Patent Publication Number: US-11661218-B2

Title: Exploration method, exploration system, probe, hydrogen supply method, and image processing method

Description:
TECHNICAL FIELD 
     The present disclosure relates to an exploration method, an exploration system, a space probe, a hydrogen supply method, and an image processing method. 
     BACKGROUND ART 
     A space probe used for a moon or planet exploration activity has been known. For example, a vehicle (see JP 2010-132261 A) for space exploration which is capable of traveling on a moon surface or a planet, such as the Mars rover of United States has been known as the space probe. 
     SUMMARY OF INVENTION 
     An exploration method according to an aspect of the present disclosure includes: a step of exploring a natural resource on a satellite, a minor planet, or a planet; a step of acquiring the natural resource detected by the exploration; and a step of storing the acquired natural resource. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a flowchart showing a flow of an exploration method according to the present embodiment. 
         FIG.  2    is a diagram schematically showing an exploration system according to a first embodiment. 
         FIG.  3    is a flowchart showing an example of a flow of the exploration method according to the first embodiment. 
         FIG.  4    is a diagram schematically showing an exploration system according to a second embodiment. 
         FIG.  5    is a diagram schematically showing an exploration system according to a third embodiment. 
         FIG.  6    is a diagram schematically showing a configuration of an exploration system according to a fourth embodiment. 
         FIG.  7    is a diagram schematically showing a configuration of an exploration system according to a fifth embodiment. 
         FIG.  8    is a diagram schematically showing a configuration of an exploration system according to a sixth embodiment. 
         FIG.  9    is a flowchart showing an example of a flow of accumulation of hydrogen and oxygen. 
         FIG.  10    is a schematic diagram showing a series of fixed examples in which a lander landing on a moon surface is refilled with hydrogen and is reused. 
         FIG.  11    is a diagram schematically showing a configuration of an exploration system according to a seventh embodiment. 
         FIG.  12    is a diagram schematically showing a configuration of an exploration system according to an eighth embodiment. 
         FIG.  13    is a diagram schematically showing a configuration of an exploration system according to a ninth embodiment. 
         FIG.  14    is a schematic diagram for describing an image processing according to the ninth embodiment. 
         FIG.  15    is a flowchart showing an example of a flow of the processing according to the ninth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     However, an activity of exploring a satellite, a minor planet, or a planet so far has been limited to photographing a state of the satellite, the minor planet, or the planet, and an effective exploration activity for a natural resource has not been specified. 
     The present disclosure has been made to solve the problems described above, and an object of the present disclosure is to provide an exploration method, an exploration system, and a space probe which enable effective use of a natural resource on a satellite, a minor planet, or a planet. 
     An exploration method according to a first aspect of the present disclosure includes: a step of exploring a natural resource on a satellite, a minor planet, or a planet; a step of acquiring the natural resource detected by the exploration; and a step of storing the acquired natural resource. 
     According to the configuration, a natural resource on a satellite, a minor planet, or a planet is stored, such that it is possible to effectively use the stored natural resource later. 
     In the exploration method according to a second aspect of the present disclosure described in the exploration method according to the first aspect, the natural resource is water, and in the acquiring step, the water is acquired by collecting vapor obtained by evaporating ice included in soil or a rock. 
     According to the configuration, water can be acquired and stored, and thus it is possible to use water on the moon. 
     In the exploration method according to a third aspect of the present disclosure described in the exploration method according to the second aspect, the satellite is the moon, in the exploring step, a recess corresponding to permanent shadow of the moon is explored, and in the acquiring step, the water is acquired by collecting vapor obtained by evaporating ice through heating of soil or a rock in the recess corresponding to the permanent shadow. 
     According to the configuration, water can be acquired and stored in a recess of the moon, and thus it is possible to use water on the moon. 
     The exploration method according to a fourth aspect of the present disclosure described in the exploration method according to any one of the first to third aspects further includes a step of generating, by a solar cell disposed on a moon surface other than the permanent shadow, power, wherein in the acquiring step, the water is acquired by collecting vapor obtained by evaporating ice through heating of soil or a rock using the generated power. 
     According to the configuration, even in a case of the recess corresponding to the permanent shadow, it is possible to heat soil or a rock in the recess by using power generated by the solar cell disposed on the moon surface other than the permanent shadow. 
     In the exploration method according to a fifth aspect of the present disclosure described in the exploration method according to the first to fourth aspects, in the storing step, the acquired water is delivered to a tank through a pipe to be stored in the corresponding tank. 
     According to the configuration, water is stored in the tank, and thus it is possible to use water in outer space. 
     An exploration system according to a sixth aspect of the present disclosure includes: a detection unit which detects a natural resource on a satellite, a minor planet, or a planet; an acquisition unit which acquires the natural resource detected by the detection unit; and a storage which stores the acquired natural resource. 
     According to the configuration, water can be acquired and stored, and thus it is possible to use water on the moon. 
     In the exploration system according to a seventh aspect of the present disclosure described in the exploration system according to the sixth aspect, the natural resource is water, and the acquisition unit acquires the water by collecting vapor obtained by evaporating ice included in soil or a rock. 
     According to the configuration, it is possible to acquire water from ice included in soil or a rock. 
     In the exploration system according to an eighth aspect of the present disclosure described in the exploration system according to the sixth or seventh aspect, the natural resource is water, the storage is a tank, the exploration system further includes a pipe connected to the tank, and the water acquired by the acquisition unit is delivered to the tank through the pipe. 
     According to the configuration, water is delivered to a tank through a pipe to thereby accumulate water in the tank. 
     The exploration system according to a ninth aspect of the present disclosure described in the exploration system according to the eighth aspect includes a space probe which includes the detection unit and the acquisition unit, is connected to one end portion of the pipe, and is disposed in a recess corresponding to permanent shadow of the moon, and a spacecraft which includes the tank connected to the other end portion of the pipe and is disposed on a moon surface other than the recess. 
     According to the configuration, even in a case where the space probe cannot move from the recess to the moon surface due to a factor such as a slope of the recess, an obstacle present on the slope of the recess, or the like, water is accumulated in the tank of the spacecraft through the pipe, such that it is possible to deliver the water to the outside from the recess. 
