Airbus receives go-ahead for twin GRACE-FO satellites

press release



NASA-JPL and GFZ will continue a series of vital Earth system measurements

with new satellites in spring 2018

Transport to Vandenberg launch site in California planned for December

Friedrichshafen / Ottobrunn, 10/11/2017 – After a successful year-long test campaign by

Airbus at IABG in Ottobrunn near Munich, the twin GRACE-FO (Gravity Recovery and

Climate Experiment Follow-On) satellites will soon travel to their launch site in California.

During testing, the gravity-measuring satellites, which will track the continuous movement of

liquid water, ice and the solid Earth due to Earth's changing seasons, weather and climate

processes, earthquakes and even human activities, were subjected to conditions similar to

those they will experience during launch and in low Earth orbit. Both satellites, each weighing

600 kilograms, will be flown to the Vandenberg Air Force Base launch site in California in

December to begin final launch preparations.

The project is a partnership between NASA’s Jet Propulsion Laboratory, located in

Pasadena, California, together with the German Research Centre for Geosciences (GFZ,

Potsdam). Both GRACE-FO research satellites will be launched into a polar orbit at an

altitude of around 500 km and at a distance of 220 km apart. Both satellites will then take

continuous, very precise measurements of the distance variations between each other and

make monthly maps of the changes in Earth’s gravitational field, which are used to track the

monthly movement of liquid water, ice and the solid Earth.

The launch of the GRACE-FO twin satellites is planned for spring 2018 on a mission planned

to last at least five years.

A Global Positioning System and a microwave ranging system measure the distance

between the satellites to within a few microns and a sensitive accelerometer accounts for

non-gravitational effects, such as atmospheric drag and solar radiation. The GRACE-FO

satellites will also feature an additional element: a new, more precise inter-satellite laser

ranging instrument, developed by a German/American joint venture, which will be tested for

use in future generations of gravitational research. Each satellite also makes up to

200 profiles of temperature distribution and water-vapour content in the atmosphere and the

ionosphere on a daily basis to aid weather forecasting.

The German/American GRACE satellites, which have been in space since 2002, are the only

satellites that have been capable of monitoring the transport of mass within the Earth system.

These include changes in continental water distribution, the melting of polar ice masses or

large inland glaciers, and mass redistributions following earthquakes. Data from the GRACE

satellites are used to detect groundwater extractions, to monitor droughts and floods, to

improve hydrological models, and to precisely quantify the contribution of land glacier and

polar ice melt to sea level rise.

Long-duration data sets are vital to provide statistically significant information about climate

changes and variations. The GRACE-FO mission will continue the important job started by

GRACE and collect essential climate variables.