Three Generations of C-Band Wind Scatterometer Systems From ERS-1/2 to MetOp/ASCAT, and MetOp Second Generation

The C-band wind scatterometer service to the meteorological community started with the launch of the first European radar satellite ERS-1 on July 17, 1991, followed by its twin-satellite ERS-2 launched on April 21, 1995. The continuity of the ocean surface wind observations after ERS was ensured by the first series of operational polar orbiting meteorological satellites, with MetOp-A and MetOp-B satellites launched on October 19, 2006 and September 17, 2012, respectively. The launch of MetOp-C is planned in 2018 which will ensure a gap-less service until the start of the second generation MetOp mission (MetOp -SG) in 2021/22 for a mission duration of 21 years for the latter. This paper presents an overview of the developments and operations of the ERS and MetOp wind scatterometer systems, concluding with the initial definition of the MetOp-SG scatterometer requirements and design. Technical challenges encountered during the development of the first C-band system (ERS) are briefly described. Lessons learned from the experience of the ERS mission have been reflected in the definition of the MetOp/ASCAT mission, which is currently operated by EUMETSAT. Driven by the progress in the NWP models and increasing demands on providing accurate observations of extreme weather events, such as high intensity storms, the third generation of wind scatterometer on-board MetOp-SG will provide yet higher spatial resolution data with extended wind speed dynamic range. The latter enhancement is enabled by the addition of a cross-polarized backscatter component measurement on top of the VV-polarization capability as implemented in the ERS and MetOp systems.