GB/T 42646-2023 (English Version)

Standard No.: GB/T 42646-2023
Language: Chinese, Available in English version
Release Date: 2023
Published By: General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
Latest: GB/T 42646-2023

Scope: This document specifies the general requirements, layout requirements, measurement content, measurement procedures, measurement data processing methods and uncertainty analysis for the measurement of ground detectors for field calibration of spaceborne laser altimeters. This document is applicable to the layout and measurement of ground detectors for field calibration of spaceborne laser altimeters. The use of other similar ground detectors shall be implemented in reference.

Introduction

1. Background and significance of standard formulation

Spaceborne laser altimeters are an important part of modern remote sensing technology, and their on-orbit calibration is directly related to the accuracy of ground elevation data products. This standard aims to standardize the detector layout and measurement methods for field calibration of spaceborne laser altimeters to ensure the reliability of ground control information.

2. Comparative analysis of standard frameworks

Standard dimensions	GB/T 42646—2023	International similar standards	Industry reference standards
Requirements for measuring instruments	Laser ground detectors must meet technical indicators such as wavelength response range and energy density coverage	...	Refer to the positioning accuracy requirements of GB/T18314
Measurement weather conditions	Sunny and cloudless, wind force less than level 4, dry and clean atmosphere	...	Consistent with the geodetic technical requirements in GB22021
Deployment site requirements	The site is open, without obstructions, and the inclination is less than $2^{\circ}$	...	Refer to the international laser ranging technical specifications

3. Interpretation of core technical requirements

Deployment requirements for laser ground detectors:

Deployed along the direction of the satellite orbit, the vertical and along-track ranges shall not be less than the sum of the laser footprint diameter and the point prediction error
The deployment spacing is less than one-fourth of the laser footprint diameter
There are no obstructions within the zenith angle of $3^{\circ}$

Measurement data processing method:

The energy level square weighted centroid method is used to calculate the coordinates of the laser footprint center of mass to ensure measurement accuracy. The formula is as follows: $$ \left. \begin{array}{c} {{\displaystyle x^{\prime}=\frac{\sum x I^{2}\left(x,y\right)}{\sum I^{2}\left(x,y\right)}}}\\ {{\displaystyle y^{\prime}=\frac{\sum y I^{2}\left(x,y\right)}{\sum I^{2}\left(x,y\right)}}} \end{array} \right\} $$

4. Implementation Suggestions and Precautions

Implementation Case Study:

In a certain satellite-borne laser altimeter calibration mission, the site was selected in a flat area with convenient transportation, and the detector array was arranged in strict accordance with standard requirements. The effectiveness of this method was verified by comparing the actual measurement data with the expected results.

GB/T 42646-2023 Referenced Document

GB 22021 National basic technical regulations for geodetic surveying
GB/T 18314 Specifications for survey and measurement of global navigation satellite system*， 2024-08-23 Update
GB/T 34509.2 In orbit field radiometric calibration for optical remote sensor of land observation satellite—Part 2:Thermal infrared

GB/T 42646-2023 history

2023 GB/T 42646-2023 Layout and measurement method of spaceborne laser altimeter site calibration detector