CN116840851B - Method for arranging ground detectors of satellite-borne ground laser altimeter - Google Patents

Abstract

The invention provides a ground detector layout method for a spaceborne ground-to-ground laser altimeter, which includes: Step 1: Calculate each element according to the orbital height of the space-borne ground-to-ground laser altimeter, the laser beam, the angle between the beams, and the emission frequency. Interval between laser footprint centers; Step 2: Calculate the diameter of a single laser footprint based on the orbital height and divergence angle of the spaceborne ground-mounted laser altimeter; Step 3: Capture footprints based on laser footprint intervals, size and expectations The number determines the detector layout method. The invention can determine the number of ground footprint spots and the position of the footprint spots of the spaceborne ground-to-ground laser altimeter, thereby providing high-precision ground footprint coordinates for subsequent elimination of the installation angle error of the spaceborne laser altimeter.

Description

A method of laying out ground detectors for spaceborne ground-to-ground laser altimeters

Technical field

The invention relates to the technical field of data processing of spaceborne laser altimeter, and in particular to a method for laying out ground detectors of a spaceborne laser altimeter.

Background technique

During the development and testing of spaceborne ground-to-ground laser altimeters, the instruments generally have high pointing and ranging accuracy after ground calibration. However, due to factors such as vibration during satellite launch and changes in the space environment after entering orbit, system parameters such as the pointing and ranging of the laser altimeter will change relative to the ground measurement values before launch, which will cause errors in the calculation of laser footprint coordinates. Therefore, in order to obtain high-precision spaceborne laser altimetry data, the systematic error of the altimetry lidar must be eliminated through on-orbit geometric calibration methods.

At present, the on-orbit geometric calibration methods of spaceborne ground-to-ground laser altimeters mainly include: airborne infrared imaging method, ground detector calibration method, satellite maneuvering scanning method, and laser echo analysis method. The airborne infrared imaging method requires the aircraft and the satellite to fly over the calibration field synchronously, and it is difficult to extract the laser footprint image from the infrared image, and the success rate is low. The ground detector calibration method requires pre-arrangement of energy detectors in the area where the laser will be irradiated to determine the true position of the laser footprint. The calibration reliability and accuracy are high. The disadvantage is that the position of the laser footprint needs to be accurately estimated in advance. Calibration The construction requirements of the site are high and the testing is difficult. The satellite maneuvering scanning method cannot be used when the satellite's attitude maneuvering capability is weak. The laser echo analysis method can only be used when the laser altimeter provides ranging waveform data.

Contents of the invention

In view of the existing problems in the on-orbit calibration of the current spaceborne ground-to-ground laser altimeter, based on an in-depth study of the impact of the theoretical design parameters of the spaceborne ground-to-ground laser altimeter on the size and spacing of the laser altimeter's ground footprints, The invention provides a ground detector layout method for a spaceborne ground-to-ground laser altimeter. With a limited number of ground detectors, as many ground detectors as possible can be used to respond to a single laser footprint and increase the number of captured laser footprints. , and ultimately provide high-precision ground footprint coordinates to eliminate the installation angle error of the spaceborne laser altimeter. This invention can calculate the ground spot diameter and separation distance of the laser altimeter based on the theoretical design parameters of the orbital height of the spaceborne ground-to-ground laser altimeter, laser beam, angle between the beams, emission frequency and divergence angle. According to the spot diameter and separation distance can determine the distance between each detector array and the distance between each laser detector within each detector array. Finally, through this ground laser detector layout plan, the ground footprint of the spaceborne ground-to-ground laser altimeter can be determined. The number of light spots and the location of the footprint light spots can provide high-precision ground footprint coordinates for subsequent elimination of the placement angle error of the spaceborne laser altimeter.

The invention belongs to a method among the ground detector calibration methods. The ground detector calibration method mainly determines the true position of the laser footprint by arranging energy detectors in the area to be irradiated by the laser altimeter. The difference value between the position and the laser footprint position calculated from the theoretical design parameters realizes the on-orbit geometric calibration of the spaceborne ground-based laser altimeter. In this process, how to accurately arrange ground detectors in the area that the laser altimeter will illuminate, and with the limited number of ground detectors, use as many ground detectors as possible to respond to a single laser footprint and improve the capture of the laser footprint. The number of prints is the most critical content in the ground detector calibration method.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for laying out ground detectors for a spaceborne ground-to-ground laser altimeter, including the following steps:

Step 1: Calculate the distance between the center positions of each laser footprint based on the orbital height of the spaceborne ground-to-ground laser altimeter, laser beam, angle between the beams, and emission frequency;

Step 2: Calculate the diameter of a single laser footprint based on the orbital height and divergence angle of the spaceborne ground-to-ground laser altimeter;

Step 3: Determine the detector layout method based on the laser footprint spacing, size and expected number of captured footprints.

Further, the step one includes:

If the satellite's orbital height around the earth is H, the sub-satellite point velocity is v, the laser beam is n, the angle between the beams is α and the emission frequency is a, then the minimum distance between the laser footprint centers X is calculated as follows:

_{In the formula ,} , |X _v -X _α |} represents the minimum distance value between laser footprints generated by different lasers at adjacent moments.

