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The Drifting Phase of SARAL: Securing Stable Ocean Mesoscale Sampling with an Unmaintained Decaying Altitude

Centre National d’Etudes Spatiales, 31400 Toulouse, France
Collecte Localisation Satellites, 31520 Ramonville Saint-Agne, France
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(7), 1051;
Received: 20 April 2018 / Revised: 24 May 2018 / Accepted: 2 July 2018 / Published: 3 July 2018
(This article belongs to the Special Issue Satellite Altimetry for Earth Sciences)
PDF [5612 KB, uploaded 3 July 2018]


The French/Indian altimeter project Satellite with ARGOS and AltiKa (SARAL) completed its nominal 3-year mission on the historical European Remote-sensing Satellite (ERS) orbit in Spring 2016. In order to extend the lifetime of the satellite as much as possible, the agencies in charge of SARAL decided to initiate a so-called drifting phase where the satellite altitude is no longer maintained. In this paper we describe how the ocean mesoscale sampling capability of SARAL has been preserved during the drifting phase by initiating it at a specific altitude: the optimal starting point was approximately 1 km above the historical ERS/ENVIronment SATellite (ENVISAT) orbit. This strategy secured the ocean mesoscale sampling capability of SARAL drifting phase (DP) for 6 years or more. We also generalize these findings: any altimeter could follow SARAL’s drifting phase strategy if their maneuvering capability is limited. Lastly, we explain how an altimetry mission or an entire altimeter constellation could be operated without any form of altitude control: some specific altitude bands (e.g., near 1230 km) guarantee a high-quality mesoscale sampling for years or decades even if the altitude is not maintained. View Full-Text
Keywords: altimetry; orbit decay; drifting orbit; geodetic orbit altimetry; orbit decay; drifting orbit; geodetic orbit

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Dibarboure, G.; Lamy, A.; Pujol, M.-I.; Jettou, G. The Drifting Phase of SARAL: Securing Stable Ocean Mesoscale Sampling with an Unmaintained Decaying Altitude. Remote Sens. 2018, 10, 1051.

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