Phase difference maintaining method and system for sun-synchronous satellite

Abstract

The application provides a phase difference keeping method and system of sun synchronous satellites, and relates to the field of satellite orbit control. The phase difference keeping method comprises the following steps: obtaining a plurality of sets of first operation parameter data of a first sun synchronous satellite, and obtaining a plurality of sets of second operation parameter data of a second sun synchronous satellite; fitting the first operation parameter data to obtain a first flat semi-major axis trend line formula; fitting the second operation parameter data to obtain a second flat semi-major axis trend line formula; calculating a difference value as a height difference trend line formula; sequentially calculating a predicted height difference of the double satellites according to the height difference trend line formula; and respectively performing orbit control at the epoch time when the present orbit control starts, so as to adjust the actual height difference to be within a height difference threshold value, and keep the phase difference between the double satellites unchanged. One of the double sun synchronous satellites can be controlled at a certain fixed height, or the height difference of the double satellites can satisfy a certain fixed value, so that the orbit height is accurately controlled.

Description

Technical Field

[0001] This invention relates to the field of satellite orbit control, and in particular to a method and system for maintaining the phase difference of a sun-synchronous satellite. Background Technology

[0002] A sun-synchronous satellite is a satellite that operates in a sun-synchronous orbit. Its orbital plane passes through the Earth's North and South Poles and moves eastward by 0.9856 degrees each day. This angle corresponds exactly to the eastward shift of the Earth's orbit around the sun. These satellites have the following characteristics:

[0003] 1. Timed Observation: Sun-synchronous orbits allow satellites to pass over specific ground points at fixed time intervals, which is crucial for tasks requiring timed observations, such as Earth observation, meteorological monitoring, and ocean monitoring. The fact that sun-synchronous satellites pass over the Earth at almost the same time each time makes the observation data more comparable and facilitates long-term trend analysis and time-series observations.

[0004] 2. Global Coverage: Sun-synchronous orbits enable continuous global observation coverage of the Earth. Due to the characteristics of their orbits, the inclination of sun-synchronous satellites is typically close to 90 degrees, allowing them to cover approximately the same longitude range each time they enter an Earth hemisphere, thus achieving balanced observation of different regions of the Earth.

[0005] 3. Sunlight Conditions: A sun-synchronous orbit ensures that the satellite receives similar sunlight conditions above the Earth. The orbital inclination and altitude of a sun-synchronous satellite are precisely designed so that the satellite receives similar sunlight in different seasons and locations, maintaining consistent illumination conditions and making the observation data more stable and reliable.

[0006] 4. Communication and Data Downlink: The relatively fixed time and position of the sun-synchronous orbit above the Earth facilitates communication and data downlink between the satellite and ground stations. This enables the satellite to transmit observation data, control commands, and status information in a timely manner, ensuring the normal acquisition and processing of data.

[0007] Therefore, many low-Earth orbit satellites choose sun-synchronous orbits to provide stable observation conditions and data continuity, enabling the satellites to perform their missions more effectively.

[0008] A satellite constellation is a system that distributes multiple satellites at specific locations in Earth's orbit. These satellites cooperate to form a constellation, providing global communication, navigation, and remote sensing services. To achieve a specific mission, users establish different phase differences between the satellites in the constellation. The phase difference between two satellites must be maintained within a certain range over a long period. Once this range is exceeded, orbit control is required. For two satellites with the same decay rate, the change in phase difference is determined by the difference in their orbital altitude. The greater the altitude difference, the faster the phase difference widens, the shorter the phase difference maintenance period, the more frequent the orbit control operations, and the shorter the satellite's lifespan. Therefore, when implementing precise orbit control, it is necessary to accurately calculate the satellite's altitude to extend the phase difference maintenance period.

[0009] Satellites are subject to various perturbations during their orbital operation, which can cause deviations and changes in their orbits. Common perturbations include the Earth's non-spherical perturbation, the gravitational pull of the Sun and Moon, atmospheric drag, solar radiation pressure, and tidal forces.

[0010] In existing technologies, satellite orbits are represented by instantaneous root and average root. An instantaneous root refers to the orbital element of a satellite at a specific moment, describing the satellite's position and velocity at that time. An average root refers to the average element obtained by averaging the satellite orbit, describing the average properties of the orbit. The difference between the average root and the instantaneous root is that the average root considers the influence of perturbations on the orbit. Because the average root eliminates short-period variations and only considers long-term variations, it reflects the long-term trend of orbital changes, greatly simplifying orbital perturbation analysis. Therefore, the average root is frequently used to calculate satellite orbital altitude.

[0011] Using the root mean square of a satellite at a specific moment to calculate its orbital altitude is a simple and quick method, suitable only for applications requiring real-time orbital information. It fails to consider long-term orbital changes and only provides an instantaneous root mean square value, resulting in relatively low accuracy. This is particularly problematic when maintaining precise orbital control by controlling the satellite's phase difference to a fixed altitude or ensuring a specific altitude difference between two satellites; in such cases, this single-point calculation method is clearly unreasonable and inaccurate. Summary of the Invention

[0012] This invention relates to a method and system for maintaining the phase difference of a sun-synchronous satellite. It solves the problem in the prior art where, in order to maintain the precise orbit control of satellite phase difference in satellite constellations, it is necessary to control the satellite at a certain fixed altitude or when the altitude difference between two satellites meets a certain fixed value. This is caused by using the square root of a certain moment to calculate the satellite orbital altitude, which is unreasonable and inaccurate.

[0013] To achieve the above objectives, the first aspect of the present invention provides a method for maintaining the phase difference of a sun-synchronous satellite, comprising:

[0014] Step 11: For the first and second sun-synchronous satellites with unchanged phase difference and the same decay, after the first sun-synchronous satellite enters the first operating orbit, continuously acquire multiple sets of first operating parameter data of the first sun-synchronous satellite in real time; wherein, unchanged phase difference means that the phase difference between the first and second sun-synchronous satellites is maintained within a preset phase range; the first operating parameters include: the first epoch time and the corresponding first semi-major axis;

[0015] After the second sun-synchronous satellite enters its second operational orbit, multiple sets of second operational parameter data for the second sun-synchronous satellite will be continuously acquired in real time; among them, the second operational parameters include: the second epoch time and the corresponding second semi-major axis;

[0016] Step 12: For the first sun-synchronous satellite, based on the changing trend of the first semi-major axis with the first epoch in multiple sets of first operating parameter data, fit multiple sets of first operating parameter data to obtain the formula for the trend line of the first semi-major axis of the first sun-synchronous satellite.

[0017] For the second sun-synchronous satellite, based on the variation trend of the second semi-major axis with the second epoch in multiple sets of second operating parameter data, the multiple sets of second operating parameter data are fitted to obtain the formula for the trend line of the second semi-major axis of the second sun-synchronous satellite.

[0018] Step 13: Calculate the difference between the first semi-major axis trend line formula and the second semi-major axis trend line formula to obtain the difference formula. Use the difference formula as the altitude difference trend line formula for the first and second sun-synchronous satellites.

[0019] Step 14: Based on the formula for the height difference trend line, sequentially calculate the predicted height difference between the first and second sun-synchronous satellites at multiple subsequent epochs.

[0020] Step 15: Before the predicted altitude difference exceeds the altitude difference threshold, formulate the orbit control strategy for this orbit control cycle; wherein, the orbit control strategy for this orbit control cycle includes: the epoch time at which this orbit control cycle begins, the epoch time at which this orbit control cycle ends, and the altitude difference adjustment value between the first sun-synchronous satellite and the second sun-synchronous satellite, the altitude difference adjustment value being determined based on the predicted altitude difference and the altitude difference threshold.

[0021] Step 16: According to the orbit control strategy, at the epoch when this orbit control begins, orbit control is performed on the first and second sun-synchronous satellites respectively; until the epoch when this orbit control ends, the actual altitude difference between the first and second sun-synchronous satellites is adjusted to within the altitude difference threshold, so that the phase difference between the first and second sun-synchronous satellites remains unchanged.

