JP4719658B2 - Satellite observation plan program and satellite observation plan creation device - Google Patents

Description

  The present invention relates to a satellite observation plan program for creating a satellite observation plan using a plurality of satellites, and an apparatus for creating a satellite observation plan.

  Earth observation satellites are used for the purpose of observing any point on the earth, such as land, ocean, and atmospheric conditions. The earth observation satellite rotates in a quasi-regressive orbit where a point directly below the satellite has the same longitude after a certain number of cycles so that an arbitrary point on the earth can be observed. In addition, observation satellites are equipped with different sensors depending on the purpose of measurement. Some sensors can be observed only during the day and others can be observed at night.

  Conventionally, various methods for preparing an observation operation plan for a satellite according to an observation request have been studied. For example, in Patent Document 1, a certain observation request frame is set for an observation requester. A method is described in which, when the total amount of resources of observation requests exceeds the requirement, the observation request plan of the observation requester is set at a low priority.

Patent Document 2 describes that the priority is set to the observation element and the observation area, the priority of the observation element and the observation area is determined, and the observation plan is changed.
The above-described observation planning method is merely a method for planning an observation plan for a specific satellite.

In recent years, with the increase in the number of observation satellites worldwide and the increasing momentum of international cooperation, there is a demand for observing a target point as soon as possible because any satellite can be used. In particular, observations aimed at emergency disasters and disaster prevention can be performed quickly because any satellite can be used.
JP 2004-272427 A JP 2005-241455 A

  Conventionally, however, it has not been considered to select a satellite capable of observing a target point from many observation satellites. In observations that require urgency, such as when a disaster occurs, it is desirable to be able to determine the observable satellites in a short time.

  An object of the present invention is to make it possible to identify a satellite capable of observing a target point in a short time.

  The satellite observation planning program of the present invention includes a step of storing data indicating Kepler elements of a plurality of satellites in a storage means, and an arbitrary position within the observation period in the inertial coordinate system when an observation target position and an observation period are designated. Calculating an observation target position vector of the observation target position and a satellite position vector of the plurality of satellites at a time of a time, and an absolute value of a difference between the observation target position vector and the satellite position vector of each satellite A step of determining whether or not the distance from the boundary of the observable area of the satellite to each of the satellites is less than or less, and the absolute value of the position vector difference is less than or less than the distance from the satellite to the boundary of the observable area Calculating the time determined as observable time, and the satellite having the earliest observable time within the observation period is the observation target position Comprising a step of identifying as observable satellites.

  According to the present invention, it is possible to identify the satellite that can observe the observation target position earliest from among a plurality of satellites. As a result, emergency observation such as when a disaster occurs can be performed quickly. In addition, after calculating the satellite position vector and the observation target position vector, it is possible to calculate the time when the satellite can observe the observation target position without performing coordinate conversion. Calculations for identifying satellites can be simplified.

  In the satellite observation planning program according to the above invention, in the determination step, the absolute value of the difference between the observation target position vector and the satellite position vector is the distance from the boundary of the observable area of the plurality of satellites to each satellite. It is determined whether it is below or below the maximum slant range shown.

  By configuring in this way, it is possible to identify a satellite capable of observing the observation target position with simple arithmetic processing by determining whether the distance from the satellite to the observation target position is less than or less than the maximum slant range. it can.

  In the satellite observation planning program of the above invention, the step of storing the data includes the distance from the satellite to the boundary of the observable region, and the moving direction of the satellite in the observable region on the ground surface as the distance from the satellite. The maximum slant range calculated from the width in the direction orthogonal to is stored in the storage means.

  With this configuration, the maximum slant range of multiple satellites is stored in the storage means, and observation is performed by comparing the distance from the multiple satellites to the observation target position at an arbitrary time with the maximum slant range of each satellite. Satellites that can observe the target position can be identified.

  In the satellite observation planning program of the above invention, the step of calculating the measurable time, when the sensor of the satellite is a visible light optical sensor, converts the observable time to a local standard time at the observation target position, It is determined whether or not the local standard time is a time that can be measured by the optical sensor.

