In-orbit calibration method when pointing angle error of satellite-borne laser altimeter is nonconstant

Abstract

The invention provides an in-orbit calibration method when pointing angle error of a satellite-borne laser altimeter is nonconstant. The method comprises the following steps: determining expression forms of laser pointing angle system error of the satellite-borne laser altimeter in the pitch and roll directions, and constructing a vector to be estimated; constructing a laser foot point observationequation when the angle system error is nonconstant; estimating an initial value by utilizing a linear least square method; carrying out iterative convergence estimation by utilizing a nonlinear least squares LM algorithm; calculating error components of the laser pointing angle in the pitch and roll directions at the current moment; and calculating a laser foot point precise coordinate after thepointing angle system error is compensated and calibrated in the current measurement time, and finishing in-orbit calibration of the pointing angle error of the satellite-borne laser altimeter. Compared with the existing pointing angle error calibration method, the method can carry out calibration when the pointing angle error is nonconstant, which cannot be finished through the existing method;and the method can be compatible with the existing situation that the pointing angle system error is constant, and is higher in universality.

Description

technical field [0001] The present invention relates to an on-orbit calibration method for the pointing angle system error of a spaceborne laser altimeter during its on-orbit operation, in particular to a method for on-orbit calibration of the pointing angle system error during the on-orbit operation of a spaceborne laser altimeter. The non-constant pointing angle error method of track calibration belongs to the field of laser remote sensing technology. Background technique [0002] The space-borne laser altimeter is the measurement equipment with the highest elevation accuracy in the three-dimensional coordinate data of the earth's surface obtained by satellite remote sensing, which can reach the decimeter level. However, due to the influence of environmental factors, target factors and device factors, the initial data error is far greater than the design accuracy. For example, in the influence of environmental factors, due to the influence of scattering and refraction pro...

AI Technical Summary

Problems solved by technology

However, the pointing angle system error of the space-borne laser altimeter during orbit operation seriously affects its accuracy index. For the GLAS system carried by the ICESat satellite, at an orbital altitude of 600km and a comprehensive incident angle of 1°, the 30″ The pointing angle error will cause the center of the laser foot point to produce a plane direction error of 87m and an elevation direction error of 1.5m on the earth's surface

Although the relative positional relationship between the load sensors on the satellite has been precisely calibrated before the satellite launch; however, during the satellite launch process and in-orbit operation, due to vibration and heat, etc., the angular system that changes with time will be caused. Offset, which is specifically expressed as the pointing angle system error of the spaceborne laser altimeter. For the laser altimeter mounted on the low-orbit satellite platform, this error is usually about 30″

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