[0022] As a second aspect of the present invention, the present invention provides a satellite orbit control method, comprising:

[0023] Step 21: After the satellite enters its third operational orbit, continuously acquire multiple sets of third operational parameter data in real time; among which, the third operational parameters include: the third epoch time and the corresponding third semi-major axis;

[0024] Step 22: Based on the variation trend of the third semi-major axis with the third epoch in multiple sets of third operational parameter data, fit multiple sets of third operational parameter data to obtain the formula for the trend line of the satellite's third semi-major axis.

[0025] Step 23: Based on the formula of the third horizontal semi-major axis trend line, calculate the predicted horizontal semi-major axis of the satellite at multiple subsequent epochs in sequence, and calculate the predicted orbital altitude of the satellite based on the predicted horizontal semi-major axis of the satellite at each subsequent epoch.

[0026] Step 24: Based on the predicted and theoretical orbital altitudes of the satellite at each subsequent epoch, formulate the orbit control strategy for this orbit control operation; wherein, the orbit control strategy for this orbit control operation includes: the epoch at which the orbit control operation begins, the epoch at which the orbit control operation ends, and the orbital altitude adjustment value;

[0027] Step 25: According to the orbit control strategy, at the epoch when the current orbit control begins, the satellite is subjected to orbit control until the epoch when the current orbit control ends, at which point the satellite's third operating orbit is raised to the adjusted orbital altitude value.

[0028] As a third aspect of the present invention, the present invention provides a phase difference preservation system for a sun-synchronous satellite, comprising:

[0029] The first parameter acquisition unit is used to continuously acquire multiple sets of first operating parameter data of the first sun-synchronous satellite in real time after the first sun-synchronous satellite enters the first operating orbit, for the first sun-synchronous satellite and the second sun-synchronous satellite with constant phase difference and the same decay. Among them, constant phase difference means that the phase difference between the first sun-synchronous satellite and the second sun-synchronous satellite is maintained within a preset phase range. The first operating parameters include: the first epoch time and the corresponding first semi-major axis.

[0030] After the second sun-synchronous satellite enters its second operational orbit, multiple sets of second operational parameter data for the second sun-synchronous satellite will be continuously acquired in real time; among them, the second operational parameters include: the second epoch time and the corresponding second semi-major axis;

[0031] The first trend line fitting unit is used to fit multiple sets of first operating parameter data based on the changing trend of the first semi-major axis with the first epoch, for the first sun-synchronous satellite, and obtain the formula for the first semi-major axis trend line of the first sun-synchronous satellite.

[0032] For the second sun-synchronous satellite, based on the variation trend of the second semi-major axis with the second epoch in multiple sets of second operating parameter data, the multiple sets of second operating parameter data are fitted to obtain the formula for the trend line of the second semi-major axis of the second sun-synchronous satellite.

[0033] Construct a difference formula unit to calculate the difference between the first half-major axis trend line formula and the second half-major axis trend line formula, obtain the difference formula, and use the difference formula as the altitude difference trend line formula for the first sun-synchronous satellite and the second sun-synchronous satellite.

[0034] The first calculation unit is used to sequentially calculate the predicted altitude difference between the first and second sun-synchronous satellites at multiple subsequent epochs based on the altitude difference trend line formula.

[0035] The first orbit control strategy formulation unit is used to formulate the orbit control strategy for this orbit control before the predicted altitude difference exceeds the altitude difference threshold. The orbit control strategy for this orbit control includes: the epoch time at which this orbit control begins, the epoch time at which this orbit control ends, and the altitude difference adjustment value between the first sun-synchronous satellite and the second sun-synchronous satellite. The altitude difference adjustment value is determined based on the predicted altitude difference and the altitude difference threshold.

[0036] The first orbit control unit is used to perform orbit control on the first and second sun-synchronous satellites respectively at the epoch when the current orbit control begins, according to the orbit control strategy; and until the epoch when the current orbit control ends, to adjust the actual altitude difference between the first and second sun-synchronous satellites to within the altitude difference threshold, so that the phase difference between the first and second sun-synchronous satellites remains unchanged.

[0037] As a fourth aspect of the present invention, the present invention provides a satellite orbit control system, comprising:

[0038] The second parameter acquisition unit is used to continuously acquire multiple sets of third operational parameter data of the satellite in real time after the satellite enters the third operational orbit; among which, the third operational parameters include: the third epoch time and the corresponding third semi-major axis;

[0039] The second trendline fitting unit is used to fit multiple sets of third operating parameter data based on the changing trend of the third semi-major axis with the third epoch, and obtain the formula for the trendline of the satellite's third semi-major axis.

[0040] The third calculation unit is used to sequentially calculate the predicted semi-major axis of the satellite at multiple subsequent epochs based on the formula of the third semi-major axis trend line, and to calculate the predicted orbital altitude of the satellite based on the predicted semi-major axis of the satellite at each subsequent epoch.

[0041] The second orbit control strategy formulation unit is used to formulate the orbit control strategy for the current orbit control based on the predicted orbit altitude and theoretical orbit altitude of the satellite at each subsequent epoch. The orbit control strategy for the current orbit control includes: the epoch at which the current orbit control begins, the epoch at which the current orbit control ends, and the orbit altitude adjustment value.

[0042] The fourth orbit control unit is used to perform orbit control on the satellite at the beginning of the current orbit control cycle, according to the orbit control strategy, until the end of the current orbit control cycle, and then raise the satellite's third operating orbit by the orbital altitude adjustment value.

[0043] The advantages of this invention are as follows: For sun-synchronous satellites with the same decay rate, the semi-major axis of their orbits exhibits a linear trend. Therefore, after the sun-synchronous satellites enter their respective operational orbits, their operational parameter data (epoch time and corresponding semi-major axis) is continuously acquired in real time. Based on this operational parameter data, a first and second semi-major axis trend line formula are formed. This fully considers the long-term trend of the sun-synchronous satellites' orbits and reduces the random errors caused by individual semi-major axis data, resulting in a more stable and reliable semi-major axis. The difference between the first and second semi-major axis trend line formulas is calculated to obtain a difference formula, which is used as the altitude difference trend line formula for the first and second sun-synchronous satellites. Using the altitude difference trend line formula to calculate the altitude difference between the two satellites, in situations requiring precise orbit control due to phase difference, it is possible to control one of the sun-synchronous satellites at a fixed altitude or to ensure that the altitude difference between the two satellites meets a fixed value, thus achieving precise orbital altitude control. Attached Figure Description

[0044] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0045] Figure 1 A flowchart illustrating a phase difference preservation method for a sun-synchronous satellite according to an embodiment of the present invention is shown.

[0046] Figure 2 A flowchart illustrating a satellite orbit control method according to an embodiment of the present invention is shown schematically.

[0047] Figure 3 This schematic diagram illustrates the structure of a phase difference preservation system for a sun-synchronous satellite according to an embodiment of the present invention.

[0048] Figure 4 This schematic diagram illustrates the structure of a satellite orbit control system according to an embodiment of the present invention.

[0049] Figure 5 The diagram illustrates the variation of the semi-major axis of stars A and B over a single day.

[0050] Figure 6 The diagram illustrates the changing trends of the semi-major axis difference between stars A and B. Detailed Implementation

[0051] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0052] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0053] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0054] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0055] It should be understood that although the terms first, second, third, etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this application. As used herein, the term "and / or" includes all combinations of any one and more of the associated listed items.

[0056] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0057] like Figure 1 As shown, in conjunction with an embodiment of the present invention, a method for maintaining the phase difference of a sun-synchronous satellite is provided, comprising:

[0058] Step 11: For the first and second sun-synchronous satellites with unchanged phase difference and the same decay, after the first sun-synchronous satellite enters its first operational orbit, continuously acquire multiple sets of first operational parameter data of the first sun-synchronous satellite in real time; wherein, unchanged phase difference means that the phase difference between the first and second sun-synchronous satellites is maintained within a preset phase range; the first operational parameters include: the first epoch time and the corresponding first semi-major axis; the same decay means that the theoretical rate of decay of orbital altitude is the same for the first and second sun-synchronous satellites during their respective operational orbits;

[0059] After the second sun-synchronous satellite enters its second operational orbit, multiple sets of second operational parameter data for the second sun-synchronous satellite will be continuously acquired in real time; among them, the second operational parameters include: the second epoch time and the corresponding second semi-major axis;

[0060] Step 12: For the first sun-synchronous satellite, based on the changing trend of the first semi-major axis with the first epoch in multiple sets of first operating parameter data, fit multiple sets of first operating parameter data to obtain the formula for the trend line of the first semi-major axis of the first sun-synchronous satellite.