  With this configuration, it is possible to determine whether or not the time when the satellite passes the observation target position is the time that can be observed by the visible light optical sensor.

  According to the present invention, the satellite that can observe the observation target position earliest can be identified in a short time.

  Preferred embodiments of the present invention will be described below with reference to the drawings. The orbit of the satellite can be represented by time and six elements of the orbit. First, the orbital 6 element (Kepler element) will be described with reference to FIG. The Kepler element consists of an orbital radius a defined by equatorial plane coordinates (inertial coordinate system), an eccentricity e, an orbital inclination angle i, an ascending intersection red longitude Ω, a near-point argument ω, a near-point separation angle (average near-point separation) It consists of six elements (angle) f.

  The orbital length radius a is the radius of the satellite orbit, the eccentricity e is a value indicating how close the satellite orbit is to a perfect circle, and the eccentricity e is 0 when the satellite orbit is a perfect circle. The ascending intersection eclipse Ω is an angle based on the equinox of the point where the orbit of the satellite intersects the equatorial plane from the bottom to the top, and the orbit inclination angle i is the angle formed by the orbital plane of the satellite and the equatorial plane. . Further, the near point argument ω is an angle formed between the peripheral point of the satellite and the equator plane, and the near point separation angle f is an angle formed between the position of the satellite and the peripheral point in the satellite orbit.

  FIG. 2 is a diagram showing a peripheral point and an apogee point. As shown in FIG. 2, the peripheral point is a point on the satellite orbit where the distance between the earth and the satellite is the shortest, and the apogee point is a point on the satellite orbit where the distance between the earth and the satellite is the longest.

  The periphery radius indicating the distance from the earth to the periphery point can be expressed as a × (1−e) using the orbital length radius a and the eccentricity e. Further, the apogee radius indicating the distance between the earth and the apogee point can be expressed as a × (1 + e) using the orbital length radius a and the eccentricity e.

Next, FIG. 3 is a diagram illustrating a configuration of a satellite observation system (satellite observation plan creation device) that determines a satellite observation plan when an observation target position and an observation request period are designated by a user.
The trajectory element acquisition unit 11 acquires the latest trajectory element via the Internet. Next, the satellite information table update unit 12 updates the satellite information table 13 based on the orbit element acquired by the orbit element acquisition unit 11.

  FIG. 4 is a diagram showing the configuration of the satellite information table 13. The satellite information table 13 includes a satellite name, a sensor type, an observation width Ws of the observable area of the satellite, a maximum slant range ρmax indicating the distance from the satellite to the left and right boundaries of the observable area of the ground surface, an orbital element epoch (time ), Orbital radius a (km) that is Kepler element, eccentricity e, orbit inclination angle i (deg), ascending intersection red longitude Ω (deg), near point argument ω (deg), average near point separation angle (nearest) The point separation angle) M (deg), the orbit period P (1 / sec), the orbit altitude h (km), and the like are registered.

The orbital period P and the orbital height h have the following relationship with the orbital length radius a.
P = 2πa · (a / μ) ^1/2 μ: Geocentric gravity constant h = aa · e a · e: Earth equatorial radius Earth shape non-spherical effect, sun / moon attraction, atmospheric resistance, solar radiation Since the orbit of the satellite changes due to pressure or the like, the orbit control is performed by a propulsion device mounted on the satellite to correct the influence. As a result, the orbital radius of the satellite does not necessarily satisfy the quasi-regression condition. Therefore, if the trajectory length radius is updated every moment and the trajectory prediction is performed using the trajectory length radius, there arises a problem that the quasi-regression condition is not satisfied. Therefore, when the satellite information table 13 is updated, parameters other than the orbital length radius are updated, and the orbital length radius holds a fixed value that satisfies the quasi-regressive condition.

  In the satellite information table 13, for example, as information on the satellite SATA, the sensor type is “optical”, the observation width is 800 km, the maximum slant range ρmax is 1044.6 km, the ascending intersection red longitude is 327.7 deg, and the like. It is registered. In addition, as information regarding the satellite SATB, it is registered that the sensor type is “optical”, the observation width is 30 km, the maximum slant range ρmax is 698 km, the ascending intersection red longitude is 287.2 deg, and the like.

