Navigation trajectory calculation device, navigation trajectory calculation method and program

Abstract

This navigation trajectory computation device (1) comprises an observable region computation unit (201) and a navigation trajectory computation unit (202). The observable region computation unit (201) calculates an observable range that can be observed with a sensor (100) mounted in a spacecraft. The navigation trajectory computation unit (202) calculates a navigation trajectory that includes an observation starting point and an observation endpoint included in the observable range calculated by the observable region computation unit (201). The distance between the observation starting point and an approaching object being observed by the sensor (100) is greater than the distance between the observation endpoint and the approaching object.

Description

[Technical field]

[0001] The present disclosure relates to a navigation trajectory calculation device, a navigation trajectory calculation method, and a program. [Background technology]

[0002] Patent Document 1 describes a position estimation system including an optical sensor provided on a spacecraft that captures images continuously in a time series, and a control unit. The control unit includes a boundary surface direction acquisition unit, a first time acquisition unit, a line of sight angle acquisition unit that acquires a line of sight angle from the spacecraft to a target at the first time, a second time acquisition unit, a spacecraft travel distance acquisition unit between the first time and the second time, and a first target relative position estimation unit that estimates the relative position of the target with respect to the spacecraft at the first time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-59190 Summary of the Invention [Problem to be solved by the invention]

[0004] When a moving body uses optical sensors to navigate relative to an object in space, if the distance to the object is far, only information about the relative direction between the moving body and the object can be obtained. This navigation method is called Angles-Only Navigation (AON), and is not observable if the relative motion with the object follows linear dynamics. In the absence of observability, the final error depends on the initial estimation error and initial conditions, and the estimation error of the relative position and velocity cannot be reduced beyond a certain level even with long-term observation.

[0005] The device described in Patent Document 1 observes the vicinity of the boundary between the shadowed and sunlit areas, and estimates the relative position and speed of an approaching object from the time it reaches the boundary. This method requires observation of the vicinity of the boundary, and there is a problem in that it cannot estimate in a short time depending on the orbit altitude.

[0006] The present disclosure has been made in consideration of such problems, and aims to provide a navigation trajectory calculation device, a navigation trajectory calculation method, and a program that can reduce estimation errors in relative position and velocity without observing near the boundary surface between shaded and sunlit areas by making the distance between the observation start point and the approaching target greater than the distance between the observation end point and the approaching target. [Means for solving the problem]

[0007] In order to achieve the above object, a navigation trajectory calculation device according to the present disclosure includes an observable area calculation unit and a navigation trajectory calculation unit. The observable area calculation unit calculates an observable range that can be observed by a sensor mounted on a spacecraft. The navigation trajectory calculation unit calculates a navigation trajectory including an observation start point included in the observable range calculated by the observable area calculation unit and an observation end point included in the observable range. The distance between the observation start point and an approaching target observed by the sensor is greater than the distance between the observation end point and the approaching target. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a navigation trajectory calculation device, a navigation trajectory calculation method, and a program that can reduce estimation errors in relative position and velocity without observing near the boundary surface between shaded and sunlit areas by making the distance between the observation start point and the approaching target greater than the distance between the observation end point and the approaching target. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a configuration of a navigation trajectory calculation device according to a first embodiment. [Diagram 2] FIG. 1 is a diagram showing an observable area calculated by an observable area calculation unit according to the first embodiment; [Diagram 3]FIG. 1 is a diagram showing a navigation trajectory calculated by a navigation trajectory calculation unit according to the first embodiment; [Figure 4] FIG. 13 is a diagram showing an example of an initial estimation error and an estimation error at the observation end time in the first embodiment; [Diagram 5] FIG. 13 is a diagram showing another example of the initial estimation error and the estimation error at the observation end time in the first embodiment; [Figure 6] FIG. 1 shows a transition start point, an observation start point, and a transition orbit according to the first embodiment. [Figure 7] 1 is a flowchart showing a navigation trajectory calculation process executed by a navigation trajectory calculation device according to a first embodiment. [Figure 8] FIG. 13 is a diagram showing an example of an initial estimation error, an error after the start of observation, and an error after the end of observation in the third embodiment. [Figure 9] FIG. 13 is a diagram showing another example of the initial estimation error, the error after the start of observation, and the error after the end of observation in the third embodiment. [Figure 10] FIG. 13 is a diagram showing an observation start point, a maneuver point, and an observation end point according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) A navigation trajectory calculation device 1 according to a first embodiment of the present disclosure will be described with reference to Figs. 1 to 7. In the drawings, identical or corresponding parts are given the same reference numerals. The navigation trajectory calculation device 1 according to the embodiment is a device mounted on a spacecraft, and calculates a navigation trajectory O of the spacecraft to control the spacecraft.

