NASA Pinning Down Where "Here" is Better Than Ever

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Priscilla Vega 818-354-1357
Jet Propulsion Laboratory, Pasadena, Calif.
Priscilla.r.vega@jpl.nasa.gov

Elizabeth Zubritsky 301-614-5438
Goddard Space Flight Center, Greenbelt, Md.
Elizabeth.a.zubritsky@nasa.gov

News feature: 2012-049 Feb. 23, 2012

NASA Pinning Down Where "Here" is Better Than Ever

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2012-049&cid=release_2012-049

Before our Global Positioning System (GPS) navigation devices can tell us where we are,
the satellites that make up the GPS need to know exactly where they are. For that, they
rely on a network of sites that serve as "you are here" signs planted throughout the world.
The catch is, the sites don't sit still because they're on a planet that isn't at rest, yet
modern measurements require more and more accuracy in pinpointing where "here" is.

To meet this need, NASA is helping to lead an international effort to upgrade the four
systems that supply this crucial location information. NASA's Jet Propulsion Laboratory,
Pasadena, Calif., in partnership with NASA's Goddard Space Flight Center in Greenbelt,
Md., where the next generation of laser ranging and radio interferometry systems is being
developed and built, is bringing all four systems together in a state-of-the-art ground
station. This demonstration station and merger of technique processing, known as the
Space Geodesy Project, will serve as an example of what is required to measure Earth's
properties to keep up with the ever-changing, yet subtle, movements in land as it rises
and sinks along with shifts in the balances of the atmosphere and ocean. All of these
movements tweak Earth's shape, its orientation in space and its center of mass -- the point
deep inside the planet that everything rotates around. The changes show up in Earth's
gravity field and literally slow down or speed up the planet's rotation.

"NASA and its sister agencies around the world are making major investments in new
stations or upgrading existing stations to provide a network that will benefit the global
community for years to come," says John LaBrecque, Earth Surface and Interior Program
Officer at NASA Headquarters.

GPS won't be the only beneficiary of the improvements. All observations of Earth from
space -- whether it's to measure how far earthquakes shift the land, map the world's ice
sheets, watch the global mean sea level creep up or monitor the devastating reach of
droughts and floods -- depend on the International Terrestrial Reference Frame, which is
determined by data from this network of designated sites.

For more information, visit: http://www.nasa.gov/topics/technology/features/here-pin-
down.html .

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