An on-board planning method for autonomous orbit maintenance of ultra-low earth orbit satellites

Abstract

The application provides an on-board planning method for autonomous orbit maintenance of an ultra-low earth orbit satellite. It relates to the field of satellite navigation. The following steps are performed: the start time of a new orbit maintenance plan and the time length of the new orbit maintenance plan are determined cooperatively; the end time of the new orbit maintenance plan is calculated based on the start time and the time length; it is judged whether the end time of the new orbit maintenance plan is less than or equal to the end time of the current traversed task-free period; if not, the new orbit maintenance plan is determined again; if yes, it is further judged whether the end time of the new orbit maintenance plan exceeds the end time of the orbit maintenance window; if not, the new orbit maintenance plan is inserted into the end of the orbit maintenance plan sequence, the average semi-major axis after the execution of the orbit maintenance plan sequence is estimated based on the updated orbit maintenance plan sequence, the average semi-major axis is compared with a preset height upper boundary to update a height state judgment flag; then the subsequent new orbit maintenance plan is determined repeatedly until a preset planning end condition is reached.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation, and in particular to an onboard planning method for autonomous orbit maintenance of ultra-low orbit satellites. Background Technology

[0002] Very low Earth orbit (VLEO) satellites operate in low Earth orbit at altitudes of approximately 300 to 180 kilometers. Due to their low altitude and high atmospheric drag, their orbital altitude decays rapidly. VLEO satellites typically use high-specific-impulse electric propulsion for orbit maintenance. However, due to low thrust and high power consumption, electric propulsion requires multiple orbits and operations to achieve the required orbital maintenance, constrained by the satellite's energy resources. This places significant pressure on ground control and operations for VLEO satellites. Compared to the traditional model of "ground-based orbit maintenance planning and satellite-based program execution," autonomous orbit maintenance is more conducive to the long-term management and use of VLEO satellites in orbit.

[0003] To achieve autonomous orbit maintenance for ultra-low Earth orbit (UEO) satellites using electric propulsion, the satellite can employ either a ground-triggered, onboard orbit maintenance plan or a real-time planning method based on satellite status feedback. The former is a semi-autonomous approach, requiring ground control support for orbit maintenance planning. The latter achieves higher orbit maintenance accuracy but suffers from uncertainties regarding the triggering timing and planning window, and can only generate single or short-term orbit maintenance plans. This makes it difficult for ground control to obtain onboard orbit maintenance plans in a timely manner, impacting routine ground control operations such as ephemeris prediction, debris collision warning, and telemetry and data transmission for UEO satellites. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention aims to provide an onboard planning method for autonomous orbit maintenance of ultra-low orbit satellites, which can provide multiple orbit maintenance plans within a planning window at once, thus meeting the needs of ground operations and control for timely acquisition of onboard orbit maintenance plans and daily related operations.

[0005] To achieve the above-mentioned objectives, this invention provides an onboard planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites. When orbit maintenance planning is triggered, the method obtains the nearest orbit maintenance window after the trigger time, as well as the remaining sequence of no-task periods after the previous orbit maintenance planning, and performs the following steps:

[0006] Based on the preset altitude status determination flag, the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, the preset minimum interval between adjacent orbit maintenance plans, and the currently traversed no-task period in the no-task period sequence, the start time of the new orbit maintenance plan is determined collaboratively; the orbit maintenance plan sequence includes at least one planned orbit maintenance plan arranged in chronological order; the altitude status determination flag is used to indicate whether the satellite has reached the preset upper altitude boundary.

[0007] The duration of the new orbit maintenance plan is determined collaboratively based on the longest single propulsion time and the maximum allowable propulsion time determined by the satellite's altitude status after the completion of the orbit maintenance plan sequence.

[0008] Based on the start time and duration, the end time of the newly added track maintenance plan is calculated;

[0009] Determine whether the end time of the newly added track maintenance plan is less than or equal to the end time of the currently traversed no-task period:

[0010] If not, abandon the current calculation and iterate to the next no-task period, redetermine and calculate the start time, duration and end time of the new track maintenance plan, and repeat until the end time of the new track maintenance plan is less than or equal to the end time of the currently iterated no-task period.

[0011] If so, it is determined that the newly added track maintenance plan can be inserted into the no-task period, and it is further determined whether the end time of the newly added track maintenance plan exceeds the end time of the track maintenance window:

[0012] If so, then this track maintenance planning will end;

[0013] If not, the newly added track maintenance plan is inserted at the end of the track maintenance plan sequence, and the average semi-major axis after the execution of the track maintenance plan sequence is estimated based on the updated track maintenance plan sequence. The average semi-major axis is then compared with the preset upper boundary of height to update the height status determination flag. Then, the subsequent newly added track maintenance plans are repeatedly determined until the preset planning end condition is reached.

[0014] According to one technical solution of the present invention, a preset offset time difference is provided between the trajectory planning trigger time and the start time of the nearest trajectory planning window after the trajectory planning trigger time;

[0015] Each of the stated track-keeping windows is consecutive in time and has the same duration. The trigger time interval between two adjacent track-keeping planning trigger times is consistent with the duration of the stated track-keeping window.

