An inter-satellite communication window calculation method for remote sensing satellite task

Abstract

This invention discloses a method for calculating inter-satellite communication windows for remote sensing satellite missions, belonging to the field of satellite communication technology. The technical implementation steps are as follows: Setting the orbital parameters and simulation time period of the satellite constellation; establishing an inter-satellite communication geometric constraint model considering Earth obstruction and maximum distance limitations; based on orbital dynamics principles, analytically deriving the upper bound of the distance change rate and the upper bound of the line-of-sight tangent point altitude change rate, characterizing the relative motion of the constellation; initializing the simulation time; calculating the geometric margin based on the current relative positions of the two satellites; and calculating the adaptive safety step size for the current time in conjunction with the aforementioned upper bounds of the change rates; if a visibility state jump is detected, numerical iterative search is used within the step size interval to lock the window boundary. This invention introduces dynamic boundary parameters to construct an adaptive step size mechanism, significantly reducing the number of invalid calculations while ensuring the accuracy of communication window calculation, thus significantly improving the computational efficiency of inter-satellite link planning.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication technology, specifically relating to a method for calculating inter-satellite communication windows for remote sensing satellite missions. Background Technology

[0002] With the rapid development of aerospace technology, large-scale low Earth orbit (LEO) remote sensing satellite constellations have become an important means of acquiring high spatiotemporal resolution global data. In these constellation systems, inter-satellite links are fundamental for achieving collaborative observation between satellites, data relay transmission, and dynamic mission scheduling. To efficiently utilize inter-satellite link resources, it is essential to quickly and accurately calculate the "time window" during the mission planning phase to ensure communication conditions between satellites are met. For constellations with a large number of satellites or mission scenarios requiring long-term simulations, the real-time performance and accuracy of inter-satellite communication window calculations directly determine the efficiency and quality of mission planning.

[0003] Traditional inter-satellite window calculations mainly employ a fixed-step numerical advancement method (brute-force search). This method faces a dilemma between computational accuracy and efficiency: if the step size is too small, the computational load for full-time simulations increases dramatically, resulting in significant time consumption; if the step size is too large, it is easy to miss short-time windows during the high-speed relative motion of two satellites or lead to inaccurate boundary positioning, making it difficult to meet real-time planning requirements.

[0004] In recent years, existing adaptive variable step size methods have provided an acceleration approach, but most are based on empirical formulas or simple geometric fitting, lacking a rigorous theoretical definition of the relative motion dynamics of satellites. Especially when dealing with complex Earth occlusion constraints, existing methods struggle to provide definite safe step size boundaries, limiting their application in high-reliability mission planning. Summary of the Invention

[0005] To address the shortcomings of the aforementioned technologies, this invention provides an adaptive and rapid calculation method for inter-satellite communication windows for remote sensing satellite missions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for calculating inter-satellite communication windows for remote sensing satellite missions, comprising the following steps:

[0008] Step 1: Set the orbital parameters and simulation time period of the satellite constellation, and establish a geometric constraint model for inter-satellite communication that considers Earth's obstruction and maximum distance limitations;

[0009] Step 2: Based on the principles of orbital dynamics, analyze and derive the dynamic boundary parameters that characterize the relative motion of the constellation. The dynamic boundary parameters include the upper bound of the distance change rate and the upper bound of the line-of-sight tangent point height change rate.

[0010] Step 3: At the current simulation moment, calculate the geometric margin and determine the communication visibility based on the relative state of the two satellites;

[0011] Step 4: Combine the geometric margin and the dynamic boundary parameters to calculate the adaptive propulsion step size that satisfies each constraint condition at the current moment;

[0012] Step 5: If the visibility state changes before and after the advance, perform a precise boundary search within the advance step size to determine the precise boundary of the communication window.

[0013] Step 6: Repeat steps 3 to 5 until the simulation ends, and output the inter-satellite communication window data.

[0014] Furthermore, in step 2, the dynamic boundary parameters include: calculating the satellite's maximum orbital speed at perigee based on the vitality formula. :

[0015] (1)

[0016] in, The gravitational constant of Earth, For the semi-major axis of the track, The orbital eccentricity;

[0017] Set maximum distance variation The relative velocity limit when two satellites meet head-on in orbit:

[0018] (2)

[0019] Based on the envelope theorem, the instantaneous rate of change of the maximum tangent point height is set. For the satellite's instantaneous orbital velocity:

[0020] (8)

[0021] in, This is a preset safety factor used to compensate for calculation errors and perturbation effects.

