Orbital object detection device, orbital object detection method, orbital object detection program, and recording medium

Abstract

When the background sky is bright relative to the target orbiting object, it is desirable to further improve the detection accuracy of orbiting objects with low synchrotron radiation or reflected light intensity. [Solution] The orbital object detection device comprises an imaging optical system 11 that receives incident light including light from a target orbital object, guides the incident light from the orbital object, and forms an image; a photodetector 12 positioned on the focal plane focused by the imaging optical system 11 and outputting image information; a polarization device 13 positioned between the imaging optical system 11 and the photodetector 12 and transmitting the incident light to the photodetector 12 as polarized light; a polarization direction changing device 14 that receives feed amount information and changes the polarization direction of the polarization device 13 based on the received feed amount information; and an optical system control device 30 having a changing device control unit 34 that provides the polarization direction changing device 14 with feed amount information such that the direction of the line connecting the position coordinates relative to the sun and the tracking orbit coordinates relative to the target orbital object is the polarization direction.

Description

[Technical Field]

[0001] This disclosure relates to an orbital object detection device, an orbital object detection method, an orbital object detection program, and a recording medium for detecting orbital objects such as artificial satellites or space debris. [Background technology]

[0002] In recent years, the increased activity in space development has led to the launch of numerous artificial satellites and rocket bodies into space. In particular, there are concerns about the possibility of inter-satellite collisions or collisions with space debris in near-Earth orbits and geostationary orbits. Therefore, there is a need to predict the trajectories of on-orbit objects such as artificial satellites, rocket bodies, or space debris through ground-based observations and to use that information to avoid collisions.

[0003] Under these circumstances, Patent Document 1 proposes a mobile object identification device that can identify a mobile object (orbital object) even during times when the brightness of its synchrotron radiation or reflected light is low. The mobile object identification device described in Patent Document 1 compares the position and brightness of a mobile object calculated from a light intensity image captured by a photodetector with the position and brightness of multiple mobile objects stored in a database at each time point, and identifies the mobile object to be identified based on the position and brightness comparison result.

[0004] The mobile object identification device shown in Patent Document 1 includes an imaging optical system, a light-shielding section, a light-transmitting section, and a photodetector in the optical path through which incident light is received and reaches the photodetector. Examples of light transmission components include a filter wheel that sequentially switches between wavelength filters, a wavelength filter that selectively removes unwanted light, a polarizing beam splitter, a wavelength filter that reflects unwanted light and transmits desired light, and multiple polarizing filters with different polarizations for transmitted light. Furthermore, it is stated that "by using multiple polarizing filters, even when the target moving object is difficult to see due to the influence of light from, for example, stars or other moving objects, it becomes possible to easily detect it on the light intensity image." [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-072888 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 describes that by using multiple polarizing filters with different polarizations of transmitted light, detection can be easily performed on a light intensity image. However, when the brightness of the sky, which serves as the background for the orbiting object, is bright, it is desirable to further improve the detection accuracy of orbiting objects with low luminance of synchrotron radiation or reflected light.

[0007] This disclosure has been made in view of the above-mentioned points, and aims to provide an orbiting object detection device that has a high signal-to-noise ratio (signal-to-noise ratio) of light from orbiting objects to background light, facilitates the detection of orbiting objects, and has high detection accuracy. [Means for solving the problem]

[0008] The orbital object detection device according to this disclosure comprises: an imaging optical system that receives incident light including light from a target orbital object, guides the incident light from the orbital object, and forms an image; a photodetector positioned on the focal plane focused by the imaging optical system and outputting image information; a polarization device positioned between the imaging optical system and the photodetector and transmitting the incident light to the photodetector as polarized light; a polarization direction changing device that receives feed amount information and changes the polarization direction of the polarization device based on the received feed amount information; and an optical system control device having a changing device control unit that provides the polarization direction changing device with feed amount information such that the polarization direction is the direction of the line connecting the position coordinates relative to the sun and the tracking orbit coordinates relative to the target orbital object. [Effects of the Invention]

[0009] According to this disclosure, the signal-to-noise ratio of light from orbiting objects to background light is high, making it easy to detect orbiting objects and resulting in high detection accuracy. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing an object detection device on a track according to Embodiment 1. [Figure 2] This is a configuration diagram showing the hardware configuration of the optical system control device in the orbital object detection device according to Embodiment 1. [Figure 3] This flowchart shows the operation of the orbital object detection device according to Embodiment 1. [Figure 4] This is a block diagram showing an object detection device on a track according to Embodiment 2. [Figure 5] This flowchart shows the operation of the orbital object detection device according to Embodiment 2. [Figure 6] This is a block diagram showing an object detection device on a track according to Embodiment 3. [Figure 7] This is a flowchart showing the operation of the orbital object detection device according to Embodiment 3. [Figure 8] This is a block diagram showing an object detection device on an orbit according to Embodiment 4. [Figure 9]It is a flowchart showing the operation of the on-orbit object detection device according to Embodiment 4.

Embodiments for Carrying Out the Invention

[0011] Embodiment 1. The on-orbit object detection device according to Embodiment 1 will be described with reference to FIGS. 1 to 3. The on-orbit object detection device according to Embodiment 1 is an on-orbit object detection device that detects on-orbit objects such as artificial satellites or space debris which is space garbage. When the on-orbit object detection device according to Embodiment 1 optically observes an on-orbit object, even when the brightness of the background sky is bright, that is, when the luminance of the background light is high and the luminance of the light from the on-orbit object is low, the signal-to-noise ratio of the light from the on-orbit object with respect to the background light is high, and it is an on-orbit object detection device that enables easy detection of on-orbit objects and has high detection accuracy.

[0012] The background light is, for example, light that reaches an observer after being scattered by the atmosphere from light from the sun or the moon. The light from the on-orbit object is light that reaches an observer, such as emitted radiation light from the on-orbit object itself, reflected and scattered reflected light or scattered light of light from the sun or the moon reflected by the on-orbit object, and reflected and scattered reflected light or scattered light of laser light emitted from the ground and reflected by the on-orbit object.

[0013] As shown in FIG. 1, the on-orbit object detection device according to Embodiment 1 includes an optical telescope 10, a drive device 20, and an optical system control device 30. The optical telescope 10 is a device aimed at being able to observe incident light with a high signal-to-noise ratio. The optical telescope 10 has an imaging optical system 11, a photodetector 12, a polarizing device 13, and a polarization direction changing device 14.

[0014] Since the light from the on-orbit object and the background light reach the optical telescope 10 through different optical paths, the information on the degree of polarization of the light is different. The optical telescope 10 utilizes this difference in the degree of polarization of light, that is, the difference in polarization direction, to change the polarization direction of the polarizer 13 using a polarization direction changing device 14. This allows the polarizer 13 to pass light from objects in orbit, absorb or reflect background light, and improve the signal-to-noise ratio in the photodetector 12.

[0015] The imaging optical system 11 receives incident light, including light from the orbiting object, guides the incident light from the orbiting object, and forms an image. The imaging optical system 11 has the function of focusing incident light that enters the aperture at a certain angle to a single point using a reflector and a lens.

