The main subject of the cruise is the coastal sea-level in New Caledonia, using geodetic measurements of sea surface height above ellipsoid by GNSS and seafloor pressure measurements (deployment of 5 pressure gauges). Today, coastal sea level evolution around Noumea is a non resolved issue. Indeed, altimetry, tide gauge and land vertical motion data do not give a coherent picture  (Aucan et al., 2017, Martinez-Asensio et al., 2019) : absolute sea-level rise given by altimetry differs from Nouméa tide gauge trend by about 1,4mm/year (Aucan et al, 2017). This discrepancy is not explained by GNSS-observed vertical land motion (Ballu et al., 2019). Up to today, coastal altimetric data processing in Noumea region do not include high resolution hydrodynamic models, land based tropospheric delay measurements and local geoid gradients. Therefore, we believe that there is room for improvement, which is one of the goals of the GEOCEAN-NC cruise. 

One of the unknown is due to the wave-induced set-up and set-up trend between the coastal tide gauge area and the remote zone sampled by altimetric products. 

During the GEOCEAN-NC cruise, we have collected data aiming at:

• quantify the wave set-up between inside and outside of the lagoon, 
• improving altimetric data processing (for long-term reprocessing) thanks to a new local geoid (Bonnefond et al., 2013).
• contribute to altimetry mission calval activities (Bonnefond et al., 2010, project FOAM, PI Pascal Bonnefond) by collecting in-situ data below Jason3 during 2 flybys (4 and 14 of october) and under Sentinel 3A tracks (flyby on Oct. 12th on track 359 and Oct. 15th on flyby 458).
• improve sea height data collection procedures and processing  (Bonnefond et al., 2003, Bouin et al., 2009, PhD work of C. Chupin)