This is a RA Geophysical Data Record (GDR) product containing radar range, orbital altitude, wind speed, wave height and water vapour from the ATSR/MWR as well as geophysical corrections.
The REAPER (REprocessing of Altimeter Products for ERS) product is generated by applying a similar processing as for Envisat RA-2 on the Level 1b consolidated waveforms using 4 different re-trackers, RA calibration improvement, new precise orbit solution (POD), new ionospheric corrections (NICO09 until 1998 and GIM up to 2003), ECMWF ERA-interim model and updated SSB tables.
This product contains two data rates: a low rate of 1Hz and a high rate of 20Hz.
Most 1Hz data is also represented at 20Hz, while microwave radiometer (ATSR/MWR) data and the atmospheric and geophysical corrections are only given at 1 Hz.
The REAPER GDR (ERS_ALT_2_) is a global product including data over ocean, ice and land.
It should be noted that this product differs from the Envisat RA2 in the following ways:
- the product format; which is NetCDF (more details can be found in the Product Handbook, and not PDS
- the product is delivered based on orbit acquisition and not per pass (pole-to-pole)
This product is extended through Envisat RA-2 data