WO2014115753A1

WO2014115753A1 - Method for controlling orbital plane of artificial satellite

Info

Publication number: WO2014115753A1
Application number: PCT/JP2014/051228
Authority: WO
Inventors: 宏之小泉; 順一青山
Original assignee: 国立大学法人東京大学; 次世代宇宙システム技術研究組合
Priority date: 2013-01-22
Filing date: 2014-01-22
Publication date: 2014-07-31
Also published as: JP2014141108A

Abstract

[Problem] To provide a method for controlling the orbital plane of an artificial satellite that is capable of achieving orbit control that is substantially equivalent to that of an artificial satellite equipped with a propulsion system having a high thrust level, with the intention of reducing the size and weight of the artificial satellite without impairing the mission of a main satellite. [Solution] This method for controlling the orbital plane of artificial satellite involves directing a plurality of small artificial satellites (11, 12), which are launched together with a main satellite, to respective target orbits, and is characterized in that the orbital altitudes of the small artificial satellites (11, 12), which are directed to a target orbit (S1) of the main satellite, are altered by using propulsion systems having a low thrust level, and the plurality of artificial satellites (11, 12) is introduced to respective target orbits (S5, S9) by utilizing transitions in the orbital planes caused by the flatness of the Earth's gravity field at said orbital altitudes.

Description

Satellite orbital plane control method

The present invention relates to an orbital plane control method for an artificial satellite, and more particularly to an orbital plane control method for an artificial satellite using a propulsion device having low propulsive force and high propellant efficiency.

In recent years, the launch of artificial satellites requires technological development and enormous costs, so in recent years, it has been carried out by using several extra small satellites to take advantage of the surplus capacity of rockets equipped with main satellites. Such a small satellite (mass of about 50 kg) is called a “piggyback satellite”. Because this piggyback satellite provides launch opportunities within the range that does not impair the mission of the main satellite, it will be put into the orbit of the main satellite different from the original target orbit of the piggyback satellite It is necessary to change the trajectory to a desired target trajectory. Here, as a method for changing the orbit of a plurality of artificial satellites into a desired orbit, there is, for example, Patent Document 1.

In the orbit conversion disclosed in Patent Document 1, first, a plurality of artificial satellites are introduced into a common parking orbit having a shorter orbit length than the target orbit, or different parking orbits for each artificial satellite, and the perturbation due to the flat shape of the earth When the orbital plane of the parking orbit matches the orbital plane of the transition orbit to each of the target orbits, each artificial satellite on the parking orbit is inserted into each transition orbit, and each artificial satellite on each transition orbit is It is characterized by shifting to each orbit.

Japanese Patent Laid-Open No. 7-187091

However, the method of Patent Document 1 is to introduce a plurality of artificial satellites into a target parking orbit from the beginning. In the case of a piggyback satellite, a launch opportunity is provided as long as the mission of the main satellite is not impaired. Therefore, it cannot be expected to enter a parking orbit preferable for the piggyback satellite from the beginning.

In addition, for small satellites that are required to be extremely compact and lightweight, the propulsion device (thruster) for performing the necessary orbit control has high specific thrust characteristics that enable efficient propellant consumption. It is preferable that it is a propulsion device. However, the propulsion device with high specific thrust has been considered to be unsuitable for track surface control that requires a high thrust level because the thrust level is extremely low. Therefore, the track surface control has so far been performed using a propulsion device with a high thrust level and a low specific thrust at the expense of propellant consumption.

Therefore, the present invention has been made in view of such problems, and without sacrificing the mission of the main satellite, and further reducing the size and weight of the artificial satellite and providing the artificial satellite with a high thrust level propulsion device It is an object to provide an orbital plane control method for an artificial satellite capable of realizing orbit control substantially equivalent to the above.

In order to solve the above-mentioned problem, the invention according to claim 1 is an orbital plane control method for an artificial satellite in which a plurality of small artificial satellites launched together with a main satellite are introduced into respective target orbits.
Change the orbital altitude of the small satellite inserted into the target orbit of the main satellite using a propulsion device with a low thrust level, and use the transition of the orbital plane due to the flatness of the earth gravity field at the orbital altitude Then, a plurality of the artificial satellites are thrown into each target orbit.

In order to solve the above-mentioned problem, the present invention according to claim 2 is the orbital plane control method for artificial satellite according to claim 1, wherein the change of the orbital height is performed by changing the propulsion device to the orbital traveling direction of the artificial satellite. And a second step of injecting the propulsion device in the direction opposite to the first step for the same amount of time. Features.

In order to solve the above-mentioned problem, the present invention according to claim 3 is the orbital plane control method for an artificial satellite according to claim 1 or 2, wherein the propulsion device is an ion engine.