[0016] The focusing position of the imaging optical system 11 depends on the angle of incidence to the aperture. The imaging optical system 11 forms an image on a plane (focal plane) perpendicular to the optical axis. In order to detect incident light from orbiting objects, which are generally dark objects, with a high signal-to-noise ratio, the imaging optical system 11 should ideally have an optical system with a large aperture capable of focusing more light.

[0017] The imaging optical system 11 is a generally known imaging optical system used in telescopes such as refracting telescopes, reflecting telescopes, or telescopes that combine both refracting and reflecting elements. The imaging optical system 11 is mounted on the drive unit 20 and is driven and controlled by the drive unit 20 in two axes at each observation time to track an object in orbit.

[0018] The photodetector 12 is positioned, or installed, on the focal plane that is focused by the imaging optical system 11. The photodetector 12 detects the light focused by the imaging optical system 11 at each observation time and outputs image information. The photodetector 12 converts the amount or intensity of light incident on each of the numerous pixels spread in two dimensions on the focal plane, which is focused by the imaging optical system 11, into a digital value for each observation time, and outputs it as two-dimensional image data. The image information from the photodetector 12 shows an image based on the amount or intensity of light incident from the imaging optical system 11. The image information from the photodetector 12 allows for the detection of light from the target, i.e., the target object in orbit that is being tracked.

[0019] The photodetector 12 receives sensor control information from the optical system control device 30 at each observation time in order to acquire two-dimensional image data, and outputs it as two-dimensional image data. Sensor control information includes sensor parameters such as the timing of exposure start (the start time of observation for acquiring one image data), exposure time, frame rate, gain, and the pixels to be read out. In order to detect incident light from orbiting objects, which are generally dark objects, with a high signal-to-noise ratio, the photodetector 12 performs imaging of multiple images using long exposure times or high frame rates.

[0020] The mirrors and lenses constituting the imaging optical system 11, as well as the support materials for the mirrors and lenses, undergo thermal deformation. In other words, the focal position of the imaging optical system 11 depends on temperature. Therefore, assuming a change in the light-gathering position of the imaging optical system 11, a photodetector driving mechanism may be provided to move the photodetector 12 to the focal position of the imaging optical system 11 in order to fine-tune the distance between the imaging optical system 11 and the photodetector 12.

[0021] The photodetector 12 is either a thermal image sensor or a quantum image sensor. A thermal image sensor is a sensor that converts the light intensity incident on each element arranged in two dimensions into heat and reads it out as a voltage value; examples include bolometers and thermopiles. Quantum image sensors are sensors that use semiconductor elements to convert photons into electrons through the internal photoelectric effect and read them out. Examples include visible light CCD (Charge Coupled Device) sensors or CMOS (Complementary Metal Oxide Semiconductor) sensors, and infrared InGaAs, InSb, or HgCdTe sensors.

[0022] The polarization device 13 is positioned between the imaging optical system 11 and the photodetector 12, and transmits the incident light focused by the imaging optical system 11 to the photodetector 12 as polarized light. The polarization device 13 is driven and controlled by the polarization direction changing device 14, and the polarization direction is changed. In other words, the polarization direction of the polarization device 13 is changed by the polarization direction changing device 14 so that, of the incident light focused by the imaging optical system 11, light from the object in orbit passes through and background light is absorbed or reflected.

[0023] The polarizing device 13 is, for example, a polarizing plate. When the polarizing device 13 is a polarizing plate, the polarizing plate is positioned so that its optical axis aligns with the optical axis of the imaging optical system 11. The polarizing plate is rotated around the optical axis by a polarization direction changing device 14.

[0024] A polarizing filter (PL filter) that transmits only linearly polarized light in a predetermined direction can be used as the polarizing plate. When a PL filter is used, the PL filter is rotated by a polarization direction changing device 14 around the optical axis so that it absorbs or reflects background light from the incident light focused by the imaging optical system 11, that is, so that the linear polarization component of the PL filter does not match the polarization direction of the background light.

[0025] Alternatively, a filter wheel in which multiple polarizing filters are arranged around a rotation axis may be used as the polarizing device 13. Each of the multiple polarizing filters transmits a different linearly polarized component; in other words, each polarizing filter has a different polarization direction.

[0026] The filter wheel is rotated by a polarization direction changing device 14 around its rotation axis, and the optical axis of one of the multiple polarizing filters is aligned with the optical axis of the imaging optical system 11 so as to absorb or reflect background light from the incident light focused by the imaging optical system 11. Since a filter wheel can also be considered a type of polarizer, it will be treated as such in the following explanation.

[0027] As the polarizing device 13, polarizing plates with different polarization directions may be used, corresponding to the pixels of the photodetector 12 and at positions corresponding to the spaces between adjacent pixels. When polarizing plates with different polarization directions are used at adjacent positions, and an image sensor is used as the photodetector 12, the polarizing plates may be placed on the sensor surface of the image sensor.

[0028] The polarizing device 13 may also include a wavelength filter. If a wavelength filter is further included, the polarizing plate constituting the polarizing device 13 is positioned in front of or behind the optical axis of the imaging optical system 11. Wavelength filters include those that transmit only specific wavelengths of light, those that do not transmit only specific wavelengths of light, and those whose transmittance changes continuously with respect to the wavelength of light.

[0029] Wavelength filters include, for example, wideband filters such as those used in the Sloan / SDSS (Sloan Digital Sky Survey) system or the Johnson system, narrowband filters that transmit only the wavelength of laser light, or ND (Neutral Density) filters that have a constant low transmittance with no wavelength dependence.

[0030] The polarization direction changing device 14 receives feed amount information from the optical system control device 30 at each observation time and changes the polarization direction of the polarization device 13. The polarization direction changing device 14 is attached to the imaging optical system 11. The polarization direction changing device 14 rotates the polarization device 13 using the optical axis of the imaging optical system 11 as its axis of rotation, based on feed amount information from the optical system control device 30.

[0031] The polarization direction changing device 14 rotates the polarization device 13 according to the angle indicated by the feed amount information from the optical system control device 30, and sets the polarization direction of the polarization device 13 to a polarization direction that absorbs or reflects background light from the incident light focused by the imaging optical system 11. As a result, the incident light incident on the polarizing device 13 absorbs or reflects the background light, and the incident light from which the background light has been removed is imaged onto the sensor surface of the photodetector 12, that is, the focal position (focal plane) of the imaging optical system 11. Therefore, the photodetector 12 can detect incident light from the target orbiting object with a high signal-to-noise ratio.

[0032] The polarization direction changing device 14 outputs rotational position information indicating the rotational position of the polarization device 13 to the optical system control device 30 for each observation time. The polarization direction changing device 14 is an image rotator. The polarization direction changing device 14 may rotate the photodetector 12 around the optical axis of the imaging optical system 11 as the axis of rotation, in conjunction with the rotation of the polarization direction changing device 14.

[0033] The drive unit 20 receives two-axis drive amount information from the optical system control unit 30 and drives the optical telescope 10, including the mounted imaging optical system 11, according to the two-axis drive amount indicated by the two-axis drive amount information. The drive unit 20 is a German equatorial mount, a fork equatorial mount, or an altazimuth mount, having two different axes of rotation.

