A method for formulating thermal control indexes of space remote sensors based on a force-thermal coupling algorithm

Abstract

The present invention discloses a method for formulating thermal control indexes of a space remote sensor based on a force-thermal coupling algorithm, including: establishing four assumed working conditions of force-thermal coupling; calculating the value of MTF according to the force-thermal coupling elastic deformation theory and the conversion relationship between the opto-mechanical structure deformation and the optical system to quantitatively evaluate the imaging quality; determining the corresponding comprehensive imaging quality index under the coupling of the thermal control subsystem and the mechanical subsystem of the remote sensor according to the relationship between the overall index and the subsystem index of the imaging quality; performing iterative calculation on the coupling working condition and taking the temperature corresponding to when the imaging quality threshold is reached as the thermal control index to complete the conversion from the optical index to the thermal control index. The indexes of the present invention can reduce the power consumption of the thermal control system by about 20% and shorten the development cycle of the remote sensor to a certain extent while ensuring that the imaging quality of the remote sensor in orbit meets the indexes.

Description

Technical Field

[0001] The present invention relates to aerospace remote sensing technology, and particularly to a method for formulating thermal control indexes of an aerospace remote sensor based on a force-thermal coupling algorithm. Background Art

[0002] With the rapid development of the aerospace industry, optical remote sensing technology has been applied to various fields. Developing optical remote sensors with high performance (high imaging quality, strong mobility, etc.) and low cost (low energy consumption, small volume, light weight, etc.) is one of the requirements for the development of the industry. The imaging quality of an optical remote sensor is very sensitive to temperature. To ensure the smooth completion of space observation tasks, the temperature of the remote sensor needs to be maintained within an appropriate range through a thermal control system. The thermal control indexes of the remote sensor are the premise for designing and formulating the thermal control system. If the requirements for the thermal control indexes are too low, the design of the thermal control system cannot meet the requirements of the imaging quality indexes for temperature. If the requirements for the thermal control indexes are too high, it will bring a series of adverse effects such as an increase in the power consumption of the thermal control system, an increase in the design difficulty of the thermal control system, and an increase in the development cycle. Therefore, in engineering applications, there is an urgent need for a more reasonable method for formulating thermal control indexes to accurately predict the appropriate temperature level of the remote sensor in orbit.

[0003] Currently, there is little research on the method for formulating thermal control indexes of remote sensors. In the initial stage of the development of the aerospace industry, experienced designers would formulate relatively strict indexes for the overall temperature level of the remote sensor to ensure that the thermal control system has a sufficiently high safety margin. However, this method lacks sufficient theoretical basis, and the strict thermal control system indexes will lead to energy consumption redundancy of the thermal control system and an increase in the development cycle. With the development of the aerospace industry, a new method for formulating thermal control indexes of remote sensors has been proposed through computer-aided engineering. This method assumes the temperature load in orbit, conducts thermal deformation analysis using finite element software, fits polynomials to the optical surfaces under different thermal loads, and analyzes through optical software; finally, the temperature corresponding to when the optical index threshold is reached is used as the thermal control index. The thermal control indexes of the remote sensor are restricted by the imaging quality indexes during formulation, but the origin of the imaging quality indexes in this method is not clear enough, and the influence of gravity release on the imaging quality after the remote sensor is put into orbit is not considered during the formulation of the thermal control indexes. The above factors will lead to inaccurate thermal control indexes calculated.