     In the exploration method according to a tenth aspect of the present disclosure described in the exploration method according to the ninth aspect, the spacecraft includes a solar cell, and a control unit which performs a control to supply power generated by the solar cell to the space probe, and the acquisition unit included in the space probe acquires water by evaporating ice through heating of soil or a rock using the generated power. 
     According to the configuration, the solar cell disposed on the moon surface other than the permanent shadow generates power and the generated power is supplied to the space probe. For this reason, the acquisition unit in the space probe can acquire water by collecting vapor obtained by evaporating ice through heating of soil or a rock with the generated heat. 
     In the exploration system according to an eleventh aspect of the present disclosure described in the exploration system according to the ninth or tenth aspect, the spacecraft is a space probe which includes wheels and is able to travel. 
     According to the configuration, it is possible to supply the water accumulated in the tank to a desired place on the moon surface. 
     In the exploration system according to a twelfth aspect of the present disclosure described in the exploration system according to the ninth or tenth aspect, the spacecraft is a lander which includes a communication unit which is communicable with an earth station on the earth. 
     According to the configuration, water is stored in the lander on the moon, such that it is possible to effectively use the stored water later. 
     A space probe according to a thirteenth aspect of the present disclosure includes: a detection unit which detects a natural resource on a satellite, a minor planet, or a planet; and an acquisition unit which acquires the natural resource detected by the detection unit, wherein the acquired natural resource is stored in a storage. 
     According to the configuration, a natural resource on a satellite, a minor planet, or a planet is stored, such that it is possible to effectively use the stored natural resource later. 
     An exploration system according to a fourteenth aspect of the present disclosure includes: an artificial satellite which orbits a satellite, a minor planet, or a planet; and a space probe which is communicable with the artificial satellite wirelessly. 
     According to the configuration, the space probe can receive a signal from the artificial satellite. 
     In the exploration system according to a fifteenth aspect of the present disclosure described in the exploration system according to the fourteenth aspect, the number of artificial satellites is three or more, and the space probe receives positioning signals for positioning from the plurality of artificial satellites to specify a position where the corresponding space probe is present on the satellite, the minor planet, or the planet according to the plurality of received positioning signals. 
     According to the configuration, the space probe can specify a position where the corresponding space probe is present on a satellite, a minor platen, or a planet. 
     In the exploration system according to a sixteenth aspect of the present disclosure described in the exploration system according to the fourteenth or fifteenth aspect, the artificial satellite wirelessly transmits a position signal indicating a position where a natural resource is present to the space probe, and the space probe receives the position signal and moves to approach the position indicated by the received position signal. 
     According to the configuration, the space probe can move to a position where a natural resource is present. 
     In the exploration system according to a seventeenth aspect of the present disclosure described in the exploration system according to any one of the fourteenth to sixteenth aspects, the artificial satellite wirelessly transmits a route signal indicating a route to the position where a natural resource is present to the space probe, and the space probe receives the route signal and moves based on the received route signal. 
     According to the configuration, the space probe can easily move to a position where a natural resource is present. 
     An exploration system according to an eighteenth aspect of the present disclosure includes: at least one space probe; and at least one lander, wherein the respective landers, the lander and the space probe, and/or the respective space probes are connected to each other through a power cable and a communication cable. 
     According to the configuration, respective landers, a lander and a space probe, and respective space probes are connected to each other by the power cable and the communication cable, and thus an exchange of data and an exchange of power can be performed, such that it is possible to realize more flexible and efficient exploration. 
     An exploration system according to a nineteenth aspect of the present disclosure includes a reflecting plate and a space probe which includes a solar panel, wherein when the space probe is in a place shaded from sunlight, the sunlight is reflected by the reflecting plate to allow the space probe to be irradiated with the sunlight, such that power is generated by the solar panel of the space probe. 
     According to the configuration, power can be generated even in a place where the space probe is shaded from sunlight, such that it is possible to continue exploration by using the generated power. 
     In the exploration system according to a twentieth aspect of the present disclosure described in the nineteenth aspect, the reflecting plate is provided on a lander or another space probe, and the lander or the other space probe is disposed at a position where sunlight directly reaches. 
     According to the configuration, it is possible to reflect sunlight by using the reflecting plate. 
     A hydrogen supply method according to a twenty-first aspect of the present disclosure includes: a step of collecting water in a satellite, a minor planet, or a planet; a step of electrolyzing the collected water; a step of filling a tank of a space probe with hydrogen obtained by the electrolysis; and a step of supplying the hydrogen from the tank of the space probe to a target of a supply destination. 
     According to the configuration, it is possible to supply hydrogen to a target of a supply destination. 
     In the hydrogen supply method according to an twenty-second aspect of the present disclosure described in the exploration system according to the twenty-first aspect, the target is a tank of a lander, in the supplying step of the hydrogen, the hydrogen is supplied from the tank of the space probe to the tank of the lander, and the hydrogen supply method further includes a step of taking off the lander using the supplied hydrogen, and a step of supplying hydrogen to a spacecraft as a hydrogen supply target in outer space or in an orbit of the satellite, the minor planet, or the planet. 
     According to the configuration, it is possible to supply hydrogen to a spacecraft as a hydrogen supply target. 
     An exploration method according to a twenty-third aspect of the present disclosure includes: a step of supplying fuel from a lander including a tank filled with the corresponding fuel to a tank of a space probe; and a step of driving, by the space probe, a power source by using the supplied fuel. 
     According to the configuration, it is possible to utilize fuel remaining in the tank of the lander as fuel of the space probe. 
     An exploration method according to a twenty-fourth aspect of the present disclosure includes: a step of ejecting a camera from a space probe including an ejection mechanism; a step of performing, by the camera, photographing at a spot where the camera lands after being ejected; and a step of transmitting, by the camera, an image obtained by the photographing to the space probe. 
     According to the configuration, even in a place where it is difficult for the space probe to enter, it is possible to obtain an image of an area in the vicinity of the corresponding place where it is difficult for the space probe to enter by flying a camera. 