[0022] Furthermore, in step 4, the adaptive propagation step size that satisfies each constraint condition at the current moment is calculated. The specific process is as follows:

[0023] First, calculate the prediction step size that satisfies the distance constraint. and prediction step size that satisfies occlusion constraints :

[0024] (9)

[0025] (10)

[0026] in, This represents the inter-satellite distance at the current moment. As a constraint on maximum communication distance, The current tangent height. Safety height constraints for shielding the Earth;

[0027] Take the height of the tangent point at the previous moment. and Earth occlusion safety height constraints The minimum value in the interval is used to obtain the basic step size, and the minimum value is then compared with the preset minimum step size. and maximum step size By comparing the results, the final adaptive propulsion step size is obtained:

[0028] (11).

[0029] Furthermore, in step 5, the precise boundary search employs a numerical iteration method; when a visibility state transition is detected, the time before the advancement is used. and the moment after advancement The initial interval is set; the state at the midpoint of the interval is calculated and the visibility is determined. Based on the visibility result, the search interval is reduced by half; steps 3 to 5 are repeated until the interval length is less than the preset time precision threshold, and the final midpoint time is output as the boundary of the communication window.

[0030] Furthermore, in step 3, at each moment of the simulation propagation... Calculate the position vectors of the two satellites based on the satellite orbit model. , ;

[0031] Calculate the inter-satellite distance at the current time The altitude of the point of tangency between the interstellar line and the Earth's center. If both conditions are met and If both satellites are visible at the current moment and within the communication window, they are determined to be invisible; otherwise, they are determined to be invisible. Simultaneously, the geometric margin between the current state and the constraint boundary is calculated. and the geometric margin from the occlusion boundary .

[0032] The advantages of this invention over existing technologies are as follows: This method is applicable to orbit window analysis and planning for inter-satellite communication missions of remote sensing satellites, and can significantly reduce the amount of computation and improve planning efficiency while ensuring computational accuracy; it rigorously derives the upper bound of the rate of change of distance and tangent point height as dynamic boundary parameters based on orbital dynamics principles and the envelope theorem; it constructs an adaptive step-size calculation mechanism using the current geometric margin and boundary parameters, achieving rapid advancement with variable step size while ensuring that constraints are not violated; and it accurately locks the window boundary by combining state transition detection and iterative search strategies, effectively solving the problem of high computational resource consumption and difficulty in maintaining accuracy in traditional fixed-step-size search in complex multi-satellite scenarios. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0034] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0035] The present invention provides a method for calculating inter-satellite communication windows for remote sensing satellite missions, comprising the following steps:

[0036] Step 1: Set the orbital parameters and simulation time period of the satellite constellation, and establish a geometric constraint model for inter-satellite communication that considers Earth's obstruction and maximum distance limitations;

[0037] Step 2: Based on the principles of orbital dynamics, analyze and derive the dynamic boundary parameters characterizing the relative motion of the constellation, including the upper bound of the distance change rate and the upper bound of the line-of-sight tangent point height change rate;

[0038] Step 3: At the current simulation moment, calculate the geometric margin and determine the communication visibility based on the relative state of the two satellites;

[0039] Step 4: Combine the geometric margin and the dynamic boundary parameters to calculate the adaptive propulsion step size that satisfies each constraint condition at the current moment;

[0040] Step 5: If the visibility state changes before and after the advance, perform a precise boundary search within the advance step size to determine the precise boundary of the communication window.

[0041] Step 6: Repeat steps 3 to 5 until the simulation ends, and output the inter-satellite communication window data.

[0042] Furthermore, step 1 specifically includes: setting the remote sensing satellite constellation and mission environment parameters. First, Earth model parameters are defined, including the Earth's gravitational constant. Earth's radius as well as Perturbation coefficients. Next, satellite orbital parameters are defined, using the Kepler orbital six-root number system. Describe the initial state of each satellite. Finally, set communication mission constraint thresholds, including maximum communication distance constraints. Earth occlusion safety height constraints .

[0043] Furthermore, step 2 specifically includes: constructing dynamic boundary parameters based on the envelope theorem. This is the core computational basis of this invention. First, the maximum velocity of the satellite at perigee in its elliptical orbit is calculated according to the vitality formula. :

[0044] (1)

[0045] in, The gravitational constant of Earth, For the semi-major axis of the track, Let be the orbital eccentricity.