[0004] In actual engineering, the rationality of thermal control indicators is indirectly verified by simulating and experimenting on the thermal control system. Many scholars have conducted research in this area. Some have carried out numerical analysis on the space thermal environment of remote sensors and calculated the variation of external heat flux density under corresponding orbital parameters. By means of orbital thermal simulation, the transient temperature distribution of remote sensors is calculated, and compared with the corresponding thermal control indicators according to the simulation results, and then the thermal control system design is formulated. Some use the temperature distribution results in orbital thermal analysis as input conditions to calculate the thermal deformation of the optical machine structure of the remote sensor in orbit. After fitting the surface shape of the deformed optical element, it can be seen that the surface shape of each mirror meets the tolerance requirements of optical design. Subsequently, through the thermal vacuum test, it is verified that the imaging quality of the remote sensor under the condition of unidirectional gravity meets the requirements, and the effectiveness of the thermal control system design is verified by the combination of simulation and experiment. Some verify the effectiveness of the thermal control design according to the coincidence of the thermal balance experiment results and the simulation results.

[0005] However, in the above research on simulation verification, only the tolerances of individual optical elements are considered, while the overall performance of the optical system is ignored, and it is impossible to accurately judge whether the imaging quality in orbit meets the indicators. In addition, the thermal balance experiment and the thermal vacuum test under the condition of unidirectional gravity cannot detect the imaging quality of the remote sensor under the coupling of gravity release and temperature change, and are not sufficient to prove the rationality of the thermal control indicators and the effectiveness of the thermal control system design. Summary of the Invention

[0006] The main object of the present invention is to provide a method for formulating thermal control indicators of a remote sensor based on force-thermal coupling. By analyzing the environmental differences between space and ground, the coupling influence mechanism of gravity release and temperature change on the imaging quality of the system is studied, and taking the requirements of the imaging quality index for temperature as a constraint condition, the thermal control indicators formulated by this method can effectively reduce the power consumption of the thermal control system, reduce the design difficulty of the thermal control system, and shorten the development cycle on the premise of ensuring that the thermal control system design meets the requirements of the imaging quality index.

[0007] The technical solution adopted by the present invention is: a method for formulating thermal control indicators of a spaceborne remote sensor based on a force-thermal coupling algorithm, including:

[0008] Establish four assumed working conditions of force-thermal coupling;

[0009] According to the force-thermal coupling elastic deformation theory and the conversion relationship between the deformation of the optical-mechanical structure and the optical system, calculate the value of MTF for quantitatively evaluating the imaging quality;

[0010] According to the relationship between the overall index and the subsystem index of the imaging quality, determine the corresponding comprehensive imaging quality index under the coupling of the thermal control subsystem and the mechanical subsystem of the remote sensor;

[0011] Iteratively calculate the coupled conditions and use the temperature corresponding to when the imaging quality threshold is reached as the thermal control index to complete the conversion from optical index to thermal control index.

[0012] Furthermore, the establishment of the four force-thermal coupling hypothetical conditions includes:

[0013] Before formulating the thermal control index, it is necessary to first describe and assume the force-thermal environment of the remote sensor in orbit. When formulating the thermal control index of the remote sensor, a unified temperature range is usually defined for the entire system. Considering from two aspects of uniform temperature load and temperature load with uniform gradient change, four temperature conditions are established;

[0014] According to the gravity direction of the actual assembly and debugging, assume the gravity condition of the remote sensor. After combining the four assumed temperature conditions with one gravity condition, four coupled conditions are established, namely (ΔT) &G, X(ΔT) &G, Y(ΔT) &G and Z(ΔT) &G.

[0015] Even further, the calculation of the MTF value for quantitatively evaluating the imaging quality includes:

[0016] Adopt the finite element analysis method of coupled elasticity mechanics to calculate the elastic deformation of the remote sensor under the coupled conditions to ensure the accuracy of formulating the thermal control index. Through the force-thermal coupling calculation of the FEM of the remote sensor, the coordinate information of each finite element node after deformation can be obtained, which can be used as the input condition for optical calculation;

[0017] Through optical calculation, the influence of the structural deformation of the remote sensor on the imaging quality can be analyzed. By using the method of wavefront fitting based on Zrenike polynomial, the optical surface nodes are reconstructed into a form available for software, and then all the reconstructed optical surfaces are input into the optical software in turn to generate a new optical system, and further analyze the change of MTF under the force-thermal coupling condition;

[0018] Among them, the mathematical description of Zrenike height error is:

[0019]

[0020] In the formula, K is the conic coefficient, c is the curvature, A i is the coefficient of the polynomial, Z i is the polynomial, is the normalized radius, is the argument;

[0021] By iterating different coupled conditions, the corresponding MTF values can be obtained; by comparing the calculated MTF with the MTF required by the imaging quality index, the temperature corresponding to when the imaging quality threshold is reached in the coupled conditions is used as the thermal control index.