     An image processing method according to a twenty-fifth aspect of the present disclosure includes: a step of substituting, by a lander or a space probe, an image region of an obstacle included in an image photographed by a camera mounted in the space probe with an object constituted by polygons, or an object constituted by predetermined image units; and a step of transmitting an image obtained after the substitution from the lander to an earth station. 
     According to the configuration, it is possible to suppress an amount of traffic between the lander and the earth station. 
     A natural resource according to the present embodiment is a raw material which can be obtained from nature. Examples of the natural resource include water, a mineral, an organism, and the like. Hereinafter, the present embodiment will be described with reference to the accompanying drawings. 
       FIG.  1    is a flowchart showing a flow of an exploration method according to the present embodiment. 
     (Step S 101 ) First, a natural resource on a satellite, a minor planet, or a planet is explored. 
     (Step S 102 ) Next, the natural resource detected by the exploration is acquired. 
     (Step S 103 ) Next, the acquired natural resource is stored. 
     In the exploration method according to the present embodiment described above, a natural resource on a satellite, a minor planet, or a planet is stored, such that it is possible to effectively use the stored natural resource later. 
     In each of embodiments described below, a case where an exploration system is used for a moon exploration activity will be described as an example. Further, in each embodiment, water will be described as an example of the natural resource. It should be noted that the exploration system according to each embodiment can also be used for an activity of exploring a planet, a minor planet, another satellite, or the like. 
     First Embodiment 
     First, a first embodiment will be described.  FIG.  2    is a diagram schematically showing an exploration system according to a first embodiment. As indicated by an arrow A 1  in  FIG.  2   , sunlight is incident in parallel to a moon surface LS in the vicinity of the North Pole of the moon M. For this reason, an inner portion of a recess R formed in the vicinity of the North Pole of the moon M becomes permanent shadow permanently shaded from sunlight. The recess R is, for example, a crater. 
     As shown in  FIG.  2   , an exploration system S 1  includes a space probe  1 , a tank  3 , and a pipe  2  which connects the space probe  1  and the tank  3  to each other and through which water passes. The tank  3  is an example of a storage and is installed on the moon surface LS. 
     The space probe  1  is an unmanned probe and is operated according to a command from an earth station on the earth. The space probe  1  includes wheels  11  and  12  and can travel on the moon surface LS. The space probe  1  travels to enter the inside of the recess R as shown in  FIG.  2   . 
     Further, the space probe  1  includes a detection unit  13  and an acquisition unit  14 . 
     The detection unit  13  detects a natural resource on a satellite, a minor planet, or a planet. According to the present embodiment, the detection unit  13  detects water in the recess R corresponding to the permanent shadow of the moon M. For example, the detection unit  13  detects a presence or absence of hydrogen and heavy hydrogen by using a neutron spectrometer, thereby detecting a presence or absence of water. The detection unit  13  may detect a presence or absence of water by detecting conductivity, or may detect water by a mass spectrometer, chromatography, or imaging. 
     The acquisition unit  14  acquires the natural resource detected by the detection unit  13 . According to the present embodiment, the acquisition unit  14  acquires water detected by the detection unit  13 . According to the present embodiment, the acquisition unit  14  includes a heating unit  141 . The acquisition unit  14  heats soil or a rock by using the heating unit  141  as indicated by an arrow A 2  in the recess R corresponding to the permanent shadow. By doing so, ice included in the soil or the rock evaporates. Thereafter, the acquisition unit  14  acquires water by collecting vapor rising as indicated by an arrow A 3 . Here, the soil includes regolith of the moon surface LS. With this arrangement, it is possible to acquire water by collecting vapor obtained by evaporating ice included in soil (for example, regolith) or a rock. 
     According to the present embodiment, the natural resource is water, the storage is the tank  3 , and the pipe connects the acquisition unit  14  and the tank  3  to each other. With this arrangement, the water acquired by the acquisition unit  14  is delivered to the tank  3  through the pipe  2 . 
       FIG.  3    is a flowchart showing an example of a flow of the exploration method according to the first embodiment. 
     (Step S 201 ) First, the space probe  1  explores the recess R corresponding to the permanent shadow of the moon. 
     (Step S 202 ) Next, the space probe  1  determines whether or not water is detected. 
     (Step S 203 ) When the water is detected in step  202 , the space probe  1  acquires the water by collecting vapor obtained by evaporating ice included in soil or a rock through heating of the soil or the rock. 
     (Step S 204 ) Next, the acquired water is delivered to the corresponding tank  3  through the pipe  2 , such that the water is stored in the corresponding tank  3 . 
     As described above, the exploration system S 1  according to the first embodiment includes the detection unit  13  which detects water on the moon, the acquisition unit  14  which acquires the water detected by the detection unit  13 , and the tank which stores the acquired water. 
     With this arrangement, water is stored on the moon, such that it is possible to effectively use the stored water later. 
     Second Embodiment 
     Next, a second embodiment will be described. In the first embodiment, the tank  3  is installed on the moon surface LS as it is, whereas in the second embodiment, one space probe includes a tank and supplies power generated by a solar cell to the other space probe. 
       FIG.  4    is a diagram schematically showing an exploration system according to the second embodiment. The same elements as those shown in  FIG.  2    are denoted by the same reference numerals, and a description thereof will be omitted. An exploration system S 2  according to the second embodiment includes a space probe  1  and a space probe  4 . The space probe  1  is also called a slave probe. The space probe  1  according to the second embodiment is the same as the space probe  1  according to the first embodiment, and thus a description thereof will be omitted. 
     The space probe  4  is an example of a spacecraft, and is also called a master probe. The space probe  4  is an unmanned probe and is operated according to a command from an earth station on the earth. 
     The space probe  1  and the space probe  4  are bound by a rope  20  which is called a tether. The rope  20  accommodates a pipe  21  through which water passes and a wiring  22  for supplying power. That is, one end portion of the pipe  21  is connected to the space probe  1  and the other end portion of the pipe  21  is connected to a tank  43  of the space probe  4 . 
     The space probe  4  includes wheels  41  and  42  and can travel on the moon surface LS. The space probe  4  can move to a position at which the space probe  4  can be exposed to sunlight on the moon surface LS. Further, the space probe  4  includes the tank  43 , a solar cell  44 , and a control unit  45 . 
