A multi-temporal absolute radiometric calibration method for remote sensing satellites

Abstract

The application discloses a kind of multi-temporal absolute radiometric calibration method of remote sensing satellite, using multi-star absolute radiometric calibration coefficient, obtain the apparent reflectivity of multi-star target point;Using the linear relationship of the apparent reflectivity of multi-star target point and the real reflectivity of multi-star target point;Determine the linear slope deviation value under multiple times by multiple linear relationship.The multi-temporal absolute radiometric calibration method of remote sensing satellite disclosed by the application monitors the absolute radiometric calibration accuracy of different calibration periods of multi-star to evaluate the stability of remote sensor responsivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of space remote sensing satellites, and relates to a multi-time-phase absolute radiation calibration method for remote sensing satellites. BACKGROUND

[0002] During the in-orbit service of a remote sensing satellite, absolute radiation calibration is required. Domestic and foreign scholars mainly measure the linear relationship between the apparent radiation value and the DN value of the remote sensing satellite image through the synchronous test of the atmospheric optical characteristic parameters, the measurement of the ground optical characteristics, the measurement of the meteorological parameters, the measurement of the site longitude and latitude information, the satellite synchronous measurement of the remote sensor parameters, so as to obtain the absolute calibration parameters of each load and perform satellite image ground object inversion. However, no effective literature or works have been found for the multi-time-phase absolute radiation calibration of remote sensing satellites.

[0003] After the multi-time-phase absolute radiation calibration of a remote sensing satellite obtains the absolute radiation calibration parameters, it is determined whether the absolute radiation calibration results in each time period during the in-orbit service of the satellite meet the business use requirements, and the stability of the response of the remote sensor in different calibration periods can be monitored. SUMMARY

[0004] The technical problem solved by the application is to overcome the shortcomings of the prior art and provide a multi-time-phase absolute radiation calibration method for remote sensing satellites, so as to evaluate the absolute radiation calibration accuracy of each load of the remote sensing satellite at different calibration times and monitor the stability of the response of the remote sensor in different calibration periods.

[0005] The technical scheme of the application is a multi-time-phase absolute radiation calibration method for remote sensing satellites, comprising:

[0006] The apparent reflectivity at the target point of the multi-satellite is obtained by using the multi-satellite absolute radiation calibration coefficient.

[0007] The linear relationship is fitted by using the true reflectivity of the ground at the target point of the multi-satellite and the apparent reflectivity at the target point of the multi-satellite.

[0008] The linear slope deviation values at multiple times are determined through multiple linear relationships.

[0009] The apparent reflectivity at the target point of the multi-satellite is obtained by using the multi-satellite absolute radiation calibration coefficient, comprising: the absolute radiation calibration coefficient of the multi-satellite is obtained based on the radiation transfer model by measuring the parameters in the absolute radiation calibration field test of the multi-satellite in the same time period on the same day; the equivalent radiance value at the entrance pupil of the target point of the multi-satellite is obtained by combining the obtained absolute radiation calibration coefficient of the multi-satellite and measuring the DN value of the target point in the multi-satellite synchronous overflight image; and the apparent reflectivity at the target point of the multi-satellite is calculated according to the solar zenith angle.

[0010] The field test parameters include meteorological parameters, atmospheric optical characteristic parameters, ground reflectivity, and observation geometry parameter data.

[0011] The calculation obtains the apparent reflectivity p of the target point of the multiple satellites λ , comprising:

[0012]

[0013] Wherein, L λ is the equivalent radiance at the entrance pupil of the satellite payload channel, d is the distance from the earth to the sun, ESUN λ is the solar irradiance, and theta is the solar elevation angle.

[0014] The linear relationship is fitted by using the ground true reflectivity of the target point of the multiple satellites and the apparent reflectivity of the target point of the multiple satellites, and the linear relationship is fitted by using the ground true reflectivity of the target point of the multiple satellites and the apparent reflectivity of the target point of the multiple satellites.

[0015] The linear relationship is fitted by using the ground true reflectivity of the target point of the multiple satellites and the apparent reflectivity of the target point of the multiple satellites, and the linear relationship is fitted by using the ground true reflectivity of the target point of the multiple satellites and the apparent reflectivity of the target point of the multiple satellites.