[0061] For the second sun-synchronous satellite, based on the variation trend of the second semi-major axis with the second epoch in multiple sets of second operating parameter data, the multiple sets of second operating parameter data are fitted to obtain the formula for the trend line of the second semi-major axis of the second sun-synchronous satellite.

[0062] Step 13: Calculate the difference between the first semi-major axis trend line formula and the second semi-major axis trend line formula to obtain the difference formula. Use the difference formula as the altitude difference trend line formula for the first and second sun-synchronous satellites.

[0063] Step 14: Based on the formula for the height difference trend line, sequentially calculate the predicted height difference between the first and second sun-synchronous satellites at multiple subsequent epochs.

[0064] Step 15: Before the predicted altitude difference exceeds the altitude difference threshold, formulate the orbit control strategy for this orbit control cycle; wherein, the orbit control strategy for this orbit control cycle includes: the epoch time at which this orbit control cycle begins, the epoch time at which this orbit control cycle ends, and the altitude difference adjustment value between the first sun-synchronous satellite and the second sun-synchronous satellite, the altitude difference adjustment value being determined based on the predicted altitude difference and the altitude difference threshold.

[0065] Step 16: According to the orbit control strategy, at the epoch when this orbit control begins, orbit control is performed on the first and second sun-synchronous satellites respectively; until the epoch when this orbit control ends, the actual altitude difference between the first and second sun-synchronous satellites is adjusted to within the altitude difference threshold, so that the phase difference between the first and second sun-synchronous satellites remains unchanged.

[0066] For constellations, the general goal of orbit control is to maintain the phase difference between two adjacent satellites (a binary system) within a predetermined phase range over a long period. Once the phase difference exceeds the boundary value, orbit control measures must be implemented for the two adjacent satellites. However, the drift rate of the phase difference is caused by the altitude difference between the two satellites. The greater the altitude difference between the two satellites, the faster the drift rate and the shorter the phase difference maintenance time. Therefore, considering the number of orbit control operations, satellite lifespan, and user benefits, the slower the phase difference drift, the better; that is, the more accurately the altitude difference between the two satellites is calculated, the better. Therefore, when designing orbit control strategies, to extend the phase difference maintenance period (i.e., the slower the drift rate), it is necessary to accurately calculate and predict the altitude difference. By predicting the altitude difference, precise control of the actual altitude difference of the orbit can be achieved, thereby realizing fine-grained orbit control to maintain the phase difference.

[0067] In addition, the time interval between two orbit control operations is determined based on the effect of the previous orbit control operation and is finalized before the next orbit control operation. Taking the phase difference orbit control of two satellites as an example, during operation, the closer the altitude difference between the two satellites at the previous and subsequent epochs is, the slower the drift rate and the longer the duration.

[0068] In this embodiment of the invention, since the semi-major axis of the orbit of a sun-synchronous satellite with the same decay rate changes linearly, after the sun-synchronous satellites enter their respective operating orbits, their respective operating parameter data (epoch time and corresponding semi-major axis) are continuously acquired in real time. Based on their respective operating parameter data, a first semi-major axis trend line formula and a second semi-major axis trend line formula are formed. This fully considers the long-term change trend of the orbit of the sun-synchronous satellite and reduces the random errors caused by a single semi-major axis data, resulting in a more stable and reliable semi-major axis.

[0069] The difference between the first and second semi-major axis trend line formulas is calculated to obtain the difference formula. This difference formula is then used as the altitude difference trend line formula for the first and second sun-synchronous satellites. The altitude difference calculated using the altitude difference trend line formula can, in cases where precise orbit control is required to maintain phase difference, control one of the sun-synchronous satellites at a fixed altitude or ensure that the altitude difference between the two satellites meets a fixed value, thus achieving precise orbital altitude control.

[0070] Preferably, step 11 specifically includes:

[0071] After the first sun-synchronous satellite enters its first operational orbit, the first GNSS data representing the operational information of the first sun-synchronous satellite will be continuously acquired in real time.

[0072] For the first sun-synchronous satellite, the first GNSS data is used to calculate the first instantaneous root of the first orbit of the first sun-synchronous satellite. The first instantaneous root includes: the first epoch, the first semi-major axis, the first eccentricity, the first inclination, the right ascension of the first ascending node, the argument of the first perigee, and the first mean perigee.

[0073] Eliminating the corresponding short-period variation term from the first instantaneous root yields the first horizontal root of the first orbit of the first sun-synchronous satellite. The first horizontal root includes the first epoch time and the first horizontal semi-major axis.

[0074] Multiple consecutive first epoch times and their corresponding first semi-major axes are used as multiple sets of first operational parameter data for the first sun-synchronous satellite;

[0075] After the second sun-synchronous satellite enters its second operational orbit, second GNSS data representing the operational information of the second sun-synchronous satellite will be continuously acquired in real time.

[0076] For the second sun-synchronous satellite, the second GNSS data is calculated to obtain the second instantaneous root of the second orbit of the second sun-synchronous satellite. The second instantaneous root includes: the second epoch, the second semi-major axis, the second eccentricity, the second inclination, the right ascension of the second ascending node, the argument of the second perigee, and the second mean perigee.

[0077] Eliminating the corresponding short-period variation term from the second instantaneous root yields the second horizontal root of the second orbit of the second sun-synchronous satellite. The second horizontal root includes: the second epoch time and the second horizontal semi-major axis.

[0078] Multiple consecutive second epoch times and their corresponding second semi-major axes are used as multiple sets of second operational parameter data for the second sun-synchronous satellite.

[0079] The first and second operational parameter data can be operational parameter data before or after orbit control, but they cannot include operational parameter data during orbit control. This is necessary to reflect the variation trend of the semi-major axis of the sun-synchronous satellite under the influence of various perturbations, and to make the calculation formulas for the first and second semi-major axis trend lines more accurate. Common perturbations include the Earth's non-spherical perturbation, the gravitational pull of the Sun and Moon, atmospheric drag, solar radiation pressure, and tidal forces.

[0080] Preferably, the method for maintaining the phase difference of a sun-synchronous satellite further includes:

[0081] After the current track control cycle is completed, the next track control cycle will be updated to the current track control cycle. Steps 14, 15 and 16 will be executed in sequence.

[0082] or,

[0083] After this orbit control cycle is completed, steps 17 and 18 will be executed sequentially, wherein:

[0084] Step 17: After the completion of this orbit control cycle, acquire the first and second operating parameter data in real time. Take the difference between the first and second semi-major axes at the same epoch as the altitude difference between the first and second sun-synchronous satellites. Calculate the average of multiple sets of altitude differences between the two satellites that are not less than the second preset duration after the completion of this orbit control cycle. Take the average of the altitude differences between the two satellites as the predicted altitude difference between the first and second sun-synchronous satellites at the epoch when the next orbit control cycle ends.

[0085] Step 18: Update the next orbit control cycle to the current orbit control cycle. At the beginning epoch of the current orbit control cycle, perform orbit control on the first and second sun-synchronous satellites respectively until the end epoch of the current orbit control cycle. Adjust the actual altitude difference between the first and second sun-synchronous satellites to within the altitude difference threshold so that the phase difference between the first and second sun-synchronous satellites remains unchanged.