[0011] Fig. 1 is a block diagram showing the configuration of a navigation trajectory calculation device 1 according to embodiment 1. As shown in Fig. 1, the navigation trajectory calculation device 1 includes a sensor 100 that observes an approaching target 3, a navigation trajectory determination unit 200 that determines a navigation trajectory O of a spacecraft based on an observable area R of the sensor 100, and an orbit injection unit 300 that injects the spacecraft into the navigation trajectory O determined by the navigation trajectory determination unit 200.

[0012] The sensor 100 is a device mounted on a spacecraft and observes an approaching target 3 to measure the relative position between the spacecraft and the approaching target 3. The sensor 100 may include an optical camera, but is not limited to this.

[0013] The navigation orbit determination unit 200 determines a navigation orbit O of the spacecraft based on the observable area R of the sensor 100. The navigation orbit determination unit 200 includes an observable area calculation unit 201 that calculates an observable area R that is an area in which the approaching target 3 is observable, and a navigation orbit calculation unit 202 that calculates the navigation orbit O of the spacecraft.

[0014] The observable area calculation unit 201 calculates the minimum observable distance L min , maximum observation distance L max Based on the positional relationship between the approaching target 3 and the sun S, the observable area R in which the approaching target 3 can be observed is calculated. Specifically, the observable area calculation unit 201 calculates an observable area R in which the approaching target 3 can be observed, with the approaching target 3 as the center and the distance to the approaching target 3 being the minimum observation distance L min Maximum observation distance L max The area that is not the backlit area B is calculated as the observable area R.

[0015] The approach target 3 is an object that is approached by a spacecraft equipped with the navigation trajectory calculation device 1, and may include spacecraft including artificial satellites, asteroids, and space debris, but is not limited to these.

[0016] 2 is a diagram showing a measurable area calculated by the measurable area calculation unit 201 of the navigation trajectory calculation device 1 according to the first embodiment. In FIG. 2, the measurable area R and the minimum observation distance L min , and the maximum observable distance L max Although the boundary surfaces are represented as spherical cross sections, the shape of these boundary surfaces is not limited to a sphere and may be any shape.

[0017] The observable area calculation unit 201 calculates the minimum observable distance L from the approachable distance to avoid collision with the approaching target 3, the initial estimated position error, and the safety factor. minWhen the approaching target 3 is a cooperative object, the observable area calculation unit 201 determines the initial estimated position error by downlinking the GPS positioning information of the approaching target 3. When the approaching target 3 is a non-cooperative object, the observable area calculation unit 201 determines the initial estimated position error from the observation results by a ground-based telescope or radar.

[0018] The observable area calculation unit 201 determines the maximum observable distance from the performance of the sensor 100 and the relative positional relationship with the sun S. Specifically, the observable area calculation unit 201 determines the maximum observable distance as the distance at which a sufficient amount of light is obtained to allow the sensor 100 to extract the approaching target 3 as a bright point.

[0019] Direct observation of the sun S with the sensor 100 may damage the imaging element included in the sensor 100, so to prevent this, the observable area calculation unit 201 excludes the backlit area, i.e., backlit area B, from the observable area R. The range of backlit area B depends on the viewing angle of the sensor 100.

[0020] The navigation trajectory calculation unit 202 calculates the navigation trajectory O of the spacecraft using information on the observable area R calculated by the observable area calculation unit 201.

[0021] 3 is a diagram showing a navigation trajectory O calculated by the navigation trajectory calculation unit 202. The position of the spacecraft at the observation start time is the observation start point P s The position of the spacecraft at the end of the observation is the observation end point P e As shown in Fig. 3, the navigation trajectory calculation unit 202 calculates a navigation trajectory O that includes in an observable area at least the position of the spacecraft at the observation start time and the observation end time, and that makes the distance between the approach target 3 and the spacecraft at the observation end time smaller than the distance between the approach target 3 and the spacecraft at the observation start time.

[0022] Fig. 4 is a diagram showing an example of an initial estimation error and an estimation error at the observation end time. As shown in Fig. 4, the position of the spacecraft at the observation start time has an initial estimation error represented by an initial estimation error ellipse. Similarly, the position of the spacecraft at the observation end time has an estimation error represented by an estimation error ellipse at the observation start time. The navigation trajectory calculation unit 202 can reduce the estimation error at the observation end time by calculating a navigation trajectory O so as to reduce the distance between the approaching target 3 and the spacecraft.

