Radar altimeter processors require knowledge of platform and radar antenna attitude to provide accurate range and datation measurements. Although the attitude solution generated at real-time by the on-board computer may be accurate enough for ground applications, it is actually of interest to reprocess the star-trackers raw measurements on-ground with consolidated orbit data for validation purposes. Additionally, having more than one star-tracker on-board allows to derive independent Roll-Pitch-Yaw attitude estimates as observed from each star-tracker, what...

The maritime traffic around the Loop current of the Gulf of Mexico is large enough to help retrieving the oceanic surface current. Using Automatic Identification System (AIS) data streams for the period 2019-2020, a distance-weighted least-squares approach [Le Goff et al 2021] is used to estimate ocean surface currents at a depth corresponding to the mean draught of the commercial vessels (about 7m). The calculated gridded data product has spatial resolution of 0.125⁰ × 0.125⁰...

Wave breaking is a common phenomenon when there is high to medium wind speeds over the ocean. But the wave breaking can have various sources, being the wind only one of them. For instance, wave breaking occurs near inhomogeneous unsteady currents, when waves propagate into an opposing current steepen, shorten and may break; or more simply, as waves shoal over shallow bathymetry. Wave breaking limits the height of surface waves, mixes the ocean surface, generates...

Because of the repeat period of the satellite altimetry missions (from 10 days for the Topex/Jason suite to more than one year for CryoSat-2), the high-frequency ocean tidal signals are aliased in the altimeter sea surface height measurements at periods that correspond to other ocean dynamics processes. To access the ocean circulation dynamics with the centimetric accuracy expected by the users, it is thus necessary to accurately remove the ocean tide signals from the altimeter...

Accurate time-variable Earth’s gravity field information is essential for precise orbit determination (POD) of low Earth orbiters (LEO). In particular the POD of altimeter satellites relies on accurate modelling of the time-variable gravity field. The Combination Service for Time-variable Gravity Fields (COST-G) provides monthly gravity fields based on a combination of GRACE/GRACE-FO derived monthly gravity field solutions from different analysis centers. These monthly solutions are available with a latency of 2-3 months. They serve as...

The Center for Topography of the Oceans and Hydrosphere (CTOH) is a French Observation Service created in 1989 and dedicated to satellite altimetry studies. It focuses on the development and promotion of new processing approaches of the altimetric data for emerging research domains (coastal ocean, oceanic sub-mesoscale phenomenons, continental surface water, sea ice, polar caps). It works in close relationship with space agencies (mainly CNES and ESA) at different levels for satellite altimetry missions: preparation...

A new model of marine free-air gravity anomalies has been determined. It is based on the same data set used in the CNES CLS 2022 Mean Sea Surface determination. Particular attention was paid to the shortest wavelengths of less than 30 km. Furthermore, data sampling at 1 Hz (~7km) along track is not sufficient in this context. It is necessary to focus this new determination on the use of high-resolution data that are provided by...

In large parts of the Southern Ocean stratification and dynamics are relatively uniform and allow the application of the “Gravest Empirical Mode” (GEM) concept. Among other characteristics, the concept describes how variations of heat content are linearly related to those of salt content and steric height. The slope of the function depends on the local stratification. Furthermore heat content variations are a function of vertical acoustic travel time. This leads to the conclusion that measuring...

One of the most novel concepts in coastal altimetry is the Fully Focused SAR (FF SAR) processing. FF SAR introduces improvements in terms of along-track resolution in high Pulse Repetition Frequency (PRF) radar altimeters. The processing is similar to the SAR altimetry, but the along-track resolution up to the theoretical limit equal to half the antenna length (~0.5 m). This is in contrast to the ~300 m unfocused SAR along-track resolution given in coastal altimeter...

The concept of a small radar altimeter constellation has already been proposed but not yet implemented due to technological limitations or high costs associated with the operation of such a constellation. Yet, some oceanic processes are still poorly studied and understood due to the lack of adequate sampling of the ocean by past and current satellite altimetry missions. With the increase in popularity of the CubeSat concept and the current availability of low-cost and high-performance...