A Method for Planning the Rendezvous Launch Window of a Near-Earth Spacecraft

Abstract

The present invention discloses a method for planning the rendezvous launch window of a near-Earth spacecraft, which can analyze the launch windows of the tracking and target spacecraft when neither the target spacecraft nor the tracking spacecraft has been launched. First, corresponding to the initial epoch moment, an objective orbit with the initial right ascension of the ascending node corresponding to the initial epoch moment is established. A variation curve of the angle between the orbital plane and the illumination position vector within a period of time is constructed; according to the illumination conditions and the time period during the launch of the on-orbit spacecraft, the time periods that meet the illumination constraints are screened out. The illumination position vector is the position vector from the center of mass of the on-orbit spacecraft to the center of mass of the sun. According to the launch site positions of the target spacecraft and the tracking spacecraft, the launch descending orbit zero windows of the tracking spacecraft and the target spacecraft are found, which are the launch window lists corresponding to the initial right ascension of the ascending node at the initial epoch moment. Traverse the initial right ascension of the ascending node. For different initial right ascensions of the ascending node, launch window lists corresponding to different initial right ascensions of the ascending node are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of spacecraft mission planning, and in particular to a method for planning the rendezvous launch window of a near-earth spacecraft. Background Art

[0002] The mission analysis and planning of the rendezvous launch window of near-earth orbit spacecraft play a very crucial role in the success or failure of space missions. However, the mission analysis and planning of the launch window are also a complex task. The mission analysis and planning of the launch window need to be carried out on the basis of comprehensively considering each subsystem of the spacecraft and space constraint conditions, including illumination constraint conditions, sensor constraint conditions, coplanar constraint conditions, phase constraint conditions, etc. On this basis, according to the actual mission situation, based on the space orbit calculation and launch window calculation methods, the launch window of the spacecraft is solved.

[0003] Zhu Renzhang et al. studied the selection and determination of the launch time of spacecraft rendezvous and docking considering illumination constraint conditions including orbital coplanarity, the solar panel sunlight incidence angle, and the illumination of the final translation section, and proposed a method for selecting and determining the launch time of the chasing spacecraft and the target spacecraft. Zhang Liyan et al. preliminarily studied related issues such as the constraint conditions of the launch window of the rendezvous and docking mission, the phase difference of the launch time interval, etc. Li Gefei et al. established a calculation method and process for the rendezvous and docking launch window under various constraint conditions such as the orbital sunlight incidence angle, the sunlight suppression angle of the optical navigation equipment, and orbital coplanarity, and gave the annual launch window set of the spacecraft through simulation examples. Li Haiyang associated the constraint conditions with the launch time, and established a mathematical model for solving the launch time and a calculation process for the launch window. The above studies have studied the illumination, coplanarity, phase and other constraint conditions and launch window calculation methods of spacecraft rendezvous missions, but most of them are for the analysis of the launch window of the chasing spacecraft, and the target spacecraft mainly analyzes the illumination constraint conditions. There are few studies on the comprehensive analysis of the launch windows of the chasing spacecraft and the target spacecraft. In addition, the above studies mostly calculate based on the analysis of multiple constraint conditions and the method of finding the intersection of launch windows, involving a large number of space orbit calculations such as illumination, coplanarity, and phase constraint analysis. Due to the different algorithms and models used, the results given by the simulation examples are not universal and are difficult to guide engineering practice tasks.

[0004] At present, the software and methods for mission analysis and planning of the launch window of near-earth orbit spacecraft rendezvous missions are generally for the situation where the target spacecraft is already in orbit, and the launch window of the chasing spacecraft is planned. However, for the situation where the target spacecraft has not been launched yet, there are few studies on comprehensively analyzing the launch windows of the chasing spacecraft and the target spacecraft. Summary of the Invention

[0005] In view of this, the present invention provides a method for planning the rendezvous launch window of a near-Earth spacecraft, which can comprehensively analyze the launch windows of a tracking spacecraft and a target spacecraft when neither the target spacecraft nor the tracking spacecraft has been launched.

[0006] To achieve the above object, the technical solution of the present invention for launch window planning includes the following steps:

[0007] Step 1: Corresponding to the initial epoch moment, establish the initial right ascension of the ascending node, and establish the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment.

