2024-08-30

Structure

Working Groups

WG Q.1: Quantum gravimetry in space and on ground

Chair: Franck Pereira (France)
Vice-Chair: Marvin Reich (Germany)

Terms of Reference

On ground, quantum sensors based on matter wave interferometry with cold atoms are very well suited for rapid and very precise gravity sensing. They can be used as registration instruments and as absolute gravimeters with sub-μGal accuracy. Mobile devices are developed for field campaigns and large-scale stationary devices for achieving extreme precision. While the former enable new strategies for local and regional gravity surveys, the latter will provide a new gravity standard in the future. In space, the long-term stability and low noise level of quantum sensors will allow improving the spatial gravity field models in GOCE-type gradiometer missions. The determination of mass transport processes on Earth at low and medium degrees in GRACE-type missions will benefit from quantum accelerometers providing measurement of the specific non-conservative forces. In addition, hybrid systems (i.e. a combination of electrostatic and atom-interferometric accelerometers) can cover a wider spectral range, which will greatly support navigation and inertial sensing on ground and in space. The goal of this WG is to elaborate the major benefits and most promising applications of atom interferometry for gravimetry and inertial sensing in space and on ground.

Objectives

  • Terrestrial quantum gravimeters and applications scenarios (including airborne and marine instruments);
  • (Hybrid) accelerometers for space missions and spacecraft navigation;
  • Atom interferometric gradiometry;
  • Elaboration of further applications (like atmosphere research, relativity tests, etc.) and corresponding space demonstrators (e.g., pathfinder missions);
  • Elaboration of synergies among different science topics in a single mission (Earth observation and fundamental physics, navigation and space exploration, several scenarios for Earth observation, e.g. gravimetry, atmospheric research andmagnetometry).
Members

  • Franck Pereira (France); Chair
  • Marvin (Reich); Vice-Chair
  • Roland Pail (Germany)
  • Ernst Maria Rasel (Germany)
  • Thomas Lévèque (France)
  • Oliver Carraz (Netherlands)
  • Steffen Schön (Germany)
  • Yuichi Imanishi (Japan)
  • Jeffrey Kennedy (USA)
  • Shuqing Wu (China)
  • Nan Yu (USA)
  • Andre Gebauer (Germany)
  • Markus Krutzik (Germany)
  • Bastian Leykauf (Germany)
  • Ashton Flinders (USA)
  • Rainer Dumke (Singapore)
  • Nassim Zahzam (France)
  • Przemyslaw Dykowski (Poland)
  • Brynle Barrett (Canada)
  • Federica Migliaccio (Italy)

WG Q.2: Laser interferometry for gravity field missions

Chair: Samuel Francis (USA)
Vice-Chair: Kirk McKenzie (Australia)

Terms of Reference

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 resolutionand to extend the time series, GRACE Follow-On (GRACE-FO) was launched in May 2018, carrying as demonstrator a Laser Ranging Interferometer (LRI) which is able to approach an accuracy of tens of nm for inter-satellite ranging.The GRACE-FO LRI continues to operate in-orbit with performance well below requirements. No signs of optical contamination or degradation have been seen after 5 years of operation and there have been few unplanned interruptions to tracking. Gravity fields derived from LRI are consistent with those derived from primary microwave instrument, while offering improved performance at high frequencies. The LRI will be the primary instrument on the NASA/ DLR GRACE Continuity (GRACE-C) mission. 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 in 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 novel concepts including optical sensing for inter-satellite tracking, accelerometry and gradiometry, and its applications for next generation gravity field missions.

Objectives

  • Interferometric Laser Ranging between swarms of satellites;
  • Accelerometry with optical readout and application scenarios;
  • Gradiometry with optical readout;
  • Hybrid sensors and measurement concepts;
  • New concepts for future satellite gravity missions.
Members

  • Samuel Francis (USA); Chair
  • Kirk McKenzie (Australia); Vice-Chair
  • Michael Murböck (Germany)
  • Robert Spero (USA)
  • Vitali Müller (Germany)
  • Gerhard Heinzel (Germany)
  • Jürgen Kusche (Germany)
  • Felix Landerer (USA)
  • David Wiese (USA)
  • Peter Bender (USA)
  • Gilles Metris (France)
  • Christophe Le Poncin-Lafitte (France)
  • Shuanggen Jin (China)
  • Christopher Woodruff (USA)
  • Brent Ware (USA)
  • Frank Flechtner (Germany)
  • Markus Hauk (Germany)
  • Thomas Papanikolaou (Denmark)
  • Andrew Wade (Australia)
  • Emily Rose Rees (Australia)
  • Clément Courde (France)
  • Julien Chabé (France)
  • Julie Rolla (USA)

WG Q.3: Relativistic geodesy with clocks

Chair: Jakob Flury (Germany)
Vice-Chair: Pacôme Delva (France)
Consultant from Physics: Christian Lisdat (Germany)

Terms of Reference

Optical clocks are sensitive to the gravity potential in which they are operated. The comparison of two clocks will reveal a frequency offset from the value expected from side-by-side comparisons, that can directly be related to the potential difference between both clocks. The best optical clocks now reach resolutions of better than 0.1m2/s2, transportable ones about 1 m2/s2. They can be achieved already after few hours of averaging. We will evaluate how this technique can be used to generate unified and long-term stable height networks and reference systems. This includes discussing the feasibility of realizing a datum by reference to e.g., a space-borne clock with ideally negligible gravitational interference. Future clock networks might also be used as ground-truth for space missions or even to bridge gaps in satellite observations. Other aspects to be addressed are the application of observed time-variable signals in de-aliasing of satellite observations. Sensor fusion concepts will be discussed to utilize the different spatial integration characteristics of clocks and other gravity sensors so as to disentangle local and extended signal sources. In summary, the goal of this WG is to use clock measurements for determining differences of physical heights and gravity potential for various geodetic applications.

Objectives

  • Clock networks for unification of height systems;
  • Gravity field recovery on ground;
  • Application to realize reference systems, including dedicated space clocks;
  • Further applications (height/potential variations);
  • Potential satellite missions for long-wavelength gravity field recovery, including optical links for comparing the space clocks.
Members

  • Jakob Flury (Germany); Chair
  • Pacôme Delva (France); Vice-Chair
  • Christian Lisdat (Germany)
  • Claude Boucher (France)
  • Davide Calonico (Italy)
  • Pascale Defraigne (Belgium)
  • Ropesh Goyal (India)
  • Jochen Kronjäger (Germany)
  • Hua Guan (China)
  • Chris Hughes (UK)
  • Sergei Kopeikin (USA)
  • Jürgen Kusche (Germany)
  • Claus Lämmerzahl (Germany)
  • Marie-Françoise Lequentrec (France)
  • Guillaume Lion (France)
  • Andrew Ludlow (USA)
  • Helen Margolis (UK
  • )Elena Mazurova (Russia)
  • Nathan Newbury (USA)
  • Bijunath Patla (USA)
  • Nikos Pavlis (USA)
  • Paul-Eric Pottie (France)
  • Ulrich Schreiber (Germany)
  • WenBin Shen (China)
  • Simon Stellmer (Germany)
  • Yoshiyuki Tanaka (Japan)
  • Giulio Tagliaferro (France)
  • Pieter Visser (Netherlands)

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