CN-122016057-A - On-orbit calibration method for correcting self-radiation of hot mirror of microwave imager based on reference radiation

CN122016057ACN 122016057 ACN122016057 ACN 122016057ACN-122016057-A

Abstract

The invention discloses an on-orbit calibration method for correcting self-radiation of a hot mirror of a microwave imager based on reference radiation, which comprises the following steps of calculating an included angle between the hot mirror of the microwave imager and the sun; the method comprises the steps of calculating ground observation bright temperature of a microwave imager, calculating observation bright temperature of a reference microwave radiometer, obtaining simulated bright temperature of the reference microwave radiometer and the microwave imager based on simulation of a radiation transmission model, calculating system error between the reference microwave radiometer and the microwave imager based on deviation of the observed bright temperature and simulated bright Wen Piancha, fitting by adopting an included angle of a hot mirror of the microwave imager and sun as a functional relation based on the system error, calculating self-radiation bright temperature of the hot mirror of the reference microwave radiometer, calculating an included angle of the hot mirror of the microwave imager and the sun in real time on orbit, and observing the bright temperature of the ground based on the self-radiation bright Wen Dingzheng microwave imager of the hot mirror. The invention takes the double deviation of the observed brightness and the simulated brightness and temperature as the constraint, solves the self-radiation of the heat mirror in real time, and solves the problem that the temperature of the heat mirror of the microwave imager cannot be actually measured in an on-orbit manner.

Inventors

XIE XINXIN
SONG YUEHUI
YANG CHEN

Assignees

北京理工大学(珠海)

Dates

Publication Date: 20260512
Application Date: 20260128

Claims (10)