[0086] Because the altitude difference between the two stars remains relatively constant after they enter their orbits, the difference between their semi-major axes within a period of at least 3 hours or 1 day after orbit control ends can be used as the altitude difference between the two stars. The average of multiple altitude differences between the two stars within the same period of at least 3 hours can be used as the predicted altitude difference for precise orbit control. After the first use of the trend line formula, it is no longer necessary to use the trend line formula, which is simple and convenient.

[0087] Therefore, after the initial track control, both using the trend line formula and not using the trend line formula can achieve precise track control.

[0088] Preferably, the method for maintaining the phase difference of the sun-synchronous satellite further includes:

[0089] Step 19: Set the minimum altitude threshold for both the first and second sun-synchronous satellites to 500km. If the actual orbital altitude of either the first or second sun-synchronous satellite decreases to 500km, then directly perform orbit control on that sun-synchronous satellite and synchronously adjust the actual altitude difference between the first and second sun-synchronous satellites to keep the actual altitude difference between them within the altitude difference threshold.

[0090] In the event that the actual orbital altitude of a sun-synchronous satellite suddenly decreases to 500km, orbit control can be performed directly. At the same time, the altitude difference between the two satellites that maintain the phase difference needs to be adjusted so that the actual altitude difference between the two satellites is within the altitude difference threshold, so that the phase difference between the two satellites can be maintained within the phase range.

[0091] like Figure 2 As shown, in conjunction with an embodiment of the present invention, a satellite orbit control method is provided, comprising:

[0092] Step 21: After the satellite enters its third operational orbit, continuously acquire multiple sets of third operational parameter data in real time; among which, the third operational parameters include: the third epoch time and the corresponding third semi-major axis;

[0093] Step 22: Based on the variation trend of the third semi-major axis with the third epoch in multiple sets of third operational parameter data, fit multiple sets of third operational parameter data to obtain the formula for the trend line of the satellite's third semi-major axis.

[0094] Step 23: Based on the formula of the third horizontal semi-major axis trend line, calculate the predicted horizontal semi-major axis of the satellite at multiple subsequent epochs in sequence, and calculate the predicted orbital altitude of the satellite based on the predicted horizontal semi-major axis of the satellite at each subsequent epoch.

[0095] Step 24: Based on the predicted and theoretical orbital altitudes of the satellite at each subsequent epoch, formulate the orbit control strategy for this orbit control operation; wherein, the orbit control strategy for this orbit control operation includes: the epoch at which the orbit control operation begins, the epoch at which the orbit control operation ends, and the orbital altitude adjustment value;

[0096] Step 25: According to the orbit control strategy, at the epoch when the current orbit control begins, the satellite is subjected to orbit control until the epoch when the current orbit control ends, at which point the satellite's third operating orbit is raised to the adjusted orbital altitude value.

[0097] The satellite orbital altitude control method of this invention is applicable to: sun-synchronous satellites, high-inclination low-Earth orbit satellites, and sun-synchronous satellites (satellite constellations) with the same decay rate. The semi-major axis of the orbits of these satellites exhibits a linear trend. Therefore, after the satellites enter their respective operational orbits, their operational parameter data—epoch time and corresponding semi-major axis—is continuously acquired in real time. The operational parameter data is fitted to obtain the semi-major axis trend line formula. Thus, this satellite orbital altitude control method fully considers the long-term trend of the satellite's operational orbit, reduces the random errors caused by individual semi-major axis data, and obtains a more stable and reliable predicted semi-major axis with high accuracy. The predicted orbital altitude of the satellite is calculated based on the predicted semi-major axis of the satellite at each subsequent epoch. The orbital altitude adjustment value is obtained based on the predicted orbital altitude and the theoretical orbital altitude at each subsequent epoch. At the beginning of each orbit control cycle, orbit control is performed on the satellite until the end of the cycle. At the end of each orbit control cycle, the satellite's third orbit is raised to the required altitude adjustment value. Because the accuracy of the predicted semi-major axis is high, the accuracy of the orbit control altitude adjustment value is high. The adjusted orbit of the satellite is closer to the theoretical orbit altitude, thus achieving precise orbit control.

[0098] Preferably, step 21 specifically includes:

[0099] After the satellite enters its third operational orbit, it continuously acquires third GNSS data that represents satellite operational information in real time.

[0100] The instantaneous roots of the satellite's third orbit are calculated from the third GNSS data. The instantaneous roots of the third orbit include: the third epoch, the third semi-major axis, the third eccentricity, the third inclination, the right ascension of the third ascending node, the argument of the third perigee, and the third mean perigee.

[0101] Eliminating the corresponding short-period variation term from the instantaneous root of the third orbit yields the flat root of the satellite's third orbit. The flat root of the third orbit includes the third epoch time and the third semi-major axis.

[0102] Multiple consecutive third epoch times and their corresponding third semi-major axes are used as multiple sets of third operational parameter data for the satellite.

[0103] Operational parameter data can be from before or after orbit control, but it cannot include operational parameter data during the orbit control period. This is necessary to reflect the trend of the satellite's semi-major axis change under the influence of various perturbations. The formula for the third semi-major axis trend line will be more accurate. Common perturbations include the Earth's non-spherical perturbation, the gravitational pull of the Sun and Moon, atmospheric drag, solar radiation pressure, and tidal forces.

[0104] Preferably, the satellite orbit control method further includes:

[0105] After the current track control is completed, the next track control will be updated to the current track control. Steps 23, 24 and 25 will be executed in sequence.

[0106] or,

[0107] After the track control is completed, steps 26 and 27 are executed sequentially, wherein:

[0108] Step 26: After the orbit control ends, the third operating parameter data is acquired in real time. Based on the third semi-major axis in the third operating parameter data and the theoretical orbital altitude at the corresponding third epoch, the corresponding orbital altitude difference is calculated. The average value of multiple orbital altitude differences that are not less than the first preset duration after the end of the orbit control is calculated. The average value of the orbital altitude difference is used as the orbital altitude adjustment value to be raised in the third operating orbit of the satellite at the epoch of the next orbit control end.

[0109] Step 27: Update the next orbit control to the current orbit control. At the epoch when the current orbit control begins, perform orbit control on the satellite until the epoch when the current orbit control ends, and raise the satellite's third operating orbit by the orbital altitude adjustment value.

[0110] Because the altitude difference of a satellite does not change much within a certain period of time after it enters its operational orbit, the orbital altitude difference can be calculated on the horizontal half-major axis within a period of not less than the first preset duration (e.g., more than 3 hours or 1 day) after orbit control. The average value of multiple orbital altitude differences of not less than the first preset duration is used as the orbital altitude adjustment value for precise orbit control. After the trend line formula is used for the first time, it can be discontinued, which is simple and convenient.

[0111] Therefore, after the initial track control, both using the trend line formula and not using the trend line formula can achieve precise track control.

[0112] Preferably, the satellite orbit control method further includes:

[0113] Step 28: When the satellite is a sun-synchronous satellite, set the minimum altitude threshold for sun-synchronous satellites to 500km. If the actual orbital altitude of the sun-synchronous satellite decreases to 500km, then directly perform orbit control on the sun-synchronous satellite to adjust its operating orbit to the theoretical orbital altitude.

[0114] In the event of a sudden decrease in the actual orbital altitude of a sun-synchronous satellite to 500km, orbit control can be directly implemented to adjust the satellite's orbit back to its theoretical orbital altitude.

[0115] like Figure 3 As shown, in conjunction with an embodiment of the present invention, a phase difference maintenance system for a sun-synchronous satellite is provided, comprising:

[0116] The first parameter acquisition unit 31 is used to continuously acquire multiple sets of first operating parameter data of the first sun-synchronous satellite in real time after the first sun-synchronous satellite enters the first operating orbit, for the first sun-synchronous satellite and the second sun-synchronous satellite with constant phase difference and the same decay. Among them, constant phase difference means that the phase difference between the first sun-synchronous satellite and the second sun-synchronous satellite is maintained within a preset phase range. The first operating parameters include: the first epoch time and the corresponding first semi-major axis.

