Monitoring the Ocean Surface Topography Virtual Constellation: Lessons Learned from the Contribution of SARAL/AltiKa

Altimetry missions are usually presented to the user communities with rather short lifetime durations of the order of five years. However in practice, most altimeters can remain in operations for twice as long, although often in a degraded state (coverage and/or accuracy) and with a higher risk of mission loss. Early in the design of the SARAL/AltiKa mission, this Ka-band technology demonstrator has been envisioned as a contributing mission to the so-called Ocean Surface Topography Virtual Constellation (OST-VC) of the Committee of Earth Observation Satellites (CEOS). This article uses the experience feedback from SARAL and its launch delay on the OST-VC. Using a simple yet quantified probability model, we illustrate the value of anticipating the periods where the constellation is fragile, and we identify the next periods where actions can be undertaken by CEOS Agencies to strengthen the OST-VC.