[0016] According to a technical solution of the present invention, the judgment process for triggering orbit planning includes:

[0017] Obtain the current satellite time; the satellite time includes: clock data generated by the satellite's local clock source, and time data calculated based on an external time reference source and synchronized to the satellite.

[0018] The difference between the current satellite time and the pre-configured trigger reference time is calculated, and the resulting difference is moduloed by the trigger time interval.

[0019] When the result of the modulo operation is zero, it is determined that the dimensional orbit planning is triggered.

[0020] According to one technical solution of the present invention, the process of collaboratively determining the start time of the newly added track maintenance plan includes:

[0021] Based on the difference between the trajectory planning trigger time and the offset time, the start time of the trajectory window is calculated, and based on the start time and duration of the trajectory window, the end time of the trajectory window is calculated, thereby obtaining the trajectory window.

[0022] Based on the altitude status determination flag, the earliest permissible start time of the orbit maintenance plan is determined as follows: When the altitude status determination flag indicates that the satellite has reached the preset upper altitude boundary, the latest time is selected from the sum of the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, and the minimum interval between adjacent orbit maintenance plans, and the sum of the end time of the orbit maintenance plan sequence and the maximum permissible free decay time of the orbit, as the earliest permissible start time; when the altitude status determination flag indicates that the satellite has not reached the preset upper altitude boundary, the latest time is selected from the sum of the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, and the minimum interval between adjacent orbit maintenance plans, as the earliest permissible start time.

[0023] Choose the later time between the start time of the currently traversed no-task period and the earliest allowed start time as the start time of the new track maintenance plan.

[0024] According to one technical solution of the present invention, the process of obtaining the maximum permissible free decay time of the orbit includes:

[0025] The average semi-major axis of the satellite after the completion of the orbit maintenance plan sequence is calculated by subtracting it from the preset lower altitude boundary to obtain the current remaining amount of the attenuable semi-major axis.

[0026] Obtain the estimated half-major axis decay rate of atmospheric drag;

[0027] The maximum allowable free decay time of the orbit is obtained by calculating the ratio of the current remaining amount of the decayable semi-major axis to the decay rate of the atmospheric drag semi-major axis.

[0028] According to one technical solution of the present invention, the process of obtaining the estimated half-major axis attenuation rate of atmospheric drag includes:

[0029] The satellite's descending node passage sequence and propulsion record sequence are acquired; the descending node passage sequence includes at least one descending node passage event ordered by time; the descending node passage event includes two adjacent sets of orbit determination and navigation data when the satellite passes through the descending node; the orbit determination and navigation data includes navigation satellite time, the satellite's position component and velocity component relative to the Earth-fixed frame; the propulsion record sequence includes at least one propulsion record ordered by time.

[0030] Based on the last descending intersection event and the N-orbit preceding descending intersection event in the descending intersection sequence, the navigation satellite time in the corresponding orbit determination and navigation data is obtained and the difference is calculated to obtain the estimated time period as the denominator of the time period.

[0031] Based on the position and velocity components corresponding to the terminal descent intersection event and the N-orbit pre-descent intersection event, the average semi-major axis of the terminal descent intersection and the average semi-major axis of the N-orbit pre-descent intersection are calculated and the difference is obtained. Then, the change in the average semi-major axis caused by the total working stroke of electric propulsion during the estimated time period calculated based on the propulsion record in the propulsion record sequence is subtracted to obtain the net natural decay as the numerator.

[0032] The estimated atmospheric drag half-major axis decay rate is obtained by calculating the ratio of the net natural decay to the denominator of the time period.

[0033] According to one technical solution of the present invention, the process of obtaining the descending intersection sequence includes:

[0034] The satellite's time and orbit determination / navigation data are acquired at set time steps;

[0035] Based on whether the Z component of the position component in two adjacent sets of orbit determination and navigation data changes from positive to negative, it is determined whether the satellite has passed through the descending intersection point; and each time it is determined that the satellite has passed through the descending intersection point, a descending intersection point passing event is recorded and added to the descending intersection point passing event sequence in sequence.

[0036] According to a technical solution of the present invention, the process of obtaining the propulsion recording sequence includes:

[0037] The satellite's time and propulsion thrust data are acquired at a set time step; the propulsion thrust data includes thrust values.

[0038] Based on the changes in thrust values ​​in adjacent propulsion thrust data, it is determined whether the satellite has started propulsion, is propulsing, and has ended propulsion in sequence; and each time it is determined that the satellite has started propulsion, is propulsing, and has ended propulsion in sequence, a propulsion record is recorded and added to the propulsion record sequence in sequence; the propulsion record includes the corresponding start propulsion time, end propulsion time, average thrust value during propulsion, and remaining propellant mass.

[0039] According to one technical solution of the present invention, the process of collaboratively determining the duration of the newly added track maintenance plan includes:

[0040] Based on the start time of the new orbit maintenance plan and the average semi-major axis of the satellite after the end of the orbit maintenance plan sequence, the average semi-major axis of the start time of the new orbit maintenance plan is calculated.

[0041] The maximum permissible propulsion time is calculated using the average semi-major axis at the start of the orbit maintenance plan and the upper boundary of the altitude.

[0042] Between the preset longest single advance time and the maximum allowable advance time, the smaller time value is selected as the duration of the new orbit maintenance plan.