[0117] After the second sun-synchronous satellite enters its second operational orbit, multiple sets of second operational parameter data for the second sun-synchronous satellite will be continuously acquired in real time; among them, the second operational parameters include: the second epoch time and the corresponding second semi-major axis;

[0118] The first trend line fitting unit 32 is used to fit multiple sets of first operating parameter data based on the changing trend of the first semi-major axis with the first epoch in multiple sets of first operating parameter data for the first sun-synchronous satellite, and obtain the formula for the first semi-major axis trend line of the first sun-synchronous satellite.

[0119] For the second sun-synchronous satellite, based on the variation trend of the second semi-major axis with the second epoch in multiple sets of second operating parameter data, the multiple sets of second operating parameter data are fitted to obtain the formula for the trend line of the second semi-major axis of the second sun-synchronous satellite.

[0120] Construct a difference formula unit 33 to calculate the difference between the first half-major axis trend line formula and the second half-major axis trend line formula, obtain the difference formula, and use the difference formula as the altitude difference trend line formula of the first sun-synchronous satellite and the second sun-synchronous satellite.

[0121] The first calculation unit 34 is used to sequentially calculate the predicted altitude difference between the first and second sun-synchronous satellites at multiple subsequent epochs based on the altitude difference trend line formula.

[0122] The first orbit control strategy formulation unit 35 is used to formulate the orbit control strategy for this orbit control before the predicted altitude difference exceeds the altitude difference threshold. The orbit control strategy for this orbit control includes: the epoch time at which this orbit control begins, the epoch time at which this orbit control ends, and the altitude difference adjustment value between the first sun-synchronous satellite and the second sun-synchronous satellite. The altitude difference adjustment value is determined based on the predicted altitude difference and the altitude difference threshold.

[0123] The first orbit control unit 36 ​​is used to perform orbit control on the first and second sun-synchronous satellites respectively at the epoch of the start of this orbit control cycle, according to the orbit control strategy; until the epoch of the end of this orbit control cycle, adjust the actual altitude difference between the first and second sun-synchronous satellites to within the altitude difference threshold, so that the phase difference between the first and second sun-synchronous satellites remains unchanged.

[0124] For constellations, the general goal of orbit control is to maintain the phase difference between two adjacent satellites (a binary system) within a predetermined phase range over a long period. Once the phase difference exceeds the boundary value, orbit control measures must be implemented for the two adjacent satellites. However, the drift rate of the phase difference is caused by the altitude difference between the two satellites. The greater the altitude difference between the two satellites, the faster the drift rate and the shorter the phase difference maintenance time. Therefore, considering the number of orbit control operations, satellite lifespan, and user benefits, the slower the phase difference drift, the better; that is, the more accurately the altitude difference between the two satellites is calculated, the better. Therefore, when designing orbit control strategies, to extend the phase difference maintenance period (i.e., the slower the drift rate), it is necessary to accurately calculate and predict the altitude difference. By predicting the altitude difference, precise control of the actual altitude difference of the orbit can be achieved, thereby realizing fine-grained orbit control to maintain the phase difference.

[0125] In addition, the time interval between two orbit control operations is determined based on the effect of the previous orbit control operation and is finalized before the next orbit control operation. Taking the phase difference orbit control of two satellites as an example, during operation, the closer the altitude difference between the two satellites at the previous and subsequent epochs is, the slower the drift rate and the longer the duration.

[0126] In this embodiment of the invention, since the semi-major axis of the orbit of a sun-synchronous satellite with the same decay rate changes linearly, after the sun-synchronous satellites enter their respective operating orbits, their respective operating parameter data (epoch time and corresponding semi-major axis) are continuously acquired in real time. Based on their respective operating parameter data, a first semi-major axis trend line formula and a second semi-major axis trend line formula are formed. This fully considers the long-term change trend of the orbit of the sun-synchronous satellite and reduces the random errors caused by a single semi-major axis data, resulting in a more stable and reliable semi-major axis.

[0127] The difference between the first and second semi-major axis trend line formulas is calculated to obtain the difference formula. This difference formula is then used as the altitude difference trend line formula for the first and second sun-synchronous satellites. The altitude difference calculated using the altitude difference trend line formula can, in cases where precise orbit control is required to maintain phase difference, control one of the sun-synchronous satellites at a fixed altitude or ensure that the altitude difference between the two satellites meets a fixed value, thus achieving precise orbital altitude control.

[0128] Preferably, the first parameter acquisition unit 31 includes:

[0129] The first parameter acquisition subunit is used to continuously acquire first GNSS data representing the operational information of the first sun-synchronous satellite in real time after the first sun-synchronous satellite enters the first operational orbit.

[0130] The first parameter processing subunit is used to calculate the first GNSS data for the first sun-synchronous satellite to obtain the first instantaneous root of the first orbit of the first sun-synchronous satellite. The first instantaneous root includes: the first epoch, the first semi-major axis, the first eccentricity, the first inclination, the right ascension of the first ascending node, the argument of the first perigee, and the first mean perigee.

[0131] Eliminating the corresponding short-period variation term from the first instantaneous root yields the first horizontal root of the first orbit of the first sun-synchronous satellite. The first horizontal root includes the first epoch time and the first horizontal semi-major axis.

[0132] The first parameter construction subunit is used to take multiple consecutive first epoch times and the corresponding first horizontal semi-major axis as multiple sets of first operating parameter data for the first sun-synchronous satellite;

[0133] The second parameter acquisition subunit is used to continuously acquire second GNSS data representing the operational information of the second sun-synchronous satellite in real time after the second sun-synchronous satellite enters the second operational orbit.

[0134] The second parameter processing subunit is used to calculate the second GNSS data for the second sun-synchronous satellite to obtain the second instantaneous root of the second orbit of the second sun-synchronous satellite. The second instantaneous root includes: the second epoch, the second semi-major axis, the second eccentricity, the second inclination, the right ascension of the second ascending node, the argument of the second perigee, and the second mean perigee.

[0135] Eliminating the corresponding short-period variation term from the second instantaneous root yields the second horizontal root of the second orbit of the second sun-synchronous satellite. The second horizontal root includes: the second epoch time and the second horizontal semi-major axis.

[0136] The second parameter construction sub-unit is used to take multiple consecutive second epoch times and the corresponding second semi-major axis as multiple sets of second operating parameter data for the second sun-synchronous satellite.

[0137] The first and second operational parameter data can be operational parameter data before or after orbit control, but they cannot include operational parameter data during orbit control. This is necessary to reflect the variation trend of the semi-major axis of the sun-synchronous satellite under the influence of various perturbations, and to make the calculation formulas for the first and second semi-major axis trend lines more accurate. Common perturbations include the Earth's non-spherical perturbation, the gravitational pull of the Sun and Moon, atmospheric drag, solar radiation pressure, and tidal forces.

[0138] Preferably, the phase difference maintaining system of the sun-synchronous satellite includes:

[0139] After the current track control cycle is completed, the next track control cycle will be updated to the current track control cycle. The current track control cycle will be carried out through the first calculation unit 34, the first track control strategy formulation unit 35 and the first track control unit 36.

[0140] or,

[0141] After this round of track control is completed, the next round of track control will be carried out through the second calculation unit and the second track control unit, wherein:

[0142] The second calculation unit is used to calculate the average of multiple sets of double-satellite altitude differences that are not less than the second preset duration after the end of this orbit control cycle. The average of the double-satellite altitude differences is used as the predicted altitude difference between the first and second sun-synchronous satellites at the end of the next orbit control cycle.

[0143] The second orbit control unit is used to update the next orbit control cycle to the current orbit control cycle. At the beginning epoch of the current orbit control cycle, orbit control is performed on the first and second sun-synchronous satellites respectively. Until the end epoch of the current orbit control cycle, the actual altitude difference between the first and second sun-synchronous satellites is adjusted to within the altitude difference threshold so that the phase difference between the first and second sun-synchronous satellites remains unchanged.

[0144] Because the altitude difference between the two stars remains relatively constant after they enter their orbits, the difference between their semi-major axes within a period of at least 3 hours or 1 day after orbit control ends can be used as the altitude difference between the two stars. The average of multiple altitude differences between the two stars within the same period of at least 3 hours can be used as the predicted altitude difference for precise orbit control. After the first use of the trend line formula, it is no longer necessary to use the trend line formula, which is simple and convenient.