[0022] Advantages of the present invention:

[0023] The indicators of the present invention can reduce the thermal control power consumption by about 20% and shorten the development cycle of the remote sensor to a certain extent. From the prediction results of the change of MTF of the remote sensor during on-orbit operation, it can be seen that this method can just ensure that the imaging quality during on-orbit operation meets the indicators, and has higher reliability compared with the indicators formulated only considering temperature.

[0024] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. Description of the drawings

[0025] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0026] Figure 1 is a flowchart of a method for formulating thermal control indicators of a spaceborne remote sensor based on a force-thermal coupling algorithm according to an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of the optical design of the remote sensor according to an embodiment of the present invention;

[0028] Figure 3 is the temperature fluctuation of each optical component of the remote sensor within 10 cycles according to an embodiment of the present invention;

[0029] Figure 4 is a comparison chart of MTF at a certain moment during on-orbit operation and the initial MTF of the optical system with different indicators according to an embodiment of the present invention;

[0030] Figure 5 is a schematic diagram of each system of the present invention installed on a vacuum chamber platform according to an embodiment of the present invention.

[0031] Reference numerals:

[0032] 1 is an interferometer, 2 is a collimator, 3 is a vacuum chamber, 4 is an infrared radiator, 5 is a remote sensor, and 6 is a satellite platform. Detailed implementation manners

[0033] In order to make the purposes, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Method for formulating thermal control indicators

[0035] The present invention proposes a method for formulating thermal control indicators under the condition of force-thermal coupling, with imaging quality indicators as requirements.Figure 1 The specific process of this method is described as follows: First, since the space environment can cause gravity release and temperature changes in the remote sensor, four hypothetical working conditions of force-thermal coupling are established. Second, according to the force-thermal coupling elastic deformation theory and the conversion relationship between the opto-mechanical structure deformation and the optical system, the MTF value is calculated to quantitatively evaluate the imaging quality. Then, according to the relationship between the overall index and the subsystem index of the imaging quality, the corresponding comprehensive imaging quality index is determined under the coupling of the thermal control subsystem and the mechanical subsystem of the remote sensor. Finally, iterative calculations are performed on the coupling working conditions, and the temperature corresponding to when the imaging quality threshold is reached is used as the thermal control index to complete the conversion from the optical index to the thermal control index.

[0036] Working condition assumption

[0037] Since the on-orbit imaging quality of the remote sensor will be affected by the coupling of temperature changes and gravity release, the opto-mechanical-thermal integrated analysis method is used in this invention to calculate the structural deformation of the remote sensor caused by the force-thermal coupling environment and the imaging quality of the optical system after deformation.

[0038] There are differences between the space environment (microgravity, space thermal environment) where the remote sensor is located and the ground environment. This difference will cause gravity release and temperature changes in the remote sensor when it is on orbit. The influence of gravity release and temperature changes on the imaging quality of the remote sensor is inseparable. Therefore, it is necessary to comprehensively consider the force-thermal coupling effect to formulate the thermal control index. Before formulating the thermal control index, it is necessary to first describe and assume the force-thermal environment of the remote sensor when it is on orbit:

