CoAuthors

Carole DUFOUR (Thales Alenia Space, France); Magali TELLO (Centre National d'Etudes Spatiales, France); Nathalie STEUNOU (Centre National d'Etudes Spatiales, France)

SWOT satellite (Surface Water and Ocean Topography) is born from a cooperation between CNES and NASA, with a platform developed by Thales Alenia Space and a payload under Jet Propulsion Laboratory responsibility. It was launched on December 2022, and after successful commissioning and Calibration / Validation Phase, it began the first global survey of Earth’s surface water and measurements of the circulation patterns of oceans. Thanks to its wide-swath Ka-band radar interferometer, KaRIn (Ka band Radar Interferometer), combined with a nadir altimeter as well as support instruments, it offers a new opportunity for measuring the height of lakes, rivers and flood zones, and for seeing mesoscale and sub-mesoscale circulation patterns of oceans. Preliminary science data shows excellent results, opening new perspectives in hydrology and oceanography fields.

Satellite raw altimetry measurement provides the distance between the water surface and the instrument center of phase. In order to retrieve the water level, it shall be combined with orbital information, as well as fine localization of antennas with respect to the satellite center of gravity.
These aspects are mainly driven by satellite characteristics such as propellant mass and position within tank or solar arrays orientations, and include frozen and varying contributions. This paper addresses the SWOT platform contributions to the overall precise orbit determination budgets. It will present the analysis done at satellite level to derive the uncertainty budget on the center of gravity localization knowledge, by reviewing the list of contributors, and assessing whether their uncertainty can be absorbed in the budget or shall be corrected by dedicated model.