An overriding issue facing the altimetry community today is sustaining the present observational capability. In Europe and the United States this involves transitioning altimetry as a research endeavor within the R&D agencies into a sustained capability within their operational counterparts. Additionally, meeting operational and scientific objectives requires multiple missions, namely, a constellation. Requirements for such a constellation in the near-term include maintaining continuity of the low-inclination, Jason-class altimeter series to ...