     The water supplied from the space probe  1  through the pipe  21  is stored in the tank  43 . 
     The control unit  45  is a controller which performs a control to supply power generated by the solar cell  44  to the space probe  1 . In the present embodiment, power is supplied to the space probe  1  through the wiring  22 . It should be noted that the power may be supplied in a wireless manner or in a wired manner. 
     As described above, the exploration system S 2  according to the second embodiment includes the space probe  1  including the detection unit  13  and the acquisition unit  14  and connected to one end portion of the pipe  21 , and the space probe  4  including the tank  43  connected to the other end portion of the pipe  21 . The detection unit  13  detects water on the moon M and the acquisition unit  14  acquires the water detected by the detection unit  13 . 
     With this arrangement, water is stored in the space probe  4  on the moon, such that it is possible to effectively use the stored water later. 
     In addition, the space probe  1  is disposed in a recess corresponding to permanent shadow, and the space probe  4  is disposed on the moon surface other than the permanent shadow and includes the solar cell  44  and the control unit  45  which performs a control to supply power generated by the solar cell  44  to the space probe  1 . The acquisition unit  14  included in the space probe  1  acquires water by collecting vapor obtained by evaporating ice through heating of soil or a rock with the generated heat. 
     With this arrangement, the solar cell  44  disposed on the moon surface other than the permanent shadow generates power and the generated power is supplied to the space probe  1 . As a result, the acquisition unit  14  included in the space probe  1  can acquire water by collecting vapor obtained by evaporating ice through heating of soil or a rock with the generated heat. 
     In addition, the space probe  4  according to the present embodiment includes wheels and can travel. With this arrangement, it is possible to supply the water accumulated in the tank to a desired place on the moon surface. 
     It should be noted that the space probe  4  may include a communication unit which is communicable with an earth station on the earth. 
     Third Embodiment 
     Next, a third embodiment will be described. The spacecraft disposed on the moon surface other than the permanent shadow according to the second embodiment is a space probe, whereas a spacecraft disposed on a moon surface other than the permanent shadow according to the third embodiment is a lander. The lander is a spacecraft which can land and stand still on a surface of a celestial body (for example, a satellite such as the moon, a minor planet, a planet, or the like). 
       FIG.  5    is a diagram schematically showing an exploration system according to the third embodiment. The same elements as those shown in  FIG.  2    are denoted by the same reference numerals, and a description thereof will be omitted. An exploration system S 3  according to the third embodiment includes a space probe  1  and a lander  5 . The space probe  1  according to the third embodiment is the same as the space probe  1  according to the first embodiment, and thus a description thereof will be omitted. 
     The lander  5  lands on a position at which the lander  5  can be exposed to sunlight on the moon surface LS. 
     The space probe  1  and the lander  5  are bound by a rope  20  which is called a tether, similarly to the second embodiment. The rope  20  accommodates a pipe  21  through which water passes and a wiring  22  for supplying power. That is, one end portion of the pipe  21  is connected to the space probe  1  and the other end portion of the pipe  21  is connected to a tank  51  of the lander  5 . 
     The lander  5  includes a tank  51 , a solar cell  52 , a control unit  53 , a communication unit  54 , and an antenna  55 . 
     Water supplied from the space probe  1  is stored in the tank  51 . 
     The control unit  53  is a controller which performs a control to supply power generated by the solar cell  52  to the space probe  1 . In the present embodiment, the power is supplied to the space probe  1  through the wiring  22 . 
     The communication unit  54  can communicate with an earth station on the earth through the antenna  55 . 
     As described above, the exploration system S 3  according to the third embodiment includes the space probe  1  including the detection unit  13  and the acquisition unit  14  and connected to one end portion of the pipe  21 , and the lander  5  including the tank  51  connected to the other end portion of the pipe  21 . The detection unit  13  detects water on the moon M and the acquisition unit  14  acquires the water detected by the detection unit  13 . 
     With this arrangement, water is stored in the lander  5  on the moon, such that it is possible to effectively use the stored water later. 
     Although the space probe  1  includes the detection unit  13  and the acquisition unit  14  in the respective embodiments, the present disclosure is not limited thereto, and one space probe may include the detection unit  13  and the other space probe may include the acquisition unit  14 . For example, when two space probes enter a recess R, the detection unit  13  of one space probe may detect water and the acquisition unit  14  of the other space probe may acquire the water. In addition, in each embodiment, the space probe  1  may generate power by nuclear fusion. 
     Although the heating unit  141  directly heats soil or a rock in the respective embodiments, the present disclosure is not limited thereto, and soil may be collected or a rock may be mined and then collected materials may be heated. In addition, the acquisition unit  14  may perform heating by the heating unit  141  after digging soil up to a predetermined depth. 
     Fourth Embodiment 
     Next, a fourth embodiment will be described. According to the fourth embodiment, an artificial satellite is present in an orbit of the moon, a lander and a space probe can directly and wirelessly communicate with the artificial satellite and receive a signal from the artificial satellite. Examples of the signal include a position signal indicating a position where a natural resource is present, a route signal indicating a route to the position where the natural resource is present, a positioning signal for positioning, an image signal indicating the latest image of the moon surface, and/or the like. In addition, according to the fourth embodiment, the lander and the space probe have a wireless communication function, and landers, a lander and a space probe, and space probes can wirelessly communicate with each other. Further, respective landers, a lander and a space probe, and respective space probes are bound to each other with a rope which is called a tether, and a power cable and a communication cable are accommodated inside the cable. As described above, respective landers, a lander and a space probe, and respective space probes are connected by the power cable and the communication cable. 
       FIG.  6    is a diagram schematically showing a configuration of an exploration system according to the fourth embodiment. As shown in  FIG.  6   , an exploration system S 4  includes artificial satellites ST 1 , ST 2 , ST 3 , and ST 4  disposed in the orbit of the moon, landers L 1  and L 2 , and space probes R 1 , R 2 , and R 3 . The artificial satellites ST 1 , ST 2 , and ST 3 , the landers L 1  and L 2 , and the space probes R 1 , R 2 , and R 3  can perform wireless communication, respectively, and can mutually perform peer to peer communication. The space probe R 3  is disposed in a recess (for example, a crater) of the moon. 
