Retracked TOPEX Data for the Climate Data Record

Philip Callahan (Jet Propulsion Laboratory, United States)


Joseph McMichael (Jet Propulsion Laboratory, United States); Shailen Desai (Jet Propulsion Laboratory, United States)

Event: 2016 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Measurement and retracking (SAR and LRM)

Presentation type: Type Oral

We will report progress on delivering the TOPEX Climate Data Record product. The main effort for this product is retracking the data to account for waveform leakages and point target response (PTR) changes, and it also includes updating other components of the record to be compatible with Jason GDRs.

Previous reports on this work included:
(1) Determining that leakages limited the use of the Cal-1 data for generating PTRs to the first seven lobes.
(2) Determining that it was not feasible to improve upon the original WFF waveform weights.
(3) Developing methods to extend the PTR to the necessary 30 lobes to reach full accuracy.

The resulting PTRs and the original waveform weights were used to retrack all of the TOPEX data in three modes: fixed skewness of 0 and 0.1 and solving for skewness. During the process of evaluating these data, we became aware of a difference between the original GDRs and the MGDR-B from PODAAC that is widely used. The latter includes the WFF range calibration correction derived from specialized processing of internal calibration data. We have investigated the properties of this correction and attempted to determine whether the retracking process includes it. We find that the broadening PTR of Alt-A spreads signal into the range gates originally used for noise estimation in the retracking. By shifting the range gates earlier so that they are less contaminated, we find a change in range that closely mimics the range calibration values. Full evaluation of these data will be presented.

The final climate product will include a format as closely aligned with Jason Ver E as possible and geophysical and orbits updated to the Jason Ver E standards. After these enhancements are made, a final sea state bias correction will be determined.

The work reported here was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Oral presentation show times:

RoomStart DateEnd Date
Auditorium Tue, Nov 01 2016,16:15 Tue, Nov 01 2016,16:30
Philip Callahan
Jet Propulsion Laboratory
United States