[0043] According to a technical solution of the present invention, the process of obtaining the maximum permissible propulsion time includes:

[0044] The difference between the upper boundary of the height and the average semi-major axis at the start of the new orbit maintenance plan is used to obtain the maximum allowable lifting height of the semi-major axis as the numerator.

[0045] The summation of the estimated atmospheric drag semi-major axis decay rate and the nominal lift rate determined by the nominal thrust of electric propulsion, the dry mass of the satellite, and the current remaining propellant mass obtained from the propulsion record sequence yields the resultant motion semi-major axis change rate as the denominator.

[0046] The maximum permissible lifting height of the semi-major axis is calculated by ratioing the rate of change of the resultant motion semi-major axis to obtain the maximum permissible propulsion time.

[0047] This invention provides an on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites, which has the following beneficial effects:

[0048] (1) This invention enables ultra-low orbit satellites to achieve fully autonomous electric propulsion orbit maintenance;

[0049] (2) This invention facilitates timely acquisition of the onboard electric propulsion orbit maintenance plan of ultra-low orbit satellites by ground operation and control;

[0050] (3) This invention is beneficial for ground operation and control to carry out daily tasks such as ephemeris prediction, debris collision warning, telemetry and control data transmission for ultra-low orbit satellites in conjunction with the on-board electric propulsion orbit maintenance plan. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0052] Figure 1 The illustration shows a rolling planning sequence diagram in an onboard planning method for autonomous orbit maintenance of an ultra-low orbit satellite according to an embodiment of the present invention.

[0053] Figure 2 The flowchart illustrates an onboard planning method for autonomous orbit maintenance of a very low Earth orbit satellite according to one embodiment of the present invention.

[0054] Figure 3 This schematically illustrates a flowchart of determining the next orbit maintenance plan during a non-mission period in an onboard planning method for autonomous orbit maintenance of a very low Earth orbit satellite according to an embodiment of the present invention. Detailed Implementation

[0055] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0056] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims. Figures 1-3 As shown; Detailed Implementation

[0057] In this implementation, several preliminary steps are required, including real-time online acquisition of relevant satellite operational data, acquisition of descending node sequences, and acquisition of propulsion record sequences, which serve as data sources for the onboard planning method for autonomous orbit maintenance of ultra-low Earth orbit (ULE) satellites. Although these steps occur before the onboard planning method for autonomous orbit maintenance of ULE satellites in this implementation, they are decoupled and performed asynchronously in terms of timeline and execution thread.

[0058] I. Acquire relevant satellite operation data online in real time, including:

[0059] It acquires the latest satellite time, orbit determination and navigation data, and electric propulsion thrust data from the satellite every second.

[0060] Specifically, navigation data is denoted as ,in, When used as a navigation satellite, , , This represents the position component of the satellite relative to the Earth-fixed system. , , This represents the velocity component of the satellite relative to the Earth-fixed system.

[0061] II. Obtaining the sequence of descending intersections, the process includes:

[0062] The satellite's time and orbit determination / navigation data are acquired at set time steps;

[0063] Based on whether the Z component of the position component in two adjacent sets of orbit determination and navigation data changes from positive to negative, it is determined whether the satellite has passed through the descending intersection point; and each time it is determined that the satellite has passed through the descending intersection point, a descending intersection point passing event is recorded and added to the descending intersection point passing event sequence in sequence.

[0064] Specifically, satellite crossing-landing node events are calculated based on the obtained orbit determination and navigation data, forming a sequence of crossing-landing node events, including:

[0065] Step 01-1) Determine whether a descending intersection event has occurred based on the navigation data obtained from the two previous and subsequent steps.

[0066] The newly acquired navigation data is denoted as The last navigation data obtained was k represents the current time (star time);

[0067] like and If so, it is determined that a descending intersection event has occurred, and the navigation parameters for this event are... , Calculate the current descending intersection event according to steps 01-2) to 01-8); otherwise, no descending intersection event has occurred.

[0068] Step 01-2) Calculate the longitude of the descending node :

[0069]

[0070] Step 01-3) Calculate the descending intersection direction vector :

[0071]

[0072] Steps 01-4) Calculate the angle between the satellite position vectors before and after the descending intersection point. :

[0073]

[0074] In the formula, , .

[0075] Steps 01-5) Calculate the descending intersection direction vector Satellite position vector before intersection with descent point The included angle :

[0076]

[0077] Steps 01-6) Calculate the time of the descending intersection. :

[0078]

[0079] Steps 01-7) Calculate the longitude deviation of the descending intersection point relative to the nominal trajectory. :

[0080] If a satellite needs to maintain its ground trajectory in addition to maintaining its orbital altitude, then...

[0081]

[0082] In the formula, The longitude of the descending intersection point of the nominal trajectory is set in advance.

[0083] otherwise, .

[0084] Steps 01-8) Calculate the average descending node longitude deviation and deviation drift rate :

[0085] If satellites need to maintain their ground trajectory in addition to maintaining their orbital altitude, then continuous tracking, including the current descending node event, should be used. Calculation of the longitude difference of the descending node for each descending node event

[0086] ,

[0087] otherwise, , .

