JP7345705B2 - Space object ranging device - Google Patents

Description

The disclosed technology relates to a space object ranging device.

Techniques have been disclosed for observing space objects such as space debris and artificial satellites using laser light. For example, Patent Document 1 discloses a technique for scanning an irradiation beam using prior observation information of a space object by another system, and measuring and observing a space object.

JP 2017-88072 Publication

When measuring distance from space objects, the reflected light is so weak that it can be expressed in units of photons. In other words, high-energy light beams are required to measure distances to space objects. Lasers generally used for distance measurement of space objects include, for example, those that use a flash lamp to excite a high-energy pulsed laser.

Flash lamps do not have a high repetition rate. For this reason, distance measurement of space objects according to the prior art has a problem in that it takes time to collect enough photon detection events to perform statistical processing. This is a big problem, especially for low-orbit objects whose observable time is short.

The space object distance measuring device according to the disclosed technology includes a first wavelength light source unit that outputs a light signal having a wavelength of λa, and a second wavelength light source unit that _outputs a light signal having a wavelength of λb _different from λa _. A wavelength light source section , a filter controller that determines the transmission wavelength band while synchronizing by adding _an offset time T_offset to the oscillation timing of the first wavelength light source section and the second wavelength light source section; and a wavelength tunable filter that is controlled to have characteristics of a transmission wavelength band.

Since the space object ranging device according to the disclosed technology has the above configuration, it is possible to increase the repetition frequency of the high-energy pulsed laser in a pseudo manner. Due to this effect, the space object ranging device according to the present disclosure can shorten the time required to collect enough photon detection events to perform statistical processing.

FIG. 1 is a block diagram showing the configuration of a space object ranging device according to the first embodiment. FIG. 2 is an example of a timing chart showing events on the time axis of the space object ranging device according to the first embodiment. FIG. 3 is a schematic diagram showing an example of setting the transmission wavelength of the wavelength tunable filter 12. FIG. 4 is a graph showing an image of a photon detection event in the space object ranging device according to the first embodiment. FIG. 5 is a block diagram showing the configuration of a space object ranging device according to the second embodiment. FIG. 6 is a schematic diagram showing the irradiation range of the space object ranging device according to the second embodiment. FIG. 7 is an example of a histogram of photon detection events by wavelength of the space object ranging device according to the second embodiment. FIG. 8 is a schematic diagram showing the operation of a plurality of space object ranging devices according to the third embodiment. FIG. 9 is a schematic diagram illustrating wavelengths employed by a plurality of space object ranging devices according to the third embodiment. FIG. 10 is an example of a histogram of photon detection events by wavelength of the space object ranging device (61) according to the third embodiment.

Embodiment 1.
FIG. 1 is a block diagram showing the configuration of a space object ranging device 1 according to the first embodiment. As shown in FIG. 1, the space object ranging device 1 according to the first embodiment includes a light source section 2 (a first wavelength light source section 2a, a second wavelength light source section 2b, a third wavelength light source section 2c, ), a light source controller 3, a multiplexer 4, a transmitting telescope 5, a receiving telescope 11, a variable wavelength filter 12, a photodetector 13, a gate controller 14, an event timer 15, It includes a filter controller 16, a ranging information processing section 21, a trajectory information storage section 51, and a pointing direction controller 52.

Specifically, the light source section 2 (the first wavelength light source section 2a, the second wavelength light source section 2b, the third wavelength light source section 2c, etc.) may be a pulse laser.

The operation of each component of the space object ranging device 1 will become clear from the following explanation. Here, the distance from the space object ranging device 1 to the space object (31) is assumed to be L. The pulse repetition interval of the light source section 2 (the first wavelength light source section 2a, the second wavelength light source section 2b, and the third wavelength light source section 2c) is assumed to be T _rep . It is assumed that the wavelength of the light source section 2a of the first wavelength is λ _a , the wavelength of the light source section 2b of the second wavelength is λ _b , and the wavelength of the light source section 2c of the third wavelength is λ _c . λ _a , λ _b , and λ _c may be different wavelengths within a range of approximately 1 to 10 [nm], for example.

The space object ranging device 1 shown in FIG. 1 includes a first wavelength light source section 2a, a second wavelength light source section 2b, and a third wavelength light source section 2c, but the present disclosure technology The number of light source units 2 of the space object ranging device 1 according to the above is not limited to three. The number of light source units 2 of the space object distance measuring device 1 according to the disclosed technology may be two or more.

