[rain drops]
[natural sound]
[wind, rain]
[water flowing]
Dalia: Freshwater is extremely important on Earth. Only three
percent of our water is actually in the form of freshwater.
And only a fraction of that is actually usable
freshwater on the surface. Gail: If we don't know what
kind of freshwater availability we have, then we may
have issues in terms of droughts, we might have landslides,
floods and things like that, and we need to be able to track those
long term. Dalia: Understanding how freshwater moves
through the system is extremely important, both at the local scale, looking at how much water
we have in our reservoir, to the larger scale, looking at how precipitation
moves from ice pack, to the ocean, and then is
evaporated from there. Sensors
on the ground can look at a point source, so we understand how much rain is
falling at a specific location, but there aren't very many
gauges around the world that can provide that information for us.
Arthur: If we were to take all the existing rain gauges in the
world, they would fit into an area about the size of two
basketball courts. [rocket launching]
Dalia: So what satellites enable us to do is provide a much more global picture
of the rain that we observe. Arthur: GPM is an
international satellite mission that will set a new standard for precipitation measurement
from space, providing a new generation of observations
of rain and snow in all parts of the world, every three hours.
The GPM mission consists of a
constellation of nine satellites, provided by a consortium of partners
in the United States, Japan, France, India, and
Europe. The GPM Constellation is
united by a common reference satellite, known as the
GPM Core Observatory, provided by NASA and JAXA.
Candace: GPM is one of the largest spacecraft
we've ever built here at Goddard. It's about 13 meters by
6.5 meters by 5 meters. That's about the wingspan--
tip to tip--of a small corporate jet, but only one-
third as long. In the particular case of
GPM, we're a follow-on mission to the Tropical Rainfall
Measuring Mission which was launched in 1997. So part of what GPM
was supposed to do was just continue those measurements, but also
GPM is to improve those measurements by being able to, for example,
measure finer precipitation.
Art: The more channels you have within one instrument,
then you can cover a wide spectrum
of precipitation products. All the way from rain
to ice. Gail: The GPM Core has
an active radar and a passive radiometer, and these two
instruments are just like what a doctor might use, in terms of an X-ray
for the radiometer, and a CAT scan
for the radar to diagnose what's happening in clouds and to understand what's
happening with the precipitation. Arthur: The data collected by the GPM Core
Observatory will provide a unique data set that will allow
us to translate satellite measurements into the rain or snow
that hits the ground, anywhere on the globe.
[rain drops]