     The lander L 1  includes an antenna AT 1  for wireless communication and a wireless communication circuit CC 1 . Similarly, the lander L 2  includes an antenna AT 2  for wireless communication and a wireless communication circuit CC 2 . Further, the lander L 1  is bound to the lander L 2  with a rope TE 1  which is called a tether, and a power cable PC 1  and a communication cable NC 1  are accommodated inside the rope TE 1 . As described above, the landers L 1  and L 2  are connected to each other by the power cable PC 1  and the communication cable NC 1 . 
     The space probe R 1  includes an antenna AT 3  for wireless communication and a wireless communication circuit CC 3 . Similarly, the space probe R 2  includes an antenna AT 4  for wireless communication and a wireless communication circuit CC 4 . Similarly, the space probe R 3  includes an antenna AT 5  for wireless communication and a wireless communication circuit CC 5 . 
     The space probe R 1  is bound to the lander L 1  with a rope TE 2  which is called a tether, and a power cable PC 2  and a communication cable NC 2  are accommodated inside the rope TE 2 . As described above, the space probe R 1  and the lander L 1  are connected to each other by the power cable PC 2  and the communication cable NC 2 . 
     Similarly, the space probe R 1  is bound to another space probe R 2  with a rope TE 3  which is called a tether, and a power cable PC 3  and a communication cable NC 3  are accommodated inside the rope TE 3 . As described above, the space probe R 1  and the space probe R 2  are connected to each other by the power cable PC 3  and the communication cable NC 3 . 
     Similarly, the space probe R 2  is bound to another space probe R 3  with a rope TE 4  which is called a tether, and a power cable PC 4  and a communication cable NC 4  are accommodated inside the rope TE 4 . As described above, the space probe R 2  and the space probe R 3  are connected to each other by the power cable PC 4  and the communication cable NC 4 . 
     With this arrangement, respective landers, a lander and a space probe, and respective space probes are connected to each other by the power cable and the communication cable, and thus an exchange of data and an exchange of power can be performed, such that it is possible to realize more flexible and efficient exploration. In addition, even in a case where the wireless communication circuit or the antenna fails, it is possible to continue the exchange of data through the communication cable. 
     The artificial satellites ST 1  to ST 4  may also function as global positioning system (GPS) satellites. In this case, the space probes R 1  to R 3  may receive positioning signals for positioning from a plurality of artificial satellites ST 1  to ST 4 , to specify positions where the corresponding space probes R 1  to R 3  are present on the moon according to the plurality of received positioning signals. 
     Here, the positioning signal from the artificial satellite ST 1  includes, for example, transmission time data from an atomic clock mounted in the corresponding artificial satellite ST 1 , information of ephemerides (orbit) of the corresponding artificial satellite ST 1 , and the like. The same goes for the positioning signals from the artificial satellites ST 2  to ST 4 . The space probes R 1  to R 3  receive electric waves from the artificial satellites ST 1  to ST 4 , acquire a transmission time of each of the electric waves, and determine a distance from each corresponding artificial satellite by multiplying a difference between a corresponding transmission time and a reception time by a propagation speed (300,000 km/second, which is the same as the speed of light) of the electric wave. 
     Here, the space probes R 1  to R 3  each include a GPS receiver and a clock. The space probes R 1  to R 3  receive electric waves from four artificial satellites ST 1  to ST 4  and calculate a reception time of each of the electric waves and coordinates (points in a three-dimensional space) of the space probes R 1  to R 3  by positioning calculation. An existing GPS positioning method may be used for the positioning calculation. With this arrangement, it is possible to specify the positions of the space probes R 1  to R 3 . 
     For example, the artificial satellites ST 1  to ST 4  may wirelessly transmit a position signal indicating a position where a natural resource is present to the space probe R 1 , R 2 , or R 3 . In this case, the space probe R 1 , R 2 , or R 3  may receive the position signal and move to approach the position indicated by the received position signal. With this arrangement, the space probe R 1 , R 2 , or R 3  can move to the position where the natural resource is present. 
     In addition, for example, the artificial satellites ST 1  to ST 4  may wirelessly transmit a route signal indicating a route to a position where a natural resource (for example, water) is present to the space probe R 1 , R 2 , or R 3 . In this case, the space probe R 1 , R 2 , or R 3  receives the route signal and moves based on the received route signal. In detail, for example, the space probe R 1 , R 2 , or R 3  may move along a route indicated by the route signal. With this arrangement, the space probe R 1 , R 2 , or R 3  can easily move to the position where the natural resource is present. 
     As described above, the exploration system. S 4  according to the fourth embodiment includes the artificial satellites ST 1  to ST 4  orbiting the moon and the space probes R 1  to R 3  which can wirelessly communicate with the artificial satellites ST 1  to ST 4 . With this arrangement, the space probes R 1  to R 3  can receive a signal from the artificial satellites ST 1  to ST 4 . 
     In addition, the exploration system S 4  according to the fourth embodiment includes the space probes R 1  to R 3  and the landers L 1  and L 2 . The landers L 1  and L 2 , the lander L 1  and the space probe R 1 , and the space probes R 1  and R 2 , and the space probes R 2  and R 3  are connected to each other through the power cable and the communication cable. With this arrangement, respective landers, a lander and a space probe, and respective space probes are connected to each other by the power cable and the communication cable, and thus an exchange of data and an exchange of power can be performed, such that it is possible to realize more flexible and efficient exploration. 
     Alternatively, only a lander and a space probe, or only space probes may be connected to each other through the power cable and the communication cable. Further, the number of space probes is three, but the present disclosure is not limited thereto, and it is sufficient that at least one space probe is present. In addition, the number of landers is two, but the present disclosure is not limited thereto, and it is sufficient that at least one lander is present. 
     In the present embodiment, the case where there are four artificial satellites for positioning is described by way of example, but the present disclosure is not limited thereto, and three or four or more artificial satellites may be provided for positioning. Further, in a case where the positioning is not performed, the number of artificial satellites may be one or two. 