[0039] Assumption 1: Temperature working condition

[0040] Since the temperature distribution of each node inside the remote sensor is irregular in the space environment, a unified temperature range is usually defined for the entire system when formulating the thermal control index of the remote sensor. This invention considers from two aspects of uniform temperature load and uniformly gradient-changing temperature load, and establishes four temperature working conditions as shown in Table 1. Considering the actual temperature during ground processing and alignment, the initial temperature of all working conditions is set to 20 °C. No. 1 is the uniform temperature load working condition, and the temperature value of the working condition is changed by changing the value of the temperature change ΔT (20 ± ΔT). Nos. 2-4 are the uniformly gradient-changing temperature load working conditions. Due to the asymmetry of the remote sensor structure, the temperature gradient change will have a directionality. Therefore, the X, Y, and Z directions of the Cartesian coordinate system are used to describe this working condition; the temperature value with 20 °C as the symmetry center is 20 - ΔT / 2 ~ 20 + ΔT / 2, where the positive and negative of the temperature change ΔT represent the changing trend.

[0041] Table 1 Working condition description

[0042]

[0043] Hypothesis 2: Gravity condition

[0044] When the remote sensor is on the ground, the deformation caused by gravity to the structure will be offset through assembly and debugging. However, after being put into orbit, new structural internal stresses will be generated due to the release of gravity, which will in turn cause new deformations of the remote sensor structure. Therefore, it is necessary to make a gravity condition hypothesis for the remote sensor according to the actual gravity direction of assembly and debugging. The gravity direction of the remote sensor in the present invention is -Y, and the gravity condition will be named G hereinafter.

[0045] The present invention combines the four assumed temperature conditions with one gravity condition to establish four coupling conditions, which are (ΔT) &G, X(ΔT) &G, Y(ΔT) &G and Z(ΔT) &G respectively. Among them, the present invention simplifies the naming of the conditions with & as the coupling symbol.

[0046] Determination of thermal control index

[0047] Since the imaging quality is very sensitive to the deformation of the opto-mechanical structure of the remote sensor, an accurate method is needed to calculate the structural deformation. The literature has proved that the result of calculating the elastic deformation by the force-thermal coupling method is more accurate than the method of calculating the force and thermal deformation separately and then superimposing them. Therefore, the present invention adopts the finite element analysis method of coupling elasticity mechanics to calculate the elastic deformation of the remote sensor under the coupling condition to ensure the formulation accuracy of the thermal control index. Through the force-thermal coupling calculation of the FEM of the remote sensor, the coordinate information of each finite element node after deformation is obtained, which can be used as the input condition for optical calculation.

[0048] The influence of the structural deformation of the remote sensor on the imaging quality can be analyzed through optical calculation. Considering that the optical software does not have a data interface for finite element discrete nodes, the present invention reconstructs the optical surface nodes into a form available for the software through the method of wavefront fitting based on Zrenike polynomials. Subsequently, all the reconstructed optical surfaces are input into the optical software in turn to generate a new optical system, and then the change of MTF under the force-thermal coupling condition is analyzed.

[0049] The mathematical description of the Zrenike height error is as follows:

[0050]

[0051] In the formula, K is the conic coefficient, c is the curvature, A i is the coefficient of the polynomial, Z i is the polynomial, is the normalized radius, is the argument.

[0052] By iterating through different coupling conditions, the corresponding MTF values can be obtained. By comparing the calculated MTF with the required MTF for imaging quality, the temperature corresponding to the imaging quality threshold in the coupling condition is used as the thermal control index.

[0053] Example calculation

[0054] Opto-mechanical structure description

[0055] The present invention takes a coaxial reflective remote sensor as the research object, with the imaging range in the visible light band. Its structural components include: the payload body (main mirror assembly, secondary mirror assembly, tertiary mirror assembly, mirror assembly, focusing mechanism, main load-bearing assembly, sunshade assembly, etc.), the electronics system, the thermal control system, etc. As Figure 2 shown, the optical design of the remote sensor takes the main optical axis direction as the +Z axis, the refraction direction of the refractive mirror as the +Y axis, and establishes a Cartesian coordinate system through the right-hand rule. Moreover, the geometric model and the finite element model of the remote sensor use the same coordinate system.