The light source section 2 is controlled by a light source section controller 3.

FIG. 2 is an example of a timing chart showing events on the time axis of the space object ranging device 1 according to the first embodiment. As shown in FIG. 2, the first wavelength light source section 2a, the second wavelength light source section 2b, and the third wavelength light source section 2c are all oscillated at a pulse repetition interval (T _rep ). Further, the first wavelength light source section 2a, the second wavelength light source section 2b, and the third wavelength light source section 2c are oscillated at different timings. Specifically, the oscillation timing of the second wavelength light source section 2b is controlled to be delayed by Δ from the oscillation timing of the first wavelength light source section 2a. Similarly, the oscillation timing of the third wavelength light source section 2c is controlled to be delayed by Δ from the oscillation timing of the second wavelength light source section 2b. The oscillation timing delay Δ is set shorter than the pulse repetition interval (T _rep ).

The light source unit controller 3 controls the light source units 2 (a first wavelength light source unit 2a, a second wavelength light source unit 2b, and a third wavelength light source unit 2b) so that the laser beam is oscillated at the timing illustrated in FIG. The light source section 2c,...) is controlled. Laser light oscillated by the light source section 2 (first wavelength light source section 2a, second wavelength light source section 2b, third wavelength light source section 2c, etc.) is output to the multiplexer 4. The laser light oscillated by the light source section 2 is represented by a thick arrow in FIG. 1 indicating that it is an optical signal.

The multiplexer 4 multiplexes the laser beams output from the light source sections 2 (a first wavelength light source section 2a, a second wavelength light source section 2b, a third wavelength light source section 2c, etc.). The combined laser light is output to the transmitting telescope 5.

The transmitting telescope 5 irradiates the combined laser light toward the space object (31) as transmitted light (41). The transmitted light (41) is represented by a thick arrow in FIG. 1 indicating that it is an optical signal.

The fourth row from the top of FIG. 2 shows the transmitted light (41) irradiated by the transmitting telescope 5 on the time axis. As shown in the fourth row of FIG. 2, the transmitted light (41) irradiated by the space object ranging device 1 according to the first embodiment has an apparent pulse repetition period that is higher than that of the conventional one using a single pulse laser. is short.

The transmitted light (41) propagates in outer space and is irradiated onto a space object (31). Specifically, the space object (31) is assumed to be a geostationary orbit satellite, a low orbit satellite, space debris, or the like.

The orbit information storage unit 51 stores orbit information about the space object (31). The trajectory information may be in the form of TLE (Two-Line Elements), for example. The orbit information is information on the past and present orbit of the space object (31). The prediction of the future trajectory of the space object (31) is referred to as orbit prediction information to distinguish it from orbit information. The orbit prediction information is used to track the space object (31). When tracking a space object (31), trajectory prediction information of the target space object (31) is passed from the trajectory information storage section 51 to the pointing direction controller 52. The pointing direction controller 52 drives and controls the telescope drive system 53 based on the received trajectory prediction information. A transmitting telescope 5 and a receiving telescope 11 are mounted on the telescope drive system 53.

The transmitted light (41) is reflected according to the surface characteristics of the space object (31), and reflected light (42) is generated.
Depending on the type of space object (31), the reflectance of the laser may be high. For example, in the case of a geodetic satellite used for geodesy, etc., it may be equipped with a mirror surface or a corner cube retroreflector (CCR) having retroreflective characteristics.
The space object (31) assumed by the disclosed technology may not have a mirror surface or the like, and therefore does not have high reflectance. Note that when comparing an object with a CCR with a diameter of several meters and an object of the same size without a CCR, it is estimated that the reflection characteristics differ by about 5 to 6 orders of magnitude.

When the space object (31) is space debris, its optical cross section is narrower than that of a satellite. Therefore, in the case of space debris, the intensity of the reflected light (42) is weaker than that of a satellite. For this reason as well, the laser beam used in the space object ranging device 1 is required to have high pulse energy.

The receiving telescope 11 receives reflected light (42) reflected by a space object (31). The space object ranging device 1 according to the first embodiment can measure the distance to the space object (31) based on Time of Flight (hereinafter referred to as "TOF"), that is, based on the flight time of light. When the flight time of light is τ, the distance from the space object ranging device 1 to the space object (31) is L, and the speed of light is c, the relational expression τ=2L/C holds true.

