JP7829828B2 - Coordinate determination device, coordinate determination method, program, and recording medium for low orbit objects. - Google Patents

Description

This disclosure relates to a coordinate determination device, coordinate determination method, program, and recording medium for determining the coordinate position of low orbit objects such as space debris.

Patent Document 1 describes a method for detecting flying objects that, in order to avoid inter-satellite collisions or collisions with space debris in near-Earth orbit or distant geostationary orbit, allows for the prior determination of the trajectory of space debris or flying objects such as meteors through ground-based observations.

The line image detection method described in Patent Document 1 involves performing image data processing for all directions of the planar image, which consists of a division process that divides the image data of a planar image, which is a CCD image of the sky taken by a camera equipped with a CCD image sensor installed on a telescope, into a plurality of parallel columnar image data, and a representative value selection process that sets the median value obtained for each columnar image data as the representative value of that columnar image data. Subsequently, an analysis process is performed, which consists of a significance value detection process that detects whether or not the representative value of each columnar image data is a significant value, and a line image position identification process that sets the column position of the columnar image data in which the representative value is a significant value as the line image position.

Japanese Patent Publication No. 2003-132357

The line image detection method described in Patent Document 1 is configured as described above, and therefore, it has the problem of high image processing costs because it performs image processing by brute-force assuming the direction of motion of flying objects based on planar image data, which is a CCD image of the sky captured by a camera.

This disclosure has been made in view of the above-mentioned points, and aims to provide a low-Earth orbit object coordinate determination device that facilitates the determination of the position coordinates of orbital objects such as satellites, space debris, or meteors, i.e., low-Earth orbit objects.

The low-Earth orbit object coordinate determination device according to this disclosure comprises: a narrow-field optical telescope having a narrow-field imaging optical system with a narrow field of view and high resolution; a narrow-field light selection means for selecting light from low-Earth orbit objects from the light focused by the narrow-field imaging optical system; and a narrow-field image sensor that outputs the light selected by the narrow-field light selection means as narrow-field image data; a wide-field optical telescope having a wide-field imaging optical system with a wider field of view and lower resolution than the narrow-field imaging optical system and directed in the same direction as the direction of the narrow-field imaging optical system; a wide-field light selection means for selecting light from stars from the light focused by the wide-field imaging optical system; and a wide-field image sensor that outputs the light selected by the wide-field light selection means as wide-field image data; and a low-Earth orbit object position coordinate calculation device that identifies the celestial coordinates of low-Earth orbit objects using the detected position coordinates of low-Earth orbit objects detected from narrow-field image data from the narrow-field image sensor and the detected position coordinates of stars detected from wide-field image data from the wide-field image sensor.

According to this disclosure, determining the position coordinates of low orbit objects becomes easier.

This is a configuration diagram showing a coordinate determination device for low orbit objects according to Embodiment 1. This flowchart shows the tracking control function in the coordinate determination device for low orbit objects according to Embodiment 1. This flowchart shows the data acquisition control function in the coordinate determination device for low orbit objects according to Embodiment 1. This is a flowchart showing the position coordinate calculation function in the coordinate determination device for low orbit objects according to Embodiment 1. This is a configuration diagram showing the hardware configuration of the position coordinate calculation device in the coordinate determination device for low orbit objects according to Embodiment 1. This is a configuration diagram showing a coordinate determination device for low orbit objects according to Embodiment 2. This is a flowchart showing the position coordinate calculation function in the coordinate determination device for low orbit objects according to Embodiment 2.

Embodiment 1.
A coordinate determination device for low orbit objects according to Embodiment 1 will be described with reference to Figures 1 to 5.
The low Earth orbit object coordinate determination device according to Embodiment 1 is a low Earth orbit object position measurement device that tracks orbital objects such as satellites, space debris, or meteors, i.e., low Earth orbit objects, in near-Earth orbit and distant geostationary orbit using a highly sensitive primary telescope, and identifies the position coordinates of the low Earth orbit object from the position of a star captured by a secondary telescope with a wide field of view that has the same pointing direction as the primary telescope.

The coordinate determination device for low-Earth orbit objects according to Embodiment 1 detects low-Earth orbit objects as faint line images using a low-resolution secondary telescope in the tracking mode. However, by performing tracking of the low-Earth orbit objects with a highly sensitive primary telescope, it becomes possible to detect low-Earth orbit objects as bright point images. On the other hand, during tracking of low-Earth orbit objects, a star that serves as a reference for determining the position of the low-Earth orbit objects is observed simultaneously with the low-Earth orbit objects using a secondary telescope with a wide field of view, and a bright star is brought into the field of view.

The coordinate determination device for low orbit objects according to Embodiment 1 comprises a narrow-field optical telescope 10, a wide-field optical telescope 20, an optical axis adjustment device 30, a drive device 40, a position coordinate calculation device 50, and a database 60.
The narrow-field optical telescope 10 is a highly sensitive primary telescope for tracking low-orbit objects, and it has a narrow field of view and high resolution.

The narrow-field optical telescope 10 is designed to observe light arriving at the telescope from low-orbit objects with a high signal-to-noise ratio.
Light from low-orbit objects refers to a general term encompassing light that is reflected or scattered by low-orbit objects from sunlight, light that is reflected or scattered by low-orbit objects from laser light emitted from the ground, or light emitted by low-orbit objects themselves.

The narrow-field optical telescope 10 includes a narrow-field imaging optical system 11, a narrow-field light selection means 12, and a narrow-field image sensor 13.
The narrow-field imaging optical system 11 is an optical system with a narrow field of view and high resolution, and efficiently guides the received light.

The narrow-field imaging optical system 11 has a reflecting mirror and a lens, and has the function of focusing plane wave light incident on the aperture to a single point.
The focusing position depends on the angle of incidence to the aperture, and the narrow-field imaging optical system 11 forms an image on a plane (focal plane) perpendicular to the optical axis direction, which is located at a distance equal to the focal length from the narrow-field imaging optical system 11.
The narrow-field imaging optical system 11 is designed to detect even faint low-orbit objects, that is, weak light from low-orbit objects, with a high signal-to-noise ratio. Therefore, it has an optical system with a large aperture capable of focusing more light.

Since the mirrors and lenses that constitute the narrow-field imaging optical system 11, as well as the support material that supports the mirrors and lenses, are subject to thermal deformation, the focusing position of the narrow-field imaging optical system 11 also depends on temperature.
Therefore, the narrow-field optical telescope 10 has a distance fine-adjustment mechanism that fine-tunes the distance from the narrow-field imaging optical system 11 to the light-receiving surface of the narrow-field image sensor 13, which serves as the focal plane.
The distance fine-adjustment mechanism may be either a mechanism that automatically or manually adjusts the distance between the narrow-field imaging optical system 11 and the narrow-field image sensor 13.

The narrow-field light selection means 12 is connected to the narrow-field imaging optical system 11, selects the light focused by the narrow-field imaging optical system 11, and guides the selected light to the light-receiving surface of the narrow-field image sensor 13.
The light selected by the narrow-field light selection means 12 is primarily light from low-orbit objects.
The narrow-field light selection means 12 includes a plurality of light filters and a filter wheel.

When the narrow-field light selection means 12 selects an optical filter from the filter wheel, it receives control information from the control unit 52 regarding the filter selection, the timing of the exposure start for the light from the narrow-field imaging optical system 11 incident via the narrow-field light selection means 12, and the frame rate, and is controlled by the control unit 52.

The control information input to the narrow-field light selection means 12 from the control unit 52 as control information, which indicates the filter selection, the timing of exposure start for light from the narrow-field imaging optical system 11, and the frame rate, will be hereinafter referred to as narrow-field filter selection information.
The information indicating the selection of an optical filter is the information about which optical filter to select from the filter wheel.
The information indicating the timing of the start of exposure for light from the narrow-field imaging optical system 11 corresponds to the timing when the narrow-field optical telescope 10 detects a low-Earth orbit object in observation mode and begins tracking the detected low-Earth orbit object as a target.

The narrow-field light selection means 12 receives information from the control unit 52 indicating the timing of exposure start in the narrow-field filter selection information, and selects a light filter based on the information from the control unit 52 indicating the filter selection in the narrow-field filter selection information.
Furthermore, the narrow-field light selection means 12 receives information indicating the frame rate in the narrow-field filter selection information from the control unit 52, and selects an optical filter according to the frame rate based on the information indicating the filter selection in the narrow-field filter selection information from the control unit 52.

Note that information indicating the frame rate does not necessarily have to be included in the narrow-field filter selection information. The control unit 52 may hold this information and select the optical filter based on the frame rate by receiving information indicating the filter selection from the control unit 52.
Furthermore, even if the optical filter selected based on information indicating the timing of exposure commencement and information indicating filter selection is to be the same throughout the tracking period of the target low-orbit object, the control information indicating the frame rate does not need to be included in the narrow-field filter selection information.

An optical filter is either a wavelength filter or a polarization filter, or both.
Wavelength filters include those that transmit only specific wavelengths, those that block only specific wavelengths, and those whose transmittance changes continuously with respect to wavelength.
When using wavelength filters, for example, wideband filters such as the Sloan/SDSS system or Johnson system, or narrowband filters that transmit only the wavelength of laser light are used.

Furthermore, when using a polarizing filter, a PL filter that transmits only linearly polarized components in a specific direction, or a C-PL filter that transmits only circularly polarized components in a specific direction, is used.
To efficiently select light from low-orbit objects, wavelength filters and polarization filters are prepared to match the wavelength and polarization components of the light from these objects.

The filter wheel has multiple optical filters installed, and the desired optical filter is selected from the multiple installed optical filters either manually or automatically based on narrow-field filter selection information from the control unit 52.
For example, the filter wheel receives the filter selection information from the control unit 52, which is the filter slot number on the filter wheel, and rotates it so that the specified filter slot is on the optical axis of the narrow-field imaging optical system 11.
The light filter selected by the filter wheel selects the desired light from the light focused by the narrow-field imaging optical system 11 and guides it to the light-receiving surface of the narrow-field image sensor 13.

The narrow-field image sensor 13 is connected to the narrow-field light selection means 12 and is positioned on the focal plane where the light-receiving surface is focused by the narrow-field imaging optical system 11.
The narrow-field image sensor 13 converts the amount or intensity of incident light into a digital value for each of the numerous pixels spread in two dimensions on the light-receiving surface and outputs it as narrow-field image data, which is two-dimensional image data.

When acquiring narrow-field image data, the narrow-field image sensor 13 receives sensor parameters such as the exposure start timing, exposure time, frame rate, gain, and pixels to be read out as control information from the control unit 52, and is controlled by the control unit 52.