[0023] Fig. 5 is a diagram showing another example of the initial estimation error and the estimation error at the observation end time. In the example of Fig. 5, it is assumed that the navigation trajectory calculation unit 202 calculates a navigation trajectory O that makes the distance between the approach target 3 and the spacecraft at the observation end time larger than the distance between the approach target 3 and the spacecraft at the observation start time. As shown in Fig. 5, when the navigation trajectory calculation unit 202 calculates the navigation trajectory O so that the distance between the approach target 3 and the spacecraft increases, the estimation error of the relative direction at the observation end time becomes worse. As shown in Figs. 4 and 5, the estimation error of the relative direction depends more strongly on the relative distance between the approach target 3 and the spacecraft than on the observation time.

[0024] A specific method for the navigation trajectory calculation unit 202 to calculate the navigation trajectory O will be described. s is within the observable area and is within a sphere whose distance from the approach target 3 is constant, and the observation end point P e is within another sphere that is within the observable region R and is at a constant distance from the approaching target 3. In this case, the distance between the approaching target 3 and the spacecraft at the observation end time is set to be smaller than the distance between the approaching target 3 and the spacecraft at the observation start time.

[0025] The navigation trajectory calculation unit 202 determines the intersection of the line segment connecting the approach target 3 and the sun S with the sphere at the observation start time and the intersection of the line segment with the sphere at the observation end time as the observation start point P, so that the sensor 100 can observe with its back to the sun S. s and observation end point P e Let us assume that.

[0026] The navigation trajectory calculation unit 202 solves a two-point boundary value problem to obtain the observation start point P s Spacecraft speed and observation end point P e The velocity of the spacecraft at and is calculated, and the orbit connecting them is calculated as the navigation orbit O.

[0027] The orbit injection unit 300 controls the spacecraft to inject it into the navigation orbit O determined by the navigation orbit determination unit 200. The orbit injection unit 300 includes a maneuver amount calculation unit 301 that calculates a maneuver amount for injecting the spacecraft into the navigation orbit O, and an orbit control unit 302 that realizes the maneuver amount and controls the orbit of the spacecraft.

[0028] The maneuver amount calculation unit 301 calculates the amount of maneuver to inject the spacecraft into the navigation orbit O. As an example, a method in which the maneuver amount calculation unit 301 calculates the amount of maneuver when the spacecraft transfers orbit with two impulses will be described.

[0029] Figure 6 shows the transition start point P1 and the observation start point P s 6 is a diagram showing a transition orbit O1 and a transition start point P1 and an observation start point P s The transfer orbit O1 connecting the two follows natural dynamics, and the maneuver amount calculation unit 301 solves a two-point boundary value problem to obtain the velocity of the spacecraft at the transfer start point P1 and the observation start point P s The maneuver amount calculation unit 301 calculates the difference between the velocity before the start of the transition and the velocity immediately after the start of the transition as the first maneuver amount, and calculates the difference between the velocity at the end of the transition and the velocity at the start of observation as the second maneuver amount.

[0030] The orbit control unit 302 realizes the maneuver amount calculated by the maneuver amount calculation unit 301 and controls the orbit of the spacecraft. The orbit control unit 302 calculates the ejection amount of each thruster from the attitude of the spacecraft and the arrangement of the thrusters equipped in the spacecraft, controls the thrusters to eject the calculated ejection amount, realizes the maneuver amount calculated by the maneuver amount calculation unit 301, and controls the orbit of the spacecraft. A specific method for the maneuver amount calculation unit 301 to calculate the ejection amount of the thruster may be, but is not limited to, a method of calculating the ejection amount by solving a linear programming problem.

[0031] 7 is a flowchart showing the navigation trajectory calculation process executed by the navigation trajectory calculation device 1 according to the embodiment 1. The navigation trajectory calculation process will be described with reference to the flowchart in FIG.

[0032] When the navigation trajectory calculation process is started, the observable area calculation unit 201 of the navigation trajectory calculation device 1 calculates the minimum observation distance L min , maximum observation distance L max An observable area R is calculated based on the positional relationship between the approaching object 3 and the sun S (step S101).

[0033] When the observable area calculation unit 201 calculates the observable area R, the navigation trajectory calculation unit 202 calculates the navigation trajectory O using the information of the observable area R calculated by the observable area calculation unit 201 (step S102).