[0034] The optical system control device 30 includes a tracking trajectory determination unit 31, a drive unit control unit 32, a photodetector control unit 33, a change unit control unit 34, and a recording unit 35. The tracking trajectory determination unit 31 takes information about the target object in orbit as input and obtains tracking trajectory information, which is a time-series tracking trajectory coordinate, for each observation time. To obtain time-series data of tracking trajectory coordinates for each observation time as tracking trajectory information for a target object in orbit, the output coordinate system is converted to celestial coordinates centered on the observation position to obtain tracking trajectory information consisting of tracking trajectory coordinates.

[0035] Furthermore, when obtaining time-series data of tracking trajectory coordinates for each observation time, using two-line elements (TLE) containing information on Kepler orbital elements in the geocentric coordinate system as input values ​​for tracking trajectory information of a target object in orbit, the tracking trajectory is calculated based on the TLE, and the obtained tracking trajectory coordinates are converted to celestial coordinates centered on the observation position to obtain tracking trajectory information consisting of tracking trajectory coordinates. The computational algorithm used in this case is Simplified General Perturbations Satellite Orbit Model 4 (SGP4). However, the computational algorithm is not limited to SGP4.

[0036] The drive unit control unit 32 calculates the required drive amount for both axes at each observation time based on the tracking trajectory information obtained by the tracking trajectory determination unit 31, and outputs the two-axis drive amount information to the drive unit 20. At each observation time, the drive unit control 32 calculates the amount of two-axis drive in the drive unit 20 to change the direction of the imaging optical system 11 in the optical telescope 10 to the direction of the target object in orbit, based on the tracking trajectory information obtained by the tracking trajectory determination unit 31 and the pointing direction information from the drive unit 20 at the current time, and outputs this as two-axis drive amount information to the drive unit 20.

[0037] The drive unit control unit 32 calculates the difference between the coordinates of the expected target object on the orbit, which are the tracking trajectory coordinates indicated by the tracking trajectory information obtained by the tracking trajectory determination unit 31, and the coordinates of the direction of the imaging optical system 11 indicated by the direction of direction information from the drive unit 20 at the current time. Based on the obtained angle separation information, it obtains two-axis drive amount information indicating the two-axis drive amount. The information regarding the angle of separation indicates the amount of drive angle of the two drive shafts of the drive unit 20.

[0038] If the target object deviates from the sensor surface of the photodetector 12 while tracking the target object, that is, if the difference calculation result between the expected coordinates of the target object and the coordinates of the direction of the imaging optical system 11 exceeds a threshold that causes the object to deviate from the sensor surface of the photodetector 12, the drive unit control unit 32 applies an offset to the expected coordinates of the target object.

[0039] The drive control unit 32 calculates the difference between the coordinates of the object on the trajectory with an offset and the coordinates of the direction of the imaging optical system 11, and uses the obtained information as two-axis drive amount information. As a result, light from the target object in orbit is imaged onto the sensor surface of the photodetector 12 by the imaging optical system 11.

[0040] The photodetector control unit 33 outputs sensor information to the photodetector 12 as sensor control information for each observation time. The photodetector control unit 33 includes a sensor information storage unit 33a and a time control unit 33b. The sensor information storage unit 33a stores sensor information including sensor parameters such as the exposure start timing, exposure time, frame rate, gain, and the pixels to be read out. The time control unit 33b in the photodetector control unit 33 reads sensor information from the sensor information storage unit 33a at each observation time and outputs it to the photodetector 12 as sensor control information.

[0041] The sensor control information indicating the timing of exposure commencement is the trigger input signal for the photodetector 12 to initiate imaging. The photodetector control unit 33 outputs sensor control information to the photodetector 12 at each observation time, and the photodetector 12 continuously captures multiple images at each observation time based on the sensor control information indicating the frame rate, and the sensor control information indicating the exposure time, gain, and readout pixels, etc.

[0042] The photodetector control unit 33 maintains the frame rate and outputs a trigger input signal to the photodetector 12 multiple times according to the frame rate for each observation time. Along with the trigger input signal, it also changes sensor control information indicating the exposure time, gain, and readout pixel for each image and outputs it to the photodetector 12, so that the photodetector 12 can continuously take multiple images for each observation time.

[0043] The polarization direction control unit 34 provides the polarization direction changing device 14 with feed amount information for each observation time, where the direction of the line connecting the position coordinates relative to the sun and the tracking trajectory coordinates relative to the target orbital object is the polarization direction. As background light, we consider Rayleigh scattering of sunlight by atmospheric molecules (atmospheric scattered light). Atmospheric scattered light is known to be polarized because Rayleigh scattering is angle-dependent.

[0044] Therefore, it can be said that atmospheric scattered light is polarized in a direction perpendicular to the line connecting the sun and the target orbiting object. Therefore, if the polarization direction of the light transmitted through the polarizing device 13 is perpendicular to the polarization direction of the atmospheric scattered light, the atmospheric scattered light can be attenuated to the maximum extent. Thus, the polarization direction change control unit 34 outputs feed amount information to the polarization direction change device 14 so that the polarization direction of the light transmitted through the polarizing device 13 is directed in the direction of the line connecting the sun and the target orbiting object. In other words, the polarization direction in the polarization device 13 is optimal when it is in the direction of the line connecting the sun and the target orbiting object, allowing the photodetector 12 to detect incident light from the target orbiting object with a high signal-to-noise ratio.

[0045] The change device control unit 34 includes a polarization direction calculation unit 34a and a time control unit 34b. The polarization direction calculation unit 34a calculates, for each observation time, the direction on the celestial sphere connecting the coordinates of the expected target object in orbit, which are the tracking orbit coordinates indicated by the tracking orbit information obtained by the tracking orbit determination unit 31, with the position coordinates relative to the sun. The direction of the line connecting these two coordinates is defined as the polarization direction, and the obtained polarization direction is converted into rotational position information of the polarization direction changing device 14. The rotational position of the polarization direction changing device 14 obtained at this time becomes the optimal rotational position relative to the polarization device 13 at the time of observation.

[0046] The time control unit 34b in the polarization direction control unit 34 performs a difference calculation between the rotation position information obtained by the polarization direction calculation unit 34a and the rotation position information at the current time from the polarization direction changing device 14, and outputs feed amount information with the result of the difference calculation as the rotation angle. The rotation angle obtained at this time is the angle at which the polarization direction of the light passing through the polarizing device 13 points in the direction of the line connecting the sun and the target orbiting object.

[0047] The tracking trajectory determination unit 31, the drive unit control unit 32, the time control unit 33b in the photodetector control unit 33, and the time control unit 34b in the change device control unit 34 are linked, that is, synchronized, to perform their respective functions at each observation time. The recording unit 35 stores, for each observation time, two-dimensional image data from the photodetector 12, along with sensor control information from the time control unit 33b in the photodetector control unit 33 and the observation time. The two-dimensional image data, which includes sensor control information stored in the recording unit 35, is read out by a display device (not shown), such as a liquid crystal display, and an image of the target object in orbit is displayed on the display device.

