- G-TERN constellation
- © J. Wickert (GFZ)
G-TERN [1, 2] stands for „GNSS Transpolar Earth
Reflectometry moNitoring system“. It is an innovative climate
research experiment, which was proposed within the highly competitive
ESA call for Earth Explorer missions (9) on June 15, 2017. The
international G-TERN team consists of 25 scientists from 11 countries
and an industry consortium of 7 partners. The proposal was jointly
coordinated by Estel Cardellach (IEEC, Spain) and Jens Wickert (GFZ,
Germany). The industry consortium was led by OHB, Germany.
Within G-TERN it is planned to use navigation satellite signals for
remote sensing of ocean, ice and land surfaces and also for atmosphere
sounding to derive information on climate change. Main mission goal is
the precise determination of the height and roughness information of
ice and ocean surfaces with main focus to polar regions to investigate
the complex interactions of the cryosphere with the other components
of the Earth system with new aspects. Ocean surfaces on a global scale
can be very precisely monitored as well. Additional mission goal is
the observation of land surfaces and their variation in context of
The technical concept of G-TERN is based on the GEROS-ISS-Mission [3,
4], which finished it’s Phase A in 2016. In total 13 mission
proposals were submitted for the revised Earth Explorer Call 9. End of
November ESA decided, that the mission FORUM  and SKIM  will go
to Phase A, G-TERN, together with three other concepts, was
recommended for further studies. The launch of one of these missions
with the European VEGA-C can be expected in 2025.
 Wickert, J./Cardellach, E. et al., G-TERN: GNSS Transpolar Earth Reflectometry moNitoring system, Proposal for an Earth Explorer 9 Mission, European Space Agency, 2017.
 Cardellach, E./Wickert, J., et al., GNSS Transpolar Earth Reflectometry exploriNg system (G-TERN): Mission concept, IEEE Access, DOI 10.1109/ACCESS.2018.2814072, 2018.
 Wickert, J., et al., GEROS-ISS: GNSS REflectometry, Radio Occultation, and Scatterometry Onboard the International Space Station, IEEE Journal of selected topics in applied Earth observations and Remote Sensing, Vol. 9, Issue: 10, p. 1_30, 10.1109/JSTARS.2016.2614428, 2016.
 GARCA team, GNSS-R assessment of requirements and consolidation of retrieval algorithms, Final Project Report, ESA-AO1-7850/14-GARCA-FR, pp 463, 2016.