Instead of generating direct orbital surface control force by a thruster, the present invention controls the orbital altitude with a thruster with high specific thrust and high propellant efficiency but low thrust level, such as an ion engine. It is characterized in that the artificial satellite is thrown into the desired orbital plane by utilizing the transition of the orbital plane due to the flatness of the earth gravity field.

According to the orbital plane control method for an artificial satellite according to the present invention, there is an effect that a small piggyback satellite can be put into a desired target orbit without impairing the mission of the main satellite. Moreover, propulsion efficiency can be greatly improved by using a propulsion device with a relatively low thrust level such as an ion engine, so that the equipment required for the piggyback satellite can be installed instead of propellant. effective. In addition, since the piggyback satellite can be further reduced in size, the number of piggyback satellites to be mounted can be increased.

It is a figure which shows the orbital element of an artificial satellite. It is explanatory drawing which shows a track surface transition at the time of raising, after once reducing orbit altitude. It is a graph which shows the injection of the propulsion apparatus in FIG. 2, the change of a track height, and the change of a track surface transition. It is explanatory drawing which shows a track surface transition at the time of raising a track height once and then lowering it. It is a graph which shows the injection of the propulsion apparatus in FIG. 4, the change of a track height, and the change of a track surface transition.

Hereinafter, a preferred embodiment of an orbital plane control method for an artificial satellite according to the present invention will be described in detail with reference to the drawings. First, orbital elements that are parameters used for designating the orbit of the artificial satellite will be described. FIG. 1 is a diagram showing orbital elements of an artificial satellite.

In FIG. 1, reference numeral 10 denotes an artificial satellite, and the artificial satellite 10 rotates around the earth 1 while drawing an elliptical orbit 11 having a major radius “a” in the opposite direction to the clock. The angle formed by the orbital plane 3 and the equator plane 5 at this time is the orbital inclination angle i, and the orbit passes through the equator plane 5 from the south side (lower side in FIG. 1) to the north side (upper side in FIG. 1). The longitude is the ascending intersection longitude (rising intersection red diameter) Ω. Further, γ in FIG. 1 indicates the equinox point direction.

Here, the earth is not a perfect sphere, but is shaped like a spheroid that is crushed to the north and south close to the spheroid centered on the earth axis. When the force in the direction perpendicular to the orbital plane 3 of the artificial satellite 10 is applied as a perturbation due to the bulge of the earth 1 near the equator due to the flatness, the orbital angular momentum vector direction of the artificial satellite 10 changes. This change in the angular momentum vector direction represents the rotation of the track surface 3 at a predetermined angular velocity. The rotation of the orbital plane is more easily affected by the lower orbital altitude, and the transition amount is larger. The higher the orbital altitude, the smaller the amount of transition.

In the present invention, a low thrust / high propellant efficiency propulsion device such as an ion engine mounted on an artificial satellite is continuously injected in the opposite direction (or the same direction) of the orbital speed for a predetermined time to increase (or lower) the orbital altitude. Then, the orbital altitude is increased (or lowered) by a predetermined value by continuously injecting (maneuvering) in the opposite direction for the same time, and the flatness of the earth's gravitational field due to the change in the orbital altitude at this time The artificial satellite is thrown into the target orbital plane by using the change in the amount of transition of the orbital plane.

Here, the increase (or decrease) of the transition angular velocity of the raceway surface is obtained by increasing (or decelerating) the propulsion unit over the orbit N times in the orbital traveling direction (or the opposite direction). When the speed is increased (or decelerated), the orbital speed remains increased by NΔV with respect to the initial speed VI. Thereafter, the increase (or decrease) proceeds at the transition speed corresponding to. Therefore, in order to return to the initial orbital surface angular velocity, it is necessary to inject the maneuver in the reverse direction by the same number of orbits (N rounds). Therefore, as a maneuver for controlling the raceway surface, it is necessary to perform both the first half and the second half maneuver with the injection direction reversed. This point will be further described with reference to FIGS.

First, the orbital plane control method when the satellite's orbital altitude is lowered and then raised will be explained. FIG. 2 is an explanatory diagram showing the orbital plane transition when the orbital altitude is once lowered and then raised, and FIG. 3 is a graph showing the injection of the propulsion device, changes in the orbital altitude and changes in the orbital plane transition. In FIG. 2, reference numeral 11 denotes one of a plurality of piggyback satellites launched together with a main satellite (not shown) and put into the target orbit of the main satellite. As described above, the piggyback satellite is a small satellite having a weight of about 50 kg, and is a satellite that can be launched together with the main satellite by utilizing the surplus capacity of the launch vehicle. A piggyback satellite (hereinafter simply referred to as “satellite”) 11 is equipped with a propulsion device having a high propellant efficiency but a relatively low thrust level, such as an ion engine.