The narrow-field image sensor 13 is set to have a long exposure time in order to detect weak light from low-orbit objects with a high signal-to-noise ratio.
The control information input to the narrow-field image sensor 13 from the control unit 52, which indicates sensor parameters such as the timing of exposure start for light from the narrow-field imaging optical system 11, exposure time, frame rate, gain, and pixels to be read out, is hereinafter referred to as narrow-field optical control information.

The narrow-field image sensor 13 receives information from the control unit 52 indicating the timing of exposure start in the narrow-field light control information and starts imaging in tracking mode.
The narrow-field image sensor 13 receives information indicating the frame rate in the narrow-field optical control information from the control unit 52, and continuously performs imaging according to the frame rate and exposure time in the narrow-field optical control information until the end of the tracking mode.

Furthermore, control information indicating the frame rate does not necessarily have to be included in the optical control information for the narrow field of view. The control unit 52 may hold the frame rate and perform imaging based on the frame rate received from the control unit 52.

The narrow-field light control information and the narrow-field filter selection information are synchronized, and the narrow-field light selection means 12 and the narrow-field image sensor 13 are controlled in synchronization with the narrow-field filter selection information and the narrow-field light control information.
By synchronizing the narrow-field optical control information and the narrow-field filter selection information, it is also possible to change the filter used each time narrow-field image data is acquired according to the frame rate in the narrow-field optical control information from the control unit 52.

The narrow-field image sensor 13 uses either a thermal sensor or a quantum sensor.
When using a thermal sensor, a sensor such as a bolometer or thermopile is used, which converts the light intensity incident on each element (corresponding to each pixel) into heat, and then reads it out as a voltage value.
Furthermore, when using quantum sensors, sensors are used that convert photons into electrons through the internal photoelectric effect using semiconductor elements such as visible light sensors such as CCD sensors or CMOS sensors, or infrared sensors such as nGaAs sensors, InSb sensors, or HgCdTe sensors.

The wide-field optical telescope 20 is a secondary telescope with a wide field of view that is used to introduce stars into the field of view, which serve as a reference for determining the position of low-orbit objects, and is used for simultaneous observation with the narrow-field optical telescope 10. It has a wider field of view and lower resolution than the narrow-field optical telescope 10.
The wide-field optical telescope 20 is designed to observe light reaching the telescope from numerous bright stars located around low-orbit objects.

The wide-field optical telescope 20 includes a wide-field imaging optical system 21, a wide-field light selection means 22, and a wide-field image sensor 23.
The wide-field imaging optical system 21 is connected to the narrow-field imaging optical system 11 by an optical axis adjustment device 30 so that its direction of focus is the same as that of the narrow-field imaging optical system 11.

The wide-field imaging optical system 21 is mounted on the narrow-field imaging optical system 11 and fixed to the narrow-field imaging optical system 11 by two three-point holding mechanisms in the optical axis adjustment device 30.
The screws of the three-point holding mechanism in the optical axis adjustment device 30 are used as push-pull screws, and the misalignment of the directional direction of the wide-field imaging optical system 21 relative to the narrow-field imaging optical system 11 is adjusted in two axes using the screws of the three-point holding mechanism.

As a result, the directional direction of the narrow-field imaging optical system 11 and the directional direction of the wide-field imaging optical system 21 can be aligned using the optical axis adjustment device 30.
In other words, the optical axis of the wide-field imaging optical system 21 is made parallel to the optical axis of the narrow-field imaging optical system 11 by the optical axis adjustment device 30.
In short, the optical axis adjustment device 30 fixes the wide-field imaging optical system 21 to the narrow-field imaging optical system 11 so that the difference in direction of direction between the wide-field imaging optical system 21 and the narrow-field imaging optical system 11 can be adjusted on two axes.

The wide-field imaging optical system 21 has a wider field of view and lower resolution than the narrow-field imaging optical system 11, and is an optical system capable of collecting light from a wide field of view.
Since the wide-field imaging optical system 21 is an optical system capable of collecting light from a wide field of view, it is possible to detect as many bright stars as possible located around low-orbit objects within the field of view, even with low resolution.

The wide-field imaging optical system 21 has a reflecting mirror and a lens, and has the function of focusing plane wave light incident on the aperture to a single point.
The focusing position depends on the angle of incidence to the aperture, and the wide-field imaging optical system 21 forms an image on a plane (focal plane) perpendicular to the optical axis direction, which is located at a distance equal to the focal length from the wide-field imaging optical system 21.

Since the mirrors and lenses that constitute the wide-field imaging optical system 21, as well as the support material that supports the mirrors and lenses, are subject to thermal deformation, the focusing position of the light produced by the wide-field imaging optical system 21 also depends on temperature.
Therefore, the wide-field optical telescope 20 has a distance fine-adjustment mechanism that fine-tunes the distance from the wide-field imaging optical system 21 to the light-receiving surface of the wide-field image sensor 23, which is the focal plane.
The distance fine-adjustment mechanism may be either a mechanism that automatically or manually adjusts the distance between the wide-field imaging optical system 21 and the wide-field image sensor 23.

The wide-field light selection means 22 is connected to the wide-field imaging optical system 21, selects the light focused by the wide-field imaging optical system 21, and guides the selected light to the light-receiving surface of the wide-field imaging optical system 21.
The light selected by the wide-field light selection means 22 is mainly light from stars located around low-orbit objects.

The wide-field light selection means 22 includes a plurality of light filters and a filter wheel.
When the wide-field light selection means 22 selects an optical filter from the filter wheel, it receives control information from the control unit 52, including the filter selection, the timing of the exposure start for light from the wide-field imaging optical system 21, and the frame rate, and is controlled by the control unit 52.
The control information input to the wide-field light selection means 22 from the control unit 52 as control information, which indicates the filter selection, the timing of exposure start for light from the wide-field imaging optical system 21, and the frame rate, is hereinafter referred to as wide-field filter selection information.

The information indicating the timing of exposure start for light from the wide-field imaging optical system 21 and the frame rate in the wide-field filter selection information from the control unit 52 are the same as the information indicating the timing of exposure start for light from the narrow-field imaging optical system 11 and the frame rate in the narrow-field filter selection information.

The wide-field light selection means 22 receives information from the control unit 52 indicating the timing of exposure start in the wide-field filter selection information, and selects a light filter based on the information from the control unit 52 indicating the filter selection in the wide-field filter selection information.
Furthermore, the wide-field light selection means 22 receives information indicating the frame rate in the wide-field filter selection information from the control unit 52, and selects an optical filter according to the frame rate based on the information indicating the filter selection in the wide-field filter selection information from the control unit 52.

Note that information indicating the frame rate does not necessarily have to be included in the wide-field filter selection information. The control unit 52 may hold the frame rate and receive information indicating the filter selection from the control unit 52 according to the frame rate to select the optical filter.
Furthermore, even if the optical filter selected based on information indicating the timing of exposure commencement and filter selection is to be the same as the tracking period for the low-orbit object being tracked, the control information indicating the frame rate does not need to be included in the wide-field filter selection information.

The optical filter is either a wavelength filter or a polarization filter, or both, similar to the optical filter in the narrow-field light selection means 12.
When using wavelength filters as optical filters, for example, wideband filters such as the Sloan/SDSS system or Johnson system, or narrowband filters that transmit only the wavelength of laser light, are used.
Furthermore, when using a polarizing filter as an optical filter, a PL filter or a C-PL filter should be used.

To efficiently select light from stars, wavelength filters and polarization filters are prepared to match the wavelength and polarization components of the light from the stars.
The filter wheel has multiple optical filters installed, and the desired optical filter is selected from the multiple optical filters installed manually or automatically based on wide-field filter selection information from the control unit 52.

For example, the filter wheel receives the filter selection information from the control unit 52, which is the filter slot number on the filter wheel, and rotates it so that the specified filter slot is on the optical axis of the wide-field imaging optical system 21.
The light filter selected by the filter wheel selects the desired light from the light focused by the wide-field imaging optical system 21 and guides it to the light-receiving surface of the wide-field image sensor 23.

The wide-field image sensor 23 is connected to the wide-field light selection means 22 and is positioned on the focal plane where the light-receiving surface is focused by the wide-field imaging optical system 21.
The wide-field image sensor 23 converts the amount or intensity of incident light into a digital value for each of the numerous pixels spread in two dimensions on the light-receiving surface and outputs it as wide-field image data, which is two-dimensional image data.

When acquiring wide-field image data, the wide-field image sensor 23 receives sensor parameters such as the exposure start timing, exposure time, frame rate, gain, and pixels to be read out as control information from the control unit 52 for light from the wide-field imaging optical system 21 incident via the wide-field light selection means 22, and is controlled by the control unit 52.

The control information input to the wide-field image sensor 23 from the control unit 52, which indicates sensor parameters such as the timing of exposure start for light from the wide-field imaging optical system 21, exposure time, frame rate, gain, and pixels to be read out, is hereinafter referred to as wide-field optical control information.

The wide-field image sensor 23 receives information from the control unit 52 indicating the timing of exposure start in the wide-field optical control information and starts imaging in tracking mode.
The wide-field image sensor 23 receives information indicating the frame rate in the wide-field optical control information from the control unit 52, and continuously performs imaging according to the frame rate and exposure time in the wide-field optical control information until the end of the tracking mode.

Furthermore, control information indicating the frame rate does not necessarily have to be included in the wide-field optical control information. The control unit 52 may hold this information and perform imaging based on the frame rate received from the control unit 52.

The wide-field optical control information and the wide-field filter selection information are synchronized, and the wide-field optical selection means 22 and the wide-field image sensor 23 are controlled in synchronization with the wide-field filter selection information and the wide-field optical control information.
By synchronizing the wide-field optical control information and the wide-field filter selection information, it is also possible to change the filter used each time wide-field image data is acquired according to the frame rate in the wide-field optical control information from the control unit 52.
Furthermore, the wide-field optical control information and wide-field filter selection information are synchronized with the narrow-field optical control information and narrow-field filter selection information.

The wide-field image sensor 23 uses a thermal or quantum sensor, similar to the narrow-field image sensor 13.
When using a thermal sensor as the wide-field image sensor 23, a sensor such as a bolometer or thermopile is used.
Furthermore, when a quantum-type sensor is used as the wide-field image sensor 23, a sensor is used that converts photons into electrons by the internal photoelectric effect using semiconductor elements such as a visible light band sensor of a CCD sensor or CMOS sensor, or an infrared band sensor of an InGaAs sensor, InSb sensor, or HgCdTe sensor.

