EDT (1002:08 GMT) on Friday in an early-morning space shot from
Vandenberg Air Force Base in California.
"I know I
speak for the entire team when I say it's been a long road," NASA's CloudSat
project manager Kevin Brown, of the agency's Langley Research Center, in a
Wednesday press briefing.
Originally
delayed from a summer 2005 launch, CloudSat and CALIPSO were also unable to
lift off last November due a labor strike
by Boeing's aerospace workers. That strike ended in
February 2006.
Now the two
probes are set to join three others already in orbit and generate the first
comprehensive, three-dimensional (3-D) views of Earth's clouds and extremely
fine particles called aerosols. The data will not only aid weather studies, but
also help researchers understand the impact humans have on Earth's climate and
their contribution to global warming, mission scientists said.
"These
satellite missions are experimental missions, they're firsts," said Hal Maring,
NASA's CloudSat and CALIPSO program scientist at the agency's Washington D.C.
headquarters, during the briefing. "If these missions are successful, as I
believe they will be, they could be the foreshadowing of operations or routine
measurements that could come later."
A radar
eye
At the
heart of the CloudSat and CALIPSO is their ability to generate 3-D views of
Earth's cloud and aerosols, where past spacecraft have made primarily
two-dimensional observations.
For
CloudSat, a $185 million mission aboard a 1,870-pound (894-kilogram) satellite,
that capability is centered on a powerful radar designed not only to build a
3-D map of cloud cover, but also identify specific particles of clouds, rain
and snow to pinpoint how water is globally distributed in the Earth's
atmosphere.
"The
CloudSat radar will be about 1,000 times more sensitive than your regular
radar," said David Hudak, a mission research scientist with the Science and
Technology Branch of Environment Canada, during the briefing.
Graeme
Stephens, CloudSat's principal investigator at Colorado State University in
Fort Collins, said the satellite will allow scientists to quantify the contribution
of cloud cover to the global greenhouse effect and make fundamental
observations into the Earth's water cycle.
"We haven't
seen Earth like this before," Stephens said. "There's going to be much
discovery to come from thee new missions."
Laser
vision
Where
CloudSat has a radar, CALIPSO has a laser.
Short for
the hefty title Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
Observations, CALIPSO uses a laser ranging instrument - or lidar - to measure
the levels and characteristics of aerosols in Earth's atmosphere.
The $223
million CALIPSO mission is a joint effort between NASA and the French Space Agency
(CNES) featuring a 1,294-pound (587-kilogram) spacecraft that carries three
primary instruments. In addition to the lidar, the satellite is equipped a
wide-field visible light camera and an imaging infrared radiometer to study the
atmosphere's aerosol content.
"In many
ways, clouds and aerosols...affect and in some way even control climate, weather
climate, the air we breathe and the water we drink," Maring said.
Variations
in the amount of natural and human-made aerosols in the Earth's atmosphere can
affect temperatures and contribute to the greenhouse effect and global warming,
researchers said.
"It's very
important to know what the human impact on the aerosol content is," said
Jacques Pelon, CALIPSO co-principal investigator at France's Institute Pierre
Simon Laplace, during the briefing.
Late for
the 'A Train'
CloudSat
and CALIPSO are relative latecomers to a series of Earth watching satellites
working together to build a comprehensive picture of the planet's weather and
climate.
Scientists
have dubbed the spacecraft group the 'Afternoon Train' - or 'A Train' - since
it crosses the equator during the early afternoon. All of the satellites are
aimed at an orbit 438 miles (705 kilometers) above Earth.
First in
the group is NASA's water-watching Aqua satellite launched
in May 2002, which was followed by the space agency's Aura
spacecraft in July 2004. A third satellite, France's PARASOL spacecraft
studying the microphysical properties of clouds and aerosols, launched
in December 2002.
"The value
of this combined set of measurements gives us hope to be able to constrain the
Earth's system...to the point of being able to predict it," Maring said. "And
prediction is terribly important."
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