[0145] Therefore, after the initial track control, both using the trend line formula and not using the trend line formula can achieve precise track control.

[0146] Preferably, the method for maintaining the phase difference of the sun-synchronous satellite further includes:

[0147] The third orbit control unit is used to set the minimum altitude threshold for both the first and second sun-synchronous satellites to 500km. If the actual orbital altitude of either the first or second sun-synchronous satellite decreases to 500km, orbit control will be directly applied to that sun-synchronous satellite, and the actual altitude difference between the first and second sun-synchronous satellites will be adjusted synchronously to keep the actual altitude difference between the first and second sun-synchronous satellites within the altitude difference threshold.

[0148] In the event that the actual orbital altitude of a sun-synchronous satellite suddenly decreases to 500km, orbit control can be performed directly. At the same time, the altitude difference between the two satellites that maintain the phase difference needs to be adjusted so that the actual altitude difference between the two satellites is within the altitude difference threshold, so that the phase difference between the two satellites can be maintained within the phase range.

[0149] like Figure 4 As shown in the embodiments of this method, a satellite orbit control system is provided, comprising:

[0150] The second parameter acquisition unit 41 is used to continuously acquire multiple sets of third operational parameter data of the satellite in real time after the satellite enters the third operational orbit; wherein, the third operational parameters include: the third epoch time and the corresponding third semi-major axis;

[0151] The second trendline fitting unit 42 is used to fit multiple sets of third operating parameter data according to the changing trend of the third semi-major axis with the third epoch, and obtain the formula for the trendline of the third semi-major axis of the satellite.

[0152] The third calculation unit 43 is used to sequentially calculate the predicted semi-major axis of the satellite at multiple subsequent epochs based on the formula of the third semi-major axis trend line, and to calculate the predicted orbital altitude of the satellite based on the predicted semi-major axis of the satellite at each subsequent epoch.

[0153] The second orbit control strategy formulation unit 44 is used to formulate the orbit control strategy for the current orbit control based on the predicted orbit altitude and theoretical orbit altitude of the satellite at each subsequent epoch; wherein, the orbit control strategy for the current orbit control includes: the epoch at which the current orbit control begins, the epoch at which the current orbit control ends, and the orbit altitude adjustment value.

[0154] The fourth orbit control unit 45 is used to perform orbit control on the satellite at the beginning of the current orbit control cycle according to the orbit control strategy, and to raise the satellite's third operating orbit by the orbital altitude adjustment value at the end of the current orbit control cycle.

[0155] The satellite orbital altitude control method of this invention is applicable to: sun-synchronous satellites, high-inclination low-Earth orbit satellites, and sun-synchronous satellites (satellite constellations) with the same decay rate. The semi-major axis of the orbits of these satellites exhibits a linear trend. Therefore, after the satellites enter their respective operational orbits, their operational parameter data—epoch time and corresponding semi-major axis—is continuously acquired in real time. The operational parameter data is fitted to obtain the semi-major axis trend line formula. Thus, this satellite orbital altitude control method fully considers the long-term trend of the satellite's operational orbit, reduces the random errors caused by individual semi-major axis data, and obtains a more stable and reliable predicted semi-major axis with high accuracy. The predicted orbital altitude of the satellite is calculated based on the predicted semi-major axis of the satellite at each subsequent epoch. The orbital altitude adjustment value is obtained based on the predicted orbital altitude and the theoretical orbital altitude at each subsequent epoch. At the epoch when the current orbit control begins, orbit control is performed on the satellite until the epoch when the current orbit control ends. The satellite's third operating orbit is then raised to the required altitude adjustment value. Because the accuracy of the predicted semi-major axis is high, the accuracy of the orbit control altitude adjustment value for the satellite is high. The adjusted operating orbit of the satellite is closer to the theoretical orbit altitude, thus achieving orbit control.

[0156] Preferably, the second parameter acquisition unit 41 includes:

[0157] The third parameter acquisition subunit is used to continuously acquire third GNSS data representing satellite operation information in real time after the satellite enters the third operational orbit.

[0158] The third parameter processing subunit is used to calculate the third GNSS data to obtain the instantaneous root of the satellite's third orbit. The instantaneous root of the third orbit includes: the third epoch, the third semi-major axis, the third eccentricity, the third inclination, the right ascension of the third ascending node, the argument of the third perigee, and the third mean perigee.

[0159] Eliminating the corresponding short-period variation term from the instantaneous root of the third orbit yields the flat root of the satellite's third orbit. The flat root of the third orbit includes the third epoch time and the third semi-major axis.

[0160] The third parameter construction sub-unit is used to take multiple consecutive third epoch times and the corresponding third semi-major axis as multiple sets of third operational parameter data for the satellite.

[0161] Operational parameter data can be from before or after orbit control, but it cannot include operational parameter data during the orbit control period. This is necessary to reflect the trend of the satellite's semi-major axis change under the influence of various perturbations. The formula for the third semi-major axis trend line will be more accurate. Common perturbations include the Earth's non-spherical perturbation, the gravitational pull of the Sun and Moon, atmospheric drag, solar radiation pressure, and tidal forces.

[0162] Preferably, the satellite orbit control method further includes:

[0163] After the current track control is completed, the next track control will be updated to the current track control. The current track control will be carried out through the third calculation unit 43, the second track control strategy formulation unit 44 and the fourth track control unit 45.

[0164] or,

[0165] After the track control operation is completed, the fourth calculation unit and the fifth track control unit are executed sequentially, wherein:

[0166] The fourth calculation unit is used to calculate the difference between the third semi-major axis in the real-time acquired third operating parameter data and the theoretical orbital altitude at the corresponding third epoch after the current orbit control ends, to obtain the corresponding orbital altitude difference, to calculate the average value of multiple sets of orbital altitude differences that are not less than the first preset duration after the current orbit control ends, and to use the average value of the orbital altitude difference as the orbital altitude adjustment value to be raised in the third operating orbit of the satellite at the epoch of the next orbit control end.

[0167] The fifth orbit control unit is used to update the next orbit control to the current orbit control. At the beginning of the current orbit control, the satellite is controlled for orbit until the end of the current orbit control, at which time the satellite's third operating orbit is raised to the orbital altitude adjustment value.

[0168] Because the altitude difference of a satellite does not change much within a certain period of time after it enters its operational orbit, the orbital altitude difference can be calculated on the horizontal half-major axis within a period of not less than the first preset duration (e.g., more than 3 hours or 1 day) after orbit control. The average value of multiple orbital altitude differences of not less than the first preset duration is used as the orbital altitude adjustment value for precise orbit control. After the trend line formula is used for the first time, it can be discontinued, which is simple and convenient.

[0169] Therefore, after the initial track control, both using the trend line formula and not using the trend line formula can achieve precise track control.

[0170] Preferably, the satellite orbit control system further includes:

[0171] The sixth orbit control unit is used to set the minimum altitude threshold of a sun-synchronous satellite to 500km when the satellite is a sun-synchronous satellite. If the actual orbital altitude of the sun-synchronous satellite decays to 500km, the unit will directly perform orbit control on the sun-synchronous satellite to adjust its operating orbit to the theoretical orbital altitude.

[0172] If the actual orbital altitude of a sun-synchronous satellite decays to 500km, orbit control can be directly implemented to adjust the satellite's orbit back to its theoretical altitude. Specifically, taking two sun-synchronous satellites, A and B, with the same decay rate as an example... Figure 5 The variation of the semi-major axis of satellites A and B over a day ( Figure 5 The time in the epoch is the epochal moment. Figure 6 The trend of the difference in the semi-major axis of stars A and B ( Figure 6 The time in the epoch (i.e., the epochal moment), from Figure 5 and Figure 6 It can be seen that, due to the influence of various perturbations during the operation of the sun-synchronous satellite in orbit, the semi-major axis of the orbit generally shows a linear decreasing trend.