The narrow-field imaging optical system 11 is mounted on the drive unit 40.
The narrow-field light selection means 12 is connected to the narrow-field imaging optical system 11, and the narrow-field image sensor 13 is connected to the narrow-field light selection means 12. As a result, both the narrow-field light selection means 12 and the narrow-field image sensor 13 are mounted on the drive unit 40.
In short, the narrow-field optical telescope 10 is mounted on the drive unit 40.

Since the wide-field imaging optical system 21 is mounted and fixed on the narrow-field imaging optical system 11, it is consequently mounted on the drive unit 40.
The wide-field light selection means 22 is connected to the wide-field imaging optical system 21, and the wide-field image sensor 23 is connected to the wide-field light selection means 22. As a result, both the wide-field light selection means 22 and the wide-field image sensor 23 are mounted on the drive unit 40.
In short, the wide-field optical telescope 20 is mounted on the drive unit 40 and driven together with the narrow-field optical telescope 10.

The drive unit 40 automatically drives the mounted narrow-field optical telescope 10 to change the direction of the narrow-field imaging optical system 11 in two axes, according to the input value from the control unit 52 indicating the amount of drive in two axes.
The drive unit 40 automatically drives the narrow-field optical telescope 10 on two axes, thereby allowing the direction of the narrow-field imaging optical system 11 in the narrow-field optical telescope 10 to track low-orbit objects.
The drive unit 40 is a dual-axis rotating mount, such as a German equatorial mount, a fork equatorial mount, or an altazimuth mount.

The low orbit object position coordinate calculation device 50 has a position coordinate calculation function to obtain the celestial coordinates of the low orbit object, a data acquisition control function to control the acquisition of image data from the narrow-field optical telescope 10 and the wide-field optical telescope 20, and a tracking control function to control the drive of the drive device 40 in order to track the low orbit object.
The position coordinate calculation device 50 includes a tracking trajectory determination unit 51, a control unit 52, an image recording unit 53, a preprocessing unit 54, a stationary object detection unit 55, a moving object detection unit 56, a stellar coordinate comparison unit 57, and a low-orbit object position coordinate determination unit 58.

The position coordinate calculation function in the position coordinate calculation device 50 receives narrow-field image data from the narrow-field image sensor 13 of the narrow-field optical telescope 10 and wide-field image data from the wide-field image sensor 23 of the wide-field optical telescope 20 as input. It acquires the detected position coordinates of stars detected from the wide-field image data from the wide-field image sensor 23, acquires the detected position coordinates of low-orbit objects detected from the narrow-field image data from the narrow-field image sensor 13, and uses the acquired detected position coordinates of stars to determine the celestial coordinates of the low-orbit objects.

The position coordinate calculation function in the position coordinate calculation device 50 is achieved by the image recording unit 53, the preprocessing unit 54, the stationary object detection unit 55, the moving object detection unit 56, the stellar coordinate comparison unit 57, and the position coordinate determination unit 58 for low orbital objects.
The image recording unit 53 receives narrow-field image data from the narrow-field image sensor 13 and wide-field image data from the wide-field image sensor 23, and stores narrow-field image data in which narrow-field optical control information from the control unit 52 is linked to the narrow-field image data, and wide-field image data in which wide-field optical control information from the control unit 52 is linked to the wide-field image data.

Furthermore, the narrow-field image data and wide-field image data do not necessarily have to be linked to optical control information.
Alternatively, the narrow-field image data from the narrow-field image sensor 13 and the wide-field image data from the wide-field image sensor 23 may be directly input to the preprocessor 54 without storing the data in the image recording unit 53.

The preprocessing unit 54 acquires the narrow-field image data stored in the image recording unit 53 and performs preprocessing, which involves subtracting the dark current from the narrow-field image data and correcting for sensitivity unevenness within the narrow-field image data.
The preprocessing for dark current subtraction in the preprocessing unit 54 is the process of subtracting the dark current image data stored in the database from the narrow-field image data.

Furthermore, the preprocessing for correcting sensitivity unevenness in the preprocessing unit 54 is performed using flat image data stored in the database from the narrow-field image data, and involves dividing the narrow-field image data obtained by subtracting the dark current image data from the narrow-field image data by the flat image data.

Dark current image data is image data obtained by pre-measuring the operating temperature and exposure time of the narrow-field image sensor 13 under the same conditions as when obtaining narrow-field image data, without irradiating the narrow-field image sensor 13 with light.
The flat image data is image data measured in advance under conditions in which the light-receiving surface of the narrow-field image sensor 13 is uniformly illuminated with light intensity.
Dark current image data and flat image data are stored in database 60.

Furthermore, the preprocessing unit 54 may acquire wide-field image data stored in the image recording unit 53 and perform preprocessing on the wide-field image data, similar to the preprocessing for narrow-field image data, which involves subtracting dark current and correcting sensitivity unevenness within the narrow-field image data.
In this case as well, the wide-field image sensor 23 is not irradiated with light, and the dark current image data, which was measured in advance under the same operating temperature and exposure time conditions as when obtaining wide-field image data, is stored in the database 60.

Flat image data, measured in advance under conditions where the light-receiving surface of the wide-field image sensor 23 is uniformly illuminated with light intensity, is stored in the database 60.
The preprocessing unit 54 obtains wide-field image data by preprocessing the dark current image data and flat image data stored in the database 60, respectively.

The stationary object detection unit 55 detects point images from the narrow-field image data that has been preprocessed by the preprocessing unit 54, and uses the center coordinates of the detected point images as the detection position coordinates of the low-orbit object.
The detected position coordinates of low-orbit objects are represented as a group of coordinates consisting of multiple pixels, where each pixel in the narrow-field image sensor 13 is considered to be a single position coordinate.

The algorithm for detecting point images in the stationary object detection unit 55 extracts connected pixels with values sufficiently large compared to the variation in values in the surrounding sky region. Among the extracted connected pixels, the center coordinates of the point image having a half-width of 3 to 10 arcseconds, including 5 arcseconds which is a typical image blur size for atmospheric turbulence, and having a ratio of the major axis to the minor axis of the connected pixel of 1.5 or less, are used as the detection position coordinates of the low orbit object.

The narrow-field image data obtained by the narrow-field image sensor 13 is obtained as a result of exposure of about 1 second in tracking mode to detect faint low-orbit objects. Assuming that the typical velocity of low-orbit objects is 30 arcminutes/second, even if a stellar line image appears in the narrow-field image data, the stellar line image will appear as a line image with a length of 30 arcminutes. Therefore, the stationary object detection unit 55 will not detect a stellar line image from the narrow-field image data.

In tracking mode, an example of an exposure time of about 1 second for the narrow-field image sensor 13 was shown, but the exposure time may be shortened to 0.01 seconds.
If the exposure time is 0.01 seconds, even if a stellar line image appears in the narrow-field image data, the stellar line image will appear as a line image with a length of 18 arcseconds. This is considerably longer than the typical image broadening of 5 arcseconds due to atmospheric turbulence, and the stationary object detection unit 55, which detects point images with a full width at half maximum of 3 to 10 arcseconds, will not detect a stellar line image from the narrow-field image data.

Therefore, the stationary object detection unit 55, which detects point images with a half-width of 3 arcseconds to 10 arcseconds and a ratio of the major axis to the minor axis of the connected pixels of 1.5 or less, can accurately detect point images caused by low-orbiting objects from narrow-field image data.

The moving object detection unit 56 detects a line image from the wide-field image data from the wide-field image sensor 23, and uses the center coordinates of the detected line image as the detected position coordinates of the star.
The detected position coordinates of a star are represented as a group of coordinates consisting of multiple pixels, where each pixel in the wide-field image sensor 23 is considered to have a single position coordinate.
The wide-field image data used by the moving object detection unit 56 to detect the position coordinates of a star may also be wide-field image data from the wide-field image sensor 23 that has been pre-processed by the pre-processing unit 54.

The algorithm for detecting line images in the moving object detection unit 56, similar to the detection of point images in the stationary object detection unit 55, extracts connected pixels with values sufficiently large relative to the variation in values in the surrounding sky region. Among the extracted connected pixels, the center coordinates of the line image where the major axis of the connected pixel has a full width at half maximum of 10 arcseconds or more (larger than the typical image blur size of atmospheric turbulence, which is 5 arcseconds), and the ratio of the major axis to the minor axis of the connected pixel is 2 or more, are used as the detected position coordinates of the star.

The wide-field image data obtained by the wide-field image sensor 23 is obtained as a result of an exposure time of 0.01 seconds in tracking mode. Assuming a typical velocity of low-orbit objects is 30 arcminutes/second, the line images from stars appear as line images with a size of 18 arcseconds. Therefore, the moving object detection unit 56, which detects line images with a half-width of 10 arcseconds or more, can detect line images from stars from the wide-field image data and will not detect point images from low-orbit objects.

Therefore, the moving object detection unit 56, which detects line images with a full width at half maximum of 10 arcseconds or more and a ratio of major axis to minor axis of 2 or more, can accurately detect line images caused by stars from wide-field image data.
Furthermore, even if the exposure time for the wide-field image sensor 23 is increased to 0.01 seconds or more in tracking mode, the line images of stars obtained from the wide-field image data only become longer, and the signal-to-noise ratio per pixel does not improve.

Therefore, it is preferable to shorten the exposure time for the wide-field image sensor 23 and lengthen the exposure time for the narrow-field image sensor 13 compared to the exposure time for the wide-field image sensor 23.
Furthermore, the threshold value for the ratio of the major axis to the minor axis of the line image as the object to be detected in the moving object detection unit 56 should be set considering the length of the line image, which depends on the velocity of the low-orbit object and the exposure time in the wide-field image sensor 23.

The stellar coordinate comparison unit 57 compares the detected position coordinates of the star obtained by the moving object detection unit 56 with the celestial coordinate data of known stars stored in the database 60, and obtains the correspondence between the detected position coordinates of the star and the celestial coordinate data of the star.
The correspondence between coordinates in a star represents the correspondence between coordinates obtained by mapping the position coordinates of pixels in the wide-field image sensor 23 to celestial coordinates in the celestial coordinate system.
The celestial coordinate data for known stars is the data listed in star catalogs such as the UCAC4 catalog, and is expressed in either the equatorial coordinate system (right ascension and declination) or the galactic coordinate system (galactic longitude and latitude).

