Applying the pulse-pair processing to high PRF nadir altimeter data: sensitivities to geophysical parameters and possible applications

Pierre Rieu (CLS, France)


François Soulat (CLS, France); Thomas Moreau (CLS, France); François Boy (CNES, France)

Event: 2019 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Measurement and Retracking

Presentation type: Type Poster

The pulse-pair technique [Zrnic, 1977] is widely used for estimating the first two moments of the Doppler spectrum of geophysical signals, i.e. the mean (Doppler centroid or Doppler shift) and the width. Doppler centroid estimation through pulse-pair processing is routinely performed in SAR imagery [Madsen, 1989] and in the SKIM candidate mission, that uses a near-nadir Doppler radar to estimate the Doppler shift induced by surface currents [Ardhuin, 2018].

In nadir altimetry, the correlation of complex pulses has already been studied with low-PRF altimeter data ([Abileah, 2013] on Envisat and [Quartly, 2015] on AltiKa) but, due to sparse data, sensitivities to geophysical parameters were not brought to light. For high-PRF altimeters (CryoSat-2, Sentinel-3), the Doppler history of scatterers is used through a Delay-Doppler processing [Raney, 1998], and pulse-pair processing has not yet been analyzed to our knowledge.

We have implemented the pulse-pair processing in our S3 prototype processor, and one cycle of data have been processed. The Doppler shift estimates are found to be very sensitive to several effects (surface slopes, mispointing, heterogeneous surface backscattering …) and in perfect agreement with the model derived by [Rodriguez, 1994], thus allowing direct parameter estimation. We detail our implementation of the processing and analyze the observed sensitivities to geophysical parameters. Possible applications of this easy-to-implement and computationally efficient processing are presented, ranging from mispointing monitoring to data quality flagging (correlated errors).

Zrnic, D. S. (1977). Spectral moment estimates from correlated pulse pairs. IEEE Transactions on Aerospace and Electronic Systems, (4), 344-354.
Madsen, S. N. (1989). Estimating the Doppler centroid of SAR data. IEEE transactions on aerospace and electronic systems, 25(2), 134-140
Ardhuin, F., Aksenov, Y., Benetazzo, A., Bertino, L., Brandt, P., Caubet, E., ... & Dias, F. (2018). Measuring currents, ice drift, and waves from space: the Sea surface KInematics Multiscale monitoring (SKIM) concept. Ocean Science, 14(3), 337-354.
Abileah, R., Gómez-Enri, J., Scozzari, A., & Vignudelli, S. (2013). Coherent ranging with Envisat radar altimeter: A new perspective in analyzing altimeter data using Doppler processing. Remote sensing of environment, 139, 271-276.
Quartly, G. D., & Passaro, M. (2015). Initial Examination of AltiKa's Individual Echoes. Marine Geodesy, 38(sup1), 73-85.
Raney, R. K. (1998). The delay/Doppler radar altimeter. IEEE Transactions on Geoscience and Remote Sensing, 36(5), 1578-1588.
Rodriguez, E., & Martin, J. M. (1994). Correlation properties of ocean altimeter returns. IEEE transactions on geoscience and remote sensing, 32(3), 553-561.

Poster show times:

Room Start Date End Date
The Gallery Tue, Oct 22 2019,16:15 Tue, Oct 22 2019,18:00
The Gallery Thu, Oct 24 2019,14:00 Thu, Oct 24 2019,15:45
Pierre Rieu