Satellite quartet to track most precious Earth resource
LOS ANGELES (AP) -- A successful launch next
month of a nearly $1 billion satellite would mark the
fourth spacecraft NASA has sent into orbit recently to
follow the global movement of life's most precious resource:
The satellite Aqua will follow the Jason 1 and a pair
of twin spacecraft called Grace, launched in December
and March, respectively.
Although each is different, the missions are designed
to help piece together the puzzle of how water moves between
the Earth's atmosphere, oceans and land.
"Each one of them is a critical element in this great
hydrologic cycle, which really sustains life on Earth,"
said William Patzert, a NASA research oceanographer and
scientist on the Jason 1 mission.
Scientists hope the three missions will lead to more
accurate weather forecasts, better advance notice of El
Ninos and a clearer understanding of how human activity
affects the world at large.
Water moves through the world at varying paces before
returning to the oceans that cover 70 percent of the planet.
That cycle drives both climate and weather, affecting
in turn life and its every activity.
Water lasts just days in clouds as a vapor but weeks
as a liquid in the world's rivers. As ice, it can remain
locked in the polar caps for tens of thousands of years.
Monitoring water's movement -- where, how quickly and
in what phase it moves -- requires a global perspective,
something scientists hope the flotilla of Earth-orbiting
satellites can provide.
"The whole idea of the Earth is it's a closed system.
So if you don't take global measurements, you can't model
the whole thing," said Martin Mohan, who oversaw Aqua's
development for Redondo Beach, California-based satellite
builder TRW Inc.
Aqua, Latin for "water," and its six instruments will
look almost exclusively at the hydrologic cycle, focusing
primarily on the atmosphere.
Although the atmosphere holds just a sliver of all the
world's water, that vapor is the most important greenhouse
gas. As such, it also represents the biggest unknown in
gauging the effect of global warming and its impact on
the hydrologic cycle, said Aqua project scientist Claire
"The hope is we will be able to get an indication of
whether or not the cycling through the system is speeding
up, staying steady or slowing down," he said. "The hypothesis
is it might be speeding up."
Plans call for Aqua data to be plugged into daily weather
forecasts, a first for NASA. It will also help keep tabs
on droughts, hurricanes before they make landfall, and
other markers that, together, suggest climate change.
The $952 million mission is scheduled for a May 2 launch
from Vandenberg Air Force Base in California.
Jason 1, a joint U.S.-French mission, uses radar to
measure the topography -- or shape -- of an ocean's surface.
That data gives an indication of circulation patterns
that move water and heat around the globe, influencing
both evaporation and precipitation.
Even subtle differences in those patterns can have an
enormous impact on the climate of any region of the world,
Grace, a joint U.S.-German mission, is the most unusual
of the bunch. Its twin satellites measure tiny variations
in the Earth's gravity field, including those caused by
the shifts in mass caused by large-scale movements of
When the satellites become operational this summer,
the mission will be sensitive enough to detect changes
in mass due to the siphoning off of the Ogallala Aquifer,
located east of the Rocky Mountains, and the melting of
Combining data from Grace and Jason 1 will allow scientists
to determine which variations in the surface of the oceans
are due to lumps in the planet's gravity field and which
are due to events within the ocean. They also hope to
use the two missions to study any rise in sea levels.
Data from Grace and Aqua will also sort out how water
in the Earth is split between soil moisture and aquifers
deeper below the surface, which should allow for better
management of the resource.
The overlap between the different, yet complementary
missions, is "exactly the right way to view Earth system
science," said Michael Watkins, the Grace project scientist.
"It's assembling several pieces of the puzzle together
to see what's going on," he said.