[0056] Determination of imaging quality indicators

[0057] The imaging quality indicators of the remote sensor are the premise for formulating the thermal control indicators. Each subsystem of the remote sensor has corresponding imaging quality indicators, and the indicators are quantitatively described by their respective MTF values. From the above, it can be seen that the influence of temperature and gravity on imaging quality is mutually coupled, and the imaging quality indicators corresponding to the thermal control or mechanical subsystem cannot be formulated separately. Therefore, the present invention will calculate the comprehensive imaging quality indicator (MTF D ) corresponding to the coupling of the thermal control and mechanical subsystems through the relationship between the MTFs of each system.

[0058] The static MTF (MTF S ) measured in the laboratory environment is the total indicator of the imaging quality of the remote sensor before launch. The present invention requires that when the frequency = 57.1 lp / mm, MTF S ≥0.12. MTFs can be considered as the result of the comprehensive action of the transfer function of the pixel size (MTF geometry, MTF D ), the transfer function of processing and alignment (MTF m ), and the transfer function of optoelectronic data transmission and processing (MTF CCD ), etc. They have the following relationship.

[0059]

[0060] For the CCD device, it is composed of the pixel size transfer function (MTF geometry, MTF G ) and the transfer function of the electronic system (MTF E ), and their relationship is:

[0061]

[0062] MTF G can be expressed as:

[0063]

[0064] wherein, f is the spatial frequency, f n is the Nyquist frequency, a is the CCD pixel size, d is the CCD pixel pitch. When d = a, f = f n the MTF can be calculated G = 0.637.

[0065] Among them, MTF E = 0.9 is given according to the statistics of the electronic system technology and process level by researchers. MTF M is formulated through experience and big data statistics; after the technicians tested the remote sensor of the present invention, MTF M = 0.85.

[0066] In summary, the MTF can be calculated D ≥ 0.245 to meet the imaging quality requirements.

[0067] Determination of thermal control index

[0068] According to the above opto-mechanical-thermal integration analysis method, with 0.1 °C as the temperature change step, a total of 580 iterative calculations were performed for 4 coupling conditions, and the relationship between MTF and temperature under 4 coupling conditions was obtained. The threshold of MTF is 0.245. The overall temperature level, the initial temperature is 20 °C; as the temperature changes, it generally shows a downward trend, indicating that the remote sensor has different sensitivities to the temperature gradients of various conditions, and at the same time proves the rationality of the assumption of the condition type. Since the remote sensor has different sensitivities to the temperature gradients in different directions and this type of assumption is reasonable. Among each condition, the MTF of the marginal field of view is most affected by the temperature change and reaches the threshold of MTF first, indicating that the marginal field of view is more sensitive to temperature than other fields of view. Therefore, this method takes the temperature corresponding to MTF = 0.245 in the marginal field of view as the thermal control index.

[0069] Since the spatial distribution of each optical element of the remote sensor along the Z direction is the largest, the maximum temperature difference between optical elements appears in the G&Z(ΔT) condition. From the critical condition temperature distribution calculated by force-thermal coupling, it can be known that the maximum temperature difference of the optical elements is 4.44 °C.

[0070] In summary, considering the safety and reliability of the remote sensor, its thermal control indicators are formulated as follows:

[0071] a) Overall temperature range of the remote sensor: 17.3 < T < 22.6 °C;

[0072] b) Temperature difference in the X direction < 5.6 °C, temperature difference in the Y direction < 6.6 °C, temperature difference in the Z direction < 6.9 °C;

[0073] c) Temperature difference between each optical element < 4.4 °C.

[0074] Simulation analysis and verification

[0075] Since there are still differences between the real space environment and the assumed temperature conditions, it is necessary to more accurately simulate the temperature of the remote sensor in orbit through orbital thermal simulation analysis. By calculating and comparing the changes in the on-orbit imaging quality under different thermal control indicator formulation methods, the feasibility of the remote sensor thermal control design and the rationality of the thermal control indicator formulation method can be verified.