The correspondence between the celestial sphere coordinate data of a star and the detected position coordinates of the star is obtained, for example, as follows:
The celestial coordinate data of a star is expressed primarily using angles, such as right ascension and declination, or azimuth and altitude.
On the other hand, the detected position coordinates of a star are represented by the position of each pixel in the wide-field image sensor 23, which is considered as a single position coordinate, that is, by coordinates in a two-dimensional plane of x and y coordinates.

Therefore, the correspondence between the coordinates represented by the two-dimensional plane of the wide-field image data from the wide-field image sensor 23 and the celestial coordinate data of the stars is obtained in advance, for example, as a correspondence table.
The stellar coordinate comparison unit 57 compares the detected position coordinates of the star obtained by the moving object detection unit 56 with the celestial sphere coordinate data of the star using a correspondence table, thereby determining which direction on the celestial sphere corresponds to the position coordinates of the pixels in which the star is reflected.
As a result, it becomes possible to determine which direction each pixel of the wide-field image data corresponds to on the celestial sphere.

The low-orbit object position coordinate determination unit 58 identifies the celestial coordinates of the low-orbit object based on the comparison result of the stellar coordinate comparison unit 57, that is, the correspondence between the detected position coordinates of the stellar object and the celestial coordinate data of the stellar object.
The position coordinate determination unit 58 uses the position coordinates detected by the stationary object detection unit 55, the correspondence between the detected position coordinates of the stars and the celestial sphere coordinate data of the stars, and the correspondence between the position coordinates of the pixels in the image data stored in the database 60, specifically the position coordinates of the pixels in the narrow-field image data from the narrow-field image sensor 13 and the position coordinates of the pixels in the wide-field image data from the wide-field image sensor 23, to determine the celestial sphere coordinates of the detected position coordinates of the low-orbit objects based on the correspondence between the coordinates in the stars and the correspondence between the image data coordinates of the optical system.

The correspondence between image data coordinates in the optical system is based on data measured when the wide-field imaging optical system 21 is fixed to the narrow-field imaging optical system 11 by adjusting its optical axis using the optical axis adjustment device 30, specifically the position coordinates of pixels in the narrow-field image sensor 13 relative to the narrow-field image data and the position coordinates of pixels in the wide-field image sensor 23 relative to the wide-field image data.
The data representing the correspondence between image data coordinates of the optical system is stored in the database 60.

The correspondence between the coordinates of the measured optical system's image data corresponds to the correspondence between the coordinates of the narrow-field image data from the narrow-field image sensor 13 and the wide-field image data from the wide-field image sensor 23.
The correspondence between image data coordinates in an optical system is, for example, the correspondence between the coordinates of narrow-field image data from the narrow-field image sensor 13 and wide-field image data from the wide-field image sensor 23 in a narrow-field optical telescope with a field of view of 0.5 deg × 0.5 deg and a wide-field optical telescope with a field of view of approximately 8 deg × 8 deg, with the target low-orbit object as the center of the field of view.

The identification of the celestial coordinates of the low-orbit object by the low-orbit object position coordinate determination unit 58, that is, the specific determination of the celestial coordinates of the low-orbit object, is performed, for example, as follows.
Based on the correspondence between image data coordinates in the optical system, that is, the correspondence between the coordinates of narrow-field image data and wide-field image data, and the correspondence between the coordinates of the wide-field image data and the celestial sphere coordinate data of stars, the correspondence between the coordinates of the narrow-field image data and the celestial sphere coordinate data is determined.

Next, the celestial coordinates of the low-orbit object are determined by comparing the detected position coordinates of the low-orbit object by the stationary object detection unit 55 with the celestial coordinate data using the correspondence between the coordinates of the narrow-field image data and the celestial coordinate data.

The data acquisition control function in the position coordinate calculation device 50 controls the wide-field light selection means 22 and narrow-field image sensor 13 in the narrow-field optical telescope 10, and the wide-field light selection means 22 and wide-field image sensor 23 in the wide-field optical telescope 20, thereby obtaining narrow-field image data that is easily acquired from the narrow-field image sensor 13 as point images of low-orbital objects, and wide-field image data that is easily acquired from the wide-field image sensor 23 as line images of stars.

The data acquisition control function in the position coordinate calculation device 50 is achieved by the control unit 52.
The control unit 52 provides narrow-field light selection means 12 with narrow-field filter selection information, causing the narrow-field light selection means 12 to select an appropriate filter at the timing of the start of exposure for light from the narrow-field imaging optical system 11.
The control unit 52 provides narrow-field light control information to the narrow-field image sensor 13, causing the narrow-field image sensor 13 to output narrow-field image data that can detect low-orbit objects as bright point images, based on the timing of exposure start, frame rate, and exposure time for light from the narrow-field imaging optical system 11.

The control unit 52 provides wide-field light selection means 22 with wide-field filter selection information, causing the wide-field light selection means 22 to select an appropriate filter at the timing of exposure start for light from the wide-field imaging optical system 21.
The control unit 52 provides wide-field optical control information to the wide-field image sensor 23, causing the wide-field image sensor 23 to output wide-field image data capable of detecting the position of stars over a wide field of view, based on the timing of exposure start, frame rate, and exposure time for light from the wide-field imaging optical system 21.
The control unit 52 synchronously controls the narrow-field image sensor 13, the wide-field light selection means 22, and the wide-field image sensor 23.

The tracking control function in the position coordinate calculation device 50 estimates the predicted trajectory of the target low-orbit object based on information about the low-orbit object, calculates the two-axis drive amount based on the estimated predicted trajectory and the current directional direction of the narrow-field imaging optical system 11 from the drive device 40, provides the calculated two-axis drive amount to the drive device 40, and controls the drive device 40 by the two-axis drive amount to adjust the directional direction of the narrow-field imaging optical system 11 to match the predicted trajectory of the low-orbit object.

The tracking control function in the position coordinate calculation device 50 is achieved by the control unit 52 and the tracking trajectory determination unit 51.
The tracking trajectory determination unit 51 estimates the time-series predicted trajectory coordinates of the target low Earth orbit object based on information about the low Earth orbit object.

The information about the target low Earth orbit object is, in observation mode, the coordinate position information of the observation position in the coordinate system of the narrow-field image data of the low Earth orbit object, as observed from the narrow-field image data obtained by the narrow-field optical telescope 10.
The time-series predicted orbital coordinates for low-Earth orbit objects are information converted into celestial coordinates centered on the coordinate information of the observed position in the coordinate system.

The observation location refers to the latitude, longitude, and altitude of the position where the observer is conducting the observation.
On the other hand, the predicted orbital coordinates in the information of the target low Earth orbit object are coordinates that have been converted from the latitude, longitude, and altitude of the position where the low Earth orbit object is expected to actually pass through to celestial coordinate values where the passage of the low Earth orbit object will be observed.

If the information of the target low Earth orbit object is defined as two-line elements (TLEs) that include information of Kepler orbital elements in the geocentric coordinate system, the tracking trajectory determination unit 51 calculates the predicted trajectory of the low Earth orbit object based on the observed two-line elements.
The tracking trajectory determination unit 51 converts the obtained predicted trajectory coordinates into celestial sphere coordinates centered on the coordinate information of the observed position of the low Earth orbit object, and estimates the time-series predicted trajectory coordinates of the observed low Earth orbit object.

The predicted trajectory coordinates in the time series are, for example, the coordinates estimated in the time series N times from time _t1 to time _tN , where N is a natural number greater than or equal to 2.
Time _t1 is the time one frame after time _t0 , when a point image of a low-orbit object was observed from the narrow-field image data obtained by the narrow-field optical telescope 10 in observation mode, and time _tN is the time just before the predicted orbit coordinates determined by the tracking orbit determination unit 51 exceed the observable range of the low-orbit object by the narrow-field optical telescope 10.

The interval between time points t _{and n} (n = 1 to N) is determined by the frame rate.
The calculation algorithm used by the tracking trajectory determination unit 51 is SGP4 (Simplified General Perturbations Satellite Orbit Model 4).
Note that while the time-series estimated coordinates in the predicted orbit coordinates are given intervals according to the frame rate, they may also be integer fractions of the interval according to the frame rate.

The control unit 52 calculates the two-axis drive amount for each time step in estimating the predicted trajectory coordinates based on the predicted trajectory coordinates from the tracking trajectory determination unit 51 and the directional direction of the narrow-field imaging optical system 11 from the drive unit 40, and provides the drive control signal indicating the calculated two-axis drive amount to the drive unit 40.
The two-axis drive amount at each time _tn is calculated based on separation information obtained from the difference between the position coordinates of the low-orbit object predicted in the predicted orbit coordinates from the tracking orbit determination unit 51 at time _tn and the position coordinates of the narrow-field imaging optical system 11 in the direction of direction from the drive device 40.

The control unit 52 provides the drive device 40 with a drive control signal indicating the amount of two-axis drive, thereby controlling the drive device 40 to track the target low-orbit object in the direction of the narrow-field imaging optical system 11.
Furthermore, at time _tn , if the drive of the drive device 40 controlled by the drive control signal causes the point image of a low-orbit object to move out of the narrow-field image data from the narrow-field image sensor 13, an offset is added to the predicted position coordinates of the low-orbit object in the predicted trajectory coordinates from the tracking trajectory determination unit 51, and the separation information is changed by the offset amount to change the two-axis drive amount so that the low-orbit object enters the light-receiving surface of the narrow-field image sensor 13.

The drive unit 40 drives the two drive axes using the drive control signals from the control unit 52 as drive angle amounts for the two drive axes. The drive unit 40 continuously manipulates the drive angle amounts for the two drive axes from time _t1 to time _tN , thereby enabling the narrow-field imaging optical system 11 to track the target low-orbit object.
Finally, when the predicted trajectory coordinates from the tracking trajectory determination unit 51 exceed the observable range of the narrow-field imaging optical system 11, the tracking of the target low-orbit object by the narrow-field imaging optical system 11, driven by the drive device 40, ends.

Next, the operation of the coordinate determination device for low orbit objects according to Embodiment 1 will be explained using Figures 2 to 4.
As shown in Figure 2, as a preliminary step, in step ST01, the optical axis of the narrow-field imaging optical system 11 and the optical axis of the wide-field imaging optical system 21 are adjusted using the optical axis adjustment device 30, and the optical axis of the narrow-field imaging optical system 11 and the optical axis of the wide-field imaging optical system 21 are made parallel using the optical axis adjustment device 30, and the wide-field optical telescope 20 is fixed to the narrow-field optical telescope 10.
The optical axis of the wide-field optical telescope 20 is adjusted, and when the wide-field optical telescope 20 is fixed to the narrow-field optical telescope 10, the field of view of the narrow-field optical telescope 10 and the field of view of the wide-field optical telescope 20 are measured, and the correspondence between the fields of view in the optical system is stored in the database 60.