FIG. 3 is a schematic diagram showing an example of setting the transmission wavelength of the wavelength tunable filter 12. The variable wavelength filter 12 performs filter processing on the optical signal received by the receiving telescope 11 . In the variable wavelength filter 12, a plurality of transmission wavelength bands are dynamically switched and controlled by a filter controller 16. The plurality of transmission wavelength bands include a wavelength band including λ _a , a wavelength band including λ _b , and a wavelength band including λ _c .

As shown in the fifth to seventh rows from the top of FIG. 2, the transmission wavelength band starts to be set after _{T_offset} from the time when the transmission light (41) is irradiated, and continues to be set for _{T_gate} . _{T_offset} is determined based on the expected TOF. Further, _{T_gate} is determined based on the oscillation timing delay Δ. _{T_offset} is called offset time and _{T_gate} is called gate time. The details of how to determine the offset time ( _{T_offset} ) and gate time ( _{T_gate} ) will become clear from the description below.

As described above, by including the wavelength tunable filter 12 and the filter controller 16, the space object ranging device 1 according to the first embodiment can separate the reflected light (42) to be determined and the transmitted light (41) that becomes noise. The backscattered light (44) can be separated. The details of the effect of providing the wavelength tunable filter 12 and the filter controller 16 will become clear from the explanation below.

The reflected light (42) that has passed through the variable wavelength filter 12 is received by the photodetector 13. The photodetector 13 is required to receive weak light that can be expressed in units of photons. Therefore, the photodetector 13 may be configured with, for example, a SPAD (Single Photon Avalanche Diode).

The photodetector 13 may operate only when a gate signal from the outside is turned on (hereinafter referred to as "gate operation"). FIG. 1 shows a configuration in which the photodetector 13 is controlled by a gate controller 14 to perform a gate operation.

The photodetector 13 outputs an event signal to the event timer 15 when it receives an optical signal during operation. The event signal may have a fast rise time or fall time, and may be an electrical pulse signal, for example.

In addition to the event signal from the photodetector 13, the event timer 15 receives an event signal from the light source section 2 (first wavelength light source section 2a, second wavelength light source section 2b, third wavelength light source section 2c, ...). It also receives event signals (see Figure 1). The event timer 15 can accurately measure the time when the input event signal is input. The event timer 15 tags the input event signal with a time. Information on the event signal tagged with time is output to the ranging information processing section 21 .

As shown in FIG. 1, the distance measurement information processing section 21 is roughly divided into two parts. One is an event accumulation part, and the other is a ranging information extraction part. Information from the event timer 15 is accumulated in an event accumulation section of the ranging information processing section 21. The ranging information extraction part of the ranging information processing unit 21 calculates the TOF based on the accumulated information and calculates the distance to the space object (31).

As mentioned above, the reflected light (42) that this technical field deals with is weak light on the order of the number of photons. For this reason, it is noted in the art that the signal detection process is probabilistic.

As shown in FIG. 1, in addition to the reflected light (42), background light (43) and backscattered light (44) also enter the receiving telescope 11.
Background light (43) occurs both during the day and at night. The background light (43) that occurs during the day is mainly sunlight scattered in the atmosphere. Background light (43) occurring at night is due to city lighting and other celestial bodies. The amount of background light (43) is greater during the day than at night. The background light (43) has a property that there is not much temporal variation. Furthermore, the background light (43) has no deviation or peak when the wavelength range is 1 to 10 [nm]. That is, the background light (43) has a property of not having much wavelength dependence.
Backscattered light (44) is the transmitted light (41) scattered in the atmosphere. The amount of backscattered light (44) is highest immediately after the transmitted light (41) is output, and then decreases exponentially.

Here, the transmitted light (41), reflected light (42), and backscattered light (44) for one light source have the same wavelength. On the other hand, the transmitted light (41), reflected light (42), and backscattered light (44) for one light source are generated at different times. The schematic diagram shown in the fifth row from the top of FIG. 2 shows this.