[0076] Orbital environment analysis

[0077] When the remote sensor is in space, temperature changes in the optomechanical structure will occur due to factors such as vacuum, cold black, internal heat sources, thermal radiation, and heat conduction. And temperature changes will cause displacements, distortions, and thermal deformations in the optical elements, etc., which will in turn lead to a decline in the imaging quality of the remote sensor. Therefore, the remote sensor needs to reach thermal equilibrium with the help of the thermal control system before it can perform normal imaging work.

[0078] The heat balance equation can be expressed as:

[0079] In the formula, is solar radiation; is earth albedo; earth infrared radiation; internal heat source of the spacecraft; heat radiated by the spacecraft into outer space; change in the internal energy of the spacecraft.

[0080] The remote sensor of the present invention is set to operate on a sun-synchronous orbit. The orbital parameters are shown in Table 2. Through the orbital information, the change trend of the solar illumination angle ( β angle) can be calculated, and then the change in the external heat flux of the remote sensor can be calculated. β The change in the

[0081]

[0082] In the formula, i is the inclination angle between the satellite orbital plane and the earth's equatorial plane, Iis the angle between the equatorial plane and the ecliptic plane, is the solar ecliptic longitude, Ω is the right ascension of the ascending node.

[0083]

[0084] Orbit thermal simulation analysis

[0085] According to the thermal control index of the present invention, a thermal control system design is carried out. A thermal structure analysis model of the remote sensor and the satellite platform is established. Taking the orbit environment analysis result as the input condition and 20 °C as the thermal control target temperature, the orbit thermal simulation analysis of the whole satellite is carried out, and the simulation result is used as a guide to iteratively formulate the thermal control system until the temperature meets the index requirements.

[0086] In the actual space environment, factors such as the external heat flux of the satellite, the platform temperature, and the satellite attitude will change, and the thermal control coating and various paints will degrade over time. Therefore, two extreme working conditions of high and low temperatures will be generated. In the simulation of the present invention, both extreme working conditions are analyzed and simulated for multiple orbital periods. The thermal control power consumptions required for the high and low temperature working conditions are 98.0 W and 103.5 W respectively. It can be seen that the thermal control power consumption in the low temperature working condition is greater.

[0087] Figure 3 is the temperature fluctuation of each optical component of the remote sensor within 10 cycles. It can be seen that the temperature reaches equilibrium after 3 orbits and meets the thermal control index.

[0088] Here, the threshold value (0.245) of MTF D is used as the index requirement of MTF when the remote sensor is in orbit. Considering the coupling relationship between gravity and temperature comprehensively, the temperature of each finite element node of the remote sensor obtained in the orbit thermal simulation analysis is used as the temperature working condition, and a coupling working condition is established by combining with the gravity working condition. The deformation of the opto-mechanical structure of the remote sensor when it is in orbit can be calculated through the force-thermal coupling principle. Extract the deformed optical surface node data as the input condition for surface fitting, and load the fitting result into the optical software, and the MTF at any moment during the imaging time of the remote sensor when it is in orbit can be calculated.

[0089] According to the mission requirements, the imaging time of the remote sensor per orbit is less than 10 min. The present invention selects the data during the imaging time of the 8th orbit (40176~40776 s) after the remote sensor reaches thermal equilibrium for research. Among them Figure 4 is the comparison of MTF at a certain moment in orbit with the initial MTF of the optical system for different indexes. Taking 20 s as the step length, the data during the imaging time is iteratively calculated 60 times, and the change of MTF in orbit for different indexes is obtained as Figure 4 shown.

[0090] From Figure 4It can be seen that the index of the present invention enables the MTF to meet the index during the imaging time, and the MTF reaches the lowest value (0.248) at 40616 s and 40716 s and just meets the threshold. This shows that this index can effectively ensure the imaging quality of the remote sensor in orbit and avoid the waste of power consumption of the thermal control system.

