Minimize ERS News

Reprocessed ESA ERS Altimetry (REAPER) dataset now available

11 September 2014

The full-mission reprocessing of the ESA ERS Radar Altimetry (RA) Level 2 data has been completed and the new dataset is now available online to the ESA Earth Observation user community.

The REAPER (REprocessing of Altimeter Products for ERS) project covers both the ERS-1 and the ERS-2 Altimetry missions. The reprocessed dataset spans from the start of the ERS-1 mission in July 1991 to June 2003, when the loss of the ERS-2 on-board data storage capability occurred causing the end of the ERS-2 global mission coverage. The reprocessing campaign has been performed with REAPER processor version 1.08 and use of the latest reprocessed ESA precise orbit products (see ESA news "Homogeneous reprocessed ERS-1 and ERS-2 Orbit dataset"). The output products are delivered in netCDF format (version 3.6) and are based on dump orbits (i.e. not split in pole-to-pole passes).

The REAPER Product Handbook provides exhaustive information on the new ERS RA product content, format and improvements. It provides also, for user's convenience, a list of passes with known data quality issues (i.e. orbital manoeuvres, telemetry problems, etc).

Data Access

The ERS-1/2 REAPER Altimeter dataset is composed of the following three product types and is now freely accessible online upon Fast Registration:

Data Processing and Quality Improvement

Major improvements with respect to the previous ESA RA products format (OPR - Ocean Product - and WAP - Waveform product) have been implemented (e.g. the 4 Envisat RA-2 retrackers, RA calibration improvement, new reprocessed Precise Orbit Solution, ECMWF ERA-interim model, NICO09 ionospheric correction until 1998, GIM ionospheric correction up to 2003, new SSB, etc.). The assessment of the REAPER data quality versus the ERS OPR and WAP data shows a clear improvement in terms of accuracy over the tandem periods between ERS-1, ERS-2 and Envisat missions (currently assessed periods).
However, the REAPER dataset presents some limitations (such as the use of poor MWR Wet tropospheric correction, out of range PTR corrections, etc.) that are fully described in the Product Handbook.

Validation reports for all three product types (GDR/SGDR/METEO) are available to users:

1. REAPER Calibration Monitoring
2. Cal/Val evaluation of REAPER ERS altimeter data
3. RA L2 Validation Report
4. ERS REAPER Performance & QA Website

Future Reprocessing

ESA is planning to further improve the ERS dataset by extending the time coverage up to 2011 and also continuing to increase the data quality. For this reason a future reprocessing is foreseen by the end of 2015.

Any feedback or recommendation for additional improvement from the user community is welcome through EOHelp.

See also related news of 13 May 2014.