1. An on-orbit calibration method for correcting self-radiation of a hot mirror of a microwave imager based on reference radiation is characterized by comprising the following steps: calculating an included angle between a thermal mirror of the microwave imager and the sun; calculating the ground observation bright temperature of the microwave imager; Calculating a reference microwave radiometer to observe the bright temperature; simulating to obtain simulated bright temperatures of a reference microwave radiometer and a microwave imager based on a radiation transmission model; calculating an observed bright temperature deviation and a simulated bright Wen Piancha between a reference microwave radiometer and a microwave imager, and calculating a system error between the reference microwave radiometer and the microwave imager; Based on the system error, fitting by adopting a function relation of an included angle between a hot mirror of a microwave imager and the sun, and calculating the self-radiation bright temperature of the hot mirror of the reference microwave radiometer; the included angle between the hot mirror of the microwave imager and the sun is calculated in real time on an on-orbit basis through the microwave imager, and the hot mirror self-radiating brightness Wen Dingzheng of the microwave imager based on the reference microwave radiometer observes the brightness temperature to the ground.
2. The on-orbit calibration method for correcting the self-radiation of the hot mirror of the microwave imager based on the reference radiation according to claim 1, wherein the calculation of the included angle between the hot mirror of the microwave imager and the sun comprises the following steps: The aiming direction of the heat mirror antenna is expressed as a satellite body spherical coordinate system The solar direction is expressed as The included angle between the thermal mirror of the microwave imager and the sun is expressed as: ; Wherein, the Representing the included angle between the hot mirror of the microwave imager and the sun.
3. The on-orbit calibration method based on reference radiation correction microwave imager hot mirror self-radiation according to claim 1, wherein the calculation of the bright temperature observed by the microwave imager on the ground is specifically expressed as: ; Wherein, the Indicating the gain of the count value, 、 And Respectively the brightness and temperature corresponding to the cold air, the hot calibration source and the earth observation by the microwave imager, Indicating a non-linear bright temperature.
4. The method for calibrating the self-radiation of the hot mirror of the microwave imager based on the reference radiation according to claim 3, wherein the bright temperature corresponding to the observation of the hot calibration source by the microwave imager only comprises the bright temperature of the hot calibration source.
5. The on-orbit calibration method based on reference radiation correction microwave imager hot mirror self-radiation according to claim 1, wherein calculating the bright temperature observed by the microwave imager to the ground is expressed as: ; Wherein, the Indicating the gain of the count value, 、 And Respectively the bright temperature corresponding to the cold air, the hot calibration source and the earth observation by a reference microwave radiometer, Indicating a non-linear bright temperature.
6. The method for calibrating the self-radiation of the hot mirror of the microwave imager based on the reference radiation according to claim 5, wherein the brightness Wen Juti corresponding to the observation of the hot calibration source by the reference microwave radiometer is expressed as: ; Wherein, the The heat mirror representing the reference microwave radiometer radiates itself, obtained by multiplying the emissivity measured on the ground by the physical temperature measured by the thermistor patch on the heat mirror, Indicating the hot calibration source light temperature.
7. The on-orbit calibration method based on the reference radiation correction of the thermal mirror self-radiation of the microwave imager according to claim 1, wherein the observed bright temperature deviation and the simulated bright Wen Piancha between the reference microwave radiometer and the microwave imager are calculated, and the system error between the reference microwave radiometer and the microwave imager is calculated as: ; ; Wherein, the The ground observation bright temperature of the on-orbit real-time measurement of the reference microwave radiometer is shown, The brightness temperature observed by the microwave imager on the same target ground at the same time is shown, And In order to respectively simulate the obtained brightness temperature values of the reference microwave radiometer and the microwave imager by using the radiation transmission model, Representing a systematic error.
8. The on-orbit calibration method based on the reference radiation correction microwave imager hot mirror self-radiation according to claim 7, wherein the hot mirror self-radiation bright temperature of the reference microwave radiometer is calculated as: ; Wherein, the Represents the included angle between the thermal mirror of the microwave imager and the sun, 、 And The coefficients representing the quadratic term fit are represented, Indicating the self-radiation bright temperature of the hot mirror.
9. The on-orbit calibration method based on the reference radiation correction microwave imager hot mirror self-radiation according to claim 8, wherein the hot mirror self-radiation bright Wen Dingzheng microwave imager based on the reference microwave radiometer observes the bright temperature to the ground, expressed as: ; Wherein, the And (5) indicating the brightness temperature of the corrected microwave imager.
10. An on-orbit calibration system for correcting the self-radiation of a hot mirror of a microwave imager based on reference radiation is characterized by comprising an included angle calculation module, a ground observation bright temperature calculation module of the microwave imager, a reference microwave radiometer observation bright temperature calculation module, a bright temperature simulation module, an error calculation module, a hot mirror self-radiation bright temperature calculation module and a correction module, wherein the on-orbit calibration system is used for realizing the on-orbit calibration method for correcting the self-radiation of the hot mirror of the microwave imager based on the reference radiation, which is disclosed in any one of claims 1 to 9; the included angle calculation module is used for calculating the included angle between the hot mirror of the microwave imager and the sun; the ground observation bright temperature calculation module of the microwave imager is used for calculating the ground observation bright temperature of the microwave imager; The reference microwave radiometer observation bright temperature calculation module is used for calculating the reference microwave radiometer observation bright temperature; the bright temperature simulation module is used for obtaining the simulated bright temperature of the reference microwave radiometer and the microwave imager based on the simulation of the radiation transmission model; the error calculation module is used for calculating the observed brightness temperature deviation and the simulated brightness Wen Piancha between the reference microwave radiometer and the microwave imager and calculating the system error between the reference microwave radiometer and the microwave imager; the heat mirror self-radiation bright temperature calculation module is used for calculating the heat mirror self-radiation bright temperature of the reference microwave radiometer by adopting the fitting of a function relation of the included angle between the heat mirror of the microwave imaging instrument and the sun based on the system error; The correction module is used for calculating the included angle between the hot mirror of the microwave imager and the sun in real time through the microwave imager in an on-orbit manner, and observing the brightness temperature of the microwave imager to the ground based on the self-radiation brightness Wen Dingzheng of the hot mirror of the reference microwave radiometer.