[0048] The optical system control device 30 is implemented using a computer-based hardware configuration, and as shown in Figure 2, it comprises a CPU (Central Processing Unit) 1A, a large-capacity semiconductor memory (RAM: Random Access Memory) 1B, a storage device (ROM: Read-only memory) 1C such as a hard disk drive or SSD, an input interface unit 1D, an output interface unit 1E, and a signal path (bus) 1F. CPU1A controls and manages RAM1B, ROM1C, input interface unit1D, and output interface unit1E. CPU1A loads the program stored in ROM1C into RAM1B, and CPU1A executes various processes based on the program loaded into RAM.

[0049] The tracking trajectory determination unit 31 and the drive unit control unit 32 are each composed of a program stored in ROM 1C and a CPU 1A. The photodetector control unit 33 consists of a program stored in ROM 1C, a CPU 1A, and RAM 1B in which sensor information is stored. The change device control unit 34 consists of a program stored in ROM 1C and CPU 1A. The recording unit 35 is composed of RAM 1B.

[0050] Next, the operation of the orbital object detection device according to Embodiment 1 will be explained using Figure 3. Now, let's define the tracking start time as observation time T1, and the observation time T1 is just before the tracking trajectory of the target object in orbit goes beyond the observable range. N Let's assume that. At the tracking start time T1, the tracking trajectory determination unit 31 obtains tracking trajectory information of the target object on the trajectory (step ST1).

[0051] In step ST2A, the drive unit control unit 32 calculates the difference between the tracking trajectory information of the target object on the trajectory obtained by the tracking trajectory determination unit 31 and the coordinates of the direction of the imaging optical system 11 indicated by the direction of direction information at the current time from the drive unit 20. The drive unit control unit 32 obtains separation information through the difference calculation and outputs two-axis drive amount information, which is the drive angle amount of the two drive axes of the drive unit 20, to the drive unit 20.

[0052] In step ST3A, the drive unit 20 drives the optical telescope 10, which includes the mounted imaging optical system 11, in two axes based on the two-axis drive amount information from the drive unit control unit 32, and directs the direction of the imaging optical system 11 toward the direction of the target orbiting object. This initiates the tracking of the target object in orbit.

[0053] In step ST2B1, the polarization direction calculation unit 34a in the polarization direction control unit 34 calculates the direction on the celestial sphere connecting the tracking trajectory information of the target object in orbit obtained by the tracking trajectory determination unit 31 and its position coordinates relative to the sun. The direction of the line connecting these two coordinates is defined as the polarization direction, and the obtained polarization direction is converted into rotation position information of the polarization direction changing device 14 to obtain the optimal rotation position information that attenuates the background light the most.

[0054] In step ST2B2, the time control unit 34b of the polarization direction control unit 34 performs a difference calculation between the rotation position information obtained by the polarization direction calculation unit 34a and the rotation position information at the current time from the polarization direction changing device 14, and obtains feed amount information in which the difference calculation result is the rotation angle. In step ST3B, the polarization direction changing device 14 rotates the polarization device 13 based on feed amount information from the time control unit 34b in the changing device control unit 34, thereby changing the polarization direction of the polarization device 13.

[0055] In step ST4, the photodetector control unit 33 reads the sensor information and outputs it to the photodetector 12 as sensor control information. In step ST5, the photodetector 12 takes an image based on sensor control information from the photodetector control unit 33. In step ST6, the image data captured by the photodetector 12 is stored in the recording unit 35.

[0056] The process proceeds to observation time T2, and in the same manner as the operation at observation time T1, steps ST1, ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 are executed at observation time T2. Observation time T N Steps ST1, ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 are repeatedly executed until the specified step is reached.

[0057] The processing steps ST1, ST2A, ST2B1, ST2B2, and ST4 are stored as a program in the ROM1C of the computer that constitutes the optical system control device 30. In other words, the program stored in ROM1C includes a procedure for obtaining tracking trajectory information of a target object in orbit; a procedure for calculating the difference between the tracking trajectory information of the target object in orbit and the pointing direction information of the drive unit 20 at the current time, and obtaining two-axis drive amount information for the drive unit 20 using the difference calculation result; a procedure for obtaining rotational position information using the direction of the line connecting the tracking trajectory information of the target object in orbit and its position coordinates relative to the sun; a procedure for calculating the difference between the rotational position information and the rotational position information of the polarization direction changing device 14 at the current time, and obtaining feed amount information for the polarization direction changing device 14 using the difference calculation result; and a procedure for reading sensor information and using it as sensor control information for the photodetector 12.

[0058] In Embodiment 1, each observation time is treated as one observation time period, and at each observation time, the tracking trajectory coordinates obtained by the tracking trajectory determination unit 31 and the rotational position information obtained by the polarization direction calculation unit 34a in the modification device control unit 34 may be the time-series tracking trajectory coordinates and time-series rotational position information for one observation time period, respectively.

[0059] The orbital object detection device according to Embodiment 1 is an orbital object detection device comprising an imaging optical system 11 and a photodetector 12, wherein a polarization device 13 is positioned between the imaging optical system 11 and the photodetector 12, and the optical system control device 30 has a polarization direction changing device 14 that changes the polarization direction of the polarization device 13, and a changing device control unit 34 that provides the polarization direction changing device 14 with feed amount information that sets the polarization direction to the polarization direction of the line connecting the position coordinates with respect to the sun and the tracking orbit coordinates with respect to the target orbital object. As a result, the background light is absorbed or reflected from the incident light incident on the polarization device 13, and the incident light from which the background light has been removed is imaged on the sensor surface of the photodetector 12, that is, at the focal position (focal plane) of the imaging optical system 11, so that the photodetector 12 can detect incident light from the target orbital object with a high signal-to-noise ratio.

[0060] Embodiment 2. The orbital object detection device according to Embodiment 2 will be described with reference to Figures 4 and 5. The orbital object detection device according to Embodiment 1 obtains optimal rotational position information at the time of observation in the polarization direction calculation unit 34a of the polarization direction control unit 34. This unit calculates the direction on the celestial sphere connecting the coordinates of the expected target orbital object, which are the tracking trajectory coordinates indicated by the tracking trajectory information obtained by the tracking trajectory determination unit 31, and the position coordinates relative to the sun. The direction of the line connecting these two coordinates is defined as the polarization direction, and the obtained polarization direction is converted into rotational position information of the polarization direction changing device 14.

[0061] In contrast, the orbital object detection device according to Embodiment 2 differs in that it includes a polarization direction measuring device 40 that acquires observational data, which is measured data obtained by observing the background light in multiple different polarization directions relative to the direction of direction toward the target orbital object, and obtains optimal rotational position information for the polarization device 13 at the observation time based on the multiple observational data, but is otherwise the same. Therefore, the following explanation will focus on the differences from the orbital object detection device according to Embodiment 1. In Figures 4 and 5, the same reference numerals as those used in Figures 1 to 3 indicate the same or corresponding parts.