In the wavelength tunable filter 12 according to the first embodiment, the transmission wavelength band changes by the filter controller 16 at the timing shown in the sixth row from the top in FIG. For example, the wavelength variable filter 12 has a transmission wavelength band that transmits only λ _a at the timing when it receives the reflected light (42) of the transmitted light (41) oscillated by the light source section 2a of the first wavelength, and transmits only λa. Such backscattered light (44) is blocked. The variable wavelength filter 12 operates in the same manner at the timing of receiving the reflected light (42) from the light source section 2b of the second wavelength and the light source section 2c of the third wavelength. Due to this effect, the space object ranging device 1 according to the first embodiment can reduce the backscattered light (44) that becomes noise and receive the reflected light (42) with a high S/N ratio.

As shown in FIG. 1, detector noise (45) caused by dark current or the like may be superimposed on the signal line of the photodetector 13. In this technical field, various efforts have been made to reduce detector noise (45). The space object distance measuring device 1 according to the present disclosure may also be appropriately designed to reduce detector noise (45).

The ranging information processing unit 21 determines the offset time ( _{T_offset} ) and gate time ( _{T_gate} ) for the plurality of transmission wavelength bands switched by the filter controller 16.
As mentioned above, the offset time ( _{T_offset} ) is determined based on the expected TOF. For TOF prediction, for example, trajectory information and trajectory prediction information stored in the trajectory information storage section 51 may be used. In FIG. 1, trajectory prediction information is indicated by a dotted arrow indicating that it is information.
As described above, the gate time (T _{_gate} ) is determined based on the oscillation timing delay Δ. As shown in the sixth timing chart from the top of FIG. 2, the gate time ( _{T_gate} ) cannot be made longer than the oscillation timing delay Δ. Further, the gate time (T _{_gate} ) is preferably set to satisfy T _rep >τ+T _{_gate} ÷2 in relation to the expected TOF. Note that τ here represents the expected TOF.

FIG. 4 is a graph showing an image of a photon detection event in the space object ranging device 1 according to the first embodiment. The horizontal axis of the graph represents event accumulation time. The event accumulation time is described in units of gate time ( _{T_gate} ). The vertical axis of the graph represents event information recorded by the event timer 15. Specifically, the event information is the time from the pulse transmission time to the photon reception time.

FIG. 4 shows that there is a distribution in the photon detection results. In other words, photon detection in this technical field requires probabilistic statistical processing. The factors contributing to the spread distribution of photon detection results are the weak light and the presence of background light (43), backscattered light (44), and detector noise (45). Conceivable.

The ranging information processing unit 21 of the space object ranging device 1 according to the first embodiment performs statistical processing on the accumulated event information. More specifically, the ranging information processing unit 21 calculates the frequency distribution of event information and estimates a plausible flight time (τ) of the signal light.

The space object ranging device 1 according to the first embodiment may be configured to change the gate time ( _{T_gate} ) depending on the situation. As the amount of accumulated event information increases, the accuracy of estimating the flight time (τ) improves. In other words, the estimation error of the flight time (τ) decreases as the accumulated event information increases. Therefore, the space object ranging device 1 may be configured to sequentially shorten the oscillation timing delay Δ, the gate time (T _{_gate} ), and the pulse repetition interval (T _rep ). Shortening the gate time ( _{T_gate} ) has the effect of reducing distance measurement time.

The space object ranging device 1 according to the first embodiment obtains orbit information based on the ranging information calculated from the estimated flight time (τ) and the orientation when tracking the space object (31). A configuration may be adopted in which the trajectory information stored in the storage unit 51 is updated. By adding the calculated ranging information, it is expected that the accuracy of the orbit information will improve.

Although FIG. 1 shows a configuration using a single transmitting telescope 5, the aspect of the transmitting telescope 5 according to the presently disclosed technology is not limited to this. The number of transmitting telescopes 5 of the space object ranging device 1 according to the disclosed technology corresponds to each of the light source units 2 (first wavelength light source unit 2a, second wavelength light source unit 2b, ...). Good too. That is, the transmitting telescope 5 may include a first transmitting telescope 5a corresponding to the light source section 2a of the first wavelength, a second transmitting telescope 5b corresponding to the light source section 2b of the second wavelength, and the like.
In the case of a configuration including a plurality of transmitting telescopes 5, each of the transmitting telescopes 5 (first transmitting telescope 5a, second transmitting telescope 5b, . . . ) may be oriented in the same direction. Also, the distance from the light source section 2 (first wavelength light source section 2a, second wavelength light source section 2b, ...) to the transmitting telescope 5 (first transmitting telescope 5a, second transmitting telescope 5b, ...) is , the configuration may be the same for any wavelength.