     Although the artificial satellite has been described as orbiting the moon, in a case where an exploration target is another satellite, a minor planet, or a planet, the artificial satellite may be a satellite orbiting the other satellite, the minor planet, or the planet. In addition, although the number of space probes has been described as being three, the number of space probes may two or less, or four or more. 
     Fifth Embodiment 
     Next, a fifth embodiment will be described. In an exploration system. S 5  according to the fifth embodiment of the present disclosure, when a space probe including a solar panel is in a place shaded from sunlight, the sunlight is reflected by a reflecting plate to allow the space probe to be irradiated with the sunlight, such that power is generated by the solar panel of the space probe. 
       FIG.  7    is a diagram schematically showing a configuration of the exploration system according to the fifth embodiment. As shown in  FIG.  7   , the exploration system. S 5  includes a lander L 11  on which a reflecting plate RL 1  is provided, a space probe R 11  on which a reflecting plate RL 2  is provided, and a space probe R 12  having an outer surface on which a solar plate (not shown) is provided. As shown in  FIG.  7   , the space probe R 12  explores a pit of the moon and is positioned in a shadow area SA. The space probe R 12  is in a place shaded from sunlight. 
     Here, as indicated by a light path SL 1 , the sunlight is reflected by the reflecting plate RL 1 , the space probe R 12  is irradiated with the sunlight. In addition, as indicated by a light path SL 2 , the sunlight is reflected by the reflecting plate RL 2 , the space probe R 12  is irradiated with the sunlight. With this arrangement, power is generated by the solar panel of the space probe R 12 , and the space probe R 12  is driven by using the generated power. For example, the space probe R 12  drives a power source (not shown, for example, a motor, an engine, or the like) using the generated power. With this arrangement, power can be generated even in a place where the space probe R 12  is shaded from sunlight, such that it is possible to continue exploration by using the generated power. 
     As described above, the exploration system S 5  according to the fifth embodiment includes the reflecting plates RL 1  and RL 2  and the space probe R 12  including the solar panel. When the space probe R 12  is in a place shaded from sunlight, the sunlight is reflected by the reflecting plates to allow the space probe R 12  to be irradiated with the sunlight, such that power is generated by the solar panel of the space probe R 12 . According to the configuration, power can be generated even in a place where the space probe R 12  is shaded from sunlight, such that it is possible to continue exploration by using the generated power. 
     In addition, the reflecting plates RL 1  and RL 2  are provided on the lander L 11  or another space probe R 11 , and the lander L 11  or the other space probe R 11  is disposed at a position where sunlight directly reaches. According to the configuration, it is possible to reflect sunlight by using the reflecting plate. 
     The number of reflecting plates has been described as being two, but the present disclosure is not limited thereto, and the number of reflecting plates may be one, or three or more. 
     Sixth Embodiment 
     Next, a sixth embodiment will be described. In the sixth embodiment, an empty tank of a lander is filled with fuel on the moon surface, and the lander is lifted-off from the moon surface by using the fuel used to fill the lander. Then, the fuel is supplied to a spacecraft (for example, an artificial satellite) as a hydrogen supply target. Here, the spacecraft as the hydrogen supply target is positioned in an orbit of the moon, an orbit of the earth, or in outer space. 
     In the present embodiment, a case where the fuel is hydrogen, water is collected on the moon, the collected water is electrolyzed, a tank of a space probe is filled with hydrogen obtained by the electrolysis, and the hydrogen is supplied from the tank of the space probe to a tank of a lander will be described by way of example. Thereafter, for example, the lander takes off from the moon surface by using the supplied hydrogen and supplies hydrogen to, for example, an artificial satellite positioned in an orbit of the moon. 
       FIG.  8    is a diagram schematically showing a configuration of the exploration system according to the sixth embodiment. As shown in  FIG.  8   , an exploration system S 6  includes a space probe  1   b  disposed in a recess R formed in the moon surface, a refinement unit  61  connected to the space probe  1   b  through a pipe P 1 , and a water tank  62  connected to the refinement unit  61  through a pipe P 2 . The recess R is, for example, a crater. The exploration system S 6  further includes an electrolysis unit  63  connected to the water tank  62  through a pipe P 3 , a hydrogen tank  64  connected to the electrolysis unit  63  through a pipe P 4 , and an oxygen tank  65  connected to the electrolysis unit  63  through a pipe P 5 . 
     The exploration system. S 6  further includes a lander L 21  including tanks T 1  to T 3  and a thruster TH, a space probe R 21  including tanks T 4  and T 5 , and an artificial satellite ST 5  positioned in an orbit of the moon. 
     The space probe  1   b  further includes a robot arm  15  in comparison to the space probe  1  according to the first embodiment, and includes a heater  16  and a tank  17 , instead of the acquisition unit  14 . The space probe  1   b  can dig up soil by using the robot arm  15 . 
     Hereinafter, a flow of accumulation of hydrogen and oxygen will be described with reference to  FIG.  9   .  FIG.  9    is a flowchart showing an example of a flow of accumulation of hydrogen and oxygen. In the following description, the space probe  1   b  is described as being positioned in a recess formed in the vicinity of the North Pole of the moon. 
     (Step S 301 ) First, the space probe  1   b  digs soil with the robot arm  15 . 
     (Step S 302 ) Next, after digging the soil with the robot arm  15 , the space probe  1   b , for example, moves the dug soil, soil (for example, regolith) under the dug soil, a rock, or a block of ice into the tank  17  provided inside the space probe  1   b  by using the robot arm  15 , and heats the soil, the rock, or the block of ice moved into the tank  17  by using the heater  16 . With this arrangement, it is possible to acquire water by collecting or liquefying vapor obtained by evaporating ice in soil or a rock, or a block of ice. It should be noted that the method for acquiring water is not limited thereto and another method such as a method according to another embodiment can be used. 
     (Step S 303 ) Next, the refinement unit  61  refines water supplied from the tank  17  through the pipe P 1 . Then, the refined water is supplied to the water tank  62  through the pipe P 2 , and is accumulated in the water tank  62 . 