[0062] The polarization direction measuring device 40 observes the sky, including background light, in the direction of direction toward the target orbiting object at each observation time, and acquires observation data, which is measured data of background light observed in multiple different polarization directions. The polarization direction measuring device 40 receives time-series tracking trajectory information obtained by the tracking trajectory determination unit 31 at each observation time, observes the direction indicated by the tracking trajectory information, and acquires multiple observation data, each of which observes background light with multiple different polarization directions.

[0063] The polarization direction measuring device 40 acquires observational data of background light with multiple different polarization directions by a combination of one of the observation methods and one of the polarization direction determination methods described below. The following methods 1) or 2) can be used to observe the direction indicated by tracking trajectory information for a target object in orbit: 1) A telescope is used as the polarization direction measuring device 40, and the telescope is pointed in the direction indicated by each time-series tracking trajectory information, and images of the sky are observed with different polarization directions relative to the direction in which the telescope is pointed. 2) A camera equipped with a fisheye lens is used as the polarization direction measuring device 40 to observe the entire sky at once, focusing on the direction indicated by the tracking trajectory information.

[0064] There are three methods for determining the polarization direction: 1) to 3) 1) Incident light is transmitted through a rotatable polarizing plate while it is rotating, and the polarization direction is determined by image data based on the rotational position of the polarizing plate, thus obtaining observational data indicating the polarization direction. 2) By switching the wheels of a filter wheel containing polarizers with multiple polarization directions, incident light is transmitted, and the polarization direction is determined from the image data obtained from the polarizers inserted in the wheel, and this is used as observational data indicating the polarization direction.

[0065] 3) A polarizer with different polarization directions between adjacent pixels is placed on the sensor surface of an image sensor into which incident light is incident. The polarization direction is determined by the light intensity at the pixels of the image sensor, and this is used as observational data indicating the polarization direction.

[0066] The optical system control device 30A includes a tracking trajectory determination unit 31, a drive unit control unit 32, a photodetector control unit 33, a change unit control unit 34A, and a recording unit 35. The polarization direction control unit 34A determines, based on multiple observation data from the polarization direction measuring device 40 at each observation time, the polarization direction in which the background light is most attenuated as the polarization direction that results in the optimal rotation position relative to the polarization device 13, and provides the polarization direction changing device 14 with feed amount information for the determined polarization direction.

[0067] Therefore, the polarization direction control unit 34A outputs feed amount information to the polarization direction changing device 14 so that the polarization direction of the light transmitted through the polarization device 13 is set to the polarization direction in which the background light is most attenuated, based on the observed data, which is measured data from the polarization direction measuring device 40. As a result, the photodetector 12 can detect incident light from the target orbiting object with a high signal-to-noise ratio.

[0068] The modification device control unit 34A includes a polarization direction calculation unit 34Aa and a time control unit 34Ab. The polarization direction calculation unit 34Aa estimates the polarization angle of the direction indicated by the tracking trajectory coordinates from observational data obtained by observing the background light coming from the time-series tracking trajectory coordinates from the polarization direction measuring device 40 at each observation time.

[0069] The polarization direction calculation unit 34Aa, for example, if the observed data consists of data observed in the same direction for multiple polarization directions, calculates the polarization direction in which the background light is attenuated the most from those observed data, and obtains rotational position information by converting this calculation result into rotational position information of the polarization direction changing device 14. The rotational position of the polarization direction changing device 14 obtained at this time becomes the optimal rotational position relative to the polarization device 13 at the time of observation.

[0070] The time control unit 34Ab in the polarization direction control unit 34A performs a difference calculation between the rotation position information obtained by the polarization direction calculation unit 34Aa and the rotation position information at the current time from the polarization direction changing device 14, and outputs feed amount information with the result of the difference calculation as the rotation angle. The rotation angle obtained at this time is the angle at which the polarization direction of the light transmitted through the polarizing device 13 is aligned to the polarization direction in which the background light is most attenuated.

[0071] Next, the operation of the orbital object detection device according to Embodiment 2 will be explained using Figure 5. Steps ST1, ST2A, and ST3A are the same as steps ST1, ST2A, and ST3A in the orbital object detection device according to Embodiment 1, so their description is omitted.

[0072] Step ST2B11 In this configuration, the polarization direction calculation unit 34Aa in the polarization direction control unit 34A calculates the polarization direction in which the background light is most attenuated from multiple observation data obtained from the polarization direction measuring device 40, each of which is a different polarization direction relative to the direction indicated by the tracking trajectory information obtained by the tracking trajectory determination unit 31. The polarization direction obtained through this calculation is then converted into rotation position information of the polarization direction changing device 14 to obtain optimal rotation position information.

[0073] In step ST2B2, the time control unit 34Ab of the polarization direction control unit 34A calculates the difference between the rotation position information obtained by the polarization direction calculation unit 34Aa and the rotation position information at the current time from the polarization direction changing device 14, and obtains feed amount information in which the result of the difference calculation is the rotation angle. In step ST3B, the polarization direction changing device 14 rotates the polarization device 13 based on feed amount information from the time control unit 34b in the changing device control unit 34, thereby changing the polarization direction of the polarization device 13.

[0074] Steps ST4 to ST6 are the same as steps ST4 to ST6 in the orbital object detection device according to Embodiment 1, so their explanation will be omitted. Observation time T N Up to Step ST1, Step ST2A, Step ST3A, Step ST2B 11 Steps ST2B2, ST3B, ST4, ST5, and ST6 are executed repeatedly.

[0075] Step ST1, Step ST2A, Step ST2B 11 The processing steps ST2B2 and ST4 are stored as a program in the ROM1C of the computer that constitutes the optical system control device 30. In other words, the program stored in ROM1C includes a procedure for obtaining tracking trajectory information of a target object in orbit; a procedure for calculating the difference between the tracking trajectory information of the target object in orbit and the pointing direction information of the drive device 20 at the current time, and obtaining two-axis drive amount information for the drive device 20 using the difference calculation result; a procedure for obtaining rotational position information using the deflection direction in which the background light is attenuated the most from multiple observation data obtained by observing background light with multiple different polarization directions relative to the direction indicated by the tracking trajectory information of the target object in orbit; a procedure for calculating the difference between the rotational position information and the rotational position information of the polarization direction changing device 14 at the current time, and obtaining feed amount information for the polarization direction changing device 14 using the difference calculation result; and a procedure for reading sensor information and using it as sensor control information for the photodetector 12.

[0076] The orbital object detection device according to Embodiment 2 is an orbital object detection device equipped with an imaging optical system 11 and a photodetector 12, wherein a polarization device 13 is positioned between the imaging optical system 11 and the photodetector 12, and the device includes a polarization direction changing device 14 for changing the polarization direction of the polarization device 13, a polarization direction measuring device 40 for acquiring observation data showing multiple different polarization directions, and an optical system control device 30 having a changing device control unit 34A that provides the polarization direction changing device 14 with feed amount information indicating the polarization direction determined based on the multiple observation data from the polarization direction measuring device 40. As a result, the background light is absorbed or reflected from the incident light incident on the polarization device 13, and the incident light from which the background light has been removed is imaged on the sensor surface of the photodetector 12, that is, at the focal position (focal plane) of the imaging optical system 11, so that the photodetector 12 can detect incident light from the target orbital object with a high signal-to-noise ratio.