[0008] Construct the variation curve of the angle between the orbital plane and the illumination position vector within a period of time; screen out the time periods that meet the illumination constraints according to the illumination conditions and the in-orbit spacecraft launch period.

[0009] The illumination position vector is the position vector from the centroid of the in-orbit spacecraft to the centroid of the sun.

[0010] According to the launch site positions of the target spacecraft and the tracking spacecraft, find the launch descending orbit zero windows of the tracking spacecraft and the target spacecraft, that is, obtain the launch window list corresponding to the initial right ascension of the ascending node at the initial epoch moment.

[0011] Step 2: Traverse the initial right ascension of the ascending node. For different initial right ascensions of the ascending node, use the method of Step 1 to obtain the launch window lists corresponding to different initial right ascensions of the ascending node.

[0012] Furthermore, neither the tracking spacecraft nor the target spacecraft has been put into orbit, and the tracking spacecraft and the target spacecraft are located at different launch sites.

[0013] Furthermore, corresponding to the initial epoch moment, establish the initial right ascension of the ascending node, and establish the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment. Specifically: corresponding to the initial epoch moment, establish the initial right ascension of the ascending node, and according to the established six orbital elements, establish the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment; different initial conditions correspond to the establishment of different target orbits.

[0014] Furthermore, construct the variation curve of the angle between the orbital plane and the illumination position vector within a period of time. Specifically: according to the established target orbit, use the vector calculation tool and angle calculation tool of STK to obtain the variation curve of the angle between the orbital plane and the illumination position vector within a period of time.

[0015] Furthermore, according to the launch site positions of the target spacecraft and the tracking spacecraft, find the launch descending orbit zero windows of the tracking spacecraft and the target spacecraft. Specifically:

[0016] The spacecraft includes a target spacecraft and a tracking spacecraft.

[0017] Using the STK software, establish the information of the launch site of the spacecraft. Use the vector calculation tool of the STK software to establish the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft on the launch site entity, and use the angle tool to establish the included angle between the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft.

[0018] When the included angle between the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft is 90°, it is the launch zero window of the launch site relative to the established spacecraft orbit; judge whether the launch zero window is for a descending orbit or an ascending orbit, and select the launch zero window for the descending orbit.

[0019] Furthermore, judging whether the launch zero window is for a descending orbit or an ascending orbit is specifically as follows:

[0020] Using the vector calculation tool of the STK software, establish the angular momentum vector of the target orbit and the vector from the geocenter to the launch site. Use the vector calculation function of STK to calculate the cross product of the angular momentum vector of the target orbit and the vector from the geocenter to the launch site. Use the report function of STK to check the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system;

[0021] If the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system is positive, it means that the spacecraft flies from the southern hemisphere to the northern hemisphere, that is, the launch window at this point is the ascending orbit zero window;

[0022] If the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system is negative, it means that the spacecraft flies from the northern hemisphere to the southern hemisphere, that is, the launch window at this point is the descending orbit zero window.

[0023] Beneficial effects:

[0024] 1. The present invention provides a method for planning the rendezvous launch window of a near-earth spacecraft. For the on-orbit situation of the target spacecraft, by analyzing the illumination conditions, coplanarity conditions, and phase conditions during the proposed launch period, comprehensively analyze to find the zero window that meets the mission constraints; for the situation where the target spacecraft has not been launched, it is proposed to correspond the tracking spacecraft and the target spacecraft to a certain initial epoch moment, analyze the influence of different initial right ascensions of the ascending node on the launch mission window, and find the launch window that meets the constraint conditions. This method can be used for the analysis and planning of the launch window when the target spacecraft has not been launched, and realizes the comprehensive analysis of the launch windows of the tracking spacecraft and the target spacecraft.