[0034] When the navigation trajectory calculation unit 202 calculates the navigation trajectory O, the maneuver amount calculation unit 301 calculates the amount of maneuver based on the navigation trajectory O calculated by the navigation trajectory calculation unit 202 (step S103).

[0035] When the maneuver amount calculation unit 301 calculates the maneuver amount, the trajectory control unit 302 realizes the maneuver amount calculated by the maneuver amount calculation unit 301, performs trajectory control of the spacecraft (step S104), and ends the navigation trajectory calculation process.

[0036] With the above configuration, the navigation trajectory calculation device 1 according to the first embodiment executes the navigation trajectory calculation process to obtain the observation start point P s The distance between the target 3 and the observation end point P e By making the distance between the target 3 and the shadow area larger than the distance between the target 3 and the shadow area, it is possible to reduce the estimation error of the relative position and velocity without observing the vicinity of the boundary surface between the shadow area and the sunlit area, i.e., without observing the time when the target 3 passes through the boundary surface between the shadow area and the sunlit area.

[0037] (Embodiment 2) The navigation trajectory calculation device 1 according to the second embodiment of the present disclosure will be described. The navigation trajectory calculation device 1 according to the second embodiment s The observation end point is determined on the boundary surface of the observable region R.

[0038] The navigation trajectory calculation unit 202 of the navigation trajectory calculation device 1 according to the second embodiment calculates the observation start point P s is the point within the boundary surface outside the observable area R that is the maximum distance from the approach target 3. e is the point on the inner sphere of the observable region R that is the smallest distance from the approaching target 3.

[0039] By being configured as described above and executing the navigation trajectory calculation process, the navigation trajectory calculation device 1 according to the second embodiment achieves the same effects as the navigation trajectory calculation device 1 according to the first embodiment.

[0040] According to the navigation trajectory calculation device 1 according to the second embodiment, the observation start point P s is the point with the maximum distance to the approach target 3, and the observation end point P e By setting the point at which the distance to the approaching target 3 is the smallest, the ratio of the relative distance between the observation start time and the observation end time can be increased, thereby reducing the error in the relative position and velocity at the observation end time.

[0041] (Embodiment 3) The navigation trajectory calculation device 1 according to the third embodiment of the present disclosure will be described with reference to Fig. 8. The navigation trajectory calculation device 1 according to the third embodiment s is determined from the eigenvector direction corresponding to the minor axis of the initial estimation error ellipse at the observation start time.

[0042] The navigation trajectory calculation unit 202 of the navigation trajectory calculation device 1 according to the third embodiment calculates the observation start point P s is determined from the direction of the eigenvector corresponding to the minor axis of the initial estimation error ellipse at the observation start time. The minor axis of the initial estimation error ellipse is represented by the eigenvector of the minimum eigenvalue of the error covariance matrix. The navigation trajectory calculation unit 202 locates the observation start point P on a straight line that passes through the position of the approach target 3 at the observation start time and is parallel to the eigenvector corresponding to the minor axis of the initial estimation error ellipse. s Determine.

[0043] FIG. 8 is a diagram showing an example of an initial estimation error, an error after the start of observation, and an error after the end of observation. s is determined from the direction of the eigenvector corresponding to the major axis of the initial estimated error ellipse at the observation start time. The relative direction indicates the direction of the line connecting the spacecraft and the approaching target 3. As shown in Figure 8, the component of the error ellipse perpendicular to the relative direction at the observation start time becomes smaller when observation begins. On the other hand, the component parallel to the relative direction does not shrink immediately after observation begins. As the distance between the spacecraft and the approaching target 3 becomes smaller at the observation end time, the error ellipse also becomes smaller, but because the diameter of the error ellipse parallel to the relative direction after observation begins is large, the final error ellipse is also larger than when observation begins from another direction.

[0044] 9 is a diagram showing another example of the initial estimation error, the error after the start of observation, and the error after the end of observation. sis determined from the direction of the eigenvector corresponding to the minimum eigenvalue of the initial estimated error ellipse at the observation start time. As shown in Figure 9, the component perpendicular to the relative direction of the error ellipse at the observation start time, i.e., the major axis component of the error ellipse, becomes smaller when observation starts. As the distance between the spacecraft and the approaching target 3 becomes smaller at the observation end time, the minor axis component of the error ellipse can also be made smaller.

[0045] By being configured as described above and executing the navigation trajectory calculation process, the navigation trajectory calculation device 1 according to the third embodiment achieves the same effects as the navigation trajectory calculation device 1 according to the first embodiment.