[0091] Thermal vacuum experiment

[0092] Before launch, the remote sensor needs to detect the MTFs through a thermal vacuum experiment. The thermal vacuum experiment uses a space environment simulator to simulate the orbital environment, and uses optical test equipment to calculate the energy information of the target image to reflect the imaging quality of the remote sensor. The test system includes a camera, a collimator system, an interferometer, an infrared radiator, a satellite mounting platform, and a satellite platform simulation chamber, etc. As Figure 5 shown, each system is installed on the vacuum tank platform respectively. The vacuum tank can provide a cold black temperature below 100 K and a vacuum environment of 1×10 -4 Pa to simulate the real space environment. According to the actual plan, the remote sensor is installed on the satellite platform, and a heating system is installed in the satellite platform simulation chamber to simulate the real temperature change of the platform. The infrared heater can provide the change of the external heat flux on the surfaces of the satellite. The interferometer is installed on the focal plane of the collimation system, and the light emitted by it outputs parallel light beams through the collimator; the satellite is installed on a high-precision turntable to detect the MTF S of different fields of view of the remote sensor. The experimental results are consistent with the overall temperature indexes (17.3 °C and 22.6 °C) formulated by the method of the present invention, further proving the rationality of the method of the present invention.

[0093] To ensure the smooth completion of space observation tasks, the temperature of the optical remote sensor needs to be maintained within a suitable range through the thermal control system, so as to avoid the influence of the space thermal environment on the imaging quality. The design and formulation of the thermal control system require reasonable thermal control indexes for guidance. However, the current method for formulating thermal control indexes lacks sufficient theoretical basis and is prone to waste of resources and time; or only considers the temperature change and ignores the influence of gravity release, resulting in inaccurate thermal control indexes formulated, and it is difficult to accurately predict the appropriate temperature level of the whole machine of the remote sensor in orbit. By analyzing the environmental differences between space and ground, the present invention studies the coupling influence mechanism of gravity release and temperature change on the system imaging quality, and takes the requirements of the imaging quality index for temperature as the constraint condition, and proposes a method for formulating the thermal control index of the remote sensor based on the force-thermal coupling algorithm, which can guide the thermal control design of the remote sensor FindThe optimal solution between imaging quality and the power consumption of the thermal control system. The orbital thermal simulation results show that, compared with the empirical indicators, the indicators of the present invention can reduce the thermal control power consumption by about 20% and shorten the development cycle of the remote sensor to a certain extent. In addition, from the prediction results of the change of MTF of the remote sensor in orbit, it can be seen that the method of the present invention can just ensure that the imaging quality in orbit meets the indicators, and has higher reliability compared with the indicators formulated only considering temperature. Then, the thermal vacuum experiment results show that the temperature critical value of the remote sensor under the condition of gravity release is consistent with the thermal control indicators formulated by the method of the present invention, further verifying the rationality of the method. Finally, through further verification, it can be known that this method is applicable to various types of remote sensors (off-axis reflective, transmissive, etc.).

[0094] By studying the comprehensive influence of optics, mechanics, and thermotics on the imaging quality of the remote sensor, the present invention establishes a method for formulating thermal control indicators of the remote sensor based on force-thermal coupling. This method can accurately predict the appropriate temperature level of the remote sensor in orbit to guide the design of the thermal control system to meet the temperature requirements of the imaging quality. In addition, it reduces the power consumption of the thermal control system to a certain extent, reduces the design difficulty of the thermal control system, and shortens the development cycle. The main contents are as follows:

[0095] (1) Four force-thermal coupling hypothetical working conditions are established for the remote sensor in view of the environmental differences between space and ground. According to the force-thermal coupling calculation method and the surface shape fitting method, the change of MTF of the remote sensor under the coupling working conditions is analyzed.