[0025] 2. The present invention provides a method for planning the rendezvous launch window of a near-Earth spacecraft. In the case where neither the tracking spacecraft nor the target spacecraft has been launched, by corresponding the tracking spacecraft and the target spacecraft to a certain initial epoch, analyzing the influence of different initial right ascensions of the ascending node on the launch mission window, and finding a method for the launch window that meets the constraint conditions; this method comprehensively considers the actual situations of the launch sites and launch periods of the tracking spacecraft and the target spacecraft. The tracking spacecraft and the target spacecraft may be located at different launch sites, and the launch periods are also different due to objective factors. For this situation, this paper proposes a method for finding the launch window that meets the constraint conditions by corresponding the tracking spacecraft and the target spacecraft to a certain initial epoch and analyzing the influence of different initial right ascensions of the ascending node on the illumination constraint.

[0026] 3. A method for planning the rendezvous launch window of a near-Earth spacecraft provided by the present invention uses the analysis and calculation functions of STK to quickly realize the analysis and planning of the launch window under the comprehensive consideration of sunlight constraint, coplanarity constraint, and phase constraint conditions.

[0027] 4. A method for planning the rendezvous launch window of a near-Earth spacecraft provided by the present invention. The method for analyzing and planning the rendezvous mission window of a near-Earth spacecraft based on STK can quickly realize the mission and analysis of the launch window by using the built-in calculation function of the STK software. The mission planning results have high reliability and high precision.

[0028] 5. The present invention can be implemented based on the STK software without integrating multiple analysis software. Detailed implementation manners

[0029] The following describes the present invention in detail with reference to the embodiments.

[0030] The present invention provides a method for mission planning and analysis of the rendezvous launch window of a near-Earth spacecraft based on STK, which can be used for both the analysis and planning of the launch window when the target spacecraft is already in orbit and the analysis and planning of the launch window when the target spacecraft has not been launched. By using the analysis and calculation functions of STK, the analysis and planning of the launch window can be quickly realized under the comprehensive consideration of sunlight constraint, coplanarity constraint, and phase constraint conditions. For the case where the target spacecraft is in orbit, by analyzing the illumination conditions, coplanarity conditions, and phase conditions during the proposed launch period, a zero window that meets the mission constraints is comprehensively analyzed; for the case where the target spacecraft has not been launched, a method is proposed to find the launch window that meets the constraint conditions by corresponding the tracking spacecraft and the target spacecraft to a certain initial epoch and analyzing the influence of different initial right ascensions of the ascending node on the launch mission window.

[0031] The spacecraft launch window refers to the set of times that meet the requirements for spacecraft launch. For low Earth orbit rendezvous missions (low Earth orbit refers to orbits below 1,000 kilometers), the calculation of the launch window needs to comprehensively consider spatial information such as the azimuths of the sun, the Earth, and the spacecraft, equipment parameter information of the spacecraft sensor subsystem, and orbital information such as the coplanarity of the spacecraft orbit and the initial phase angle. Selecting the launch times for the target spacecraft and the chasing spacecraft is a complex task, with far more constraints and computational requirements than a single spacecraft launch.

[0032] Analysis of Constraint Conditions

[0033] (1) Illumination condition constraint: In space rendezvous missions, the optical measurement and sensitive equipment for rendezvous and docking is the source for obtaining the relative state information of spacecraft. During use, the impact of illumination conditions needs to be considered, namely the illumination suppression angle constraint. In addition, during the rendezvous mission, the sunlight constraints on subsystems such as spacecraft thermal control, energy, and GNC can be synthesized into the constraint of the angle between the solar vector and the orbital plane, namely the orbital solar illumination angle constraint, which can be synthesized into the illumination condition constraint. According to different missions and the performance of spacecraft subsystems, the illumination constraint conditions are also different, generally with values around [5° - 45°].

[0034] (2) Coplanarity constraint: A prerequisite for ensuring the implementation of the rendezvous and docking mission is to ensure that the orbits of the chasing spacecraft and the target spacecraft are coplanar, namely the coplanarity constraint.