[0077] Embodiment 3. The orbital object detection device according to Embodiment 3 will be described with reference to Figures 6 and 7. The orbital object detection device according to Embodiment 3 differs from the orbital object detection device according to Embodiment 1 in that the optical system control device 30 further includes an initial coordinate determination unit 36 ​​for the tracking trajectory determination unit 31, but is otherwise the same. Therefore, the following explanation will focus on the differences from the orbital object detection device according to Embodiment 1. In Figures 6 and 7, the same reference numerals as those used in Figures 1 to 3 indicate the same or corresponding parts.

[0078] The optical system control device 30B includes a tracking trajectory determination unit 31A, a drive unit control unit 32, a photodetector control unit 33, a change unit control unit 34, a recording unit 35, and an initial coordinate determination unit 36. The initial coordinate determination unit 36 ​​acquires the latest image data of the target orbiting object stored in the recording unit 35, determines the initial coordinates of the target orbiting object based on the acquired image data, and provides the determined initial coordinates to the tracking trajectory determination unit 31A. The initial coordinate determination unit 36 ​​reads, for example, image data of the latest target object in orbit from the previous day, which is stored in the recording unit 35. The initial coordinate determination unit 36 ​​accurately determines the coordinates at the observation time assigned to the image data by assigning the coordinates of the target orbiting object to the read image data. The initial coordinate determination unit 36 ​​performs orbital propagation on the coordinates determined at the observation time of the previous day using a generally known method, such as a method using TLE and SGP4, to obtain the coordinates of the target orbital object at the start time of tracking observation, i.e., the initial coordinates.

[0079] The tracking trajectory determination unit 31A provides the initial coordinates from the initial coordinate determination unit 36 ​​to the drive unit control unit 32 and the modification unit control unit 34 as tracking trajectory information for the start time of tracking observation of the target object in orbit. As a result, the initial coordinates determined by the initial coordinate determination unit 36 ​​are provided to the drive unit control unit 32 as tracking trajectory information for the target on-orbit object at the start time of tracking observation. The tracking trajectory determination unit 31A calculates an offset based on the difference between the initial coordinates from the initial coordinate determination unit 36 ​​and the information of the target object in orbit at the same time as the observation time of the previous day in the initial coordinates.

[0080] The tracking trajectory determination unit 31A uses the tracking trajectory information as the initial coordinates from the initial coordinate determination unit 36. Then, similar to the tracking trajectory determination unit 31 of the optical system control device 30A in the orbital object detection device according to Embodiment 1, it obtains trajectory information for each observation time based on information of the target orbital object using a method that utilizes TLE and SGP4, and applies an offset to the obtained trajectory information to obtain the tracking trajectory information. In this way, the tracking trajectory determination unit 31A uses the initial coordinates from the initial coordinate determination unit 36 ​​to obtain tracking trajectory information by adding an offset to the trajectory information obtained from the information of the target object in orbit at each observation time, thereby enabling highly accurate tracking of the target object in orbit.

[0081] Next, the operation of the orbital object detection device according to Embodiment 3 will be explained using Figure 7. In step ST0, the initial coordinate determination unit 36 ​​acquires the latest image data showing the target orbiting object stored in the recording unit 35, and determines the initial coordinates of the target orbiting object based on the acquired image data. At observation time T1, step ST1 is performed by the tracking trajectory determination unit 31A using the initial coordinate determination unit 36 ​​as tracking trajectory information for the start time of tracking observation of the target object in orbit. From observation time T2 to observation time T N In step ST1, the tracking trajectory determination unit 31A obtains tracking trajectory information based on information about the target object in the trajectory.

[0082] Steps ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 are the same as steps ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 in the orbital object detection device according to Embodiment 1, so their description is omitted. Observation time T N Steps ST1, ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 are repeatedly executed until the specified step is reached.

[0083] Steps ST0, Step ST1, Step ST2A, Step ST2B 11 , the processing steps by Step ST2B2 and Step ST4 are stored as programs in the ROM1C in the computer that constitutes the optical system control device 30. That is, the program stored in the ROM1C determines the initial coordinates of the target object on the trajectory, obtains the tracking trajectory information at the start time of tracking observation of the target object on the trajectory, obtains the tracking trajectory information of the target object on the trajectory at the tracking observation start time word, calculates the difference between the tracking trajectory information of the target object on the trajectory and the pointing direction information at the current time in the drive device 20, and obtains the two-axis drive amount information for the drive device 20 using the difference calculation result. It includes the steps of obtaining the rotation position information using the deflection direction in which the background light attenuates the most from a plurality of observation data obtained by observing the background light with a plurality of polarization directions different from each other with respect to the direction indicated by the tracking trajectory information of the target object on the trajectory, calculating the difference between the rotation position information and the rotation position information at the current time in the polarization direction changing device 14, and obtaining the feed amount information for the polarization direction changing device 14 using the difference calculation result, and the step of reading the sensor information and using it as sensor control information for the photodetector 12.

[0084] The orbital object detection device according to Embodiment 3 is an orbital object detection device comprising an imaging optical system 11, a photodetector 12, and a drive device 20, wherein a polarization device 13 is positioned between the imaging optical system 11 and the photodetector 12, a polarization direction changing device 14 that changes the polarization direction of the polarization device 13, a drive device control unit 32 that calculates the difference between the tracking trajectory information of the target orbital object and the coordinates of the pointing direction of the imaging optical system 11 at the current time from the drive device 20, and outputs two-axis drive amount information indicating the two-axis drive amount to the drive device 20, an initial coordinate determination unit 36 ​​that determines initial coordinates based on image data showing the target orbital object, and provides the determined initial coordinates as the tracking trajectory information of the target orbital object at the start time of tracking observation in the drive device control unit 32, and The optical system control device 30 includes a polarization direction changing device control unit 34 that provides a polarization direction changing device 14 with feed amount information, where the direction of the line connecting the position coordinates relative to the sun and the tracking orbit coordinates relative to the target orbital object is the polarization direction. Therefore, the direction of the imaging optical system 11 can be set with high precision at the start time of tracking observation, especially when observation is started during the daytime. This ensures that the imaging optical system 11 reliably acquires the target orbital object. Moreover, the background light is absorbed or reflected from the incident light incident on the polarization device 13, and the incident light from which the background light has been removed is imaged on the sensor surface of the photodetector 12, that is, at the focal position (focal plane) of the imaging optical system 11. As a result, the photodetector 12 can detect the incident light from the target orbital object with a high signal-to-noise ratio.

[0085] In addition, in the orbital object detection device according to Embodiment 2, the initial coordinate determination unit 36 ​​of the orbital object detection device according to Embodiment 3 may be added, and the tracking trajectory determination unit 31 may be changed to a tracking trajectory determination unit 31A. In this case as well, it has the same effect as the orbital object detection device according to Embodiment 2, and also has the effect of being able to reliably capture the target orbital object by the imaging optical system 11 because the direction of the imaging optical system 11 can be set with high precision when the tracking observation start time, especially when observation is started during the daytime.