[0096] (2) According to the relationship between the overall indicators and subsystem indicators of the imaging quality, the corresponding comprehensive imaging quality indicator for the coupling of the thermal control and mechanical subsystems of the remote sensor is determined as MTF D > 0.245, and through iterative calculation of the coupling working conditions, the temperature corresponding to when the imaging quality indicator is reached is used as the thermal control indicator.

[0097] (3) After applying different indicators to the remote sensor of the present invention and comparing through simulation, it is verified that the method of the present invention can save about 20% of the power consumption of the thermal control system and shorten the development cycle on the premise of meeting the requirements of imaging quality. The thermal vacuum experiment results are consistent with the indicators of the present invention, further illustrating the rationality of the method of the present invention.

[0098] Through further research, the method of the present invention is also applicable to other types of remote sensors (off-axis reflective, transmissive, etc.). However, remote sensors with active optical systems can adjust the wavefront of optical elements to resist the influence of temperature on imaging quality, so the thermal control indicator formulation method of the present invention is not applicable to this type of remote sensor. To sum up, the thermal control indicator formulation method of the present invention has wide applicability, can be well applied to actual projects, and this research provides certain contributions and help for the development of the aerospace industry.

[0099] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for formulating thermal control indexes of a space remote sensor based on a force-thermal coupling algorithm, characterized in that, it includes: Establishing four assumed working conditions of force-thermal coupling; According to the force-thermal coupling elastic deformation theory and the conversion relationship between the opto-mechanical structure deformation and the optical system, calculating the value of MTF for quantitatively evaluating the imaging quality; According to the relationship between the overall index and the subsystem index of the imaging quality, determining the corresponding comprehensive imaging quality index under the coupling of the thermal control subsystem and the mechanical subsystem of the remote sensor; Performing iterative calculations on the coupling working conditions and taking the temperature corresponding to when the imaging quality threshold is reached as the thermal control index to complete the conversion from the optical index to the thermal control index; The calculating the value of MTF for quantitatively evaluating the imaging quality includes: Adopting the finite element analysis method of coupled elasticity mechanics to calculate the elastic deformation of the remote sensor under the coupling working conditions to ensure the formulation accuracy of the thermal control index. Through the force-thermal coupling calculation of the FEM of the remote sensor, the coordinate information of each finite element node after deformation can be obtained, which can be used as the input condition for optical calculation; Through optical calculation, the influence of the structure deformation of the remote sensor on the imaging quality can be analyzed. By using the method of wavefront fitting based on Zrenike polynomial, the optical surface nodes are reconstructed into a form available for software, and then all the reconstructed optical surfaces are input into the optical software in turn to generate a new optical system, and then the change of MTF under the force-thermal coupling working conditions can be analyzed; The Zrenike height error mathematical description is: ‘ where K is the cone coefficient, c is the curvature, A i is the coefficient of the polynomial, Z i is the polynomial, is the normalized radius, is the argument; By iterating different coupling working conditions, the corresponding MTF values can be obtained; by comparing the calculated MTF with the required MTF of the imaging quality, the temperature corresponding to when the imaging quality threshold is reached in the coupling working conditions is taken as the thermal control index.

2. The method for formulating thermal control indexes of a space remote sensor based on a force-thermal coupling algorithm according to claim 1, characterized in that, the establishing four assumed working conditions of force-thermal coupling includes: Before formulating the thermal control index, it is necessary to first describe and assume the force-thermal environment of the remote sensor in orbit. When formulating the thermal control index of the remote sensor, a unified temperature range is usually defined for the whole system, considering from two aspects of uniform temperature load and uniformly gradient-changing temperature load, and four temperature working conditions are established; According to the gravity direction of the actual assembly and debugging, the gravity working condition of the remote sensor is assumed, and four coupling working conditions are established by combining the four assumed temperature working conditions with one gravity working condition, which are (ΔT) &G, X(ΔT) &G, Y(ΔT) &G and Z(ΔT) &G respectively.

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