  FIG. 5 is a diagram showing the observable area 21 of the satellite. The observation width Ws is a value that is ½ of the maximum width in the direction orthogonal to the moving direction of the satellite in the observable region 21. This observation width Ws is determined by the viewing angle of the sensor, or when the sensor is observed by shaking it.

  The maximum slant range ρmax is a distance from the left and right boundaries (with respect to the moving direction of the satellite) of the satellite observable region 21 to the satellite, and can be calculated from the satellite height h and the observation width Ws.

Returning to FIG. 3, the observation condition reception unit 14 receives the coordinates of the observation target position specified by the user and the observation request period, and outputs these conditions to the observation availability determination unit 15.
The observation availability determination unit 15 acquires the latest Kepler elements of a plurality of satellites registered in the satellite information table 13, and specifies a satellite that can observe the observation target position within the designated observation request period. As a method for specifying an observable satellite, the distance between each satellite and the observation target position is calculated at regular intervals, and it is determined whether or not the distance between both is less than the maximum slant range ρmax.

  The determination result of the observability determination unit 15 is output to the determination result display unit 16, and the determination result display unit 16 displays the fastest observable time of the satellite determined to be observable on a display or the like. Thereby, the user can know the satellite that can be observed earliest within the observation request period in which the target observation point is designated.

  Next, processing for identifying a satellite capable of observing the target observation position in the satellite observation system described above will be described with reference to the flowchart of FIG. The following processing is executed by the control unit of the computer.

  First, the latest orbital elements (Kepler elements) of a plurality of satellites are acquired via the Internet (FIG. 6, S11). Next, the satellite information table 13 is updated based on the acquired Kepler element (S12).

  If the latitude and longitude of the observation target position, the observation request periods Ts to Te, and the sensor type are input as the observation conditions (S13), a plurality of the same sensor types among the plurality of satellites registered in the satellite information table 13 are input. One of the satellites is selected (S14). Next, time T (Greenwich Mean Time) is set at regular time intervals within the observation request period Ts to Te (S15). In general, since the time when the earth observation satellite is continuously viewed from one point on the ground surface is about 10 minutes, the fixed time interval is set to about 5 minutes.

  Next, the satellite position vector Rs and the observation target position vector Rp at the set time T in the inertial coordinate system are calculated, and the absolute value ΔR = | Rs−Rp | of the difference between these position vectors is calculated (S16).

  The position of the satellite is obtained by a general perturbation method or the like, and converted to a satellite position vector Rs at time T in equatorial plane coordinates. Since the observation target position is designated by the latitude and longitude λ fixed to the earth, the longitude λ is converted into the equatorial plane coordinate longitude Σ in consideration of the rotation of the earth. Specifically, the longitude Σ of the equatorial plane coordinate is calculated by the following formula. The unit of time is day, and the unit of θg is deg.

Σ = λ + θg (T)
θg (T) = 100.0755425 + 360.985647346 × (T−T0) + Δθ
T0: Reference time 1958/1/1 00:00 UTC
Δθ: Correction constant The observation target position vector Rp at time T in the equatorial plane coordinates can be calculated from the longitude Σ in the equatorial plane coordinates of the observation target position obtained from the above equation and the given latitude.

  FIG. 7 is a diagram showing the satellite position vector Rs and the observation target position vector Rp. The X and Y planes are equatorial coordinate planes indicated by broken circles in FIG. The magnitude ΔR of the difference vector between the satellite position vector Rs and the observation target position vector Rp indicates the distance between the satellite and the observation target position.

  In the flowchart of FIG. 6, it is determined whether or not ΔR is smaller than the maximum slant range ρmax (S17). Since the maximum slant range ρmax indicates the distance from the satellite to the left and right boundaries of the observable region 21, the target observation position is within the observable region 21 of the satellite by determining whether ΔR is less than ρmax. It can be determined whether or not there is. When the distance ΔR between the satellite and the observation target position is equal to or larger than ρmax, the observation target position is on or outside the boundary of the observable region 21 of the satellite. When ΔR is less than ρmax, the observation target position is the satellite. Is in the observable region 21.