[0173] Figure 5 In the diagram, the semi-major axis variation line of the binary stars can be interpreted as the semi-major axis trend line, from which it can be seen that star B is about 0.119 km higher than star A. Figure 6 The study calculated the single-point altitude difference between satellites A and B at the same epoch. Clearly, the instantaneous root-of-course value cannot reflect the true altitude of the satellites. Especially when maintaining fine orbit control by maintaining the phase difference between the two satellites, it is necessary to accurately calculate the root-of-course and altitude difference of the two satellites after control. Therefore, the method of calculating the root-of-course difference between the two satellites at a single point is not feasible.

[0174] Therefore, in this embodiment of the invention, a semi-major axis over a period of time is used. Based on the change of the semi-major axis with epoch time, a formula for the trend line of the semi-major axis is fitted. The trend line of the semi-major axis is a linearly changing straight line, and the formula for the trend line of the semi-major axis is a linear equation in one variable. The formula for the trend line of the semi-major axis is y=ax+b, where x represents time, y represents the semi-major axis, and a and b are constants. Each satellite can fit a straight line based on its own semi-major axis change.

[0175] The formula for the first horizontal semi-major axis trend line of the first sun-synchronous satellite can be expressed as y1=a1x1+b1;

[0176] The formula for the trend line of the second semi-major axis of the second sun-synchronous satellite can be expressed as y2=a2x2+b2;

[0177] The formula for the third horizontal half-length axis trend line can be expressed as y3=a3x3+b3;

[0178] The subscript numbers 1, 2, and 3 in the above formulas correspond to "first" in the first half-length axis trend line formula, "second" in the second half-length axis trend line formula, and "third" in the third half-length axis trend line formula, and are used to distinguish the symbols.

[0179] The formula for the height difference trend line is: y 2- y1 = (a2 - a1)x + b2 - b1; x represents the time at which the first and second sun-synchronous satellites are in the same epoch.

[0180] Table 1 shows the altitude difference between two satellites. This embodiment of the invention analyzes the altitude difference between two satellites at different durations one day after orbit control and the average value of the altitude difference between two satellites. By comparing Table 1 with the formulas for the first and second semi-major axis trends and the altitude difference trend line, it can be seen that the average value of the altitude difference between two satellites after orbit control ends, which is not less than the first preset duration, can be used as the calculation result, such as the average value of the altitude difference between two satellites that is more than 3 hours.

[0181] Table 1. Difference in altitude between the two stars

[0182]

[0183] Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware.

[0184] Exemplary embodiments of the present invention have been specifically shown and described above. It should be understood that the present invention is not limited to the detailed structures, arrangements, or implementations described herein; rather, the present invention is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A method for maintaining the phase difference of a sun-synchronous satellite, characterized in that, include: Step 11: For the first and second sun-synchronous satellites with unchanged phase difference and the same attenuation, after the first sun-synchronous satellite enters the first operating orbit, continuously acquire multiple sets of first operating parameter data of the first sun-synchronous satellite in real time; wherein, the unchanged phase difference means that the phase difference between the first and second sun-synchronous satellites is maintained within a preset phase range; the first operating parameters include: the first epoch time and the corresponding first semi-major axis; After the second sun-synchronous satellite enters its second operational orbit, multiple sets of second operational parameter data of the second sun-synchronous satellite are continuously acquired in real time; wherein, the second operational parameters include: the second epoch time and the corresponding second semi-major axis; Step 12: For the first sun-synchronous satellite, based on the changing trend of the first semi-major axis with the first epoch in multiple sets of the first operating parameter data, fit multiple sets of the first operating parameter data to obtain the formula for the trend line of the first semi-major axis of the first sun-synchronous satellite. For the second sun-synchronous satellite, based on the variation trend of the second semi-major axis with the second epoch in multiple sets of the second operating parameter data, the multiple sets of the second operating parameter data are fitted to obtain the formula for the trend line of the second semi-major axis of the second sun-synchronous satellite. Step 13: Calculate the difference between the first semi-major axis trend line formula and the second semi-major axis trend line formula to obtain the difference formula, and use the difference formula as the altitude difference trend line formula between the first sun-synchronous satellite and the second sun-synchronous satellite. Step 14: Based on the formula for the height difference trend line, sequentially calculate the predicted height difference between the first sun-synchronous satellite and the second sun-synchronous satellite at multiple subsequent epochs; Step 15: Before the predicted altitude difference exceeds the altitude difference threshold, formulate the orbit control strategy for this orbit control cycle; wherein, the orbit control strategy for this orbit control cycle includes: the epoch time at which this orbit control cycle begins, the epoch time at which this orbit control cycle ends, and the altitude difference adjustment value between the first sun-synchronous satellite and the second sun-synchronous satellite, wherein the altitude difference adjustment value is determined based on the predicted altitude difference and the altitude difference threshold. Step 16: According to the orbit control strategy, at the epoch when this orbit control cycle begins, orbit control is performed on the first sun-synchronous satellite and the second sun-synchronous satellite respectively; until the epoch when this orbit control cycle ends, the actual altitude difference between the first sun-synchronous satellite and the second sun-synchronous satellite is adjusted to within the altitude difference threshold, so that the phase difference between the first sun-synchronous satellite and the second sun-synchronous satellite remains unchanged.

2. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 1, characterized in that, Step 11 specifically includes: After the first sun-synchronous satellite enters its first operational orbit, the first GNSS data representing the operational information of the first sun-synchronous satellite will be continuously acquired in real time. For the first sun-synchronous satellite, the first GNSS data is calculated to obtain the first instantaneous root of the first orbit of the first sun-synchronous satellite. The first instantaneous root includes: the first epoch, the first semi-major axis, the first eccentricity, the first inclination, the right ascension of the first ascending node, the argument of the first perigee, and the first mean perigee. Eliminating the corresponding short-period variation term from the first instantaneous root yields the first flat root of the first orbit of the first sun-synchronous satellite. The first flat root includes: the first epoch time and the first semi-major axis. Multiple consecutive first epoch times and their corresponding first semi-major axes are used as multiple sets of first operational parameter data for the first sun-synchronous satellite. After the second sun-synchronous satellite enters its second operational orbit, second GNSS data representing the operational information of the second sun-synchronous satellite will be continuously acquired in real time. For the second sun-synchronous satellite, the second GNSS data is calculated to obtain the second instantaneous root of the second orbit of the second sun-synchronous satellite. The second instantaneous root includes: the second epoch, the second semi-major axis, the second eccentricity, the second inclination, the right ascension of the second ascending node, the argument of the second perigee, and the second mean perigee. Eliminating the corresponding short-period variation term from the second instantaneous root yields the second horizontal root of the second orbit of the second sun-synchronous satellite. The second horizontal root includes: the second epoch time and the second horizontal semi-major axis. Multiple consecutive second epoch times and their corresponding second semi-major axes are used as multiple sets of second operational parameter data for the second sun-synchronous satellite.

3. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 1, characterized in that, Also includes: After the current track control cycle is completed, the next track control cycle will be updated to the current track control cycle. Steps 14, 15 and 16 will be executed sequentially. or, After this orbit control cycle is completed, steps 17 and 18 will be executed sequentially, wherein: Step 17: After the current orbit control is completed, the difference between the first semi-major axis and the second semi-major axis at the same epoch obtained in real time is used as the altitude difference between the first sun-synchronous satellite and the second sun-synchronous satellite. The average value of multiple sets of the altitude differences between the two satellites after the current orbit control is completed, which is not less than the second preset duration, is calculated. The average value of the altitude differences between the two satellites is used as the predicted altitude difference between the first sun-synchronous satellite and the second sun-synchronous satellite at the epoch when the next orbit control ends. Step 18: Update the next orbit control cycle to the current orbit control cycle. At the beginning epoch of the current orbit control cycle, perform orbit control on the first sun-synchronous satellite and the second sun-synchronous satellite respectively. Until the end epoch of the current orbit control cycle, adjust the actual altitude difference between the first sun-synchronous satellite and the second sun-synchronous satellite to within the altitude difference threshold, so that the phase difference between the first sun-synchronous satellite and the second sun-synchronous satellite remains unchanged.

4. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 1, characterized in that, Also includes: Step 19: Set the minimum altitude threshold for both the first and second sun-synchronous satellites to 500km. If the actual orbital altitude of either the first or second sun-synchronous satellite decreases to 500km, then directly perform orbit control on that sun-synchronous satellite and synchronously adjust the actual altitude difference between the first and second sun-synchronous satellites to keep the actual altitude difference between the first and second sun-synchronous satellites within the altitude difference threshold.

5. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 1, characterized in that, include: Step 21: After the satellite enters the third operational orbit, continuously acquire multiple sets of third operational parameter data of the satellite in real time; wherein, the third operational parameters include: the third epoch time and the corresponding third semi-major axis; Step 22: Based on the variation trend of the third semi-major axis with the third epoch in the multiple sets of the third operating parameter data, fit the multiple sets of the third operating parameter data to obtain the formula for the trend line of the third semi-major axis of the satellite; Step 23: Based on the formula of the third horizontal semi-major axis trend line, sequentially calculate the predicted horizontal semi-major axis of the satellite at multiple subsequent epochs, and calculate the predicted orbital altitude of the satellite based on the predicted horizontal semi-major axis of the satellite at each subsequent epoch. Step 24: Based on the predicted and theoretical orbital altitudes of the satellite at each subsequent epoch, formulate the orbit control strategy for this orbit control operation; wherein, the orbit control strategy for this orbit control operation includes: the epoch at which the orbit control operation begins, the epoch at which the orbit control operation ends, and the orbital altitude adjustment value; Step 25: According to the orbit control strategy, at the epoch when the current orbit control begins, the satellite is subjected to orbit control until the epoch when the current orbit control ends, and the satellite's third operating orbit is raised by the orbital altitude adjustment value.

6. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 5, characterized in that, Step 21 specifically includes: After the satellite enters its third operational orbit, it continuously acquires third GNSS data that represents satellite operational information in real time. The instantaneous root of the third orbit of the satellite is obtained by calculating the third GNSS data. The instantaneous root of the third orbit includes: the third epoch, the third semi-major axis, the third eccentricity, the third inclination, the right ascension of the third ascending node, the argument of the third perigee, and the third mean perigee. The instantaneous root of the third orbit is eliminated by removing the corresponding short-period variation term to obtain the flat root of the third orbit of the satellite. The flat root of the third orbit includes the third epoch time and the third flat semi-major axis. Multiple consecutive third epoch times and their corresponding third semi-major axes are used as multiple sets of third operational parameter data for the satellite.

7. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 5, characterized in that, Also includes: After the current track control is completed, the next track control will be updated to the current track control, and steps 23, 24 and 25 will be executed in sequence. or, After the track control is completed, steps 26 and 27 are executed sequentially, wherein: Step 26: After the orbit control ends, calculate the difference between the third semi-major axis in the real-time acquired third operating parameter data and the theoretical orbital altitude at the corresponding third epoch, and obtain the corresponding orbital altitude difference. Calculate the average value of multiple sets of orbital altitude differences that are not less than the first preset duration after the end of the orbit control, and use the average value of the orbital altitude difference as the orbital altitude adjustment value to be raised in the third operating orbit of the satellite at the epoch of the next orbit control end. Step 27: Update the next orbit control to the current orbit control. At the epoch when the current orbit control begins, perform orbit control on the satellite until the epoch when the current orbit control ends, and raise the satellite's third operating orbit by the orbital altitude adjustment value.

8. The method for maintaining the phase difference of a sun-synchronous satellite according to claim 5, characterized in that, Also includes: Step 28: When the satellite is a sun-synchronous satellite, the minimum altitude threshold of the sun-synchronous satellite is set to 500km. If the actual orbital altitude of the sun-synchronous satellite decreases to 500km, orbit control is directly performed on the sun-synchronous satellite to adjust its orbit to the theoretical orbital altitude.

9. A phase difference preservation system for a sun-synchronous satellite, characterized in that, include: The first parameter acquisition unit is used to continuously acquire multiple sets of first operating parameter data of the first sun-synchronous satellite in real time after the first sun-synchronous satellite enters the first operating orbit, for the first sun-synchronous satellite and the second sun-synchronous satellite with constant phase difference and the same decay. The constant phase difference means that the phase difference between the first sun-synchronous satellite and the second sun-synchronous satellite is maintained within a preset phase range. The first operating parameters include: the first epoch time and the corresponding first semi-major axis. After the second sun-synchronous satellite enters its second operational orbit, multiple sets of second operational parameter data of the second sun-synchronous satellite are continuously acquired in real time; wherein, the second operational parameters include: the second epoch time and the corresponding second semi-major axis; The first trend line fitting unit is used to fit the first set of first operating parameter data to the first sun-synchronous satellite based on the changing trend of the first semi-major axis with the first epoch time in the first set of first operating parameter data, and obtain the formula of the first semi-major axis trend line of the first sun-synchronous satellite. For the second sun-synchronous satellite, based on the variation trend of the second semi-major axis with the second epoch in multiple sets of the second operating parameter data, the multiple sets of the second operating parameter data are fitted to obtain the formula for the trend line of the second semi-major axis of the second sun-synchronous satellite. Construct a difference formula unit to calculate the difference between the first half-major axis trend line formula and the second half-major axis trend line formula, obtain the difference formula, and use the difference formula as the altitude difference trend line formula between the first sun-synchronous satellite and the second sun-synchronous satellite. The first calculation unit is used to sequentially calculate the predicted altitude difference between the first sun-synchronous satellite and the second sun-synchronous satellite at multiple subsequent epochs based on the altitude difference trend line formula. The first orbit control strategy formulation unit is used to formulate an orbit control strategy for this orbit control before the predicted altitude difference exceeds the altitude difference threshold; wherein, the orbit control strategy for this orbit control includes: the epoch time at which this orbit control begins, the epoch time at which this orbit control ends, and the altitude difference adjustment value between the first sun-synchronous satellite and the second sun-synchronous satellite, wherein the altitude difference adjustment value is determined based on the predicted altitude difference and the altitude difference threshold; The first orbit control unit is configured to perform orbit control on the first sun-synchronous satellite and the second sun-synchronous satellite respectively at the epoch of the start of this orbit control cycle, according to the orbit control strategy; and adjust the actual altitude difference between the first sun-synchronous satellite and the second sun-synchronous satellite to within the altitude difference threshold at the epoch of the end of this orbit control cycle, so that the phase difference between the first sun-synchronous satellite and the second sun-synchronous satellite remains unchanged.

10. The phase difference preservation system for a sun-synchronous satellite according to claim 9, characterized in that, include: The second parameter acquisition unit is used to continuously acquire multiple sets of third operational parameter data of the satellite in real time after the satellite enters the third operational orbit; wherein, the third operational parameters include: the third epoch time and the corresponding third semi-major axis; The second trendline fitting unit is used to fit the multiple sets of the third operating parameter data according to the changing trend of the third semi-major axis with the third epoch time in the multiple sets of the third operating parameter data, and obtain the formula of the third semi-major axis trendline of the satellite. The third calculation unit is used to sequentially calculate the predicted semi-major axis of the satellite at multiple subsequent epochs according to the formula of the third semi-major axis trend line, and calculate the predicted orbital altitude of the satellite based on the predicted semi-major axis of the satellite at each subsequent epoch. The second orbit control strategy formulation unit is used to formulate the orbit control strategy for the current orbit control based on the predicted orbit altitude and theoretical orbit altitude of the satellite at each subsequent epoch; wherein, the orbit control strategy for the current orbit control includes: the epoch at which the current orbit control begins, the epoch at which the current orbit control ends, and the orbit altitude adjustment value; The fourth orbit control unit is used to perform orbit control on the satellite at the beginning of the current orbit control cycle according to the orbit control strategy, and to raise the satellite's third operating orbit by the orbital altitude adjustment value at the end of the current orbit control cycle.

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