[0046] Next, the physical upper bounds of the rates of change for the two types of constraints are derived analytically:

[0047] 1. Upper bound of the rate of change of distance Considering the worst-case scenario where two satellites meet head-on in orbit at perigee speeds, the relative speed limit is set to twice the maximum speed of a single satellite.

[0048] (2)

[0049] 2. Upper bound of height change rate : That is, the instantaneous rate of change of the maximum tangent point height This invention demonstrates that the instantaneous rate of change of the line-of-sight tangency point altitude is strictly limited by the instantaneous orbital velocity of the satellite. The specific derivation process is as follows:

[0050] Let the position vectors of the two satellites be respectively and The position vector of any point on the line connecting the two stars can be obtained through the scaling parameter. Represented as a linear combination:

[0051] (3)

[0052] The point of tangency of the line of sight is the point on the line closest to the Earth's center, and its corresponding parameters are... satisfy Minimum. Tangent height Regarding time The total derivative is:

[0053] (4)

[0054] For the Earth's radius, Let be the tangent point position parameter, and let This is the radial unit vector at the point of tangency. Since the point of tangency is an extreme point far from the Earth's center, the position vector... It must be perpendicular to the direction of the connecting line, that is... .

[0055] According to the envelope theorem, the tangency point position parameter The change over time does not contribute to the first derivative of the objective function value (height), so the total derivative above simplifies to:

[0056] (5)

[0057] in, , Let be the velocity vectors of the two satellites. Using the Cauchy-Schwarz inequality and the triangle inequality, the upper bound of the modulus of the rate of change of altitude can be obtained:

[0058] (6)

[0059] because ,and Therefore:

[0060] (7)

[0061] The above derivation proves that the rate of change of the tangent point altitude cannot exceed the satellite's own orbital speed. To compensate for discretization truncation errors and... The small deviations introduced by the perturbation model are addressed by introducing a safety factor. (range of values) Finally, the maximum tangent height change rate parameter is set as follows:

[0062] (8)

[0063] Furthermore, step 4 specifically includes: calculating an adaptive propagation step size that balances efficiency and safety. At the current simulation moment... The predicted step size for satisfying a single constraint is calculated based on the geometric margin. For distance constraints, the safe distance step size, i.e., the predicted step size for the distance constraint, is calculated. :

[0064] (9)

[0065] in, This represents the inter-satellite distance at the current moment. For the maximum distance variation, Maximum communication distance constraint;

[0066] For occlusion constraints, calculate the height safety step size, which is the prediction step size that satisfies the occlusion constraints. :

[0067] (10)

[0068] in, The current tangent height. Safety height constraints for shielding the Earth;

[0069] The minimum of the two values ​​is taken to obtain the basic step size, and then compared with the preset minimum step size. and maximum step size By comparing the results, the final adaptive propulsion step size is obtained:

[0070] (11)

[0071] Furthermore, step 5 specifically includes: precise window boundary locking based on numerical methods, such as the bisection method. When the algorithm uses an adaptive step size... Proceed to the next moment If a change in visibility is detected (i.e., from invisible to visible, or vice versa), it indicates that the start or end boundary of the communication window is within the interval. Inside. At this point, initiate the binary iterative search process: calculate visibility by taking the midpoint of the interval, and reduce the search interval by half based on the result. Repeat this process N times until the interval length is less than the preset time precision threshold, and output the final midpoint time as the precise boundary of the communication window.

[0072] Reference Figure 1 As shown, this embodiment illustrates the specific implementation process of the inter-satellite communication window calculation method for remote sensing satellite missions described above. The steps of this method are as follows:

[0073] 1) Set the orbital parameters of the satellite constellation and the relevant parameters for communication missions:

[0074] First, establish a simulation environment and define the Earth's gravity model. Perturbation model) and related constants (Earth radius) Gravitational constant Define the initial orbital elements for each satellite in the satellite constellation. Define the geometric constraints of the communication mission, including the maximum communication distance constraint. Earth occlusion safety height constraints Initialize the simulation start time. and end time .