In FIG. 2, the satellite 11 is initially inserted into a target orbit S1 of a main satellite (not shown) and orbits the orbit S1. Note that the orbit S5 is the orbital plane where the satellite 11 is to be finally inserted. Then, the satellite 11 starts to descend its orbital altitude by injecting the propulsion device in the same direction as the orbital traveling direction of the satellite 11 orbiting the orbit S1. Since the thrust of the propulsion device of the satellite 11 is at a low level, the orbital altitude decreases slightly. When the orbital altitude of the satellite 11 gradually decreases due to the injection in the same direction as the orbital traveling direction, the amount of transition of the orbital plane due to the flatness of the earth's gravitational field at the orbital altitude of the satellite 11 also changes in a direction that gradually increases. The ascending intersection longitude Ω of the satellite 11 changes to the orbit S2 while gradually changing. Further, by continuing the injection in the same direction as the orbital traveling direction, the first-half injection is terminated when the orbit S3 reaches the intermediate position until the satellite 11 reaches the target orbit S5.

When the satellite 11 reaches orbit S3, the latter half of the injection is started. This time, the orbital altitude of the satellite 11 is started to rise by injecting the propulsion device in the direction opposite to the orbital traveling direction of the satellite 11 contrary to the first half. Since the thrust of the propulsion device of the satellite 11 is at a low level, the orbital altitude increases slightly. When the orbital altitude of the satellite 11 gradually rises due to the injection opposite to the orbital traveling direction, the amount of transition of the orbital plane due to the flatness of the earth's gravitational field at the orbital altitude of the satellite 11 also changes in a direction that gradually decreases. The ascending intersection longitude Ω of the satellite 11 changes to the orbit S4 while gradually changing. Further, the satellite 11 reaches the target orbit S5 by continuing the injection in the direction opposite to the orbital traveling direction. And if the satellite 11 is thrown into the target orbit S5, the injection of the propulsion device is terminated and the orbit S5 is maintained.

Next, the orbital plane control method when the orbital altitude of the satellite is once raised and then lowered will be described. FIG. 4 is an explanatory diagram showing the orbital plane transition when the orbital altitude is once raised and then lowered, and FIG. 4 is a graph showing the injection of the propulsion device, changes in orbital altitude and changes in orbital plane transition. In FIG. 4, reference numeral 12 denotes one of a plurality of piggyback satellites launched together with a main satellite (not shown) and put into the target orbit of the main satellite. Similar to the satellite 11, the satellite 12 is equipped with a propulsion device having a relatively low thrust level such as an ion engine.

In FIG. 4, the satellite 12 is initially put into a target orbit S6 of a main satellite (not shown) and orbits the orbit S6. Note that the orbit S10 is the orbital plane where the satellite 12 is to be finally inserted. Then, by injecting the propulsion device in a direction opposite to the orbital traveling direction of the satellite 12 orbiting the orbit S6, the satellite 12 starts to increase the orbital altitude. In addition, since the thrust of the propulsion device of the satellite 12 is at a low level, the orbital altitude increases slightly. Here, when the orbital altitude of the satellite 12 is increased by jetting in the direction opposite to the orbital traveling direction, the transition of the orbital plane due to the flatness of the earth's gravitational field is caused by the torque that causes the orbital plane to transition because the earth's gravity is reduced. Therefore, the orbital plane of the satellite 12 changes in the opposite direction to that shown in FIG. Therefore, the ascending intersection longitude Ω of the satellite 12 changes to the orbit S7 while gradually changing. Further, by continuing the injection in the direction opposite to the orbit traveling direction, the first-half injection is terminated when the orbit S8 reaches the intermediate position until the satellite 12 reaches the target orbit S10.

When the satellite 12 reaches orbit S8, which is the intermediate position, the latter half of the injection is started. In this case, the orbital altitude of the satellite 12 starts to be lowered by injecting the propulsion device in the same direction as the orbital traveling direction of the satellite 10 contrary to the first half. Since the thrust of the propulsion device of the satellite 12 is at a low level, the orbital altitude decreases slightly. When the orbital altitude of the satellite 12 gradually decreases due to the injection in the same direction as the orbital traveling direction, the transition amount of the orbital plane due to the flatness of the earth's gravitational field at the orbital altitude of the satellite 12 also changes in a direction that gradually increases. The ascending intersection longitude Ω of the satellite 12 changes to the orbit S9 while gradually changing. Further, the satellite 12 reaches the target orbit S10 by continuing the injection in the same direction as the orbital traveling direction. And if the satellite 12 is thrown into the target orbit S10, the injection of the propulsion device is terminated and the orbit S10 is maintained.