[0088] Steps 01-9) Form a new sequence of events passing through descending intersections:

[0089] The calculated cross-intersection event will be used in this calculation. Add it to the end of the current descending intersection event sequence to obtain a new descending intersection time sequence. The last event in the new sequence is... for The sequence of events passing through descending intersections is denoted as... , It consists of several events that cross the descending intersection point, arranged in chronological order of the time of the crossing of the descending intersection point. These events are denoted as follows: .

[0090] III. Obtaining the propulsion record sequence, the process includes:

[0091] The satellite's time and thrust data are acquired at a set time step; the thrust data includes thrust values.

[0092] Based on the changes in thrust values ​​in adjacent propulsion thrust data, it is determined whether the satellite has started, is propulsing, and has ended propulsion in sequence; and each time it is determined that the satellite has started, is propulsing, and has ended propulsion in sequence, a propulsion record is recorded and added to the propulsion record sequence in sequence; the propulsion record includes the corresponding start propulsion time, end propulsion time, average thrust value during propulsion, and remaining propellant mass.

[0093] Specifically, the electric propulsion operation is recorded based on the obtained electric propulsion thrust data, forming an electric propulsion operation record sequence, including:

[0094] Step 02-1) Determine the operating status of electric propulsion:

[0095] The received thrust data is recorded as When electric propulsion is not working When electric propulsion is working .

[0096] The newly acquired thrust data is denoted as The last thrust data obtained was The operating status of the electric propulsion system is determined based on the thrust data received from the previous two tests.

[0097] like and If the current satellite time is used, then the electric propulsion system is considered to have started operating, and the current satellite time is taken as the start time of electric propulsion. Record the electric propulsion operation status according to steps 02-2) to 02-5).

[0098] like and If so, it can be determined that electric propulsion is in operation.

[0099] like and If the electric propulsion system is activated, then the operation is considered complete.

[0100] Step 02-2) Record the start time of electric propulsion. :

[0101] When it is determined that electric propulsion has started working, at this time (i.e., when electric propulsion starts working), When the time changes from 0 to >0, the satellite time (the moment when the time changes to >0 is taken as the start time of electric propulsion) is used as the start time of electric propulsion. .

[0102] Step 02-3) Calculate the average thrust during electric propulsion operation. :

[0103] During electric propulsion operation, thrust data is acquired every second. For average thrust Perform recursive calculations

[0104]

[0105] Steps 02-4) Record the end time of electric propulsion operation. :

[0106] When it is determined that the electric propulsion has finished working, at this time (i.e., when the electric propulsion has finished working), The satellite time (the moment when the value changes from >0 to 0, with the final moment when the value is >0 as the end time of electric propulsion operation) is used as the end time of electric propulsion operation. .

[0107] Steps 02-5) Update the remaining working propellant mass after the electric propulsion operation is completed:

[0108] When it is determined that the electric propulsion operation has ended, the remaining working fluid mass Estimate using the following formula:

[0109]

[0110] In the formula, The remaining working fluid mass before electric propulsion begins operation. This refers to the mass of working fluid consumed per second during electric propulsion.

[0111] Steps 02-6) Forming a new electric propulsion work record sequence:

[0112] Once the electric propulsion operation is deemed complete, record the operation results. Adding this to the end of the current electric propulsion work record sequence results in a new electric propulsion work record sequence, with the last record in the new sequence being... for The electric propulsion work record is as follows: The electric propulsion work record sequence is recorded as follows: , It consists of several electric propulsion work records arranged in chronological order of the start time of thrust output.

[0113] This embodiment provides an onboard planning method for autonomous orbit maintenance of a very low Earth orbit (VLEO) satellite. When orbit maintenance planning is triggered, the method obtains the nearest orbit maintenance window after the trigger time, as well as the remaining sequence of no-task periods after the last orbit maintenance planning, and then performs the following steps:

[0114] Step 1: Based on the preset altitude status determination flag, the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, the preset minimum interval between adjacent orbit maintenance plans, and the currently traversed no-task period in the no-task period sequence, collaboratively determine the start time of the new orbit maintenance plan; the orbit maintenance plan sequence includes at least one planned orbit maintenance plan arranged in chronological order; the altitude status determination flag is used to indicate whether the satellite has reached the preset upper altitude boundary.

[0115] Step 2: Based on the longest single propulsion time and the maximum allowable propulsion time determined by the satellite's altitude status after the end of the orbit maintenance program sequence, collaboratively determine the duration of the new orbit maintenance program;

[0116] Step 3: Based on the start time and duration, calculate the end time of the newly added orbit maintenance plan;

[0117] Step 4: Determine if the end time of the newly added track maintenance plan is less than or equal to the end time of the currently traversed no-task period:

[0118] If not, abandon the current calculation and iterate to the next no-task period, redetermine and calculate the start time, duration and end time of the new track maintenance plan, and repeat until the end time of the new track maintenance plan is less than or equal to the end time of the currently iterated no-task period.

[0119] If so, it is determined that the new track maintenance plan can be inserted into the no-task period, and then proceed to step five;

[0120] Step 5: Further determine whether the end time of the newly added track maintenance plan exceeds the end time of the track maintenance window:

[0121] If so, then this track maintenance planning will end;

[0122] If not, insert the new track maintenance plan at the end of the track maintenance plan sequence, and estimate the average semi-major axis after the track maintenance plan sequence ends based on the updated track maintenance plan sequence. Then compare the average semi-major axis with the preset upper boundary of height to update the height status judgment flag. Then return to step one to repeat the determination of subsequent new track maintenance plans until the preset planning end condition is reached.