[0016] The N is greater than or equal to 2.

[0017] The linear slope deviation values at multiple times are determined through the multiple linear relationships, and the linear slope deviation values at multiple times are determined through the multiple linear relationships.

[0018] The linear slope deviation values at multiple times are determined through the multiple linear relationships, and the linear slope deviation values at multiple times are determined through the multiple linear relationships.

[0019] k = p' B -(p B + p) * k B

[0020] Wherein, p' B is the B-band ground true reflectivity, p B is the B-band apparent reflectivity, p is the reflectivity theoretical deviation value, and k BThis represents the linear slope between the true surface reflectance and the corresponding apparent reflectance in the B-band.

[0021] This invention has the following advantages: Current remote sensing satellites rely on absolute radiometric calibration experiments and radiometric parameter measurements to determine their stability and responsiveness. This invention, however, utilizes multi-satellite, multi-temporal absolute radiometric calibration experiments. It employs the relationship between the actual and apparent surface reflectance across multiple satellites and time phases to determine the multi-temporal linear slope deviation. By monitoring the multi-satellite, multi-temporal linear slope deviation results, the stability of the remote sensor and the sensitivity and responsiveness of the payload are determined. Simultaneously, the multi-temporal absolute radiometric calibration results are applied to remote sensing satellite preprocessing to determine whether the absolute radiometric calibration results of each remote sensing payload at different calibration times meet operational requirements. Furthermore, it provides a reliable basis for the accuracy of satellite radiometric parameter measurements. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1 The specific implementation of this invention will be described in detail below. The main steps are as follows:

[0024] (1) Use the multi-star absolute radiation calibration coefficient to obtain the apparent reflectivity at the multi-star target point.

[0025] Obtaining the apparent reflectance at a multi-satellite target point involves calculating the multi-satellite absolute radiometric calibration coefficient, the DN value of the multi-satellite synchronous transit image, the equivalent radiance at the entrance pupil of the multi-satellite, and the apparent reflectance of the multi-satellite.

[0026] 1) The calculation of the absolute radiometric calibration coefficient of multiple satellites is carried out by measuring the field test parameters of N (N≥2) satellites passing over the same day and time period, including meteorological parameters, atmospheric optical characteristic parameters, ground reflectivity, and observation geometric parameters, and processing the synchronous measurement parameters.

[0027] 2) The DN value of multi-satellite synchronous transit imagery is obtained by calculating the average DN value of the target area by selecting a 10m*10m window for transit satellite images of N (N≥2) satellites within the same time period on the same day.

[0028] 3) The apparent reflectance of multiple stars is calculated using the equivalent radiance at the entrance pupil of the multiple star payload channel.

[0029] To obtain the equivalent radiance at the entrance pupil of a satellite payload, the DN value of the target area is fitted to the corresponding absolute radiometric calibration coefficient of N (N≥2) satellites within the same time period. The corresponding apparent reflectance is then calculated. The formula is as follows:

[0030]

[0031] Here, L λ The equivalent radiance at the entrance pupil of the satellite payload channel, d is the Earth-Sun distance, ESUN λ θ represents solar irradiance, and θ represents the solar altitude angle.

[0032] (2) A linear relationship was obtained by fitting the true reflectance of the ground surface at the multi-star target point and the apparent reflectance at the multi-star target point.

[0033] During the same time period when the two satellites passed overhead on the day of the test, the true surface reflectance of the same target point in the target area was measured using the ASD field calibration instrument. A linear relationship was fitted based on the true surface reflectance and apparent reflectance of N (N≥2) satellites.

[0034] (3) Determine the linear slope deviation values ​​at multiple times through multiple linear relationships.

[0035] Based on the actual and apparent surface reflectance of the same target point obtained from the absolute radiometric calibration field tests conducted by N (N≥2) satellites in April and September over a continuous three-year period, the linear slope deviation value k of multiple satellites and multiple time phases can be expressed by the following formula:

[0036] k=ρ′ B -(ρ B +ρ)*k B

[0037] Where, ρ' B ρ represents the true surface reflectance in the B-band. B Here, ρ is the apparent reflectance of the B-band, ρ is the theoretical deviation of the reflectance, and k is the apparent reflectance of the B-band. B This represents the linear slope between the true surface reflectance and the corresponding apparent reflectance in the B-band.

