Temporal pulse spreading of a return lidar signal

Area of Science:

• Geospatial science
• Optical remote sensing
• Laser technology

Background:

• Spaceborne lidar systems often employ cross-track or conical scanning for global coverage.
• Off-nadir laser pulse transmission introduces a slanting effect, causing temporal spreading in the return signal compared to nadir shots.
• This signal bias impacts the accuracy of topographic and atmospheric measurements.

Purpose of the Study:

• To analyze the signal bias introduced by scanning in spaceborne lidar.
• To derive fundamental equations for the return signal of topographic and diffuse targets.
• To provide a basis for correcting lidar data affected by the slanting effect.

Main Methods:

• Theoretical analysis of laser pulse return signals.
• Derivation of signal return formulas for different target types.
• Comparison of off-nadir and nadir signal characteristics.

Main Results:

• Formulas for calculating the return signal from topographic targets (laser range finders) were established.
• Formulas for calculating the return signal from diffuse targets (atmospheric lidars) were derived.
• The temporal spreading effect on the return signal due to scanning was quantified.

Conclusions:

• The slanting effect in spaceborne lidar scanning introduces a predictable bias in return signals.
• The derived formulas offer a method to correct for this bias in both topographic and atmospheric lidar applications.
• Accurate signal correction is crucial for reliable global coverage lidar data.