In step ST02, when the narrow-field optical telescope 10 detects a low-Earth orbit object in observation mode, the tracking trajectory determination unit 51 estimates the time-series predicted trajectory coordinates of the target low-Earth orbit object.
Once steps ST01 and ST02 are completed, the tracking control function, data acquisition control function, and position coordinate calculation function of the position coordinate calculation device 50 are processed.

The tracking control function starts calculating the two-axis drive amount for the drive unit 40 at time _t1 when the loop starts.
In step ST11, the control unit 52 calculates the difference between the time-series predicted trajectory coordinates of the target low-orbit object estimated by the tracking trajectory determination unit 51 at time _t1 and the coordinates of the current direction of orientation from the drive unit 40, and calculates the two-axis drive amount for the drive unit 40 at time _t1 .

In step ST12, the drive device 40 is driven according to an input value indicating the two-axis drive amount, which is a drive control signal from the control unit 52, and the mounted narrow-field optical telescope 10 automatically tracks a target low-orbit object by changing the direction of the narrow-field imaging optical system 11 on two axes.
In step ST12, when the drive to the drive device 40 at time _t1 is completed, the process proceeds to the end of the loop. Since time _t1 is not the time when the predicted trajectory coordinates from the tracking trajectory determination unit 51 exceed the observable range of the narrow-field imaging optical system 11, the process returns to the start of the loop. The drive control of the drive device 40 in steps ST11 and ST12 is repeated until time _tN , just before time _tn exceeds the observable range of the narrow-field imaging optical system 11.

When the drive control of the drive unit 40 by steps ST11 and ST12 at time t _N is completed, the tracking control function of the position coordinate calculation unit 50 is terminated at the end of the loop.
When the loop starts, the tracking control function is initiated, and the data acquisition control function in the position coordinate calculation device 50 is initiated.

As shown in Figure 3, from time _t0 when a point image of a low-orbit object is observed from the narrow-field optical telescope 10's narrow-field image data, the narrow-field optical telescope 10 and the wide-field optical telescope 20 begin imaging in tracking mode.
When the tracking control function starts and the data acquisition control function starts shooting, in step ST21, the control unit 52 sets narrow-field filter selection information for the narrow-field light selection means 12, narrow-field light control information for the narrow-field image sensor 13, wide-field filter selection information for the wide-field light selection means 22, and wide-field light control information for the wide-field image sensor 23.

In observation mode, at time _t0 immediately before imaging, when a point image of a low-orbit object is observed from the narrow-field image data obtained by the narrow-field optical telescope 10, the control unit 52 provides the narrow-field light selection means 12 with information indicating the selection of a filter in the narrow-field filter selection information.
The narrow-field light selection means 12 selects an optical filter based on information indicating filter selection, and ensures that the selected optical filter is on the optical axis of the narrow-field imaging optical system 11.

Similarly, at time _t0 , the control unit 52 provides the wide-field light selection means 22 with information indicating the selection of a filter in the wide-field filter selection information.
The wide-field light selection means 22 selects an optical filter based on information indicating filter selection, and ensures that the selected optical filter is on the optical axis of the wide-field imaging optical system 21.

At time _t0 , the control unit 52 provides the narrow-field image sensor 13 with information indicating sensor parameters for narrow-field optical control.
The narrow-field image sensor 13 has its gain and readout pixels set based on information indicating sensor parameters.
Similarly, at time _t0 , the control unit 52 provides the wide-field image sensor 23 with information indicating the sensor parameters in the wide-field optical control information.
The wide-field image sensor 23 has its gain and readout pixels set based on information indicating sensor parameters.

Once the settings are complete, in step ST22, the narrow-field image sensor 13 performs imaging with the set exposure time according to the narrow-field light control information from the control unit 52.
The process returns to step ST21 according to the frame rate indicated by the narrow-field optical control information, and steps ST21 and ST22 are repeated until time _tN just before the predicted trajectory coordinates from the tracking trajectory determination unit 51 exceed the observable range of the narrow-field imaging optical system 11, and the narrow-field image sensor 13 outputs N narrow-field image data.

Furthermore, in step ST22, the wide-field image sensor 23 performs imaging with a set exposure time according to the wide-field optical control information from the control unit 52.
The process returns to step ST21 according to the frame rate indicated by the wide-field optical control information, and steps ST21 and ST22 are repeated until time _tN , during which the wide-field image sensor 23 outputs N wide-field image data.

During the period of tracking the target low-orbit object, narrow-field image data is output from the narrow-field image sensor 13 and wide-field image data is output from the wide-field image sensor 23. When the tracking period ends, the narrow-field optical telescope 10 and the wide-field optical telescope 20 cease imaging in tracking mode.

When narrow-field image data from the narrow-field image sensor 13 and wide-field image data from the wide-field image sensor 23 are output, the position coordinate calculation function in the position coordinate calculation device 50 starts, as shown in Figure 4.
In step ST31, when the narrow-field image data from the narrow-field image sensor 13 and the wide-field image data from the wide-field image sensor 23 are input to the position coordinate calculation device 50, the narrow-field image data is stored in the image recording unit 53 as narrow-field image data with narrow-field optical control information linked to it, and the wide-field image data is stored in the image recording unit 53 as wide-field image data with wide-field optical control information linked to it.

The narrow-field image data and wide-field image data, each consisting of N images captured in succession and input to the position coordinate calculation device 50, may be input to the position coordinate calculation device 50 at time t _n intervals, or the N images from time t ₀ to time t _N may be input to the position coordinate calculation device 50 all at once.
In short, all narrow-field and wide-field image data captured during the period of tracking the target low-orbit object should be stored in the image recording unit 53.

In step ST32, the preprocessing unit 54 acquires the narrow-field image data stored in the image recording unit 53 and performs preprocessing on the narrow-field image data, which involves subtracting the dark current based on the dark current image data and correcting the sensitivity unevenness within the narrow-field image data based on the flat image data.
Similarly, the preprocessing unit 54 performs preprocessing on the wide-field image data stored in the image recording unit 53, which involves subtracting the dark current based on the dark current image data and correcting the sensitivity unevenness within the narrow-field image data based on the flat image data.

Step ST32 is a preprocessing step in which the preprocessing unit 54 performs a dark current subtraction and sensitivity unevenness correction for both the narrow-field image data and the wide-field image data, respectively.
Once the preprocessing step ST32 is completed, the preprocessed narrow-field image data is processed in step ST33, and the preprocessed wide-field image data is processed in step ST34.

In step ST33, the stationary object detection unit 55 detects a point image from the narrow-field image data that has been preprocessed by the preprocessing unit 54, and the stationary object detection unit 55 uses the center coordinates of the detected point image within the narrow-field image data as the detection position coordinates of the low-orbit object.
In step ST34, the moving object detection unit 56 detects a line image from the wide-field image data that has been preprocessed by the preprocessing unit 54, and the moving object detection unit 56 uses the center coordinates of the detected line image within the wide-field image data as the detected position coordinates of the star.

In step ST35, the stellar coordinate comparison unit 57 compares the detected position coordinates of the star obtained by the moving object detection unit 56 with the celestial coordinate data of known stars stored in the database 60, and obtains the correspondence between the detected position coordinates of the star and the celestial coordinate data of the star.

In step ST36, the celestial coordinates of the target low-Earth orbit object are obtained from the detection position coordinates of the target low-Earth orbit object, based on the correspondence between the detected position coordinates of the low-Earth orbit object obtained by the stationary object detection unit 55, the correspondence between the coordinates on the star obtained by the stellar coordinate comparison unit 57, and the correspondence between the image data coordinates of the optical systems in the narrow-field imaging optical system 11 and the wide-field imaging optical system 21 stored in the database 60.

In other words, step ST36 determines the correspondence between the coordinates of the narrow-field image data and the celestial coordinate data based on the correspondence between the image data coordinates of the optical system and the correspondence between the coordinates in the stars.
Next, step ST36 determines the celestial coordinates for the detected position coordinates of the low orbit object using the correspondence between the coordinates of the narrow-field image data and the celestial coordinate data.
Step ST36 is a step in which the position coordinate determination unit 58 identifies the celestial coordinates of the low-orbit object from the detected position coordinates of the low-orbit object based on the correspondence between coordinates in the star.

Having obtained the celestial coordinates of the low-orbit object, the position coordinate calculation function of the position coordinate calculation device 50 is terminated.
The celestial coordinates of the low-orbit object obtained by the position coordinate determination unit 58 are output to a display means (not shown).

The position coordinate calculation device 50 is implemented using a computer hardware configuration, and as shown in Figure 5, it comprises a CPU (Central Processing Unit) 50A, a large-capacity semiconductor memory (RAM: Random Access Memory) 50B, a storage device (ROM: Read-only memory) 50C such as a hard disk drive or SSD, an input interface unit 50D, an output interface unit 50E, and a signal path (bus) 50F.

The CPU 50A controls and manages the RAM 50B, ROM 50C, input interface unit 50D, and output interface unit 50E.
CPU 50A loads the program stored in ROM 50C into RAM 50B, and CPU 1A executes various processes based on the program loaded into RAM.

The tracking trajectory determination unit 51, the control unit 52, the preprocessing unit 54, the stationary object detection unit 55, the moving object detection unit 56, the stellar coordinate comparison unit 57, and the position coordinate determination unit 58 are each composed of a CPU 50A, RAM 50B, and ROM 50C.
The image recording unit 53 is composed of RAM 50B.
The database 60 may be composed of RAM 50B and ROM 50C.

The coordinate determination program stored in ROM 50C, which determines the position coordinates of a target low-Earth orbit object to be executed by CPU 50A, includes the following steps: detecting point images from narrow-field image data from a narrow-field optical telescope 10 having a narrow-field imaging optical system 11 with a narrow field of view and high resolution, and using these as the detected position coordinates of the low-Earth orbit object; detecting line images from wide-field image data from a wide-field optical telescope 20 having a wide-field imaging optical system 21 with a wider field of view than the narrow-field imaging optical system 11, lower resolution, and directed in the same direction as the narrow-field imaging optical system 11, and using these as the detected position coordinates of a star; obtaining the correspondence between the detected position coordinates of a star and the celestial coordinate data of the star; and identifying the celestial coordinates of the low-Earth orbit object from the detected position coordinates of the low-Earth orbit object based on the correspondence between the coordinates of the star.