  When the distance ΔR between the satellite and the observation target position is less than ρmax (S17, YES), that is, when the observation target position is in the observable area 21 of the satellite, the process proceeds to step 18, and whether the satellite sensor type is an optical sensor or not. Determine whether. If the sensor type is an optical sensor, the process proceeds to step 19 to calculate a local standard time LST (Local Standard Time) at the observation target position.

Here, a method of calculating the local standard time LST of the observation target position will be described with reference to FIG.
As shown in FIG. 8, αs is the ecliptic in the solar direction with reference to the equinox in the equatorial plane coordinates, and Σ is the ecliptic at the observation target position. At this time, the local standard time LST of the target observation position can be obtained from the following equation.

LST of observation target position = {Σ− (αs−180 [deg])} × 24/360 [deg]
If the LST of the observation target position is calculated, the process proceeds to step S20 in FIG. 6 and it is determined whether or not the LST falls within the range from 10:00 to 14:00. In the process of step S20, it is determined whether or not the LST falls within the range from 10:00 to 14:00. If the sensor type is an optical sensor with visible light, the observation target position is in the daytime period. This is because observation is necessary. In this embodiment, 10 o'clock to 14 o'clock suitable for observation by a visible light sensor is used as a reference for determining the observation possible time. Of course, the time for judging whether or not the measurement can be performed by the visible light optical sensor may be other than the time from 10:00 to 14:00.

When the LST falls within the range from 10:00 to 14:00, the process proceeds to step S21, and the time T is stored in the memory as the observable date / time of the corresponding satellite.
Next, it is determined whether or not the time T has reached the final time Te of the observation request period (S22). When the time T has not reached the final time Te of the observation period (S22, NO), the process returns to step S15, the time is updated by adding the constant time interval ΔT to the time T, and the above-described processing is repeated.

  On the other hand, when it is determined in step S22 that the time T has reached the final time Te of the observation period (S22, YES), the process proceeds to the next step S23, and the sensors among the satellites registered in the satellite information table 13 are detected. It is determined whether or not calculation of the positions of all the satellites having the same type as the specified sensor type has been completed.

  If there is a satellite that has not been calculated (S23, NO), the process returns to step S14 to acquire Kepler elements of other satellites registered in the satellite information table 13, and the position of the satellite at the arbitrary time T and The observation target position is calculated, and the above processing is repeated.

When the calculation of all the corresponding satellites is completed (S23, YES), the process proceeds to step S24, and the determination result is displayed.
By the above processing, the satellite that can observe the observation target position earliest can be identified.

  FIG. 9 is a diagram illustrating an example of a calculation result of the distance between the observation target position and the satellite. In FIG. 9, an optical sensor is designated as the sensor type, 35 deg is designated as the latitude of the observation target position, 135 deg is designated as the longitude, and from 3:00 on August 3, 2006 to midnight on August 6 (UTC) is designated as the observation period. The calculation result of the distance ΔR between the observation target position and the satellite is shown.

  It can be seen from the satellite information table 13 that the maximum slant range ρmax of the satellite STAA is 1044.6 km, and the distance ΔR between the satellite STAA and the observation target position becomes 787 km at 4:20 on August 4, 2006, 8 × 5 It is calculated to be 715 km at 15:50 a day. However, if 15:00 on August 5 (UTC) is converted to the local standard time of the observation target position, it will be 0:43, and this time is outside the observable time of the optical sensor, so the observable time of the satellite STAA Is only 4:20 on August 4th in Greenwich Mean Time.

  Similarly, it can be seen from the satellite information table 13 that the maximum slant range ρmax of the satellite STAB is 698 km, and the calculation results show that there is no time when the distance ΔR between the satellite SATB and the target observation position is less than the maximum slant range ρmax.