[0123] There is a preset offset time difference between the timing of the track planning trigger and the start time of the nearest track planning window after the timing of the track planning trigger;

[0124] Each track window is consecutive in time and has the same duration. The trigger time interval between two adjacent track planning trigger times is consistent with the duration of the track window.

[0125] The process for triggering orbit planning includes:

[0126] Obtain the current satellite time; satellite time includes: clock data generated by the satellite's local clock source, and time data calculated based on an external time reference source and synchronized to the satellite.

[0127] The difference between the current satellite time and the pre-configured trigger reference time is calculated, and the resulting difference is moduloed by the trigger time interval.

[0128] When the result of the modular arithmetic is zero, the dimensional orbit planning is triggered.

[0129] In step one, collaboratively determining the start time of the new orbit maintenance plan includes the following process:

[0130] Based on the difference between the timing of the trajectory planning trigger and the offset time, the start time of the trajectory window is calculated, and based on the start time and duration of the trajectory window, the end time of the trajectory window is calculated, thus obtaining the trajectory window.

[0131] Based on the altitude status determination indicator, the earliest permissible start time for the orbit maintenance plan is determined: when the altitude status determination indicator indicates that the satellite has reached the preset upper altitude boundary, the latest time is selected from the sum of the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence and the minimum interval between adjacent orbit maintenance plans, and the sum of the end time of the orbit maintenance plan sequence and the maximum permissible free decay time of the orbit, as the earliest permissible start time; when the altitude status determination indicator indicates that the satellite has not reached the preset upper altitude boundary, the latest time is selected from the sum of the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence and the minimum interval between adjacent orbit maintenance plans, as the earliest permissible start time.

[0132] Choose the later time between the start time of the currently traversed no-task period and the earliest allowed start time as the start time of the new orbit maintenance plan.

[0133] The process for obtaining the maximum permissible free decay time of the orbit includes:

[0134] After the orbit maintenance program ends, the average semi-major axis of the satellite is calculated by subtracting it from the preset lower altitude boundary to obtain the current remaining amount of the attenuable semi-major axis.

[0135] Obtain the estimated half-major axis decay rate of atmospheric drag;

[0136] The maximum allowable free decay time of the orbit is obtained by calculating the ratio of the current remaining decayable semi-major axis to the decay rate of the semi-major axis due to atmospheric drag.

[0137] The process of obtaining the estimated half-major axis decay rate of atmospheric drag includes:

[0138] Acquire the satellite's descending node passage sequence and propulsion record sequence; the descending node passage sequence includes at least one descending node passage event ordered by time; the descending node passage event includes two adjacent sets of orbit determination and navigation data when the satellite passes through the descending node; the orbit determination and navigation data includes navigation satellite time, the satellite's position component and velocity component relative to the Earth-fixed frame; the propulsion record sequence includes at least one propulsion record ordered by time;

[0139] Based on the last descending intersection event in the descending intersection sequence and the N-orbit descending intersection event, the navigation satellite time in the corresponding orbit determination and navigation data is obtained and the difference is calculated to obtain the estimated time period as the denominator of the time period.

[0140] Based on the position and velocity components of the terminal descending intersection event and the N-orbit forward descending intersection event, the average semi-major axis of the terminal descending intersection and the average semi-major axis of the N-orbit forward descending intersection are calculated and the difference is obtained. Then, the change in the average semi-major axis caused by the total working stroke of electric propulsion during the estimated time period calculated based on the propulsion record sequence is subtracted to obtain the net natural decay as the numerator.

[0141] The estimated half-major axis decay rate of atmospheric drag is obtained by calculating the ratio of the net natural decay to the denominator of the time period.

[0142] Step two, which involves collaboratively determining the duration of the newly added orbit maintenance plan, includes the following process:

[0143] Based on the start time of the new orbit maintenance plan and the average semi-major axis of the satellite after the end of the orbit maintenance plan sequence, the average semi-major axis of the start time of the new orbit maintenance plan is calculated.

[0144] The maximum allowable propulsion time was calculated using the average semi-major axis and the upper boundary of altitude at the start of the orbit maintenance plan.

[0145] Choose the smaller time value from the preset longest single advance time and maximum allowable advance duration as the duration of the new orbit maintenance plan.

[0146] The process of obtaining the maximum permissible propulsion time as described above includes:

[0147] The difference between the upper boundary of the height and the average semi-major axis at the start of the new orbit maintenance plan is used to obtain the maximum allowable lifting height of the semi-major axis as the numerator.

[0148] The summation of the estimated atmospheric drag semi-major axis decay rate and the nominal lift rate determined by the nominal thrust of electric propulsion, the dry mass of the satellite, and the current remaining propellant mass obtained from the propulsion record sequence yields the resultant motion semi-major axis change rate as the denominator.

[0149] The maximum permissible lifting height of the semi-major axis is calculated by ratioing it to the rate of change of the resultant motion semi-major axis, thus obtaining the maximum permissible propulsion time.