[0035] (3) Phase constraint: On the premise of meeting the coplanarity constraint, the chasing spacecraft and the target spacecraft often need to adjust the phase to achieve spacecraft rendezvous and docking, reducing the relative distance and adjusting the relative attitude to meet the initial docking conditions. Adjusting the phase often requires a certain amount of time and spacecraft fuel. In order to be able to complete the rendezvous and docking mission within the specified time, it is usually required that the initial phase of the target spacecraft relative to the chasing spacecraft meet certain conditions, namely the phase constraint. Initial phase constraint conditions Initial given for the analysis and planning of the launch window mission of the target spacecraft already in orbit

[0036] For the case where the target spacecraft has been launched and is in orbit, that is, under the premise that the target orbit has been determined, a fixed launch site is used to complete the established launch that meets the coplanarity constraint. At this time, while the chasing spacecraft needs to meet the illumination constraint, coplanarity constraint, and phase constraint, it also needs to meet the zero-window launch constraint (in fact, the coplanarity constraint includes the zero-window launch constraint). Due to the continuous rotation of the Earth from west to east, for a fixed launch site, launch opportunities occur regularly over time. If the latitude of the launch site is less than the orbital inclination of the target orbit, there are two launch opportunities per day, namely ascending orbit launch and descending orbit launch. Due to the issue of rocket recovery, generally descending orbit launch is used, and the zero-window of descending orbit launch needs to be completed under the condition that the sub-satellite point trajectory of the on-orbit spacecraft passes through the established launch site.

[0037] For the analysis and planning of the in-orbit launch window mission of the target spacecraft, the calculations are usually carried out in the following steps:

[0038] (1) Calculate the zero-window moment of the chasing spacecraft:

[0039] Using STK software, establish the launch site information of the chasing spacecraft and the orbital information of the on-orbit spacecraft. Using the vector calculation tool of STK, establish the vector from the geocenter to the launch site and the angular momentum vector of the target spacecraft (target spacecraft) on the launch site entity. Using the angle tool, establish the included angle between the vector from the geocenter to the launch site and the angular momentum vector of the target spacecraft. Since the angular momentum of the target orbit is directly related to the target spacecraft orbit and perpendicular to the orbital plane, when the included angle between the vector from the geocenter to the launch site and the angular momentum vector of the target spacecraft is 90°, it is the launch zero-window of the launch site relative to the established target spacecraft orbit.

[0040] (2) Determine whether the zero-window is for a descending orbit or an ascending orbit:

[0041] Using the vector calculation tool of STK software, establish the angular momentum vector of the target orbit and the vector from the geocenter to the launch site. Using the vector calculation function of STK, calculate the cross product of the angular momentum vector of the target orbit and the vector from the geocenter to the launch site, and the velocity vector direction of the target spacecraft at the launch zero-window of the (chasing spacecraft) can be obtained. Using the report function of STK, check the sign of the component of the cross product calculation result on the Z-axis in the J2000 coordinate system.

[0042] If the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system is positive, it means that the spacecraft flies from the southern hemisphere to the northern hemisphere, that is, the launch window at this point is the ascending orbit zero-window;

[0043] If the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system is negative, it means that the spacecraft flies from the northern hemisphere to the southern hemisphere, that is, the launch window at this point is the descending orbit zero-window.

[0044] Select the descending return zero-window.

[0045] (3) Calculate the illumination conditions of the descending orbit zero-window:

[0046] Using the vector calculation tool of STK, establish the orbital plane of the target spacecraft and the position vector from the center of mass of the target spacecraft to the center of mass of the sun. Using the angle calculation tool of STK, establish the included angle between the position vector from the center of mass of the target spacecraft to the center of mass of the sun and the orbital plane of the target spacecraft. Through the report analysis function, obtain the change curve of this included angle during the launch period.

[0047] Based on the deorbiting zero-window time and the included angle change curve during the launch period calculated in the previous two steps, the launch windows that meet the deorbiting zero-window and illumination constraints are screened out.

[0048] (4) Calculate the initial phase conditions of the deorbiting zero-window:

[0049] Based on the planning results of the previous three steps, the launch windows that meet the deorbiting zero-window and illumination constraints are judged. The last step is to further screen the launch windows that meet the above-mentioned constraints to obtain the final set of launch windows that meet the initial phase conditions.

[0050] Using the report function of STK, the phase angles of the target spacecraft and the tracking spacecraft at the launch window moments that meet the above-mentioned deorbiting zero-window and illumination constraints are obtained, the initial phase difference is calculated, and the launch windows with the initial phase difference within the initial phase constraint conditions are screened out, which are the final launch windows.