As described above, for a plurality of piggyback satellites placed in the target orbit of the main satellite (not shown), the orbital plane control as described above is performed in accordance with the respective target orbits, so that they are put into the target orbit of the main satellite. Each of the plurality of piggyback satellites can be introduced into the target orbital plane.

Next, the relationship between the track element and the operation of the propulsion device necessary for carrying out the above-described track surface control method will be described.
First, in the orbital motion of an artificial satellite orbiting the earth's gravitational field having flatness, the time change rate of its elevation point longitude Ω is expressed by the following equation (1).

Suppose that the satellite is orbiting a circular orbit, the orbital length radius a is expressed as a function of the orbital velocity V as shown in Equation 2.

And substituting Equation 2 into Equation 1, the time change rate is expressed as Equation 3.

V, as shown in Equation 4, plus the initial velocity V increases small thrust added continuously during the circumferential track N to _I (or decrease) the orbital velocity variation N △ V.

The change Ω of the orbital lift point longitude when jetting a continuous propulsion unit for N laps of the orbit is expressed as in Eq. 5 by substituting Eq.

Therefore, the increase (or decrease) ΔΩ in the transition angle of the raceway surface by injecting the propulsion device is expressed by Equation 6.

The increase (or decrease) in the transition angle of the raceway surface given by Equation 6 increases (or decelerates) the propulsion unit over the orbit N times in the orbital traveling direction (or the opposite direction) as described above. Although those by obtained in this state is in the state that the track speed increases to an initial velocity V _I by N △ V, the while standing raceways transition corresponding to the orbital velocity It will increase (or decrease) thereafter at the transition speed. Therefore, in order to return to the initial orbital transition angular velocity, it is necessary to inject in the reverse direction by the same number of orbits following the maneuver. Therefore, as a maneuver for controlling the raceway surface, it is necessary to perform both the first half and the second half maneuver with the injection direction reversed. Since the latter half maneuver is completely symmetric with the first half maneuver, the transition angle of the orbital plane by both maneuvers is twice the ΔΩ in equation (6). Accordingly, the amount of transition (ΔΩ _T ) of the raceway surface by this maneuver and the required orbital number of times N _T are given as shown in Equation 7.

Thus, to transition the track surface by a required angle △ Omega obtains the N satisfying than the number 7 △ Omega _T, then obtains the N _T than the N, be carried out by injecting propulsion unit by both I can do it.

As an embodiment of the invention, an implementation for controlling an orbital plane using an ion engine with a thrust of 0.25 mN mounted on a microsatellite with a mass of 50 kg put in a solar synchronous orbit at an altitude of 600 km will be described. . The specifications necessary for controlling the orbital plane by the above equation 7 in the case of this satellite are shown below.

Assuming the above specifications, 1. Based on the term control, the necessary track surface control angle Δθ is realized as shown in Table 2.

Compared with the propulsion system used as a chemical propellant conventionally used for orbit control, the required propellant amount is greatly improved as shown below.
Propellant Propellant mass ratio Hydrazine 1 / 7.5
Hydrogen peroxide 1 / 16.0
Nitrogen gas 1 / 30.0

As described above, the preferred embodiment of the present invention has been described in detail. However, the present invention is not limited to the specific embodiment, and within the scope of the gist of the present invention described in the claims, Needless to say, various modifications and changes are possible.

1 Earth 3 Orbital plane 5 Equatorial plane 10 Artificial satellite 11 Piggyback satellite 12 Piggyback satellite

Claims

In the orbital plane control method for artificial satellites, a plurality of small artificial satellites launched together with the main satellite are put into their target orbits.
Change the orbital altitude of the small satellite inserted into the target orbit of the main satellite using a propulsion device with a low thrust level, and use the transition of the orbital plane due to the flatness of the earth gravity field at the orbital altitude A method for controlling the orbital surface of the artificial satellite, wherein a plurality of the artificial satellites are introduced into respective target orbits.
The orbital plane control method for an artificial satellite according to claim 1,
The change of the orbital altitude is
A first step of injecting the propulsion device for a predetermined time in the same direction as the orbital traveling direction of the artificial satellite or in the opposite direction;
A second step of injecting the propulsion device in the opposite direction to the first step for the same amount of time;
An orbital plane control method for an artificial satellite characterized by comprising:
In the orbital plane control method of the artificial satellite according to claim 1 or 2,
The method for controlling an orbital plane of an artificial satellite, wherein the propulsion device is an ion engine.