Although FIG. 1 shows a configuration in which the transmitting telescope 5 and the receiving telescope 11 are separated, the space object ranging device 1 according to the disclosed technology is not limited to this. The transmitting telescope 5 and the receiving telescope 11 may be configured as an integrated unit, since it is sufficient that both are directed toward the space object (31).

Since the space object ranging device 1 according to the first embodiment has the above configuration, the repetition frequency of the high-energy pulsed laser can be increased in a pseudo manner. Due to this effect, the space object ranging device 1 according to the presently disclosed technique can shorten the time required to collect enough photon detection events to perform statistical processing.

Embodiment 2.
FIG. 5 is a block diagram showing the configuration of the space object ranging device 1 according to the second embodiment. The same reference numerals as in the first embodiment are used in the second embodiment, unless otherwise specified. Further, in the second embodiment, explanations that overlap with those in the first embodiment will be omitted as appropriate.

As shown in FIG. 5, the space object ranging device 1 according to the second embodiment includes an optical switch 6 in place of the multiplexer 4 of the first embodiment. Further, the space object ranging device 1 according to the second embodiment includes a plurality of transmitting telescopes 5 (a first transmitting telescope 5a, a second transmitting telescope 5b, and a third transmitting telescope 5c). Note that although the number of transmitting telescopes 5 (first transmitting telescope 5a, second transmitting telescope 5b, and third transmitting telescope 5c) in FIG. 5 is three, the technology of the present disclosure is not limited to this.

A plurality of transmitting telescopes 5 (a first transmitting telescope 5a, a second transmitting telescope 5b, and a third transmitting telescope 5c) irradiate a plurality of transmitting lights (41a, 41b, 41c) toward a space object (31). do. The space object ranging device 1 according to the second embodiment has transmitting telescopes 5 (a first transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a second transmitting telescope 5a, a A telescope 5b and a third transmitting telescope 5c) may be configured.

A plurality of optical signals are input to the optical switch 6 from the light source section 2 (a first wavelength light source section 2a, a second wavelength light source section 2b, and a third wavelength light source section 2c). The optical switch 6 selectively switches the paths of a plurality of input optical signals and transmits them to the transmitting telescopes 5 (first transmitting telescope 5a, second transmitting telescope 5b, third transmitting telescope 5c). The space object ranging device 1 according to the second embodiment may be configured to select a route based on ranging information from the ranging information processing section 21.

As described above, the plurality of transmitting telescopes 5 (the first transmitting telescope 5a, the second transmitting telescope 5b, and the third transmitting telescope 5c) have a plurality of irradiation ranges of the plurality of transmitting lights (41a, 41b, 41c) in the initial state. The pointing direction may be set so that the fields of view are different.
As described above, the orbit information and orbit prediction information of the space object (31) can be obtained, for example, in TLE format. That is, the azimuth and elevation angle of the space object (31) at a specific time can be estimated to some extent. However, the actual orbit of the space object (31) may deviate from the estimated value due to the influence of the Earth's atmospheric friction and the like.
Setting the irradiation ranges of the plurality of transmitted lights (41a, 41b, 41c) to different fields of view has the effect that the space object (31) can be tracked even when the actual orbit deviates from the estimated orbit.

FIG. 6 is a schematic diagram showing the irradiation range of the space object ranging device 1 according to the second embodiment. The left side of FIG. 6 shows the initial irradiation range of the space object ranging device 1 according to the second embodiment. The right side of FIG. 6 shows the irradiation range changed after the position of the space object (31) has been estimated based on the reflected light (42).
In this way, the space object ranging device 1 according to the second embodiment may be configured to change the aspect of the irradiation range depending on the situation.

A space object ranging device 1 according to the present disclosure includes a wavelength tunable filter 12 and a filter controller 16. With this configuration, the space object distance measuring device 1 according to the second embodiment can detect the space object (31) through the statistical processing of events, and the space object (31) can 5b and the third transmitting telescope 5c) can be determined.