[0038] It should be noted that the above solutions are preferred embodiments of the present invention. Those skilled in the art can make some changes or improvements without departing from the technical concept of the present invention, and these are all included within the protection scope of the present invention.

[0039] The parts of this invention that are not described in detail are common knowledge to those skilled in the art.

Claims

1. A multi-temporal absolute radiometric calibration method for remote sensing satellites, characterized in that, include: The apparent reflectivity at the target point of the multi-star system is obtained using the multi-star absolute radiometric calibration coefficient. A linear relationship was obtained by fitting the true surface reflectance and the apparent reflectance at multiple target points; The linear slope deviation values ​​at multiple time points were determined by multiple linear relationships. The method of fitting a linear relationship between the true surface reflectance and the apparent reflectance of multiple satellite target points includes: conducting N-satellite multi-field calibration experiments within the same time period on the same day; measuring the true surface reflectance of the same target point in the target area using an ASD (Airborne Spectrometer) during the transit time of each satellite; fitting a linear relationship between the true surface reflectance and the apparent reflectance of the N satellites to achieve the measurement of the true surface reflectance of multiple satellite target points. The method of determining the linear slope deviation value at multiple times through multiple linear relationships includes: determining the linear slope deviation value at multiple times based on multiple sets of linear relationships between the true surface reflectance and the apparent reflectance at multiple target points of the multi-star target points through absolute radiometric calibration field tests conducted at multiple times; The specific process for determining the linear slope deviation value at multiple time points is as follows: Based on the actual and apparent surface reflectance of the same target point obtained from the absolute radiometric calibration field test monitoring conducted by N satellites in April and September of a continuous three-year period, the linear slope deviation value k of multiple satellites and multiple time phases is expressed by the following formula: k=ρ' B -(r B +p)*k B Where, ρ' B ρ represents the true surface reflectance in the B-band. B Here, ρ is the apparent reflectance of the B-band, ρ is the theoretical deviation of the reflectance, and k is the apparent reflectance of the B-band. B This represents the linear slope between the true surface reflectance and the corresponding apparent reflectance in the B-band.

2. The multi-temporal absolute radiometric calibration method for remote sensing satellites according to claim 1, characterized in that, The method of using multi-satellite absolute radiometric calibration coefficients to determine the apparent reflectance at a multi-satellite target point includes: measuring parameters from an absolute radiometric calibration field experiment of multiple satellites within the same time period on the same day, and determining the multi-satellite absolute radiometric calibration coefficients based on a radiative transfer model; simultaneously measuring the DN value at the test target point using multi-satellite synchronous transit images, and combining the obtained multi-satellite absolute radiometric calibration coefficients to obtain the equivalent radiance value at the entrance pupil of the multi-satellite target point, and then calculating the apparent reflectance at the multi-satellite target point based on the solar zenith angle.

3. The multi-temporal absolute radiometric calibration method for remote sensing satellites according to claim 2, characterized in that, The field test parameters include: meteorological parameters, atmospheric optical characteristic parameters, ground reflectivity, and observation geometric parameter data.

4. The multi-temporal absolute radiometric calibration method for remote sensing satellites according to claim 2, characterized in that, The calculation yields the apparent reflectance ρ at the multi-star target point. λ ,include: Among them, L λ d represents the equivalent radiance at the entrance pupil of the satellite payload channel, where d is the Earth-Sun distance. λ θ represents solar irradiance, and θ represents the solar altitude angle.

5. A multi-temporal absolute radiometric calibration method for remote sensing satellites according to claim 2, characterized in that, The method of fitting a linear relationship between the actual surface reflectance and the apparent reflectance at the multi-satellite target point includes: measuring the actual surface reflectance at the same target point in the field of the indoor and outdoor fields during the same time period of the same day using an absolute radiometric calibration test field instrument, and fitting a linear relationship with the apparent reflectance at the multi-satellite target point.

6. The multi-temporal absolute radiometric calibration method for remote sensing satellites according to claim 1, characterized in that, The N≥2.

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