NGGM: Next Generation Gravity Mission

Measurement of the static and temporal variation of earth’s gravity field yields important information on water storage, seasonal and sub-seasonal water cycles, their impact on water levels and delivers key data to Earth’s climate models. The satellite mission GOCE (ESA) and GRACE (US-GER) resulted in a significant improvement on our understanding of the system Earth. GRACE Follow-On is currently continuing these measurements.  

SpaceTech NGGM Measurement Earth gravity field satellite to satellite trackingMeasurement principle of the earth gravity field by satellite-to-satellite tracking

NGGM mission goal

To further improve the measurement accuracy of the time-variable gravity field, ESA is investigating the concept of a ‘Next generation gravity mission’ (NGGM), consisting of two pairs of satellites and a heterodyne laser interferometer for inter-satellite ranging.
Based on the heritage of the development of the laser ranging interferometer for GRACE Follow-On and the former and ongoing studies for NGGM, STI participates in the development of NGGM under several ESA contracts.

STI's current work on NGGM

  • Development of and advanced laser sources providing significantly higher output power compared to GRACE Follow-On, while providing even higher frequency stability. This is performed under direct contract to ESA with Fraunhofer ILT and NPL as subcontractors. 
  • Investigation of several concepts for the laser metrology instrument (LMI) for NGGM, namely the on- and off-axis variants of the transponder and the retroreflector concept. This is performed as sub-contractor to Thales Alenia Space in the frame of the ESA study “Consolidation of the system concept for the next generation gravity mission”, in which STI signs responsible for the LMI.
  • Breadboarding of an optical bench for the retroreflector concept to investigate the feasibility of the retroreflector concept on real hardware. This is performed under direct contract to ESA with Thales Alenia Space as subcontractor. 

SpaceTech's NGGM relevant products

SpaceTech HSL cavity module
High Stability Laser

Laser source with sufficient power and extremely high frequency stability down to several Hz.

SpaceTech HSL cavity module

NGGM Concept Consolidation

The SpaceTech LMI concepts include two possible instrument schemes: transponder and retroreflector.