[0086] Embodiment 4. The orbital object detection device according to Embodiment 4 will be described with reference to Figures 8 and 9. The orbital object detection device according to Embodiment 4 differs from the orbital object detection device according to Embodiment 1 in that it includes an initial coordinate observation device 50, and the optical system control device 30 further includes an initial coordinate determination unit 36A for the tracking trajectory determination unit 31, but all other aspects are the same. Therefore, the following explanation will focus on the differences from the orbital object detection device according to Embodiment 1. In Figures 8 and 9, the same reference numerals as those used in Figures 1 through 3 indicate the same or corresponding parts.

[0087] The initial coordinate observation device 50 takes information about the target orbiting object as input, observes the area around the predicted orbit of the target orbiting object at the current time, and obtains observation data. Information about the target object in orbit is provided by Time Limit Exceeded (TLE), and the predicted orbit at the current time is obtained using, for example, SGP4 based on the input TLE. The observation means in the initial coordinate observation device 50 uses radar that can observe target orbiting objects even during the daytime without being significantly affected by sunlight and atmospheric absorption.

[0088] The optical system control device 30C includes a tracking trajectory determination unit 31A, a drive unit control unit 32, a photodetector control unit 33, a change unit control unit 34, a recording unit 35, and an initial coordinate determination unit 36A. The initial coordinate determination unit 36A determines the initial coordinates of the target orbiting object based on observation data from the initial coordinate observation device 50 at the start time of tracking observation of the target orbiting object, and provides the determined initial coordinates to the tracking orbit determination unit 31A.

[0089] The initial coordinate determination unit 36A can accurately determine the coordinates of the target orbiting object at the observation time at the start of tracking observation by assigning coordinates to the observation data from the initial coordinate observation device 50. In particular, by using radar as an observation method, the coordinates of the target orbiting object at the start of tracking observation can be determined even more accurately.

[0090] The tracking trajectory determination unit 31A provides the initial coordinates from the initial coordinate determination unit 36A to the drive unit control unit 32 and the modification unit control unit 34 as tracking trajectory information for the start time of tracking observation of the target object in orbit. As a result, the initial coordinates determined by the initial coordinate determination unit 36A are provided to the drive unit control unit 32 as tracking trajectory information for the target on-orbit object at the start time of tracking observation.

[0091] The tracking trajectory determination unit 31A uses the tracking trajectory information as the initial coordinates from the initial coordinate determination unit 36A, and then, similar to the tracking trajectory determination unit 31 of the optical system control device 30A in the orbital object detection device according to Embodiment 1, it obtains trajectory information for each observation time using a method that utilizes TLE and SGP4 based on information of the target orbital object, and uses the obtained trajectory information as the tracking trajectory information. In this way, the tracking trajectory determination unit 31A uses the initial coordinates from the initial coordinate determination unit 36A to determine the trajectory information obtained from the information of the target object in orbit at each observation time, thereby enabling highly accurate tracking of the target object in orbit.

[0092] Next, the operation of the orbital object detection device according to Embodiment 4 will be explained using Figure 9. In step ST01, the initial coordinate determination unit 36A acquires observation data from the initial coordinate observation device 50 at the start time of tracking observation of the target orbiting object, and determines the initial coordinates of the target orbiting object based on the acquired observation data. At observation time T1, step ST1 is performed by the tracking trajectory determination unit 31A using the initial coordinate determination unit 36A as tracking trajectory information for the start time of tracking observation of the target object in orbit. From observation time T2 to observation time T N In step ST1, the tracking trajectory determination unit 31A obtains tracking trajectory information based on information about the target object in the trajectory.

[0093] Steps ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 are the same as steps ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 in the orbital object detection device according to Embodiment 1, so their description is omitted. Observation time T N Steps ST1, ST2A, ST3A, ST2B1, ST2B2, ST3B, ST4, ST5, and ST6 are repeatedly executed until the specified step is reached.

[0094] Steps ST01, ST1, ST2A, ST2B 11 The processing steps ST2B2 and ST4 are stored as a program in the ROM1C of the computer that constitutes the optical system control device 30. In other words, the program stored in ROM1C includes a procedure for determining the initial coordinates of the target orbiting object and obtaining tracking trajectory information for the start time of tracking observation of the target orbiting object; a procedure for obtaining tracking trajectory information of the target orbiting object after the start time of tracking observation; a procedure for calculating the difference between the tracking trajectory information of the target orbiting object and the pointing direction information of the drive device 20 at the current time, and obtaining two-axis drive amount information for the drive device 20 using the difference calculation result; a procedure for obtaining rotational position information using the deflection direction in which the background light is attenuated the most from multiple observation data obtained by observing background light with multiple different polarization directions relative to the direction indicated by the tracking trajectory information of the target orbiting object; a procedure for calculating the difference between the rotational position information and the rotational position information of the polarization direction changing device 14 at the current time, and obtaining feed amount information for the polarization direction changing device 14 using the difference calculation result; and a procedure for reading sensor information and using it as sensor control information for the photodetector 12.

[0095] The orbital object detection device according to Embodiment 4 is an orbital object detection device comprising an imaging optical system 11, a photodetector 12, and a drive device 20, wherein a polarization device 13 is positioned between the imaging optical system 11 and the photodetector 12, a polarization direction changing device 14 that changes the polarization direction of the polarization device 13, a drive device control unit 32 that calculates the difference between the tracking trajectory information of the target orbital object and the coordinates of the pointing direction of the imaging optical system 11 at the current time from the drive device 20, and outputs two-axis drive amount information indicating the two-axis drive amount to the drive device 20, an initial coordinate determination unit 36A that determines the initial coordinates based on observation data from the initial coordinate observation device 50 and provides the determined initial coordinates as the tracking trajectory information of the target orbital object at the start time of tracking observation in the drive device control unit 32, and The optical system control device 30 includes a polarization direction changing device control unit 34 that provides a polarization direction changing device 14 with feed amount information, where the direction of the line connecting the position coordinates relative to the sun and the tracking orbit coordinates relative to the target orbital object is the polarization direction. Therefore, the direction of the imaging optical system 11 can be set with high precision at the start time of tracking observation, especially when observation is started during the daytime. This ensures that the imaging optical system 11 reliably acquires the target orbital object. Moreover, the background light is absorbed or reflected from the incident light incident on the polarization device 13, and the incident light from which the background light has been removed is imaged on the sensor surface of the photodetector 12, that is, at the focal position (focal plane) of the imaging optical system 11. As a result, the photodetector 12 can detect the incident light from the target orbital object with a high signal-to-noise ratio.

[0096] In addition, in the orbital object detection device according to Embodiment 2, the initial coordinate observation device 50 and initial coordinate determination unit 36A from the orbital object detection device according to Embodiment 4 may be added, and the tracking trajectory determination unit 31 may be changed to a tracking trajectory determination unit 31A. In this case as well, it has the same effect as the orbital object detection device according to Embodiment 2, and also has the effect of being able to reliably capture the target orbital object by the imaging optical system 11 because the direction of the imaging optical system 11 can be set with high precision when the tracking observation start time, especially when observation is started during the daytime.