[0075] 2) Based on the principles of orbital dynamics, the dynamic boundary parameters of the entire constellation are calculated analytically:

[0076] To achieve safe adaptive variable step-size calculations, a physical upper bound on the rate of change of the constraints must be obtained. First, the maximum orbital velocity of the satellite at perigee in its elliptical orbit is calculated using the vitality formula. Next, two key rate limits are derived: setting the maximum distance variation. The relative velocity limit when the two stars meet head-on; the instantaneous rate of change of the maximum tangent point altitude is set. Here, we introduce the envelope theorem to prove that the instantaneous rate of change of the height of the line-of-sight tangency point is strictly limited by the radial projection of the satellite's orbital velocity.

[0077] 3) At the current simulation moment, calculate the geometric margin and determine communication visibility:

[0078] At every moment of simulation advancement Calculate the position vectors of the two satellites based on the satellite orbit model. , Calculate the current inter-satellite Euclidean distance. The altitude of the point of tangency between the interstellar line and the Earth's center. If both conditions are met... and If both satellites are visible at the current moment and within the communication window, they are considered invisible; otherwise, they are considered invisible. Simultaneously, the geometric margin between the current state and the constraint boundary is calculated. and the geometric margin from the occlusion boundary .

[0079] 4) Calculate the adaptive propulsion step size and execute state-based propulsion by combining geometric margins and dynamic boundary parameters:

[0080] Using the geometric margin obtained in step 3 and the dynamic boundary parameters obtained in step 2, calculate the safe distance step size. and occlusion safety step length The minimum of the two values ​​is taken to obtain the basic step size, and then compared with the preset minimum step size. and maximum step size By comparing the results, the final adaptive propulsion step size is obtained. The simulation time was advanced to... .

[0081] 5) Detect visibility state transitions and perform precise boundary searches:

[0082] Determine the timing after the advancement The visibility state. If Time and Inconsistent visibility states at any given moment (abrupt changes) indicate that the start or end boundary of the communication window lies within the interval. Inside. At this point, the binary iterative search strategy is initiated: the visibility is calculated by taking the midpoint of the interval, and the search interval is halved based on the result. This process is repeated until the interval length is less than the preset time precision threshold, thereby accurately locking the window boundary. Steps 3 to 5 above are repeated until the simulation ends, and the start and end timetable of all inter-satellite communication windows is output.

[0083] The following example illustrates this concept using a constellation system consisting of five low Earth orbit (LEO) satellites:

[0084] Step 1: Set satellite constellation and mission-related parameters. First, the scenario is set as a constellation of near-circular orbit remote sensing satellites (N=5 satellites) operating at altitudes ranging from approximately 620km to 920km. Considering the J2 Earth perturbation effect, the simulation time period is set to 24 hours (86400 seconds). Communication mission constraints are set as follows: maximum inter-satellite link communication distance. Earth's occlusion safe height The physical constants are based on the WGS-84 model, including the Earth's gravitational constant. .

[0085] Step 2: Analyze and calculate the dynamic boundary parameters.

[0086] To ensure the completeness of the algorithm, the physical upper bound of the rate of change of the constraints needs to be calculated. First, the maximum orbital speed of the satellites in the constellation at perigee is calculated based on the vitality formula. :

[0087] ;

[0088] Based on this velocity, the dynamic boundary parameters for this scenario are derived. The maximum relative velocity limit between the two stars is then set. To determine the maximum rate of change of the tangent point altitude when the two stars meet head-on, a limit is set for the superposition of their velocities. The upper bound of the radial projection of the orbital velocity (taking a safety factor). ):

[0089] ;

[0090] ;

[0091] These two physical upper bounds and This provides a rigorous theoretical safety benchmark for subsequent adaptive step size calculations.

[0092] Step 3: Perform adaptive step size calculation and advancement.

[0093] The simulation program at every moment Based on the current interstellar distance and tangent height Calculate the geometric margin and, in conjunction with the boundary parameters from step 2, calculate the adaptive propulsion step size. :

[0094] ;

[0095] in, Set to 300 seconds. The time limit is set to 1 second. In the "idle" area outside the window, the algorithm automatically uses a large step size for rapid jumps; in the critical area of ​​the window, the step size is automatically reduced to maintain accurate tracking of the constraint boundary.

[0096] Step 4: Detect state transitions and lock window boundaries.

[0097] When the algorithm progresses to the next time step, if a change in visibility state is detected, a binary iterative search is initiated. and Using the initial interval as an example, through N=8 iterations, the positioning accuracy at the start and end times of the window is converged to [value missing]. Within the range, thus precisely locking the start time of the communication window. and end time .

[0098] Step 5: Simulation results and performance analysis.

