Artist’s rendering of NASA’s ISS-RapidScat instrument (inset), which will launch to the International Space Station in 2014 to measure
ocean surface wind speed and direction and help improve weather forecasts, including hurricane monitoring. It will be installed on the
Image: NASA/JPL-Caltech/Johnson Space Center
end of the station’s Columbus laboratory.
Watching Earth’s winds, on a shoestring
Built with spare parts and without
a moment to spare, the International Space Station (ISS)-RapidScat
isn’t your average NASA Earth science mission.
Short for Rapid Scatterometer,
ISS-RapidScat will monitor ocean
winds from the vantage point of
the space station. It will join a handful of other satellite scatterometer
missions that make essential measurements used to support weather
and marine forecasting, including
the tracking of storms and hurricanes. It will also help improve our
understanding of how interactions
between Earth’s ocean and atmosphere influence our climate.
Scientists study ocean winds for
a variety of reasons. Winds over
the ocean are an important part
of weather systems, and in severe
storms such as hurricanes they
can inflict major damage. Ocean
storms drive coastal surges, which
are a significant hazard for populations. At the same time, by driving
30
30
warm surface ocean water away
from the coast, ocean winds cause
nutrient-rich deep water to well up,
providing a major source of food for
coastal fisheries. Changes in ocean
wind also help us monitor largescale changes in Earth’s climate,
such as El Niño.
Scatterometers work by safely
bouncing low-energy microwaves the same kind used at high energy
to warm up food in your kitchen - off
the surface of Earth. In this case, the
surface is not land, but the ocean.
By measuring the strength and direction of the microwave echo, ISSRapidScat will be able to determine
how fast, and in what direction,
ocean winds are blowing.
“Microwave energy emitted by
a radar instrument is reflected back
to the radar more strongly when
the surface it illuminates is rougher,”
explains Ernesto Rodríguez, principal investigator for ISS-RapidScat at
NASA’s Jet Propulsion Laboratory,
Pasadena, Calif. “When wind blows
over water, it causes waves to develop along the direction of wind.
The stronger the wind, the larger the
waves.”
ISS-RapidScat continues a legacy of measuring ocean winds from
space that began in 1978 with the
launch of NASA’s SeaSat satellite.
Most recently, NASA’s QuikScat
scatterometer, which launched in
1999, gave us a dynamic picture of
the world’s ocean winds.
But when QuikScat lost its ability
to produce ocean wind measurements in 2009, science suffered from
the loss of the data. In the summer
of 2012, an opportunity arose to fly
a scatterometer instrument on the
space station. ISS-RapidScat was
the result.
Most scatterometer-carrying satellites fly in what’s called a sun-synchronous orbit around Earth. In other words, they cross Earth’s equator
at the same local time every orbit.
The space station, however, will carry the ISS-RapidScat in a non-sun-
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