[0051] Mission Analysis and Planning for Launch Windows when the Target Spacecraft has not been Launched

[0052] Compared with the situation where the target spacecraft is already in orbit, the mission analysis and planning of the launch window when the target spacecraft has not been launched is more complex. It is necessary to consider not only illumination constraints, coplanarity constraints, and initial phase, etc., but also comprehensively consider the actual situations of the launch sites and launch periods of the tracking spacecraft and the target spacecraft. The tracking spacecraft and the target spacecraft may be located at different launch sites, and the launch periods are different due to objective factors. For this situation, this paper proposes a method to find the launch window that meets the constraint conditions by corresponding the tracking spacecraft and the target spacecraft to a certain initial epoch moment and analyzing the influence of different initial right ascensions of the ascending node on the illumination constraints.

[0053] Step (1) Method for Calculating the Launch Windows that Meet the Illumination Constraints with the Right Ascension of the Ascending Node at the Initial Epoch Moment

[0054] Since neither the tracking spacecraft nor the target spacecraft has been put into orbit, and the rendezvous and docking mission needs to meet the coplanarity condition, the tracking spacecraft and the target spacecraft can be corresponding to a certain initial epoch moment for analysis according to this coplanarity constraint condition. The reason why the solution of the launch windows of the two spacecraft can be traversed and solved corresponding to a certain initial epoch is that the orbit forecasts of spacecraft on the same orbit are basically the same, and the most direct factor affecting the included angle between the orbit plane of the spacecraft and the direction of the solar vector is the initial right ascension of the ascending node at the time of orbit injection, and the initial right ascension of the ascending node is only related to the launch time.

[0055] Corresponding to a certain initial epoch moment, establish the initial right ascension of the ascending node. According to the established orbital elements such as the orbital inclination (six orbital elements), the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment can be established. Different initial conditions can establish different target orbits;

[0056] The initial moments of the target spacecraft and the tracking spacecraft are mapped to the epoch moment. The initial epoch moment is a fixed quantity, and the right ascension of the ascending node at the initial epoch is a variable.

[0057] For this established orbit, the vector calculation tool and angle calculation tool of STK can be used to obtain the variation curve of the angle between the orbital plane and the position vectors of the center of mass of the on-orbit spacecraft and the center of mass of the sun over a period of time. The time periods that meet the illumination constraints are selected according to the illumination conditions and the time period during the launch of the on-orbit spacecraft.

[0058] On this basis, according to the launch site positions of the target spacecraft and the tracking spacecraft, the launch descending orbit zero window for the tracking spacecraft and the target spacecraft is found. The specific method is as follows: The spacecraft includes the target spacecraft and the tracking spacecraft;

[0059] Using the STK software, the launch site information of the spacecraft is established. Using the vector calculation tool of the STK software, the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft are established on the launch site entity, and the angle between the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft is established using the angle tool;

[0060] When the angle between the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft is 90°, it is the launch zero window of this launch site relative to the established spacecraft orbit; Determine whether the launch zero window is for a descending orbit or an ascending orbit, and select the launch descending orbit zero window.

[0061] Determine whether the launch zero window is for a descending orbit or an ascending orbit, specifically as follows:

[0062] Using the vector calculation tool of the STK software, the angular momentum vector of the target orbit and the vector from the geocenter to the launch site are established. Using the vector calculation function of STK, the cross product of the target orbit angular momentum vector and the vector from the geocenter to the launch site is calculated. Using the report function of STK, check the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system;

[0063] If the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system is positive, it means that the spacecraft flies from the southern hemisphere to the northern hemisphere, that is, the launch window at this point is the ascending orbit zero window;

[0064] If the sign of the component of the cross product result on the Z-axis in the J2000 coordinate system is negative, it means that the spacecraft flies from the northern hemisphere to the southern hemisphere, that is, the launch window at this point is the descending orbit zero window.

