WG Q.2: Laser interferometry for gravity field missions

Chair: Michael Murböck, GFZ, Germany
Vice-Chair: Bob Spero JPL, USA


GRACE has excellently demonstrated the great potential of inter-satellite tracking to determine time-variable gravitational signals which are related to mass transport processes in the Earth system. Examples are ice mass loss in Greenland and Antarctica, ground water loss in Asia, droughts in USA, quantification of the global water cycle, mass contribution to sea level rise, mass variation due to land uplift in North America and Scandinavia, or mass changes related to earthquakes. To increase the resolution and to extend the time series, GRACE-FO was launched in May 2018 also carrying a Laser Ranging Interferometer (LRI) as demonstrator which is able to approach an accuracy of tens of nm for inter-satellite ranging.

Optical sensing of the motion of test masses in the gravitational field with nanometer accuracy and beyond can be realized in various measurement concepts such as for ranging between satellites like in GRACE-FO or future swarms of satellites. Further concepts apply LRI for sensing single test-mass motion (accelerometry) or multiple test-mass constellations within one satellite (GOCE-type gradiometry).

The overall goal of this WG is to study optical sensing for inter-satellite tracking, accelerometry and gradiometry, and its applications for next generation gravity field missions.


  • Interferometric Laser Ranging between swarms of satellites
  • Accelerometry with optical readout and application scenarios
  • Gradiometry with optical readout
  • New concepts for future satellite gravity missions

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