The low-orbit object coordinate determination device according to Embodiment 1 comprises a narrow-field optical telescope 10 having a narrow-field imaging optical system 11 with a narrow field of view and high resolution, and a wide-field optical telescope 20 having a wide-field imaging optical system 21 with a wider field of view and lower resolution than the narrow-field imaging optical system 11, and directed in the same direction as the narrow-field imaging optical system 11. The device acquires the detected position coordinates of low-orbit objects from narrow-field image data from a narrow-field image sensor 13 in the narrow-field optical telescope 10, and the detected position coordinates of stars from a wide-field image data from a wide-field image sensor 23 in the wide-field optical telescope 20. The device includes a low-orbit object position coordinate calculation device 50 that uses the acquired detected position coordinates of stars to identify the celestial coordinates of the low-orbit objects. As a result, the position coordinates of a target low-orbit object can be easily determined, and the celestial coordinates of the low-orbit object can be easily obtained with high accuracy.

Embodiment 2.
The coordinate determination device for low orbit objects according to Embodiment 2 will be explained with reference to Figures 6 and 7.
The low-Earth orbit object coordinate determination device according to Embodiment 1 identifies the celestial coordinates of a target low-Earth orbit object using a single narrow-field image data output from the narrow-field optical telescope 10.
In contrast, the coordinate determination device for low orbital objects according to Embodiment 2 differs in that it identifies the celestial coordinates of the target low orbital object using two narrow-field image data outputs from the narrow-field optical telescope 10, but is otherwise the same.
Therefore, the differences from the low-orbit object coordinate determination device according to Embodiment 1 will be explained below.
In Figure 6, the same reference numerals as those used in Figure 1 indicate the same or corresponding parts.

The coordinate determination device for low orbit objects according to Embodiment 2 comprises a narrow-field optical telescope 10, a wide-field optical telescope 20, an optical axis adjustment device 30, a drive device 40, a position coordinate calculation device 50, and a database 60.
The narrow-field optical telescope 10 includes a narrow-field imaging optical system 11, a narrow-field light selection means 12, a first narrow-field image sensor 13, and a second narrow-field image sensor 14.
The narrow-field light selection means 12 selects light from low-orbit objects using an optical filter from the light focused by the narrow-field light selection means 12, and splits the light selected by the optical filter into two beams having different wavelength information or polarization information.

One of the two beams of light branched from the narrow-field light selection means 12 is guided by the first optical path to the light-receiving surface of the first narrow-field image sensor 13.
The other of the two beams of light branched from the narrow-field light selection means 12 is guided to the light-receiving surface of the second narrow-field image sensor 14 by a second optical path different from the first optical path.

The narrow-field light selection means 12 uses a dichroic mirror when splitting into two light beams having different wavelength information.
Dichroic mirrors transmit light in a specific wavelength range and reflect light in other wavelength ranges, thus splitting light into transmitted and reflected light, each carrying different wavelength information.

The narrow-field light selection means 12 uses a polarizing beam splitter when splitting into two light beams having different polarization information.
A polarizing beam splitter transmits P-polarized light and reflects S-polarized light, meaning it separates P-polarized and S-polarized light. Therefore, it can split P-polarized and S-polarized light, which have different polarization information.
The selection of the optical filter in the narrow-field optical selection means 12 is the same as in the narrow-field optical selection means 12 in Embodiment 1.

The first narrow-field image sensor 13 has its light-receiving surface positioned on the focal plane where one of the two light beams is focused.
The first narrow-field image sensor 13 converts the amount or intensity of incident light into a digital value for each of the numerous pixels spread in two dimensions on the light-receiving surface and outputs it as the first narrow-field image data, which is two-dimensional image data.

The second narrow-field image sensor 14 has its light-receiving surface positioned on the focal plane where the light from the other of the two light beams is focused.
The second narrow-field image sensor 14 converts the amount or intensity of incident light into a digital value for each of the numerous pixels spread in two dimensions on the light-receiving surface and outputs it as a second narrow-field image data, which is two-dimensional image data.

The first narrow-field image sensor 13 and the second narrow-field image sensor 14 correspond to the narrow-field image sensor 13 in Embodiment 1. Similar to how the narrow-field image sensor 13 in Embodiment 1 is controlled by the control unit 52, the first narrow-field image sensor 13 and the second narrow-field image sensor 14 are each controlled by the control unit 52, and the light selected and branched by the narrow-field light selection means 12 is output as the first narrow-field image data and the second narrow-field image data, respectively, in tracking mode.

The first narrow-field image sensor 13 and the second narrow-field image sensor 14 are controlled by the same narrow-field optical control information from the control unit 52.
Therefore, the first narrow-field image data and the second narrow-field image data are synchronized and acquired simultaneously at the same time.
The first narrow-field image sensor 13 and the second narrow-field image sensor 14 are the same sensors as the narrow-field image sensor 13 in Embodiment 1.

The wide-field optical telescope 20, the optical axis adjustment device 30, and the drive device 40 are the same as those in Embodiment 1, so their descriptions are omitted.

The low orbit object position coordinate calculation device 50 has a position coordinate calculation function to obtain the celestial coordinates of the low orbit object, a data acquisition control function to control the acquisition of image data from the narrow-field optical telescope 10 and the wide-field optical telescope 20, and a tracking control function to control the drive of the drive device 40 in order to track the low orbit object.
The position coordinate calculation device 50 includes a tracking trajectory determination unit 51, a control unit 52, an image recording unit 53, a preprocessing unit 54, a division processing unit 541, a stationary object detection unit 551, a moving object detection unit 561, a stellar coordinate comparison unit 57, and a low-orbit object position coordinate determination unit 58.

The data acquisition control function and tracking control function in the position coordinate calculation device 50 are the same as those in the position coordinate calculation device 50 in Embodiment 1, so their explanation will be omitted.
The position coordinate calculation function in the position coordinate calculation device 50 is achieved by the image recording unit 53, the preprocessing unit 54, the division processing unit 541, the stationary object detection unit 551, the moving object detection unit 561, the stellar coordinate comparison unit 57, and the position coordinate determination unit 58 for low orbital objects.

The image recording unit 53 receives first narrow-field image data from the first narrow-field image sensor 13, second narrow-field image data from the second narrow-field image sensor 14, and wide-field image data from the wide-field image sensor 23. The unit stores first narrow-field image data and second narrow-field image data, each associated with first narrow-field optical control information and second narrow-field optical control information from the control unit 52, respectively, as well as wide-field image data, each associated with wide-field optical control information from the control unit 52.

The preprocessing unit 54 acquires the first narrow-field image data and the second narrow-field image data stored in the image recording unit 53, and performs preprocessing on the first narrow-field image data and the second narrow-field image data, respectively, which involves subtracting the dark current and correcting the sensitivity unevenness within the narrow-field image data.
The preprocessing for the first narrow-field image data and the second narrow-field image data is the same as the preprocessing for narrow-field image data in Embodiment 1.

Furthermore, the preprocessing unit 54 may acquire wide-field image data stored in the image recording unit 53 and perform preprocessing on the wide-field image data, similar to the preprocessing performed on the first narrow-field image data and the second narrow-field image data, which involves subtracting the dark current and correcting the sensitivity unevenness within the narrow-field image data.

The division processing unit 541 acquires the first narrow-field image data and the second narrow-field image data that have been preprocessed by the preprocessing unit 54, performs division between the first narrow-field image data and the second narrow-field image data, and obtains the resulting image data as narrow-field image data for point image detection.
The first narrow-field image data and the second narrow-field image data are narrow-field image data acquired by the first narrow-field image sensor 13 and the second narrow-field image sensor 14 at the same time.

If the target low-orbit object has different wavelength or polarization characteristics from the surrounding sky, the narrow-field image data for point image detection obtained by the division processing unit 541 from the first narrow-field image sensor 13 and the second narrow-field image data from the second narrow-field image sensor 14, which are obtained by the narrow-field light selection means 12 with light that has different wavelength or polarization characteristics, will have spatial fluctuations of the sky removed.
As a result, narrow-field image data used for point image detection has a high signal-to-noise ratio.

In particular, when observing light reflected by a low-orbit object from a laser beam emitted from the ground, the narrow-field light selection means 12 is designed to transmit only the laser wavelength and reflect only the surrounding wavelengths.
A division processing unit 541 obtains narrow-field image data for point image detection from a first narrow-field image sensor 13 using light of the transmitted laser wavelength and a second narrow-field image data from a second narrow-field image sensor 14 using light of wavelengths around the laser wavelength.

The narrow-field image data for point image detection obtained by the division processing unit 541 has a different value for the region of low-orbit objects where laser reflection occurs compared to the surrounding empty area, and the bandwidth is significantly narrowed, so it is largely unaffected by reflected solar radiation.
As a result, target low-orbit objects can be detected with a high signal-to-noise ratio from narrow-field image data used for point image detection.

The stationary object detection unit 551 detects a point image from the narrow-field image data for point image detection obtained by the division processing unit 541, and uses the center coordinates of the detected point image as the detection position coordinates of the low-orbit object.
The detection of point images from narrow-field image data for point image detection by the stationary object detection unit 551 is performed in the same manner as the detection of point images from narrow-field image data by the stationary object detection unit 55 in Embodiment 1.

By the way, in Embodiment 1, an example was described in which the exposure time according to the frame rate was about 0.01 seconds and the movement speed of the target low-orbit object was about 30 arcminutes/second. However, when the narrow-field optical telescope 10 takes an image with an exposure time shorter than 0.01 seconds, or when the movement speed of the target low-orbit object is considerably slower than 30 arcminutes/second, under the conditions described in Embodiment 1, it may be impossible to distinguish whether a point image is caused by a low-orbit object or a line image caused by a star when detecting a point image from the narrow-field image data for point image detection.

In this case, the following conditions are added to detect point images from narrow-field image data used for point image detection.
In other words, among the N first narrow-field image data and N second narrow-field image data obtained from the tracking period, point images with the same position coordinates are detected as point images caused by low-orbit objects.
On the other hand, a point image whose position coordinates move between N narrow-field image data for point image detection is considered a line image in the N narrow-field image data for point image detection and is not considered a point image caused by a low-orbit object.

In short, the system identifies whether a point image is caused by a low-orbit object based on whether it is a stationary point image with a constant position coordinate or a moving point image with a changing position coordinate.
Therefore, the stationary object detection unit 551 does not detect point images (line images) caused by stars from the N narrow-field image data for point image detection.