[0065] Step (2) Traverse the right ascension of the ascending node to calculate the launch window

[0066] The list of launch windows obtained in the above step 1 corresponds to the right ascension of the ascending node at the initial epoch. Since the initial right ascension of the ascending node is the most direct factor affecting the angle between the orbital plane of the spacecraft and the direction of the solar vector, it is necessary to calculate the influence of different initial right ascensions of the ascending node on the launch windows, that is, by traversing the initial right ascension of the ascending node, for different initial right ascensions of the ascending node, use the method in the above step 1 to obtain the list of launch windows corresponding to different initial right ascensions of the ascending node. Finally, a list of launch windows corresponding to different initial right ascensions of the ascending node can be obtained.

[0067] The present invention can realize the analysis and planning of the rendezvous launch windows of near-earth spacecraft in two cases where the spacecraft is already in orbit and not yet launched; the present invention can be implemented based on the STK software without the need to integrate multiple analysis software; the mission planning results of the present invention have high reliability and high precision.

[0068] In summary, the above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for planning the rendezvous launch window of a near-Earth spacecraft, characterized in that, The launch window planning is carried out by including the following steps: Step 1: Corresponding to the initial epoch moment, establish the initial right ascension of the ascending node, and establish the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment; Construct the variation curve of the angle between the orbital plane and the illumination position vector within a period of time; Screen out the time periods that meet the illumination constraints according to the illumination conditions and the on-orbit spacecraft launch period segment; The illumination position vector is the position vector from the center of mass of the on-orbit spacecraft to the center of mass of the sun; According to the launch site positions of the target spacecraft and the tracking spacecraft, find the launch descending orbit zero window of the tracking spacecraft and the target spacecraft, that is, obtain the launch window list corresponding to the initial right ascension of the ascending node at the initial epoch moment; The specific method of finding the launch descending orbit zero window of the tracking spacecraft and the target spacecraft according to the launch site positions of the target spacecraft and the tracking spacecraft is as follows: The spacecraft includes a target spacecraft and a tracking spacecraft; Use the STK software to establish the launch site information of the spacecraft, use the vector calculation tool of the STK software to establish the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft on the launch site entity, and use the angle tool to establish the angle between the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft; When the angle between the vector from the geocenter to the launch site and the angular momentum vector of the spacecraft is 90°, it is the launch zero window of the launch site relative to the established spacecraft orbit; Judge whether the launch zero window is a descending orbit or an ascending orbit, and select the launch descending orbit zero window; Step 2: Traverse the initial right ascension of the ascending node. For different initial right ascensions of the ascending node, use the method in Step 1 to obtain the launch window list corresponding to different initial right ascensions of the ascending node.

2. The method according to claim 1, wherein Neither the tracking spacecraft nor the target spacecraft is in orbit, and the tracking spacecraft and the target spacecraft are located at different launch sites.

3. The method according to claim 1, wherein The specific method of corresponding to the initial epoch moment, establishing the initial right ascension of the ascending node, and establishing the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment is as follows: Corresponding to the initial epoch moment, establish the initial right ascension of the ascending node, and establish the target orbit corresponding to the initial right ascension of the ascending node at the initial epoch moment according to the established six orbital elements; Different initial conditions correspond to the establishment of different target orbits.

4. The method according to claim 1, wherein The specific method of constructing the variation curve of the angle between the orbital plane and the illumination position vector within a period of time is as follows: According to the established target orbit, use the vector calculation tool and the angle calculation tool of STK to obtain the variation curve of the angle between the orbital plane and the illumination position vector within a period of time.

5. The method according to claim 1, characterized in that, The specific method of judging whether the launch zero window is a descending orbit or an ascending orbit is as follows: Use the vector calculation tool of the STK software to establish the angular momentum vector of the target orbit and the vector from the geocenter to the launch site, use the vector calculation function of STK to calculate the cross product of the angular momentum vector of the target orbit and the vector from the geocenter to the launch site, and use the report function of STK to check the sign of the component of the cross product result on the Z axis in the J2000 coordinate system; If the sign of the component of the cross product result on the Z axis in the J2000 coordinate system is positive, it means that the spacecraft flies from the southern hemisphere to the northern hemisphere, that is, the launch window is the ascending orbit zero window; If the sign of the Z-axis component of the cross product result is negative in the J2000 coordinate system, it means that the spacecraft is flying from the Northern Hemisphere to the Southern Hemisphere, that is, the launch window is the descending orbit zero window.