Waveform width of a satellite laser altimeter illuminating on the sea surface.

The echo width is one of the most essential parameters of waveforms, which can be used to evaluate the ranging performance of a laser altimeter or retrieve wind speeds when laser pulses illuminate on the sea surface. The classical expression of waveform widths is not suitable for a current satellite laser altimeter because only the waves on the sea with smaller wavelengths can be covered by a satellite laser altimeter due to its small footprint. A new expression is derived by dividing the broadening effect of echo widths into the wind wave with small wavelengths and the swell cause with large wavelengths. The Geoscience Laser Altimeter System (GLAS) and National Centers for Environmental Prediction (NCEP) data are used to verify the new expression. Based on the new echo width expression, the ranging performance is evaluated when a laser is illuminating on the ocean surface. It indicates that a laser altimeter performs a better ranging accuracy (better than 5 cm) than when it is evaluated using the classical expression (worse than 6 cm) at moderate and strong winds.