[0046] According to the navigation trajectory calculation device 1 according to the third embodiment, the observation start point P s By determining the eigenvector direction corresponding to the minimum eigenvalue of the initial estimation error ellipse at the observation start time, the major axis component of the estimation error ellipse can be reduced after the observation starts, and therefore the errors in the relative position and velocity at the end of the observation can be reduced.

[0047] (Embodiment 4) The navigation trajectory calculation device 1 according to the fourth embodiment of the present disclosure will be described. The navigation trajectory calculation device 1 according to the fourth embodiment e The navigation trajectory O is calculated so that the speed of the spacecraft at is perpendicular to the line connecting the spacecraft and the approach target 3, i.e., the line pointing in the relative direction.

[0048] The navigation trajectory calculation unit 202 of the navigation trajectory calculation device 1 according to the fourth embodiment calculates the observation end point P e is within the observable region R and within a sphere with a constant distance from the approaching target 3, and the observation end time P s Solve the two-point boundary value problem under the condition that the velocity of the spacecraft at point P is perpendicular to the relative direction. e Calculate the spacecraft's velocity at

[0049] By being configured as described above and executing the navigation trajectory calculation process, the navigation trajectory calculation device 1 according to the fourth embodiment achieves the same effects as the navigation trajectory calculation device 1 according to the first embodiment.

[0050] Observation end point P e If the spacecraft has a velocity parallel to the relative direction, there is a risk of collision if it approaches the approach target 3 further after the observation is completed. e If the distance between the target 3 and the target 4 increases, the estimation accuracy will deteriorate. If maneuvers are performed after the observation is completed to avoid a collision, this may shorten the life of the spacecraft.

[0051] According to the navigation trajectory calculation device 1 according to the fourth embodiment, the observation end point P e By calculating the navigation trajectory O so that the speed of the spacecraft at is perpendicular to the relative direction, it is possible to avoid a collision between the spacecraft and the approaching target 3 without shortening the lifespan of the spacecraft.

[0052] (Embodiment 5) A navigation trajectory calculation device 1 according to a fifth embodiment of the present disclosure will be described with reference to Fig. 10. The navigation trajectory calculation device 1 according to the fifth embodiment calculates a trajectory of a satellite from an observation start point P s and the observation end point P e A navigation trajectory O is calculated that includes one or more maneuvers between the target and the destination.

[0053] Figure 10 shows the observation start point P s , maneuver point P m , and the observation end point P e As shown in FIG. 10, the navigation trajectory calculation device 1 according to the fifth embodiment is configured to detect an observation start point P s and the observation end point P e A navigation trajectory O including one or more maneuvers between the navigation trajectory calculation device 1 and the maneuver point is calculated. The navigation trajectory calculation device 1 calculates a navigation trajectory O including a maneuver point where a maneuver is performed.

[0054] The navigation trajectory calculation unit 202 calculates a navigation trajectory O including one or more maneuver points. The maneuver amount calculation unit 301 calculates the amount of maneuver at the maneuver point.

[0055] By being configured as described above and executing the navigation trajectory calculation process, the navigation trajectory calculation device 1 according to the fifth embodiment achieves the same effects as the navigation trajectory calculation device 1 according to the first embodiment.

[0056] If there is a bright point other than the approaching target 3 in a direction close to the approaching target 3, or if there is reflected sunlight, there is a possibility that the approaching target 3 will be lost during navigation, or that it will be impossible to distinguish between the approaching target 3 and other bright points. One method to avoid this is to select a navigation trajectory O in which the approaching target 3 does not overlap with other bright points, or to select an trajectory in which observations are made with the back turned to the Sun S. However, because the positional relationships between the approaching target 3, other bright points, and the Sun S change from moment to moment, it may be difficult to design the navigation trajectory O using only natural dynamics.

[0057] According to the navigation trajectory calculation device 1 according to the fifth embodiment, the observation start point P s and the observation end point P e By calculating a navigation trajectory O that includes one or more maneuvers between the target 3 and the target 1, it is possible to avoid losing sight of the target 3 or being unable to distinguish the target 3 from other bright points, even in cases where it is difficult to design the navigation trajectory O using natural dynamics alone.

[0058] According to the navigation trajectory calculation device 1 according to the fifth embodiment, by performing maneuvers, it is possible to generate observability even in the AON, and it is possible to improve the estimation accuracy of the relative position and velocity.

