Abstract
The satellite, Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) has been equipped with a new type of spaceborne laser altimeter, which has the benefits of having small footprints and a high repetition rate, and it can produce dense footprints on the ground. Focusing on the pointing angle calibration of this new spaceborne laser altimeter, this paper proposes a fast pointing angle calibration method using only a small range of terrain surveyed by airborne lidar. Based on the matching criterion of least elevation difference, an iterative pointing angle calibration method was proposed. In the experiment, the simulated photon-counting laser altimeter data and the Ice, Cloud and Land Elevation Satellite-2 data were used to verify the algorithm. The results show that when 1 km and 2.5 km lengths of track were used, the pointing angle error after calibration could be reduced to about 0.3 arc-seconds and less than 0.1 arc-seconds, respectively. Meanwhile, compared with the traditional pyramid search method, the proposed iterative pointing angle calibration method does not require well-designed parameters, which are important in the pyramid search method to balance calculation time and calibration result, and the iterative pointing angle calibration method could significantly reduce the calibration time to only about one-fifth of that of the pyramid search method.
Highlights
The spaceborne laser altimeter, as an important instrument for earth observation, is of great significance for global ecosystem observation and for glacier and lake research [1,2,3,4,5,6]
ICESat-2 is equipped with the Advanced Topographic Laser Altimeter System (ATLAS), which is a laser characterized by being micro-pulse, multi-beam, high repetition frequency and photon-counting
The pyramid least z-difference algorithm (P-least z-difference (LZD)) method finds these errors by traversing the possible parameter space of ∆θ and ∆β with different ranges and intervals
Summary
The spaceborne laser altimeter, as an important instrument for earth observation, is of great significance for global ecosystem observation and for glacier and lake research [1,2,3,4,5,6]. Following the Geoscience Laser Altimeter System (GLAS) of the Ice, Cloud and Land Elevation Satellite (ICESat) [7], which was a single-beam instrument that recorded the received laser energy as a waveform, the National Aeronautics and Space Administration (NASA) launched the Ice, Cloud and Land Elevation Satellite-2 ICESat-2 satellite on 15 September 2018 [8,9]. ICESat-2 is equipped with the Advanced Topographic Laser Altimeter System (ATLAS), which is a laser characterized by being micro-pulse, multi-beam, high repetition frequency and photon-counting. It has a ~17 m diameter footprint, and its high-frequency laser pulses can produce 0.7 m interval footprints along the track, which can form a relatively dense terrain profile. ATLAS will form three pairs of tracks in the cross-track
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