[0099] After 24 hours of simulation, this method detected 47 valid inter-satellite communication windows in the constellation, with a total duration of approximately 13.76 hours. To verify the effectiveness of the method, a comparative experiment was conducted with the traditional full-exhaustive brute-force search method with a sampling interval of 10 seconds. Experimental results show that the number of windows detected by this method is exactly the same as that of the brute-force search method, achieving 100% recall and precision, with no missed detections or false alarms. In terms of computational efficiency, the traditional brute-force search method takes approximately 0.61 seconds, while this method takes only 0.02 seconds, improving the computational speed by approximately 30 times. Furthermore, thanks to the binary iterative strategy, the average positioning error for the start and end times of the windows is controlled to around 2.4 seconds. In summary, the method proposed in this invention significantly reduces computational costs while maintaining high accuracy, meeting the dual requirements of real-time performance and accuracy for large-scale constellation mission planning.

[0100] As can be seen from the above embodiments, the present invention can construct an adaptive step size based on the orbital dynamics boundary, and generate large-scale, high-quality inter-satellite communication window planning schemes quickly and at low cost.

[0101] This invention has many specific applications. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for calculating inter-satellite communication windows for remote sensing satellite missions, characterized in that, Includes the following steps: Step 1: Set the orbital parameters and simulation time period of the satellite constellation, and establish a geometric constraint model for inter-satellite communication that considers Earth's obstruction and maximum distance limitations; Step 2: Based on the principles of orbital dynamics, analyze and derive the dynamic boundary parameters that characterize the relative motion of the constellation. The dynamic boundary parameters include the upper bound of the distance change rate and the upper bound of the line-of-sight tangent point height change rate. Step 3: At the current simulation moment, calculate the geometric margin and determine the communication visibility based on the relative state of the two satellites; Step 4: Combine the geometric margin and the dynamic boundary parameters to calculate the adaptive propulsion step size that satisfies each constraint condition at the current moment; Step 5: If the visibility state changes before and after the advance, perform a precise boundary search within the advance step size to determine the precise boundary of the communication window. Step 6: Repeat steps 3 to 5 until the simulation ends, and output the inter-satellite communication window data.

2. The method according to claim 1, characterized in that, In step 2, the dynamic boundary parameters include: calculating the satellite's maximum orbital speed at perigee based on the vitality formula. : （1） in, The gravitational constant of Earth, For the semi-major axis of the track, The orbital eccentricity; Set maximum distance variation The relative velocity limit when two satellites meet head-on in orbit: （2） Based on the envelope theorem, the instantaneous rate of change of the maximum tangent point height is set. For the satellite's instantaneous orbital velocity: （8） in, This is a preset safety factor used to compensate for calculation errors and perturbation effects.

3. The method according to claim 2, characterized in that, In step 4, the adaptive propagation step size that satisfies each constraint condition at the current moment is calculated. The specific process is as follows: First, calculate the prediction step size that satisfies the distance constraint. and prediction step size that satisfies occlusion constraints : （9） （10） in, This represents the inter-satellite distance at the current moment. As a constraint on maximum communication distance, The current tangent height. Safety height constraints for shielding the Earth; Take the height of the tangent point at the previous moment. and Earth occlusion safety height constraints The minimum value in the interval is used to obtain the basic step size, and the minimum value is then compared with the preset minimum step size. and maximum step size By comparing the results, the final adaptive propulsion step size is obtained: （11）。 4. The method according to claim 3, characterized in that, In step 5, the precise boundary search employs a numerical iteration method; when a visibility state transition is detected, the time before the advancement is used. and the moment after advancement The initial interval is set; the state at the midpoint of the interval is calculated and the visibility is determined. Based on the visibility result, the search interval is reduced by half; steps 3 to 5 are repeated until the interval length is less than the preset time precision threshold, and the final midpoint time is output as the boundary of the communication window.

5. The method according to claim 4, characterized in that, In step 3, at each moment of the simulation propagation... Calculate the position vectors of the two satellites based on the satellite orbit model. , ; Calculate the inter-satellite distance at the current time The altitude of the point of tangency between the interstellar line and the Earth's center. If both conditions are met and If both satellites are visible at the current moment and within the communication window, they are determined to be invisible; otherwise, they are determined to be invisible. Simultaneously, the geometric margin between the current state and the constraint boundary is calculated. and the geometric margin from the occlusion boundary .

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