     (Step S 304 ) Next, the electrolysis unit  63  electrolyzes water supplied from the water tank  62  through the pipe P 3 . Hydrogen and oxygen are generated after the electrolysis. 
     (Step S 305 ) The hydrogen is supplied to the hydrogen tank  64  through the pipe P 4 , and is accumulated in the hydrogen tank  64 . Meanwhile, the oxygen is supplied to the oxygen tank  65  through the pipe P 5 , and is accumulated in the oxygen tank  65 . 
     Next, a process of refilling a lander landing on the moon surface with hydrogen and reusing the lander will be described with reference to  FIG.  10   .  FIG.  10    is a schematic diagram showing a series of fixed examples in which a lander landing on the moon surface is filled with hydrogen and is reused. 
     First, as indicated by an arrow. All, a lander L 21  lands on the moon surface. Here, tanks T 1  to T 3  are empty. 
     Next, as indicated by an arrow A 12 , hydrogen is supplied from the hydrogen tank  64  to the tanks T 4  and T 5  of the space probe R 21 . Then, the space probe R 21  moves close to the lander L 21 . 
     Next, as indicated by an arrow A 13 , hydrogen is supplied from the tanks T 4  and T 5  of the space probe R 21  to the tanks T 1  to T 3  of the lander L 21 . 
     Next, as indicated by an arrow A 14 , the lander L 21  takes off from the moon surface by burning hydrogen supplied to the tanks T 1  to T 3  as fuel. 
     Next, as indicated by an arrow A 15 , the lander L 21  detaches an empty tank (not shown) from the artificial satellite ST 5  in the orbit of the moon, and then connects the tank T 3  filled with hydrogen to the artificial satellite ST 5 . With this arrangement, it is possible to supply hydrogen to the artificial satellite ST 5 . 
     As described above, a hydrogen supply method according to the sixth embodiment of the present disclosure includes collecting water on the moon, electrolyzing the collected water; filling the tanks T 4  and T 5  of the space probe R 21  with hydrogen obtained by the electrolysis, and supplying the hydrogen from the tanks T 4  and T 5  of the space probe R 21  to a target (here, for example, the tanks T 1  to T 3  of the lander L 21 ) of a supply destination. According to the configuration, it is possible to supply hydrogen to a target of a supply destination. It should be noted that the target may also be another space probe, a hydrogen storage tank, or the like, other than the tanks T 1  to T 3  of the lander L 21 . 
     The hydrogen supply method according to the sixth embodiment further includes taking off the lander using the supplied hydrogen, and supplying hydrogen to a spacecraft (here, for example, an artificial satellite) as a hydrogen supply target in outer space or in an orbit of a satellite, a minor planet, or a planet (here, for example, the orbit of the moon). According to the configuration, it is possible to supply hydrogen to a spacecraft as a hydrogen supply target. 
     It should be noted that the spacecraft is not limited only to the artificial satellite, but may be a spaceship, a space station, an artificial planet, a space probe, or the like. 
     Seventh Embodiment 
     Next, a seventh embodiment will be described. An exploration system according to the seventh embodiment uses fuel remaining in a tank of a lander landing on the moon surface as fuel of a space probe. 
       FIG.  11    is a diagram schematically showing a configuration of the exploration system according to the seventh embodiment. As shown in  FIG.  11   , an exploration system S 7  includes a lander L 31  including tanks T 31 , T 32 , and T 33 , and a space probe R 31  including a tank T 4  and a power source E. Examples of the power source E include a small thruster. In the present embodiment, it is assumed that fuel remains in the tanks T 31 , T 32 , and T 33  of the lander L 31  landing on the moon surface. Under the assumption described above, the fuel is supplied from the tank T 33  of the lander L 31  to the tank T 34  of the space probe R 31  through a pipe P 31 . 
     Next, the space probe R 31  drives the power source E by using the supplied fuel. With this arrangement, the space probe R 31  can move on the moon surface as indicated by an arrow. A 21 . 
     As described above, an exploration method according to the seventh embodiment of the present disclosure includes supplying fuel from the lander L 31  having a tank filled with the corresponding fuel to the tank of the space probe, and driving, by the space probe R 31 , the power source E by using the supplied fuel. With this arrangement, it is possible to utilize fuel remaining in the tanks T 31  to T 33  of the lander L 31  as fuel of the space probe R 31 . 
     Eighth Embodiment 
     Next, an eighth embodiment will be described. In the eighth embodiment, a camera is ejected to a place where it is difficult for a space probe to enter (here, for example, a pit), the camera performs photographing at a spot where the camera lands after being ejected, and the camera transmits an image obtained by the photographing to the space probe. 
       FIG.  12    is a diagram schematically showing a configuration of the exploration system according to the eighth embodiment. As shown in  FIG.  12   , an exploration system S 8  includes a space probe R 41  disposed on the moon surface. The space probe R 41  includes a space probe main body B 41 , a wiring WR, a camera CR connected to the space probe main body B 41  through the wiring WR, and an ejection mechanism IJ ejecting the camera CR.  FIG.  12    shows a state in which the camera CR is ejected by the ejection mechanism IJ and lands after being ejected. In this state, the camera CR performs photographing and transmits an image by the photographing to the space probe R 41  through the wiring WR. 
     As described above, an exploration method according to the eighth embodiment of the present disclosure includes ejecting the camera CR from the space probe R 41  including the ejection mechanism IJ, performing, by the camera CR, photographing at a spot where the camera CR lands after being ejected, and transmitting, by the camera CR, an image obtained by the photographing to the space probe R 41  through the wiring WR. With this arrangement, even in a place where it is difficult for the space probe to enter, it is possible to obtain an image of an area in the vicinity of the corresponding place where it is difficult for the space probe to enter by flying the camera CR. 
     It should be noted that the space probe R 41  may further include a winding mechanism for winding the wiring WR. The winding mechanism may wind the wiring WR to ejectably store the camera CR in the ejection mechanism IJ. With this arrangement, the camera can be repeatedly ejected and the photographing can be performed at different places. 
     In addition, the camera CR and the space probe main body B 41  may have a wireless communication function, and in this case, an image may be wirelessly transmitted from the camera CR to the space probe main body B 41 . 