[0150] Specifically, based on the acquired satellite time, orbit maintenance planning is triggered according to a pre-designed rolling planning sequence, and a planning window is set. The orbit maintenance plan within the planning window is calculated based on the descending intersection sequence from step 01) and the electric propulsion work record sequence from step 02), forming an orbit maintenance plan sequence, including:

[0151] The orbit maintenance plan is recorded as ,in, When the planned orbital period begins, The planned orbital maintenance will end at this time.

[0152] The sequence of orbit maintenance plans is denoted as It consists of several orbital plans arranged in chronological order of their start times. .

[0153] Rolling planning sequence such as Figure 1 As shown, the details are as follows:

[0154] The trigger time for autonomous orbit maintenance planning is [time], and the trigger period is [period]. Time period For the triggered orbit planning window, The window start time, The window ends at the specified time, and the window duration is specified in the provided text. With trigger cycle Consistent; Window start time Relative to the trigger time Forward bias (Offset time difference), i.e. The time interval between the window's start time and the trigger time. Used for ground operation control to verify new rail maintenance plans within the planning window.

[0155] The specific steps of track maintenance planning include:

[0156] Step 1) Based on the latest received satellite time With the pre-set trigger reference star time Determine if orbit planning is triggered:

[0157] When the satellite is in time With reference star time Satisfying the relation When this occurs, it is determined that orbital planning is triggered, and star-time is triggered. Perform the planning calculations for this track maintenance planning according to steps 2) to 7); otherwise, determine that track maintenance planning has not been triggered.

[0158] Step 2) Obtain satellite data during periods of no service:

[0159] Data on periods of no service on the satellite are obtained from the onboard mission planning system to form a sequence of periods of no service.

[0160] No business hours are recorded as ,in, The start time is during periods with no business activity. The start and end times for periods without business activity.

[0161] The time series with no business is denoted as It consists of several periods of no business activity arranged in chronological order of their start time. .

[0162] Step 3) Set the triggered track planning window:

[0163] The current rail maintenance planning window will be planned according to the rolling planning sequence. The start time is set to The end time is set to .

[0164] Step 4) Set the upper and lower boundaries (i.e., upper height boundary and lower height boundary) of the average semi-major axis for this track maintenance plan:

[0165] Based on the satellite orbit maintenance strategy, set the upper boundary of the average semi-major axis of the orbit maintenance plan. Lower boundary .

[0166] If the satellite only maintains its orbital altitude, the upper and lower boundaries of its mean semi-major axis are set according to the following formula:

[0167]

[0168]

[0169] In the formula, For the pre-set reference average semi-major axis, The height difference is set in advance.

[0170] Optionally, if the satellite needs to maintain its ground trajectory in addition to maintaining its orbital altitude, the upper and lower boundaries of its mean semi-major axis shall be set according to the following formula:

[0171]

[0172] In the formula, For reference, the average semi-major axis correction amount is as follows:

[0173]

[0174] In the formula, This is the correction amount for the previous period. This is the correction amount for this period. The maximum correction amount for the nominal average semi-major axis is preset. , Take the sequence of events that have descended intersections Mid-to-late events The value, , They are respectively , Correction factor:

[0175]

[0176] In the formula, The nominal average semi-major axis, The day of the intersection of Earth's relative nominal orbit. For the pre-set completion Adjust the required number of days for the intersection.

[0177] Step 5) Estimate the average semi-major axis natural decay rate:

[0178] Based on the current descending intersection sequence and electric propulsion work record sequence Estimated average semi-major axis natural decay rate :

[0179]

[0180] In the formula, , Sequences passing through descending intersection points Mid-to-late events and Pre-orbiting events Navigation parameters navigation star time ; , Based on the descending intersection sequence Mid-to-late events and Pre-orbiting events Navigation parameters When calculating the navigation star The average semi-major axis; This represents the average change in the semi-major axis; Time period Mean semi-major axis change caused by the total stroke of internal electric propulsion:

[0181]

[0182] In the formula, The gravitational constant of Earth; The pre-set reference average semi-major axis; For satellite dry mass; The remaining working fluid mass for electric propulsion; Electric propulsion work record sequence Chinese records In time period Working hours within the period; Records of each electric propulsion operation The average thrust.

[0183] Step 6) Estimate the average semi-major axis after all the track maintenance plan sequences have been executed:

[0184] The average semi-major axis after all the track maintenance plan sequences have been executed, i.e., the average semi-major axis at the end of the current track maintenance plan sequence. Calculate using the following formula:

[0185]

[0186] In the formula, For the latest navigation data When using the navigation satellite; Based on the latest navigation data Calculate the average semi-major axis; For the current orbit maintenance plan sequence The last orbit maintenance project in China The end time; The estimated change in the average semi-major axis caused by the total working stroke of electric propulsion:

[0187]

[0188] In the formula, This refers to the nominal thrust of electric propulsion. For the current orbit maintenance plan queue China's various orbital maintenance plans When using navigation satellites The duration of subsequent track maintenance.

[0189] Step 7) Calculate the track maintenance plan within the track maintenance planning window:

[0190] Using a recursive approach, the calculations are performed one by one within the current track maintenance planning window. The track maintenance plan includes steps 7-1) to 7-7).