FIG. 7 is an example of a histogram of photon detection events by wavelength of the space object ranging device 1 according to the second embodiment. FIG. 7 shows an example in which a space object (31) exists within the irradiation range of the transmitted light (41a) having a wavelength of _λa . As shown in the upper part of FIG. 7, the histogram for wavelength λ _a has a peak at the center. This peak appears in the flight time (τ) of the transmitted light (41a). On the other hand, as shown in the middle and lower rows of FIG. 7, there is no peak in the histogram for wavelength λ _b and the histogram for wavelength λ _c .

When a space object (31) exists in the irradiation range of the transmitted light (41a) having a wavelength of _λa , the space object ranging device 1 according to the second embodiment transmits the optical signal of any wavelength to the first transmitting telescope. 5a. At this time, the optical switch 6 according to the second embodiment may be configured to select a route based on a route control signal from the ranging information processing section 21.

As described above, since the space object distance measuring device 1 according to the second embodiment has the above configuration, in addition to the effects shown in the first embodiment, the space object (31) whose position cannot be specified can be detected from a wide range using a telescope. This has the effect that detection can be performed without relying on fine beam scanning by the drive system 53.

Embodiment 3.
FIG. 8 is a schematic diagram showing the operation of a plurality of space object ranging devices (space object ranging device 61, space object ranging device 62) according to the third embodiment. The same reference numerals used in the third embodiment are used as in the previously described embodiments, unless otherwise specified. Further, in the third embodiment, explanations that overlap with those of the previously described embodiments will be omitted as appropriate.

As shown in FIG. 8, the third embodiment is a mode in which a plurality of units function in cooperation, and the space object range finder 61 and the space object range finder 62 function in cooperation. Each of the space object range finder 61 and the space object range finder 62 may have the same configuration as the space object range finder 1 according to either of the first and second embodiments.

As shown in FIG. 8, the third embodiment may have a configuration in which a space object range finder 61 and a space object range finder 62 are placed at separate locations, and a range finder control station 63 is provided. The space object range finder 61 and the space object range finder 62 may share observation information via the range finder control station 63. In addition, the space object range finder 61 and the space object range finder 62 share information about which wavelength has been selected (hereinafter referred to as "wavelength selection information") via the range finder control station 63. You can do it like this.

Although FIG. 8 shows a mode in which two devices function in cooperation, the disclosed technology is not limited to this number. The disclosed technique may also be configured in such a manner that two or more devices cooperate.

The technology disclosed herein may have a mode in which the roles played by different devices are different when a plurality of devices function cooperatively. For example, the space object range finder 61 may perform a search by overlooking a wide range, and the space object range finder 62 may measure a specific target with high precision. Further, it is desirable that the space object ranging device 61 and the space object ranging device 62 have characteristics according to their respective roles.

FIG. 9 is a schematic diagram illustrating wavelengths employed by a plurality of space object ranging devices (space object ranging device 61, space object ranging device 62) according to the third embodiment.
A space object ranging device 61 that searches a wide range may include a light source unit 2 that has a wide wavelength range. The wavelengths of the light source unit 2 (first wavelength light source unit 2a, second wavelength light source unit 2b, and third wavelength light source unit 2c) related to the space object ranging device 61 are λ _a′ and λ _b , respectively. _' , and λ _c' . λ _a' , λ _b' , and λ _c' may be determined such that their respective intervals are, for example, 100 [nm] or more.

λ _a' , λ _b' , and λ _c' may be determined depending on the properties of the object to be measured. Among the properties of the object to be measured, the reflection characteristics of the surface are particularly important factors. Reflection properties generally have wavelength dependence.
As described above, the surface of the geodetic satellite is provided with a mirror surface or CCR.
The surface of a general satellite is equipped with a heat insulating material such as MLI (Multi-Layer-Insulation) and a radiator such as OSR (Optical Solar Reflector). Further, the surface of a general satellite may be provided with a SAP (Solar Array Panel).
Space debris has a wide variety of base materials and various surface characteristics.

λ _a' , λ _b' , and λ _c' may be determined in consideration of loss during spatial propagation. Loss during spatial propagation has wavelength dependence, for example in the case of the atmosphere. It is known that atmospheric absorption has good transmittance in the 0.8 [μm] band, 1.0 [μm] band, and 1.5 [μm] band. It is also generally known that the shorter the wavelength, the greater the loss due to atmospheric disturbances.

