GFZ German research centre for geo sciences

Measuring Climate with Laser Precision

Measuring Climate with Laser Precision
17.06.2013|Potsdam: Variations in the gravitational field of the Earth can be measured much more accurately in future. A novel laser distance measurement on the GRACE follow-on satellite mission due for launch in 2017 allows an unprecedented level of accuracy in the detection of climate-induced mass changes on our planet. The funds for the German participation in the German-American satellite mission GRACE Follow-On have now been approved.

Climate satellite GRACE Follow-On takes off into space in 2017 with new technology on board - construction funds approved

17.06.2013 | Potsdam: Variations in the gravitational field of the Earth can be measured much more accurately in future. A novel laser distance measurement on the GRACE follow-on satellite mission due for launch in 2017 allows an unprecedented level of accuracy in the detection of climate-induced mass changes on our planet. The funds for the German participation in the German-American satellite mission GRACE Follow-On have now been approved.

GRACE stands for "Gravity Recovery And Climate Experiment" and is a tandem satellite mission launched in 2002.It converts the data of gravity in climate information: According to Newton, every mass exerts attraction, including for example the ice sheets of Antarctica or the ground water in the continents. If the mass of ice changes due to climate change, so does the force of gravity at this point. The two satellites make use of this principle: they fly on exactly the same orbit, but the distance between them changes slightly when they fly over areas of differing gravity. The change in distance is thus the unit of mass change: The more accurately the distance between the two satellites can be measured, the more precisely climate-driven changes in mass can be identified.

The current GRACE mission will end no later than 2017; the successor satellites GRACE Follow-On can now be built. To improve the measurement accuracy the Albert Einstein Institute in Hannover (AEI) provides a high-precision laser ranging interferometer (LRI), which will be used to supplement the microwave-based measurement of the current mission. "We are very happy that our method, which originally comes from gravitational wave research, can now contribute to climate research," says Professor Karsten Danzmann, Director at AEI and responsible for the design and management of the LRI total instrument , which was developed together with NASA's Jet Propulsion Laboratory.

The GFZ German Research Centre for Geosciences is in charge of implementing the German contribution to GRACE-FO. Furthermore, the scientific data of the mission will be analyzed at the GFZ. Professor Frank Flechtner (GFZ), who coordinates the German contribution to GRACE-FO, about the new method: "The accuracy of the gravity fields which we have derived from the distance measurements of the previous GRACE microwave instrument since 2002 will be significantly improved with the LRI on GRACE-FO. This enables us to reach more reliable conclusions on climate change."

Like GRACE, GRACE-FO will consist of two identical satellites that follow each other at a distance of about 220 kilometers in the same near polar orbit at approx. 490 km altitude. Centrepieces of the instrumentation are an ultra-precise microwave distance measuring system enabling a distance measurement between the satellites of some thousandths of a millimeter, as well as the new laser ranging interferometer (LRI), which measures up to 50 times more accurately.

Professor Reinhard Huettl, Chairman of the German Research Centre for Geosciences, thanks the funding sources: "The Federal Ministry of Education and Research, the Federal Ministry of Economics and Technology and the Helmholtz Association are funding the overall satellite project with a total of 49.2 million Euros. I would like to thank them on behalf of all project participants.". These funds are supplemented by kind contributions of the German Aerospace Center (DLR) for the LRI and the funding of mission operations by the German Research Centre for Geosciences, which in addition also provides laser retro-reflectors for both satellites.

Images of GRACE-FO in printable resolution

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