The REAPER project: Bringing ERS Altimetry data set to ENVISAT standards

Pierre Femenias (ESA, Italy)


Steve Baker (MSSL, UK); David James Brokley (MSSL, UK); Mònica Roca (isardSAT, spain); Remko Scharroo (Eumetsat, Germany); François Soulat (CLS, France); Peggy Fischer (ESA, Italy); Frédéric Paul (Ifremer, France)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Corrections

Presentation type: Type Poster

ESA's first Remote Sensing Satellite: ERS-1 was launched on July 17, 1991 and operated until June 1996, completing one year of parallel operation (Tandem Mission) with ERS-2. Launched in April 1995, ERS-2 has operated for over 14 years with all instrumentation still working well despite the loss of the on-board tape recorders and the transition to gyro-less pointing. Since the launch of Envisat in March 2002, the continuing operation of ERS-2 has provided a valuable overlap of the Radar Altimeter missions.
The existing ERS Altimetry data set is known to be not fully homogenous over the two-mission lifetime, as a result of different algorithmic evolutions performed on the ERS-1 and ERS-2 ground processing chains and of changes in the RA and MWR sensors behaviour due to ageing effects and on-board anomalies. The aim of the REAPER project is to reprocess all available ERS-1 and ERS-2 RA and MWR data, from July 1991 through to June 2003, to produce a coherent and homogeneous long-term series that is cross calibrated and offers continuity with the ENVISAT RA2 mission (V2.1).
The use of up-to-date geophysical models improves the corrections applied to the range measurement. By revisiting the instrument calibration algorithms and applying retrospectively the experience gained on the effects of instrument ageing, further improvements in measurement accuracy are gained. Derivation of a new Precise Orbit solution across the 12 year period results in a significant improvement to the orbit accuracy and hence the final surface height measurements. The resulting data set available since summer 2014 allows greater exploitation than was previously possible of the full potential of the archived ERS Altimetry data set over ocean, land and ice surfaces.
This paper describes the new processing algorithms and geophysical models that are used in the REAPER reprocessing chains, as well as the new ERS Altimetry products and respective performance, now available to the user community.

Pierre Femenias