The moving object detection unit 561 detects a line image from the wide-field image data from the wide-field image sensor 23, and uses the center coordinates of the detected line image as the detected position coordinates of the star.
The detection of line images from wide-field image data by the moving object detection unit 561 is performed in the same manner as the detection of line images from wide-field image data by the moving object detection unit 56 in Embodiment 1.

However, when the wide-field optical telescope 20 takes images with an exposure time shorter than 0.01 seconds, or when the target low-orbit object moves at a speed considerably slower than 30 arcminutes/second, the line images from the wide-field image data may not be discernible under the conditions described in Embodiment 1.

In this case, the following conditions are added to detect line images from wide-field image data.
In other words, a point image whose position coordinates move between N wide-field image data frames captured continuously during the tracking period is treated as a line image in the N wide-field image data frames and detected as a line image caused by a star.
On the other hand, point images with the same position coordinates across N wide-field image data are considered point images in the N wide-field image data and are not line images caused by stars.

In short, the method for identifying whether an image is a line image caused by a star depends on whether the point image is moving with changing position coordinates or stationary with unchanging position coordinates across N wide-field image data frames.
Therefore, the moving object detection unit 561 does not detect point images caused by low-trajectory objects from the N wide-field image data.

The stellar coordinate comparison unit 57 functions and operates in the same manner as the stellar coordinate comparison unit 57 in Embodiment 1. It compares the detected position coordinates of the star obtained by the moving object detection unit 561 with the celestial coordinate data of known stars stored in the database 60, and obtains the correspondence between the detected position coordinates of the star and the celestial coordinate data of the star.

In other words, the correspondence between the coordinates represented by the two-dimensional plane of the wide-field image data from the wide-field image sensor 23 and the celestial coordinate data of the stars is obtained in advance, for example, as a correspondence table.
The stellar coordinate comparison unit 57 compares the detected position coordinates of the star obtained by the moving object detection unit 56 with the celestial sphere coordinate data of the star using a correspondence table, thereby determining which direction on the celestial sphere corresponds to the position coordinates of the pixels in which the star is reflected.
As a result, it becomes possible to determine which direction each pixel of the wide-field image data corresponds to on the celestial sphere.

The low-orbit object position coordinate determination unit 58 functions and operates similarly to the position coordinate determination unit 58 in Embodiment 1, and identifies the celestial coordinates of the low-orbit object based on the comparison result of the stellar coordinate comparison unit 57, that is, the correspondence between the detected position coordinates of the star and the celestial coordinate data of the star, using the position coordinates detected by the stationary object detection unit 551.

In other words, the correspondence between the coordinates of the image data in the optical system, that is, the correspondence between the coordinates of the narrow-field image data and the celestial coordinate data, is determined based on the correspondence between the coordinates of the wide-field image data and the celestial coordinate data of the stars.
Next, the celestial coordinates of the low-orbit object are determined by comparing the detected position coordinates of the low-orbit object by the stationary object detection unit 55 with the celestial coordinate data using the correspondence between the coordinates of the narrow-field image data and the celestial coordinate data.

Next, the operation of the coordinate determination device for low orbit objects according to Embodiment 2 will be explained with reference to Figure 6.
Steps ST01 and ST02 as preliminary steps, steps ST11 and ST12 as tracking control functions, and steps ST21 and ST22 as data acquisition control functions are the same as steps ST01 and ST02, steps ST11 and ST12, and steps ST21 and ST22 in Embodiment 1, so their explanation will be omitted.
Note that the narrow-field image sensor 13 in steps ST21 and ST22 shall be read as the first narrow-field image sensor 13 and the second narrow-field image sensor 14.

The operation of the position coordinate calculation function in the position coordinate calculation device 50 will be explained using Figure 7.
In step ST31A, when the first narrow-field image data from the first narrow-field image sensor 13, the second narrow-field image data from the second narrow-field image sensor 14, and the wide-field image data from the wide-field image sensor 23 are input to the position coordinate calculation device 50, the first narrow-field image data and the second narrow-field image data are linked to the first narrow-field image data and the second narrow-field image data, and the wide-field image data is linked to the wide-field image data, and these are stored in the image recording unit 53 as wide-field image data.
Step ST31A corresponds to step ST31 in Embodiment 1.

In step ST32A, the preprocessing unit 54 acquires the first narrow-field image data and the second narrow-field image data stored in the image recording unit 53, and performs preprocessing on the first narrow-field image data and the second narrow-field image data, respectively, which involves subtracting the dark current based on the dark current image data and correcting the sensitivity unevenness within the narrow-field image data based on the flat image data.
Similarly, the preprocessing unit 54 performs preprocessing on the wide-field image data stored in the image recording unit 53, which involves subtracting the dark current based on the dark current image data and correcting the sensitivity unevenness within the narrow-field image data based on the flat image data.
Step ST32A corresponds to step ST32 in Embodiment 1.

In step ST32B, the division processing unit 541 simultaneously acquires the first narrow-field image data and the second narrow-field image data that have been preprocessed by the preprocessing unit 54, that is, it acquires the first narrow-field image data and the second narrow-field image data in a synchronized state, performs division between the first narrow-field image data and the second narrow-field image data, and obtains the resulting image data as narrow-field image data for point image detection.

In step ST33A, the stationary object detection unit 551 detects a point image (stationary point image) from the narrow-field image data for point image detection obtained by the division processing unit 541, and the stationary object detection unit 551 uses the center coordinates of the detected point image within the narrow-field image data for point image detection as the detection position coordinates of the low-orbit object.
Step ST33A corresponds to step ST33 in Embodiment 1.

In step ST34A, the moving object detection unit 561 detects a line image (moving point image) from the wide-field image data that has been preprocessed by the preprocessing unit 54, and the moving object detection unit 561 uses the center coordinates of the detected line image within the wide-field image data as the detected position coordinates of the star.
Step ST34A corresponds to step ST34 in Embodiment 1.

In step ST35A, the stellar coordinate comparison unit 57 compares the detected position coordinates of the star obtained by the moving object detection unit 561 with the celestial coordinate data of known stars stored in the database 60 to obtain the correspondence between the detected position coordinates of the star and the celestial coordinate data of the star.
Step ST35A corresponds to step ST35 in Embodiment 1.

In step ST36A, the celestial coordinates of the target low-Earth orbit object are obtained from the detection position coordinates of the target low-Earth orbit object, based on the correspondence between the detected position coordinates of the low-Earth orbit object obtained by the stationary object detection unit 551, the correspondence between the coordinates on the star obtained by the stellar coordinate comparison unit 57, and the correspondence between the image data coordinates of the optical systems in the narrow-field imaging optical system 11 and the wide-field imaging optical system 21 stored in the database 60.
Step ST36A corresponds to step ST36 in Embodiment 1.

The position coordinate calculation device 50 is implemented using a computer-based hardware configuration as shown in Figure 5, similar to the position coordinate calculation device 50 in Embodiment 1.
The tracking trajectory determination unit 51, the control unit 52, the preprocessing unit 54, the division processing unit 541, the stationary object detection unit 551, the moving object detection unit 561, the stellar coordinate comparison unit 57, and the position coordinate determination unit 58 are each composed of a CPU 50A, RAM 50B, and ROM 50C.
The image recording unit 53 is composed of RAM 50B.

The coordinate determination program stored in ROM 50C, which is to be executed by CPU 50A to determine the position coordinates of a target low-orbit object, performs a division between a first narrow-field image data from a narrow-field optical telescope 10 having a narrow-field imaging optical system 11 with a narrow field of view and high resolution, and a second narrow-field image data having a different wavelength or polarization from the first narrow-field image data, thereby obtaining the resulting narrow-field image data as narrow-field image data for point image detection. It then detects point images from the narrow-field image data for point image detection and determines the coordinates of the detected point images as low-orbit objects. The method comprises the steps of: obtaining the detected position coordinates of an object; detecting a line image from wide-field image data from a wide-field optical telescope 20 having a wide-field imaging optical system 21 that has a wider field of view and lower resolution than the narrow-field imaging optical system 11 and is directed in the same direction as the narrow-field imaging optical system 11, and obtaining the detected position coordinates of a star; obtaining the correspondence between the coordinates of the detected position coordinates of a star and the celestial coordinate data of the star; and identifying the celestial coordinates of a low-orbit object from the detected position coordinates of a low-orbit object based on the correspondence between the coordinates of the star.

The coordinate determination device for low orbital objects according to Embodiment 2 comprises a narrow-field optical telescope 10 having a narrow-field imaging optical system 11 with a narrow field of view and high resolution, and a wide-field optical telescope 20 having a wide-field imaging optical system 21 with a wider field of view and lower resolution than the narrow-field imaging optical system 11, and directed in the same direction as the narrow-field imaging optical system 11. The device calculates the coordinates of a low orbital object based on the division result of a first narrow-field image data from a first narrow-field image sensor 13 in the narrow-field optical telescope 10 and a second narrow-field image data from a second narrow-field image sensor 14 having a different wavelength or polarization than the first narrow-field image data. The system includes a low-orbit object position coordinate calculation device 50 that obtains the detected position coordinates of a low-orbit object from narrow-field image data for point image detection, obtains the detected position coordinates of a star from wide-field image data from a wide-field image sensor 23 in a wide-field optical telescope 20, and uses the obtained detected position coordinates of the star to identify the celestial coordinates of the low-orbit object. As a result, the narrow-field image data for point image detection has a high signal-to-noise ratio, making it easy to determine the position coordinates of the target low-orbit object, and allowing for the accurate and easy acquisition of the celestial coordinates of the low-orbit object.

Furthermore, it is possible to freely combine the embodiments, modify any component of each embodiment, or omit any component in each embodiment.

The low Earth orbit object coordinate determination device according to this disclosure is suitable for low Earth orbit object position measurement devices that determine the orbit of low Earth orbit objects such as satellites, space debris, or meteors in advance by observation from the ground.

10 Narrow-field optical telescope, 11 Narrow-field imaging optical system, 12 Light selection means for narrow field, 13 Narrow-field image sensor, 20 Wide-field optical telescope, 21 Wide-field imaging optical system, 22 Light selection means for wide field, 23 Wide-field image sensor, 30 Optical axis adjustment device, 40 Drive device, 50 Position coordinate calculation device, 51 Tracking trajectory determination unit, 52 Control unit, 53 Image recording unit, 54 Preprocessing unit, 541 Division processing unit, 55, 551 Stationary object detection unit, 56, 561 Moving object detection unit, 57 Star coordinate comparison unit, 58 Position coordinate determination unit.