Further, the second step includes:

If the height of the satellite orbit around the earth is H and the divergence angle of the laser altimeter is θ, then the laser footprint diameter R is calculated as follows:

Further, the third step includes:

Step 3.1, based on the single laser footprint diameter R calculated in step 2, and based on the requirement that at least one laser detector captures the laser footprint spot, determine the distance D between each laser detector in each detector array. ; If at least one laser detector needs to respond to the spaceborne ground-to-ground laser altimeter, then Up to four laser detectors respond to the spaceborne ground-mounted laser altimeter;

Step 3.2: Determine the distance between adjacent detector arrays and the number of detector arrays based on the minimum distance X between the laser footprint centers calculated in step 1 and the number of expected captured footprint spots.

Beneficial effects:

The invention belongs to a method among the ground detector calibration methods. The ground detector calibration method requires setting up energy detectors in advance in the area where the laser will be irradiated to determine the true position of the laser footprint. The calibration reliability and accuracy are high. , but ground laser detectors are usually expensive and usually limited in quantity. Therefore, the innovation of this application is to simplify the ground detector layout process, and at the same time, it proposes a ground detection that is directly related to the key indicators of different satellite loads and has high applicability. Finally, this application can determine the ground detector layout method according to the number of footprints expected to be captured, which improves the use efficiency of ground detectors.

Description of the drawings

Figure 1 is a flow chart of a ground detector layout method for a spaceborne ground-to-ground laser altimeter according to the present invention;

Figure 2 is a schematic diagram of a laser detector responding to a spaceborne ground-to-ground laser altimeter;

Figure 3 is a schematic diagram showing the response of four laser detectors to the spaceborne ground-mounted laser altimeter;

Figure 4 is a schematic diagram of the layout of the ground laser altimeter ground detector;

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

As shown in Figure 1, a spaceborne ground-to-ground laser altimeter ground detector layout method of the present invention includes the following steps:

Step 1. Calculate the center position interval of each laser footprint based on the orbital height of the spaceborne ground-to-ground laser altimeter, laser beam, angle between beams and emission frequency, including:

If the satellite's orbital height around the earth is H, the sub-satellite point velocity is v, the laser beam is n, the angle between the beams is α and the emission frequency is a, then the minimum distance between the laser footprint centers X can be calculated as follows:

_{In the formula ,} , |X _v -X _α |} represents the minimum distance value between laser footprints generated by different lasers at adjacent moments.

Step 2: Calculate the diameter of a single laser footprint based on the orbital height and divergence angle of the spaceborne ground-to-ground laser altimeter, including:

If the height of the satellite orbit around the earth is H and the divergence angle of the laser altimeter is θ, then the diameter of the laser footprint is R and can be calculated as follows:

Step 3: Determine the detector layout method based on the laser footprint spacing, size and expected number of captured footprints, including:

Step 3.1: Based on the diameter R of a single laser footprint calculated in step 2, and based on the requirement that at least one detector captures the laser footprint spot, determine the distance D between each laser detector in each detector array. The detector is a laser detector. If at least one laser detector needs to respond to the spaceborne ground-to-ground laser altimeter, then as shown in picture 2;

This invention can have up to 4 laser detectors responding to the spaceborne ground-to-ground laser altimeter, as shown in Figure 3;

Step 3.2: Based on the minimum distance between the laser footprint centers calculated in step 1 and the number of footprint spots expected to be captured, determine the distance between adjacent detector area arrays and the number of detector area arrays to be laid out, as shown in Figure 4 shown.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (1)

1. The method for arranging the ground detector of the satellite-borne ground laser altimeter is characterized by comprising the following steps of:

step one, calculating the center position interval of each laser footprint according to the track height, the laser beams, the included angles among the beams and the emission frequency of the satellite-borne earth laser altimeter, wherein the step one comprises the following steps:

if the satellite orbit height is H, the satellite point velocity is v, the laser beam is n, the included angle between beams is alpha and the transmitting frequency is a, the minimum value X of the laser footprint center position interval is calculated by adopting the following mode:

wherein X is _v Representing the distance value X of the laser footprint gap generated by the same laser at adjacent emission time _α Representing the distance value of the laser footprint gap generated by adjacent lasers at the same transmitting moment, min { X } _v ,X _α ,|X _v -X _α The | } represents the minimum distance value of the laser footprint interval generated by different lasers at adjacent moments;

step two, calculating the diameter of a single laser footprint according to the orbit height and the divergence angle of the satellite-borne earth laser altimeter, comprising the following steps:

if the orbit height of the satellite around the earth is H and the divergence angle of the laser altimeter is theta, the diameter R of the laser footprint is calculated by adopting the following mode:

determining a detector layout method according to the laser footprint interval, the size and the expected number of the captured footprints, wherein the method comprises the following steps:

step 3.1, determining the distance D between each laser detector in each detector area array according to the single laser footprint diameter R calculated in the step two and the requirement that at least 1 laser detector captures laser footprint light spots; if at least 1 laser detector is required to respond to the satellite-borne earth laser altimeter, thenAt most 4 laser detectors respond to the satellite-borne earth laser altimeter;

and 3.2, determining the distance between adjacent detector arrays and the number of the detector array layout according to the minimum X of the interval between the central positions of the laser marks calculated in the step one and the number of the expected captured footprint light spots.