  Similarly, it can be seen from the satellite information table 13 that the maximum slant range ρmax of the satellite STAC is 902 km, and the distance ΔR between the satellite STAC and the target observation position is 820 km at 1:55 on August 5, 2006. Is obtained. If this time is converted to local standard time on August 5, 1:55, it will be 10:48, and this time is within the observable time of the optical sensor, so the observable time of the satellite STAC is August 5, 2006 It will be 1:55 a day.

Therefore, the satellite that can observe the observation target position earliest can be identified from the calculation result of the observable time.
According to the embodiment described above, the distance between the position of each satellite at the arbitrary time within the designated observation period and the target observation position is calculated, and the time at which the calculated distance ΔR is less than the maximum slant range ρmax is obtained. Thus, the satellite that can observe the target observation position earliest among the plurality of satellites can be specified. At this time, the coordinates of the satellite and the observation target position are calculated as position vectors in the equatorial plane coordinates, and the absolute value of the difference between the position vectors and the maximum slant range ρmax can be directly compared without changing the coordinates. The calculation time for calculating the observable time of the satellite can be shortened.

The present invention is not limited to the configuration described in the embodiment, and may be configured as follows, for example.
(1) In the embodiment, the maximum slant range of each satellite is registered in the satellite information table 13, but the satellite information table 13 includes data relating to the observable area of the satellite (for example, the observation width Ws of the observable area of each satellite). Only the height h) of the satellites may be registered, and the maximum slant range ρmax may be calculated from the data.
(2) The coordinate system for calculating the position of the satellite and the observation target position is not limited to the equatorial plane coordinate, and any coordinate system may be used as long as it is an inertial coordinate system.

(Supplementary note 1) storing data indicating Kepler elements of a plurality of satellites in a storage means;
Calculating an observation target position vector of the observation target position and an arbitrary satellite position vector of the plurality of satellites at an arbitrary time within the observation period in the inertial coordinate system when an observation target position and an observation period are designated;
Determining whether the absolute value of the difference between the observation target position vector and the satellite position vector of each satellite is less than or less than the distance from the boundary of the observable region of the plurality of satellites to each satellite; and
Calculating the time at which the absolute value of the position vector difference is determined to be less than or less than the distance to the boundary of the observable region as the observable time;
A satellite observation plan program in which a computer executes a step of identifying a satellite having the earliest observable time within the observation period as a satellite capable of observing the observation target position.
(Supplementary Note 2) In the determination step, the absolute value of the difference between the target position vector and the satellite position vector is less than or less than the maximum slant range indicating the distance from the boundary of the observable area of the plurality of satellites to each satellite. A satellite observation planning program according to appendix 1 for determining whether or not.
(Supplementary Note 3) The step of storing the data includes, as a distance from the satellite to the boundary of the observable region, a height of the satellite and a width of the observable region on the ground surface in a direction orthogonal to the moving direction of the satellite. A satellite observation plan program executed by the computer according to appendix 1, wherein the maximum slant range calculated from the above is stored in the storage means.
(Supplementary note 4) The satellite observation planning program according to supplementary note 1 (Appendix 5), wherein the inertial coordinate system is an equatorial plane coordinate, and the boundary of the observable region is a boundary line parallel to the moving direction of the satellite (Appendix 5) When the satellite sensor is a visible light optical sensor, the time calculating step converts the observable time into a local standard time at the observation target position, and the local standard time can be measured by the optical sensor. A satellite observation planning program according to appendix 1 for determining whether or not it is within.
(Additional remark 6) The data which show the said Kepler element are the satellite observation plan of Additional remark 1 which consists of an orbital length radius, an eccentricity, an orbit inclination angle, an ascending intersection red longitude, a near point argument, and an average near point separation angle. program.
(Supplementary Note 7) Storage means for storing data indicating Kepler elements of a plurality of satellites;
Position calculation means for calculating the observation target position vector of the observation target position and the satellite position vectors of the plurality of satellites at an arbitrary time within the observation period in the inertial coordinate system when the observation target position and the observation period are designated When,
A determination means for determining whether an absolute value of a difference between the observation target position vector and the satellite position vector of each satellite is less than or less than a distance from the boundary of the observable region of the plurality of satellites to each satellite;
Observable time calculating means for calculating, as an observable time, a time at which the absolute value of the difference between the position vectors is determined to be less than or less than the distance to the boundary of the observable region;
A satellite observation plan creation device comprising satellite identification means for identifying a satellite having the earliest observable time within the observation period as a satellite capable of observing the observation target position.
(Additional remark 8) The said determination means determines whether the absolute value of the difference of the said position vector is below or less than the maximum slant range which shows the distance from the boundary of the observable area | region of these satellites to each satellite. Appendix 7 Satellite observation plan creation device.
(Supplementary Note 9) The storage means is calculated as the distance from the satellite to the boundary of the observable area from the height of the satellite and the width in the direction perpendicular to the moving direction of the observable area on the ground surface. The satellite observation plan creation device according to appendix 7, which stores a maximum slant range.
(Supplementary note 10) The satellite observation plan creation device according to supplementary note 7, wherein the inertial coordinate system is an equatorial plane coordinate, and a boundary of the observable region is a boundary line parallel to a moving direction of the satellite.

