Below, the draft recommendations of the Workshop are provided. These recommendations are updated from the 2007 Recommendations that were included in the output of the 2007 Workshop. To comment on the recommendations, you can either fill in the form below and submit this form by using the submit button below the form, or you can down-load the word document with the recommendations and edit this file with track-changes on. Please, e-mail the edited word document to hpplag@unr.edu.
Engaging the user community
Gravity missions provide unique information about mass and mass redistribution in the Earth system, with a wide range of societal benefits.
It is strongly recommended to further promote the use of products from gravity missions in the Earth science community and relevant application areas. Products should be easily accessible, adapted to the need of the individual user communities, and in a user-friendly format.
It is further recommended to define and perform the necessary activities to include mass transport products into Earth system models.
- GRACE
GRACE is providing continuous time series of changes in the Earth’s gravity field and is demonstrating the substantial benefit of monitoring mass redistribution for key indicators of global change, such as polar ice mass balance and deglaciation of the large ice shields of Antarctica and Greenland, continental ground water storage and variations of the global water cycle, and ocean circulation. Experience from GRACE has shown that long observation time series are essential for a reliable recovery of mass changes.
It is recommended that the mission is extended as long as the system is healthy. This should be accompanied with a major effort to better exploit the gravity field information contained in the GRACE observations.
- GOCE
GOCE has been launched in March 2009 and has been switched to science mode by the end of September 2009. It is expected to improve significantly the accuracy and spatial resolution of the global static gravity field and the geoid, which will in particular serve as reference for geodesy and for studies of global ocean circulation, ice mass balance, glacial isostatic adjustment, and sea level change.
It is recommended to exploit the expertise gained from the GOCE mission for future technological and scientific developments.
- Short-term perspective: GRACE-FO
In view of the recent success of satellite gravity missions and given the strong need from the user communities, the participants of the workshop conclude that a GRACE-type follow-on mission based on the present configuration must have highest priority in order to guarantee uninterrupted continuation of time series of global mass redistribution. Such a mission should have a lifetime objective of 10 years.
Technologically, this mission could benefit from incremental improvements of the instruments/sub-systems based on GRACE heritage and in-flight experience. Novel techniques such as Laser interferometry are not mandatory, but could be embarked as demonstration package.
- Medium-term perspective
Medium term priority should be focused on higher precision and higher resolution in space and time, as well as long mission lifetime (minimum 10 years). This step requires (1) the reduction of the current level of aliasing (of high frequency phenomena, in particular tides, into the time series), (2) improvement of directional sensitivity of observation systems, and (3) the improvement of the separability of the observed geophysical signals.
From today's point of view, laser satellite-to-satellite tracking (active laser interferometry) is the most probable candidate technology. Two or more satellite pairs are preferred, with one pair probably in a moderate inclination orbit.
It is recommended that studies to identify suitable mission architectures, as well as improved data processing methodologies are carried out. In parallel, it is recommended to analyze the impact of the results of such missions to all application areas.
Technological development involves inter-satellite laser ranging with emphasis on fine laser beam pointing control, advanced electrostatic accelerometers (with capacitive or optical sensing), active compensation of drag forces, refined attitude control, as well as enhanced platforms with high dimensional/thermal stability. The added value of complementary measurement instruments (e.g., neutral wind meter, spectrometer) should be investigated.
- Long-term perspective
The long term perspective is to establish a continuous series of gravity field satellites for the purpose of monitoring mass redistribution in system Earth, and for existing and emerging application areas.
Technologically, in addition to further improvement of established measurement techniques, the potential of innovative/breakthrough technologies needs be evaluated.
- Dissemination of workshop results
The workshop results will be offered to all relevant institutions, organizations, and agencies.
- Sustainability: working group
It is recommended to establish an international steering/working group to coordinate the future activities and actions in this field.