     Ninth Embodiment 
     Next, a ninth embodiment will be described. In an image conversion method according to the ninth embodiment of the present disclosure, a lander substitutes an image region of an obstacle included in an image photographed by a camera mounted in a space probe with an object constituted by polygons, or an object constituted by predetermined image units, and an image obtained after the substitution is transmitted from the lander to an earth station. 
       FIG.  13    is a diagram schematically showing a configuration of the exploration system according to the ninth embodiment. As shown in  FIG.  13   , an exploration system S 9  according to the ninth embodiment includes a space probe R 51  including a camera CR 2  and an antenna AT 6  and disposed on the moon surface, and a lander L 51  including a processor PS and an antenna AT 7  and landing on the moon surface. The exploration system S 9  further includes an earth station ES including an antenna AT 8  and disposed on the earth, and a terminal device TM connected to the earth station through a communication network NW. 
     Next, an image processing according to the ninth embodiment will be described with reference to  FIG.  14   .  FIG.  14    is a schematic diagram for describing the image processing according to the ninth embodiment. In  FIG.  14   , an image G 1  is a schematic diagram of an image photographed by the camera CR 2 , in which image regions R 91 , R 92 , and R 93  of obstacles are shown. An image G 2  is a schematic diagram of an image in which the image regions R 91 , R 92 , and R 93  of the obstacles included in the image G 1  are substituted by objects OJ 1 , OJ 2 , and OJ 3  constituted by polygons. 
     The processor PS of the lander L 51  extracts the image regions R 91 , R 92 , and R 93  of the obstacles, generates the objects OJ 1 , OJ 2 , and OJ 3  having sizes corresponding to those of the image regions R 91 , R 92 , and R 93 , respectively, by using polygons, and substitutes the image regions R 91 , R 92 , and R 93  of the obstacles with the generated objects OJ 1 , OJ 2 , and OJ 3 . 
     The objects OJ 1 , OJ 2 , and OJ 3  are not limited to being constituted by polygons, and may also be constituted by predetermined image units. For example, the processor PS of the lander L 51  may generate corresponding objects having sizes corresponding to those of the image regions of the obstacles by using corresponding image units. 
     Next, a flow of the processing according to the ninth embodiment will be described with reference to  FIG.  15   .  FIG.  15    is a flowchart showing an example of the flow of the processing according to the ninth embodiment. 
     (Step S 401 ) First, the space probe R 51  uses the camera CR 2  to perform photographing to acquire an image. 
     (Step S 402 ) Next, the processor PS of the lander L 51  substitutes an obstacle in the image acquired in step S 401  with an object constituted by polygons. 
     (Step S 403 ) Next, the lander L 51  transmits an image obtained after the substitution to the earth station ES. With this arrangement, the earth station ES receives the image obtained after the substitution. 
     (Step S 404 ) Next, the terminal device TM on the earth acquires and displays the image obtained after the substitution from the earth station ES through the communication network NW. With this arrangement, the image obtained after the substitution is displayed on the terminal device TM, and a user confirms the image to determine an exploration operation of a space probe. 
     (Step S 405 ) Next, the terminal device TM on the earth receives an exploration operation command from the user and transmits the exploration operation command to the earth station ES. With this arrangement, the earth station ES receives the exploration operation command from the terminal device TM. 
     (Step S 406 ) Next, the earth station ES transmits the exploration operation command to the lander L 51 . 
     (Step S 407 ) Next, the lander L 51  transmits the exploration operation command to the space probe R 51 . With this arrangement, the space probe R 51  receives the exploration operation command. 
     (Step S 408 ) Next, the space probe R 51  performs an operation according to the exploration operation command. 
     As described above, the image processing method according to the ninth embodiment includes substituting, by the lander L 51 , an image region of an obstacle included in an image photographed by the camera CR 2  mounted in the space probe R 51  with an object generated so as to have a size corresponding to a size of the corresponding image region and constituted by polygons, or an object constituted by predetermined reference images, and transmitting an image obtained after the substitution from the lander L 51  to the earth station ES. According to the configuration, it is possible to suppress an amount of traffic between the lander L 51  and the earth station ES. 
     It should be noted that a processor of a space probe, instead of a processor PS of a lander, may perform the image processing described above. 
     As described above, the present disclosure is not limited to the above embodiments as they are, and in the implementation stage, the components can be modified and specified without departing from the gist of the present disclosure. In addition, various inventions can be made by appropriate combinations of a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. In addition, components in different embodiments may be combined as appropriate. 
     REFERENCE SIGNS LIST 
     
         
           1  Space probe 
           11 ,  12  Wheel 
           13  Detection unit 
           14  Acquisition unit 
           141  Heating unit 
           2 ,  21  Pipe 
           20  Rope 
           22  Wiring 
           3  Tank 
           4  Space probe 
           41 ,  42  Wheel 
           43 ,  51  Tank 
           44 ,  52  Solar cell 
           45 ,  53  Control unit 
           5  Lander 
           54  Communication unit 
           55  Antenna 
           61  Refinement unit 
           62  Water tank 
           63  Electrolysis unit 
           64  Hydrogen tank 
           65  Oxygen tank 
         S 1  to S 9  Exploration system 
         AT 1  to AT 8  Antenna 
         B 41  Space probe main body 
         CC 1  to CC 5  Wireless communication circuit 
         CR, CR 2  Camera 
         E Power source 
         ES Earth station 
         IJ Ejection mechanism 
         L 1 , L 2 , L 11 , L 21 , L 23 , L 51  Lander 
         NC 1  to NC 4  Communication cable 
         P 1  to P 5  Pipe 
         PC 1  to PC 4  Power cable 
         R 1 , R 2 , R 3 , R 11 , R 21 , R 31 , R 41 , R 51 , R 91  Space probe 
         RL 1 , RL 2  Reflecting plate 
         ST 1  to ST 5  Artificial satellite 
         T 1  to T 3 , T 31  to T 33 , T 34  Tank 
         TE 1  to TE 4  Rope 
         TH Thruster 
         TM Terminal device 
         WR Wiring