It is explanatory drawing of a Kepler element. It is a figure which shows a periphery point and an apogee point. It is a figure which shows the structure of the satellite observation system of embodiment. It is a figure which shows the structure of a satellite information table. It is a figure which shows the observable area | region of a satellite. It is a flowchart of the process which identifies the satellite which can be observed. It is a figure which shows an observation target position vector and a satellite position vector. It is explanatory drawing of the calculation method of LST of an observation target position. It is a figure which shows an example of the calculation result of an observation target position and the distance of a satellite.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Orbital element acquisition part 12 Satellite information table update part 13 Satellite information table 14 Observation condition reception part 15 Observation availability determination part 16 Determination result display part

Claims (5)

Storing data indicating Kepler elements of a plurality of satellites in a storage means;
Calculating an observation target position vector of the observation target position and an arbitrary satellite position vector of the plurality of satellites at an arbitrary time within the observation period in the inertial coordinate system when an observation target position and an observation period are designated;
Determining whether the absolute value of the difference between the observation target position vector and the satellite position vector of each satellite is less than or less than the distance from the boundary of the observable region of the plurality of satellites to each satellite; and
Calculating the time at which the absolute value of the position vector difference is determined to be less than or less than the distance to the boundary of the observable region as the observable time;
A satellite observation plan program in which a computer executes a step of identifying a satellite having the earliest observable time within the observation period as a satellite capable of observing the observation target position.   Whether the absolute value of the difference between the observation target position vector and the satellite position vector is less than or less than the maximum slant range indicating the distance from the boundary of the observable area of the plurality of satellites to each satellite; The satellite observation planning program according to claim 1, wherein:   The step of storing the data is calculated as a distance from the satellite to the boundary of the observable region from a height of the satellite and a width in a direction perpendicular to the moving direction of the satellite in the observable region on the ground surface. The satellite observation planning program executed by a computer according to claim 1, wherein a maximum slant range is stored in said storage means.   In the step of calculating the measurable time, when the satellite sensor is a visible light optical sensor, the observable time is converted into a local standard time at the observation target position, and the local standard time can be measured by the optical sensor. 2. The satellite observation planning program according to claim 1, wherein it is determined whether or not the time is within a certain time. Storage means for storing data indicating Kepler elements of a plurality of satellites;
Position calculation means for calculating the observation target position vector of the observation target position and the satellite position vectors of the plurality of satellites at an arbitrary time within the observation period in the inertial coordinate system when the observation target position and the observation period are designated When,
A determination means for determining whether an absolute value of a difference between the observation target position vector and the satellite position vector of each satellite is less than or less than a distance from the boundary of the observable region of the plurality of satellites to each satellite;
Observable time calculating means for calculating, as an observable time, a time at which the absolute value of the difference between the position vectors is determined to be less than or less than the distance from the satellite to the boundary of the observable region;
A satellite observation plan creation device comprising satellite identification means for identifying a satellite having the earliest observable time within the observation period as a satellite capable of observing the observation target position.