[0059] (Modification) Although the navigation trajectory calculation device 1 has been described as being mounted on a spacecraft, this is not limiting. The navigation trajectory calculation device 1 may be disposed outside the spacecraft, communicate with the spacecraft to calculate the navigation trajectory, and remotely control the spacecraft to insert it into the navigation trajectory.

[0060] In Figure 6, the end point of the transfer orbit O1 and the observation start point P s The end point of the transfer orbit O1 and the observation start point P s and may be different.

[0061] The observable area calculation unit 201 calculates the observable area R based on the positional relationship between the approaching target 3 and the sun S, but this is not limited to this. What has been described as the sun S may be any luminous body including any fixed star or planet other than the sun.

[0062] A plurality of the embodiments may be combined. For example, the second embodiment and the third embodiment may be combined, and the navigation trajectory calculation device 1 may calculate the observation start point P s The observation end point is determined on the boundary surface of the observable area R, and the observation start point P s may be determined from the eigenvector direction corresponding to the minor axis of the initial estimation error ellipse at the observation start time. The same applies to any combination of other embodiments.

[0063] The means and methods for performing various processes in the navigation trajectory calculation device according to the first to fifth embodiments can be realized by either a dedicated hardware circuit or a programmed computer. The above-mentioned programs may be provided by a computer-readable recording medium including a flexible disk or a CD-ROM, or may be provided online via a network including the Internet. In this case, the programs recorded on the computer-readable recording medium are usually transmitted to and stored in a storage unit including a hard disk. The above-mentioned programs may be provided as independent application software, or may be incorporated into the software of the device as one of its functions.

[0064] Various embodiments and modifications of the present disclosure are possible without departing from the broad spirit and scope of the present disclosure. The above-described embodiments are for explaining the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the disclosure equivalent thereto are considered to be within the scope of the present disclosure. [Industrial Applicability]

[0065] The present disclosure can be used in a navigation trajectory calculation device, a navigation trajectory calculation method, and a program. [Explanation of symbols]

[0066] 1 Navigation trajectory calculation device, 3 Approaching target, 100 Sensor, 200 Navigation trajectory determination unit, 201 Observable area calculation unit, 202 Navigation trajectory calculation unit, 300 Orbit insertion unit, 301 Maneuver amount calculation unit, 302 Orbit control unit, B Backlight area, L max Maximum observation distance, L min Minimum observation distance, O Navigation orbit, O1 Transfer orbit, P1 Transfer start point, P e Observation end point, P m Maneuver point, P s Observation starting point, R observable area, S sun.

Claims

1. an observable area calculation unit that calculates an observable area that can be observed by a sensor mounted on the spacecraft; a navigation trajectory calculation unit that calculates a navigation trajectory including an observation start point included in the observable range calculated by the observable area calculation unit and an observation end point included in the observable range, a distance between the observation start point and an approaching target observed by the sensor is greater than a distance between the observation end point and the approaching target; Navigation trajectory calculation device.

2. the navigation trajectory calculation unit calculates the navigation trajectory such that the distance between the observation start point and the approaching target is maximized within the observable range, and the distance between the observation end point and the approaching target is minimized within the observable range. The navigation trajectory calculation device according to claim 1.

3. the navigation trajectory calculation unit calculates the navigation trajectory including the observation start point on a straight line that passes through the position of the approach target and is parallel to an eigenvector corresponding to a minimum eigenvalue of an error covariance matrix of the position of the approach target at an observation start time.

3. A navigation trajectory calculation device according to claim 1 or 2.

4. the navigation trajectory calculation unit calculates the navigation trajectory such that the velocity direction of the spacecraft at the observation end point is perpendicular to a straight line passing through the end point and the approach target.

3. A navigation trajectory calculation device according to claim 1 or 2.

5. the navigation trajectory calculation unit calculates a navigation trajectory including one or more maneuver points indicating positions at which the spacecraft will perform a maneuver; 3. A navigation trajectory calculation device according to claim 1 or 2.

6. Calculating an observable range that can be observed by a sensor observing the approaching target; Calculating a navigation trajectory including an observation start point included in the calculated observable range and an observation end point included in the calculated observable range; a distance between the observation start point and the approaching target is greater than a distance between the observation end point and the approaching target; Navigation trajectory calculation method.

7. On the computer, Calculating an observable range that can be observed by a sensor observing an approaching target; Calculating a navigation trajectory including an observation start point included in the calculated observable range and an observation end point included in the calculated observable range; a distance between the observation start point and the approaching target is greater than a distance between the observation end point and the approaching target; program.

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