[0097] Furthermore, it is possible to freely combine the embodiments, modify any component of each embodiment, or omit any component of each embodiment. [Industrial applicability]

[0098] The orbital object detection device described herein can be applied to orbital object detection devices that detect orbital objects such as artificial satellites or space debris. [Explanation of Symbols]

[0099] 10 Optical telescope, 11 Imaging optical system, 12 Photodetector, 13 Polarization device, 14 Polarization direction changing device, 20 Drive device, 30, 30A, 30B, 30C Optical system control device, 31, 31A Tracking trajectory determination unit, 32 Drive device control unit, 33 Photodetector control unit, 34, 34A Changing device control unit, 35 Recording unit, 36 Initial coordinate determination unit, 40 Polarization direction measuring device, 50 Initial coordinate observation device.

Claims

1. An imaging optical system receives incident light including light from a target orbiting object, guides the incident light from the target orbiting object, and forms an image. A photodetector, which is positioned on the focal plane focused by the imaging optical system and outputs image information, A polarizing device is placed between the imaging optical system and the photodetector, and transmits the incident light to the photodetector as polarized light. A polarization direction changing device that receives feed amount information and changes the polarization direction of the polarization device based on the received feed amount information, An optical system control device having a polarization direction changing device control unit that provides the polarization direction changing device with feed amount information such that the direction of the line connecting the position coordinates relative to the sun and the tracking trajectory coordinates of the target orbital object is the polarization direction, An orbital object detection device equipped with the following features.

2. The polarization device is rotated by the polarization direction changing device around a rotation axis that coincides with the optical axis of the imaging optical system. The on-orbit object detection device according to claim 1, wherein the feed amount information by the modification device control unit is defined as feed amount information in which the direction on the celestial sphere connecting the position coordinates relative to the sun and the tracking orbit coordinates relative to the target on-orbit object is defined as the polarization direction, and the rotation position information obtained by converting the resulting polarization direction into rotation position information of the polarization direction modification device is defined as the rotation angle, and the difference calculation result of the rotation position information of the polarization direction modification device at the present time is defined as the rotation angle.

3. An imaging optical system receives incident light, including light from a target orbiting object, guides the incident light from the orbiting object, and forms an image. A photodetector, which is positioned on the focal plane focused by the imaging optical system and outputs image information, A polarizing device is placed between the imaging optical system and the photodetector, and transmits the incident light to the photodetector as polarized light. A polarization direction changing device that receives feed amount information and changes the polarization direction of the polarization device based on the received feed amount information, A polarization direction measuring device that acquires observational data showing multiple different polarization directions, An optical system control device having a polarization direction changing device control unit that provides feed amount information indicating the polarization direction, determined based on multiple observation data from the polarization direction measuring device, to the polarization direction changing device, An orbital object detection device equipped with the following features.

4. The polarization device is rotated by the polarization direction changing device around a rotation axis that coincides with the optical axis of the imaging optical system. The multiple observational data acquired by the polarization direction measuring device are actual measurement data of background light observed with multiple different polarization directions relative to the directional direction indicated by the tracking trajectory coordinates for the target object in orbit. The on-orbit object detection device according to claim 3, wherein the feed amount information by the change device control unit is a feed amount information in which the rotation position information obtained by calculating the polarization direction in which the background light is most attenuated from multiple observation data from the polarization direction measuring device and converting the obtained polarization direction into rotation position information of the polarization direction change device, and the difference calculation result of the rotation position information of the polarization direction change device at the present time is used as the rotation angle.

5. The orbital object detection device according to any one of claims 1 to 4, wherein the polarizing device is a polarizing plate.

6. The orbital object detection device according to claim 5, wherein the polarizing device has a wavelength filter arranged along the optical axis of the polarizing plate.

7. The orbital object detection device according to any one of claims 1 to 4, wherein the polarization device is a filter wheel in which a plurality of polarization filters with different linear polarization components transmitted to each other are arranged along the circumference with respect to the axis of rotation.

8. The system includes a drive device for changing the direction of the imaging optical system, The optical system control device has a drive unit control that calculates the difference between the tracking trajectory information of the target object on the orbit and the coordinates of the pointing direction of the imaging optical system at the current time from the drive unit, and outputs two-axis drive amount information indicating the two-axis drive amount to the drive unit. An orbital object detection device according to any one of claims 1 to 4.

9. The orbital object detection device according to claim 8, wherein the optical system control device has an initial coordinate determination unit that determines initial coordinates based on image data showing the target orbital object, and provides the determined initial coordinates as tracking trajectory information of the target orbital object at the start time of tracking observation in the drive unit control unit.

10. The orbital object detection device according to claim 8, wherein the optical system control device has an initial coordinate determination unit that determines initial coordinates based on observation data including the target orbital object at the start time of tracking observation of the target orbital object, and provides the determined initial coordinates as tracking trajectory information of the target orbital object at the start time of tracking observation in the drive unit control unit.

11. In a method for detecting an object in orbit using an object detection device that includes an imaging optical system, a photodetector, a polarizing device, a polarization direction changing device, a polarization direction changing device control unit, and a photodetector control unit, The optical system control device controls a polarization direction change device, which provides the polarization direction change device with feed amount information such that the direction of the line connecting the position coordinates relative to the sun and the tracking orbit coordinates relative to the object in orbit is the polarization direction, thereby changing the polarization direction of the polarization device. The photodetector control unit in the optical system control device outputs sensor control information to the photodetector, the photodetector receives incident light into the imaging optical system, and the incident light, which has passed through the polarizing device and been focused, is imaged based on the input sensor control information. An orbital object detection method comprising the following features.

12. Procedure for obtaining tracking trajectory information of a target object in orbit, The procedure involves calculating the difference between the tracking trajectory information of the target object on the orbit and the directional information of the drive device at the current time, and using the difference calculation result to obtain two-axis drive amount information for the drive device, A procedure for obtaining rotational position information using the direction of the line connecting the tracking trajectory information of the target orbital object and its position coordinates relative to the sun, A procedure for calculating the difference between the rotational position information and the rotational position information at the current time in the polarization direction changing device, and obtaining feed amount information for the polarization direction changing device using the result of the difference calculation, The procedure for reading sensor information and using it as sensor control information for the photodetector, A program for detecting objects in orbit that is executed on a computer equipped with the necessary components.

13. Procedure for obtaining tracking trajectory information of a target object in orbit, The procedure involves calculating the difference between the tracking trajectory information of the target object on the orbit and the directional information of the drive device at the current time, and using the difference calculation result to obtain two-axis drive amount information for the drive device, A procedure for obtaining rotational position information using the direction of the line connecting the tracking trajectory information of the target orbital object and its position coordinates relative to the sun, A procedure for calculating the difference between the rotational position information and the rotational position information at the current time in the polarization direction changing device, and obtaining feed amount information for the polarization direction changing device using the result of the difference calculation, The procedure for reading sensor information and using it as sensor control information for the photodetector, A storage medium that stores a program that causes a computer to execute a command.

Images