Description

On-orbit calibration method for correcting self-radiation of hot mirror of microwave imager based on reference radiation Technical Field The invention relates to the technical field of on-orbit radiation calibration, in particular to an on-orbit calibration method based on reference radiation correction microwave imager hot mirror self-radiation. Background The microwave imager is used as an imaging microwave radiometer carried on a satellite, and physical parameter information such as the earth, the atmosphere and the like is obtained all the time in the day by receiving radiation information of the earth surface and the atmosphere in a microwave band. The microwave imager scales the earth observation voltage through the radiation of the periodic observation heat source and the cold source to obtain the earth observation brightness temperature value. In the calibration process, the microwave imager observes the calibration heat source radiation by reflecting the radiation from the black body through the heat mirror. Thus, during calibration, the radiation of the heat mirror itself becomes an integral part of the calibration heat source radiation. Since the microwave imager is not equipped with an effective sensor for measuring the temperature of the hot mirror, there is a great technical difficulty in accurately measuring the self-radiation of the microwave imager in an on-orbit state. If the influence of the self radiation of the heat mirror is ignored in the calibration process, the obvious deviation of the observed bright temperature of the microwave imager is caused, and the precision of the bright temperature measurement is further affected. The reference microwave radiometer is a high-precision passive radiometer for microwave remote sensing detection. The reference microwave radiometer converts the received thermal radiation signal emitted by the earth surface or the atmosphere in the microwave band into an observed bright temperature, and the observed bright temperature has the characteristic of high precision. Therefore, the observed brightness temperature of the reference microwave radiometer can be used as a reference standard for on-orbit calibration of the satellite-borne microwave radiometer to correct the brightness Wen Piancha of the microwave imager, however, when the reference microwave radiometer is utilized to correct the self-radiation of the hot mirror of the microwave imager, the difference of the two critical parameters such as the observation geometry, the orbit height, the center frequency and the like must be fully considered, and if the difference is ignored, a new systematic error may be introduced in the correcting process, so that the calibration precision is reduced. Therefore, an on-orbit calibration technology capable of correcting the self-radiation of a hot mirror of a microwave imager in real time based on a reference microwave radiometer is needed. Disclosure of Invention In order to overcome the defects and shortcomings in the prior art, the invention provides an on-orbit calibration method for correcting the self-radiation of a hot mirror of a microwave imager based on reference radiation, which takes the actual measured brightness temperature and the simulated brightness temperature of the reference microwave radiometer and the microwave imager as double constraints, the double-deviation bright Wen Dingzheng model is constructed, the reference radiation bright temperature is used as a true value, and the self-radiation component of the hot mirror of the microwave imager is calculated, so that the physical bottleneck that the temperature of the hot mirror cannot be directly measured in an on-orbit manner is solved, the system deviation caused by neglecting the self-radiation is removed, and the bright Wen Dingbiao precision of the microwave imager is improved. In order to achieve the above purpose, the present invention adopts the following technical scheme: The invention provides an on-orbit calibration method for correcting self-radiation of a hot mirror of a microwave imager based on reference radiation, which comprises the following steps: calculating an included angle between a thermal mirror of the microwave imager and the sun; calculating the ground observation bright temperature of the microwave imager; Calculating a reference microwave radiometer to observe the bright temperature; simulating to obtain simulated bright temperatures of a reference microwave radiometer and a microwave imager based on a radiation transmission model; calculating an observed bright temperature deviation and a simulated bright Wen Piancha between a reference microwave radiometer and a microwave imager, and calculating a system error between the reference microwave radiometer and the microwave imager; Based on the system error, fitting by adopting a function relation of an included angle between a hot mirror of a microwave imager and the sun, and calculating the self-radiation brigh