Claims (16)

A narrow-field optical telescope having a narrow field of view and high resolution narrow-field imaging optical system, a narrow-field light selection means for selecting light from low-orbit objects from the light focused by the narrow-field imaging optical system, and a narrow-field image sensor for outputting the light selected by the narrow-field light selection means as narrow-field image data,
A wide-field optical telescope having a wide field of view and lower resolution than the narrow-field imaging optical system, and a wide-field imaging optical system that points in the same direction as the narrow-field imaging optical system, a wide-field light selection means for selecting light from stars from the light collected by the wide-field imaging optical system, and a wide-field image sensor that outputs the light selected by the wide-field light selection means as wide-field image data,
A low-Earth orbit object position coordinate calculation device that identifies the celestial coordinates of a low-Earth orbit object using the detected position coordinates of a low-Earth orbit object detected from narrow-field image data from the narrow-field image sensor and the detected position coordinates of a star detected from wide-field image data from the wide-field image sensor,
A coordinate determination device for low orbit objects equipped with the following features. The coordinate determination device for low-orbit objects according to claim 1, further comprising an optical axis adjustment device for fixing the wide-field imaging optical system to the narrow-field imaging optical system so that the difference in direction of direction between the direction of the wide-field imaging optical system and the direction of the narrow-field imaging optical system can be adjusted in two axes. The coordinate determination device for low-orbit objects according to claim 1 or 2, further comprising the narrow-field imaging optical system and a drive device for changing the direction of the narrow-field imaging optical system on two axes. The position coordinate calculation device comprises a tracking trajectory determination unit that estimates the time-series predicted trajectory coordinates of a target low orbit object based on information of the low orbit object, and a control unit that provides a drive control signal to control the driving of the drive unit based on the predicted trajectory coordinates estimated by the tracking trajectory determination unit and the directional direction of the narrow-field imaging optical system from the drive unit, as described in claim 1 or claim 2 . The position coordinate calculation device provides the narrow-field light selection means with narrow-field filter selection information including the timing of exposure start for light from the narrow-field imaging optical system and filter selection information; provides the narrow-field light control information including the timing of exposure start for light from the narrow-field imaging optical system and exposure time to the narrow-field image sensor; provides the wide-field light selection means with wide-field filter selection information including the timing of exposure start for light from the wide-field imaging optical system and filter selection information; provides the wide-field light control information including the timing of exposure start for light from the wide-field imaging optical system and exposure time to the wide-field image sensor; and has a control unit in which the narrow-field filter selection information, the narrow-field light control information, the wide-field filter selection information , and the wide-field light control information are synchronized information. The position coordinate calculation device includes a stationary object detection unit, a moving object detection unit, a stellar coordinate comparison unit, and a position coordinate determination unit for low orbit objects.
The detection of the detection position coordinates of a low-orbit object is performed by the stationary object detection unit detecting a point image from the narrow-field image data, and detecting the center coordinates of the detected point image as the detection position coordinates of the low-orbit object.
The detection of the star's detection position coordinates is performed by the moving object detection unit detecting a line image from the wide-field image data, and detecting the center coordinates of the detected line image as the star's detection position coordinates.
The identification of the celestial coordinates of a low-Earth orbit object is performed by the stellar coordinate comparison unit comparing the detected position coordinates of a star by the moving object detection unit with the position coordinates of a known star, and the low-Earth orbit object position coordinate determination unit identifying the detected position coordinates of the low-Earth orbit object by the stationary object detection unit based on the comparison results of the stellar coordinate comparison unit.
A coordinate determination device for a low orbit object according to claim 1 or claim 2 . The coordinate determination device for low-orbit objects according to claim 6, wherein the narrow-field image data detected as a point image by the stationary object detection unit is narrow-field image data output from the narrow-field image sensor, which has been preprocessed with dark-current image data and flat-field image data, respectively. The coordinate determination device for a low-orbit object according to claim 6, wherein the point image detected by the stationary object detection unit is a point image obtained from the narrow-field image data, having a half-width of 3 arcseconds to 10 arcseconds, and having a ratio of the major axis to the minor axis of the connected pixels of 1.5 or less. The coordinate determination device for low-trajectory objects according to claim 8, wherein the line image detected by the moving object detection unit is a line image obtained from the wide-field image data, having a half-width of 10 arcseconds or more, and having a ratio of the major axis to the minor axis of the connected pixels of 2 or more. The aforementioned narrow-field light selection means splits the selected light into two beams having different wavelengths or polarizations.
The narrow-field image sensor comprises a first narrow-field image sensor that outputs one light beam branched from the narrow-field light selection means as first narrow-field image data, and a second narrow-field image sensor that outputs the other light beam branched from the narrow-field light selection means as second narrow-field image data.
The detected position coordinates of the low-orbit object acquired by the position coordinate calculation device are the detected position coordinates obtained from the narrow-field image data, which is the result of dividing the first narrow-field image data from the first narrow-field image sensor and the second field-of-view image data from the second narrow-field image sensor.
A coordinate determination device for a low orbit object according to claim 1 or claim 2 . The aforementioned narrow-field light selection means splits the selected light into two beams having different wavelengths or polarizations.
The narrow-field image sensor comprises a first narrow-field image sensor that outputs one light beam branched from the narrow-field light selection means as first narrow-field image data, and a second narrow-field image sensor that outputs the other light beam branched from the narrow-field light selection means as second narrow-field image data.
The position coordinate calculation device includes a division processing unit, a stationary object detection unit, a moving object detection unit, a stellar coordinate comparison unit, and a position coordinate determination unit for low orbital objects.
The division processing unit performs division between the first narrow-field image data and the second narrow-field image data, and obtains the resulting narrow-field image data as narrow-field image data for point image detection.
The detection of the detection position coordinates of a low-orbit object is performed by the stationary object detection unit detecting a point image from the narrow-field image data for point image detection, and detecting the center coordinates of the detected point image as the detection position coordinates of the low-orbit object.
The detection of the star's detection position coordinates is performed by the moving object detection unit detecting a line image from the wide-field image data, and detecting the center coordinates of the detected line image as the star's detection position coordinates.
The identification of the celestial coordinates of a low-Earth orbit object is performed by the stellar coordinate comparison unit comparing the detected position coordinates of a star by the moving object detection unit with the position coordinates of a known star, and the low-Earth orbit object position coordinate determination unit identifying the detected position coordinates of the low-Earth orbit object by the stationary object detection unit based on the comparison results of the stellar coordinate comparison unit.
A coordinate determination device for a low orbit object according to claim 1 or claim 2 . The first narrow-field image data and the second narrow-field image data each consist of a plurality of narrow-field image data captured sequentially at the same time.
The narrow-field image data for point image detection consists of a plurality of narrow-field image data obtained by dividing the first narrow-field image data and the second narrow-field image data acquired simultaneously.
The stationary object detection unit detects point images with the same position coordinates among multiple narrow-field image data in the narrow-field image data for point image detection as point images caused by low-orbit objects.
The aforementioned wide-field image data consists of multiple wide-field image data captured in sequence.
The moving object detection unit considers point images whose position coordinates are moving in the multiple wide-field image data to be line images in the wide-field image data, and detects them as line images caused by stars.
The coordinate determination device for low orbit objects according to claim 11. A method for determining the position coordinates of a target low-orbit object, comprising: narrow-field image data from a narrow-field optical telescope having a narrow-field imaging optical system with a narrow field of view and high resolution; and wide-field image data from a wide-field optical telescope having a wide-field imaging optical system with a wider field of view and lower resolution than the narrow-field imaging optical system, and directed in the same direction as the narrow-field imaging optical system;
The stationary object detection unit detects a point image from the narrow-field image data, and the coordinates of the detected point image are used as the detected position coordinates of the low-orbit object.
The moving object detection unit detects a line image from the wide-field image data, and the coordinates of the detected line image are used as the detected position coordinates of the star.
The stellar coordinate comparison unit obtains the correspondence between the detected position coordinates of the star and the celestial sphere coordinate data of the star,
The position coordinate determination unit identifies the celestial coordinates of the low-orbit object from the detected position coordinates of the low-orbit object based on the correspondence between coordinates in the star,
A method for determining the coordinates of a low-orbit object, comprising [a specific feature/equipment]. The narrow-field image data from the aforementioned narrow-field optical telescope consists of a first narrow-field image data and a second narrow-field image data, which are split into two beams of light having different wavelengths or polarizations.
The process further includes a step in which a division processing unit performs division between the first narrow-field image data and the second narrow-field image data, and obtains the resulting narrow-field image data as narrow-field image data for point image detection.
The detection of point images from the narrow-field image data is performed by the stationary object detection unit detecting point images from the narrow-field image data for point image detection.
The method for determining the coordinates of a low orbit object according to claim 13. A coordinate determination program for determining the position coordinates of a target low-orbit object, using narrow-field image data from a narrow-field optical telescope having a narrow-field imaging optical system with a narrow field of view and high resolution, and wide-field image data from a wide-field optical telescope having a wide-field imaging optical system with a wider field of view and lower resolution than the narrow-field imaging optical system, and directed in the same direction as the narrow-field imaging optical system.
A procedure for detecting point images from the aforementioned narrow-field image data and using them as the detected position coordinates of low-orbit objects,
A procedure for detecting line images from the aforementioned wide-field image data and using them as the detected position coordinates of a star,
A procedure for obtaining the correspondence between the coordinates of the detected position coordinates of a star and the celestial sphere coordinate data of the star,
A procedure for identifying the celestial coordinates of a low-Earth orbit object from the detected position coordinates of the low-Earth orbit object based on the correspondence between coordinates in the aforementioned star,
A program that uses a computer to determine the coordinates of low-Earth orbit objects. A recording medium storing a program for determining the position coordinates of a target low-orbit object using narrow-field image data from a narrow-field optical telescope having a narrow-field imaging optical system with a narrow field of view and high resolution, and wide-field image data from a wide-field optical telescope having a wide-field imaging optical system with a wider field of view and lower resolution than the narrow-field imaging optical system, and directed in the same direction as the narrow-field imaging optical system,
A procedure for detecting point images from the aforementioned narrow-field image data and using them as the detected position coordinates of low-orbit objects,
A procedure for detecting line images from the aforementioned wide-field image data and using them as the detected position coordinates of a star,
A procedure for obtaining the correspondence between the coordinates of the detected position coordinates of a star and the celestial sphere coordinate data of the star,
A procedure for identifying the celestial coordinates of a low-Earth orbit object from the detected position coordinates of the low-Earth orbit object based on the correspondence between coordinates in the aforementioned star,
A storage medium that stores a program that causes a computer to execute a command.