[0191] Step 7-1) Calculate the earliest start time of the next orbital maintenance plan. :

[0192]

[0193] In the formula, , The minimum interval between adjacent orbital maintenance plans (affected by satellite energy constraints and determined by satellite on-orbit usage requirements). The upper boundary is the predicted threshold. A value of 1 indicates that the upper boundary has been reached, and a value of 0 indicates that the upper boundary has not been reached.

[0194] Step 7-2) Determine the next track maintenance plan during the no-task period:

[0195] In accordance with the principle of early track maintenance, the next track maintenance plan should be determined during periods without tasks. (including steps 7-2-1) to 7-2-6).

[0196] Step 7-2-1) In the no-task time sequence The end time of the star is determined in the middle. Later The earliest no-task period The next track maintenance plan will be determined starting from this period.

[0197] Step 7-2-2) Determine the start time of the next orbit maintenance plan. :

[0198]

[0199] Step 7-2-3) Estimation The mean semi-major axis at time 1 :

[0200]

[0201] Step 7-2-4) Determine the duration of the next track maintenance plan. :

[0202]

[0203] In the formula, This represents the longest single operating time for electric propulsion.

[0204] Step 7-2-5) Calculate the end time of the next orbit maintenance plan. :

[0205]

[0206] Step 7-2-6) If the planned end time No later than the end of the no-task period Then the next orbit maintenance plan Once confirmed, repeat steps 7-2-1) to 7-2-6) to confirm each subsequent no-task period until the next track maintenance plan is obtained. .

[0207] Step 7-3) According to the next track maintenance plan End of Star Time Determine whether this track maintenance plan has concluded:

[0208] like If the plan is successful, the current track maintenance planning will continue; otherwise, the current track maintenance planning will end.

[0209] Step 7-4) Forming a new orbit maintenance plan sequence:

[0210] The next track maintenance plan Add it to the end of the current orbit maintenance plan sequence to obtain a new orbit maintenance plan sequence. The last plan in the new sequence is... for End time of the new sequence for .

[0211] Step 7-5) Calculate the end time of the new orbit maintenance plan sequence. average semi-major axis :

[0212]

[0213] Step 7-6) Set the upper boundary prediction flag :

[0214]

[0215] Step 7-7) Repeat steps 7-1) to 7-6) to continue calculating the next track maintenance plan until the current track maintenance plan is completed.

[0216] Furthermore, it should be noted that the present invention can be provided as a method, apparatus, or computer program product. Therefore, embodiments of the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, embodiments of the present invention can take the form of a computer program product implemented on one or more computer-usable storage media containing computer-usable program code.

[0217] Embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0218] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0219] It should also be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0220] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. An on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites, characterized in that, When track maintenance planning is triggered, obtain the nearest track maintenance window after the trigger time, as well as the remaining sequence of no-task periods after the last track maintenance planning, and perform the following steps: Based on the preset altitude status determination flag, the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, the preset minimum interval between adjacent orbit maintenance plans, and the currently traversed no-task period in the no-task period sequence, the start time of the new orbit maintenance plan is determined collaboratively; the orbit maintenance plan sequence includes at least one planned orbit maintenance plan arranged in chronological order; the altitude status determination flag is used to indicate whether the satellite has reached the preset upper altitude boundary. The duration of the new orbit maintenance plan is determined collaboratively based on the longest single propulsion time and the maximum allowable propulsion time determined by the satellite's altitude status after the completion of the orbit maintenance plan sequence. Based on the start time and duration, the end time of the newly added track maintenance plan is calculated; Determine whether the end time of the newly added track maintenance plan is less than or equal to the end time of the currently traversed no-task period: If not, abandon the current calculation and iterate to the next no-task period, redetermine and calculate the start time, duration and end time of the new track maintenance plan, and repeat until the end time of the new track maintenance plan is less than or equal to the end time of the currently iterated no-task period. If so, it is determined that the newly added track maintenance plan can be inserted into the no-task period, and it is further determined whether the end time of the newly added track maintenance plan exceeds the end time of the track maintenance window: If so, then this track maintenance planning will end; If not, the newly added track maintenance plan is inserted at the end of the track maintenance plan sequence, and the average semi-major axis after the execution of the track maintenance plan sequence is estimated based on the updated track maintenance plan sequence. The average semi-major axis is then compared with the preset upper boundary of height to update the height status determination flag. Then, the subsequent newly added track maintenance plans are repeatedly determined until the preset planning end condition is reached.

2. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 1, characterized in that, There is a preset offset time difference between the trigger time of the track planning and the start time of the nearest track planning window after the trigger time; Each of the stated track-keeping windows is consecutive in time and has the same duration. The trigger time interval between two adjacent track-keeping planning trigger times is consistent with the duration of the stated track-keeping window.

3. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 2, characterized in that, The process of triggering orbit planning includes: Obtain the current satellite time; the satellite time includes: clock data generated by the satellite's local clock source, and time data calculated based on an external time reference source and synchronized to the satellite. The difference between the current satellite time and the pre-configured trigger reference time is calculated, and the resulting difference is moduloed by the trigger time interval. When the result of the modulo operation is zero, it is determined that the dimensional orbit planning is triggered.

4. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 1, characterized in that, The process of collaboratively determining the start time of the newly added orbit maintenance plan includes: Based on the difference between the trajectory planning trigger time and the offset time, the start time of the trajectory window is calculated, and based on the start time and duration of the trajectory window, the end time of the trajectory window is calculated, thereby obtaining the trajectory window. Based on the altitude status determination flag, the earliest permissible start time of the orbit maintenance plan is determined as follows: When the altitude status determination flag indicates that the satellite has reached the preset upper altitude boundary, the latest time is selected from the sum of the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, and the minimum interval between adjacent orbit maintenance plans, and the sum of the end time of the orbit maintenance plan sequence and the maximum permissible free decay time of the orbit, as the earliest permissible start time; when the altitude status determination flag indicates that the satellite has not reached the preset upper altitude boundary, the latest time is selected from the sum of the start time of the orbit maintenance window, the end time of the orbit maintenance plan sequence, and the minimum interval between adjacent orbit maintenance plans, as the earliest permissible start time. The later time is selected from the start time of the currently traversed no-task period and the earliest allowed start time as the start time of the new track maintenance plan.

5. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 4, characterized in that, The process of obtaining the maximum allowable free decay time of the orbit includes: The average semi-major axis of the satellite after the completion of the orbit maintenance plan sequence is calculated by subtracting it from the preset lower altitude boundary to obtain the current remaining amount of the attenuable semi-major axis. Obtain the estimated half-major axis decay rate of atmospheric drag; The maximum allowable free decay time of the orbit is obtained by calculating the ratio of the current remaining amount of the decayable semi-major axis to the decay rate of the atmospheric drag semi-major axis.

6. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 5, characterized in that, The process of obtaining the estimated half-major axis decay rate of atmospheric drag includes: The satellite's descending node passage sequence and propulsion record sequence are acquired; the descending node passage sequence includes at least one descending node passage event ordered by time; the descending node passage event includes two adjacent sets of orbit determination and navigation data when the satellite passes through the descending node; the orbit determination and navigation data includes navigation satellite time, the satellite's position component and velocity component relative to the Earth-fixed frame; the propulsion record sequence includes at least one propulsion record ordered by time. Based on the last descending intersection event and the N-orbit preceding descending intersection event in the descending intersection sequence, the navigation satellite time in the corresponding orbit determination and navigation data is obtained and the difference is calculated to obtain the estimated time period as the denominator of the time period. Based on the position and velocity components corresponding to the terminal descent intersection event and the N-orbit pre-descent intersection event, the average semi-major axis of the terminal descent intersection and the average semi-major axis of the N-orbit pre-descent intersection are calculated and the difference is obtained. Then, the change in the average semi-major axis caused by the total working stroke of electric propulsion during the estimated time period calculated based on the propulsion record in the propulsion record sequence is subtracted to obtain the net natural decay as the numerator. The estimated atmospheric drag half-major axis decay rate is obtained by comparing the net natural decay with the denominator of the time period.

7. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 6, characterized in that, The process of obtaining the descending intersection sequence includes: The satellite's time and orbit determination / navigation data are acquired at set time steps; Based on whether the Z component of the position component in two adjacent sets of orbit determination and navigation data changes from positive to negative, it is determined whether the satellite has passed through the descending intersection point; and each time it is determined that the satellite has passed through the descending intersection point, a descending intersection point passing event is recorded and added to the descending intersection point passing event sequence in sequence.

8. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 6, characterized in that, The process of obtaining the propulsion record sequence includes: The satellite's time and propulsion thrust data are acquired at a set time step; the propulsion thrust data includes thrust values. Based on the changes in thrust values ​​in adjacent propulsion thrust data, it is determined whether the satellite has started propulsion, is propulsing, and has ended propulsion in sequence; and each time it is determined that the satellite has started propulsion, is propulsing, and has ended propulsion in sequence, a propulsion record is recorded and added to the propulsion record sequence in sequence; the propulsion record includes the corresponding start propulsion time, end propulsion time, average thrust value during propulsion, and remaining propellant mass.

9. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 1, characterized in that, The process of collaboratively determining the duration of the newly added orbit maintenance plan includes: Based on the start time of the new orbit maintenance plan and the average semi-major axis of the satellite after the end of the orbit maintenance plan sequence, the average semi-major axis of the start time of the new orbit maintenance plan is calculated. The maximum permissible propulsion time is calculated using the average semi-major axis at the start of the orbit maintenance plan and the upper boundary of the altitude. Between the preset longest single advance time and the maximum allowable advance time, the smaller time value is selected as the duration of the new orbit maintenance plan.

10. The on-board planning method for autonomous orbit maintenance of ultra-low Earth orbit satellites according to claim 8 or 9, characterized in that, The process of obtaining the maximum permissible propulsion time includes: The difference between the upper boundary of the height and the average semi-major axis at the start of the new orbit maintenance plan is used to obtain the maximum allowable lifting height of the semi-major axis as the numerator. The summation of the estimated atmospheric drag semi-major axis decay rate and the nominal lift rate determined by the nominal thrust of electric propulsion, the dry mass of the satellite, and the current remaining propellant mass obtained from the propulsion record sequence yields the resultant motion semi-major axis change rate as the denominator. The maximum permissible lifting height of the semi-major axis is calculated by ratioing the rate of change of the resultant motion semi-major axis to obtain the maximum permissible propulsion time.

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