A space object ranging device 62 that measures a specific target with high precision may include a light source unit 2 that can select one set from a plurality of sets consisting of narrow wavelength ranges. In the wavelength range selected by the light source unit 2 of the space object ranging device 62, the wavelengths in any set may be determined such that the interval between the wavelengths is, for example, 10 [nm] or less. The details of the wavelength range determined for the light source section 2 of the space object ranging device 62 will become clear from the explanation along with FIG. 10 below.

FIG. 10 is an example of a histogram of photon detection events by wavelength of the space object ranging device 61 according to the third embodiment. FIG. 10 shows that the reflected light (42a') of the transmitted light (41a') having the wavelength λ _a' has the highest intensity. That is, FIG. 10 shows that the wavelength suitable for distance measurement is near λ _a' . The information regarding the wavelength suitable for distance measurement is the wavelength selection information described above.

The wavelength range of the space object ranging device 62 is determined based on the wavelength selection information shared via the ranging device control station 63. The wavelength range may be determined by the space object ranging device 62 or by the ranging device control station 63. More specifically, the wavelengths of the optical signals output by the light source unit 2 of the space object ranging device 62 are determined to be a set of λ _a'a , λ _a'b , and λ _a'c . λ _a'a , λ _a'b , and λ _a'c are wavelengths near λ _a' . λ _a'a , λ _a'b , and λ _a'c may be determined such that their respective intervals are 10 [nm] or less. Note that any one of λ _a'a , λ _a'b , and λ _a'c may be equal to λ _a' .

In the space object ranging device 61 and the space object ranging device 62 according to the third embodiment, the wavelength of the optical signal output from the light source section 2 does not need to be continuously variable. The light source section 2 of the space object ranging device 61 may be realized, for example, by a set of pulsed lasers with wavelengths spaced apart over a wide band. Further, the light source unit 2 of the space object distance measuring device 62 may be realized by, for example, including a plurality of sets of pulsed lasers having wavelengths spaced apart in a narrow band.

As described above, the space object range finder 61 and the space object range finder 62 according to the third embodiment have the above configurations, and therefore, in addition to the effects shown in the first and second embodiments, a plurality of wavelengths suitable for distance measurement can be used. This has the effect of allowing you to select from a set.

The space object ranging device (1, 61, 62) according to the presently disclosed technology can be used as a device for observing space objects such as space debris and artificial satellites, and has industrial applicability.

1 Space object ranging device, 2 (2a, 2b, 2c) light source section, 3 light source section controller, 4 multiplexer, 5 (5a, 5b, 5c) transmitting telescope, 6 optical switch, 11 receiving telescope, 12 wavelength variable filter, 13 photodetector, 14 gate controller, 15 event timer, 16 filter controller, 21 ranging information processing section, 51 orbit information storage section, 52 pointing direction controller, 53 telescope drive system, 61, 62 space Object ranging device, 63 Range finding device control station.

Claims (8)

a first wavelength light source unit that outputs a light signal having a wavelength of λ _a ;
a second wavelength light source unit that outputs a light signal having a wavelength of λ _b different from λ _a ;
a filter controller that determines a transmission wavelength band while synchronizing the oscillation timings of the first wavelength light source section and the second wavelength light source section by adding an offset time T_offset to the oscillation timings _of the first wavelength light source section and the second wavelength light source section;
a wavelength tunable filter that is dynamically controlled by the filter controller and has characteristics of the transmission wavelength band;
Space object ranging device. further comprising a photodetector gated by a gate signal ;
The space object ranging device according to claim 1. the transmission wavelength band of the wavelength tunable filter is changed in synchronization with the gate signal ;
The space object ranging device according to claim 2. the gate signal is variable ;
The space object ranging device according to claim 3. an optical switch into which a light signal from the first wavelength light source section and a light signal from the second wavelength light source section are input and switch paths;
a first transmitting telescope connected to the path and to which a light signal from the first wavelength light source section is sent;
further comprising a second transmitting telescope connected to the path and to which a light signal from the second wavelength light source section is sent;
The first transmitting telescope and the second transmitting telescope have irradiation ranges in different pointing directions in an initial state ,
The space object ranging device according to claim 1. the pointing direction is variable ;
The space object ranging device according to claim 5. further comprising a photodetector gated by a gate signal ;
The space object ranging device according to claim 6. the transmission wavelength band of the wavelength tunable filter is changed in synchronization with the gate signal ;
The space object ranging device according to claim 7.

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