Patent Description:
Conventionally, in a spacecraft such as an artificial satellite, a radio wave is emitted to the outside and used for communication with a ground station and data observation. Patent Document <NUM> describes a satellite including a microwave transmission device mounted on a satellite comprising an antenna horn to which a generated microwave signal is input and an antenna that emits the signal to the ground. In such a satellite, in order to realize a high output power, a high output power amplifier for amplifying the microwave signal generated before being input to the antenna horn has been used.

<CIT> discloses systems and methods that provide high efficiency synthetic aperture radar satellite designs that achieve high power efficiency and high antenna aperture size to satellite mass ratios. In various embodiments, a high efficiency synthetic aperture radar satellite includes a satellite bus and a parabolic reflector antenna coupled to the satellite bus. The satellite system may further include a traveling wave tube amplifier configured to drive the parabolic reflector antenna, and a body-mounted steering system configured to mechanically steer the satellite system to direct the parabolic reflector antenna. The satellite system may further include a processor configured to combine the pulse reflections and generate image data representing the region of interest, in which the image data is effectively obtained with a synthetic aperture greater than the actual antenna aperture.

<CIT> discloses an antenna apparatus and spacecraft capable of deploying in a compactly stored state. There is provided a spacecraft, including: a main-reflection unit configured to reflect and emit a radio wave outside; a sub-reflection unit configured to face the main-reflection unit; a radiator arranged to face the sub-reflection unit and configured to radiate the radio wave in a direction of the sub-reflection unit; a main body configured to be able to accommodate at least one part of the sub-reflection unit therein; and a delivery device connected to the sub-reflection unit and configured to deliver the sub-reflection unit, at least one part of which is accommodated in the main body, to a position where the sub-reflection unit is able to reflect the radio wave radiated from the radiator to the main-reflection unit and cause the main-reflection unit to radiate the radio wave outside.

<CIT> discloses a method for implementing a satellite fleet that includes launching a group of satellites within a launch vehicle. In an embodiment, the satellites are structurally connected together through satellite outer load paths. After separation from the launch vehicle, nodal separation between the satellites is established by allowing one or more of the satellites to drift at one or more orbits having apogee altitudes below an operational orbit apogee altitude. A satellite is maintained in an ecliptic normal attitude during its operational life, in an embodiment. The satellite's orbit is efficiently maintained by a combination of axial, radial, and canted thrusters, in an embodiment. Satellite embodiments include a payload subsystem, a bus subsystem, an outer load path support structure, antenna assembly orientation mechanisms, an attitude control subsystem adapted to maintain the satellite in the ecliptic normal attitude, and an orbit maintenance/propulsion subsystem adapted to maintain the satellite's orbit.

<CIT> discloses a satellite transmission device with a moving sub- and main reflector, in which the telecommunications electronic equipment and the exciters for the information signals are connected fixedly to the satellite central body rather than being located on a moving antenna platform.

Taking account of the above-described technology, the present disclosure provides a spacecraft in which an amplifier is more effectively disposed according to various embodiments.

Embodiments of the invention are set out in the dependent claims.

According to the various embodiments of the present disclosure, it is possible to provide a spacecraft in which an amplifier is more effectively disposed.

Additionally, the effects described above are merely examples for convenience of description, and are not limited. In addition to or instead of the effects described above, any effect described in the present disclosure or an effect obvious to those skilled in the art can be exhibited.

Various embodiments of the present disclosure will be described with reference to the accompanying drawings. Additionally, common elements in the drawings are denoted by a same reference sign.

<FIG> is a view illustrating an outline of a configuration of a spacecraft <NUM> according to a first embodiment of the present disclosure. According to <FIG>, the spacecraft <NUM> comprises a main body <NUM> in which a device such as a control unit controlling navigation of the spacecraft <NUM> itself and controlling operation and an orientation of the spacecraft <NUM> or the like in space is mounted, a power supply unit <NUM> supplying electric power for driving various constituent elements including the control unit and a communication unit <NUM> in space, and the communication unit <NUM> for emitting a radio wave from the spacecraft <NUM> into space in which the ground or other spacecraft exist and for receiving a radio wave from space.

In the present embodiment, as an example, the spacecraft <NUM> can be used as a small synthetic aperture radar (SAR) satellite for mounting a SAR. Such a small SAR satellite can be used for performing observation, analysis, and the like of an observation target by emitting a radio wave in a microwave band, a millimeter wave band, or sub-millimeter wave band to the observation target and then receiving the radio wave reflected from the observation target. Here, in the SAR radar that receives the radio wave reflected from the observation target, an electric power amplifier needs to be mounted since high output electric power is required. Since the amplifier generates the high output power, the amplifier is very significant heat generating source. Therefore, particularly in a case where the spacecraft <NUM> is used as the small SAR satellite, it is very important how efficiently heat from the amplifier is dissipated. On the other hand, in the small SAR satellite, since electronic components including the amplifier need to be disposed in a limited accommodation space, it is more important to efficiently dispose the electronic components in consideration of a heat dissipation effect.

A case where the spacecraft <NUM> illustrated in <FIG> is used as the small SAR satellite will be described below. However, the present embodiment is not limited to the case of being used as the small SAR satellite, and can be applied to other applications, other forms (large satellite), and the like.

The main body <NUM> includes an accommodation space (not illustrated) for accommodating various electronic devices and mechanical components in the main body <NUM>. As an example, the main body <NUM> is formed by an octahedron having a hexagonal shape in a top view, and is formed in a hollow shape in order to form the accommodation space in the main body <NUM>. However, the shape of the main body <NUM> may be only required to be any shape capable of forming the accommodation space in the main body <NUM> and may be any other shape of a polyhedron or a sphere. Additionally, a case where the main body <NUM> is formed in an octahedral shape having a hexagonal shape in a top view will be described below.

Various electronic components such as a computer <NUM>, a sensor <NUM>, an actuator <NUM>, a power supply control circuit <NUM>, a battery <NUM>, and a communication control circuit <NUM>, and wirings for electrically connecting them are accommodated in the accommodation space formed in the main body <NUM>.

The power supply unit <NUM> includes a solar panel <NUM> in the present embodiment. As an example, the solar panel <NUM> is disposed on a wall surface of the main body <NUM> so as to cover an outer surface of the main body <NUM>. With such an arrangement, it is possible to effectively utilize the wall surface of the main body <NUM>.

In addition to a transmitter <NUM>, the communication unit <NUM> includes a radiator <NUM>, a subreflector (sub reflection mirror) <NUM> that is disposed to face the radiator <NUM> at a predetermined angle and reflects a radio wave emitted from the radiator <NUM> to a main reflector <NUM>, the main reflector <NUM> that is a main reflection mirror, disposed to face a mirror surface of the subreflector <NUM> and further reflects the radio wave reflected by the subreflector <NUM> to emit the radio wave to the outside, and a support rod <NUM> that supports the subreflector <NUM>.

The main reflector <NUM> includes a hub <NUM>, a plurality of ribs <NUM>, a planar body <NUM>, and the like. A reflection surface of the main reflector <NUM> is formed in a parabolic shape in order to function as the main reflection mirror as described above.

The hub <NUM> is disposed on an antenna axis X (also referred to as a central axis X of the hub <NUM>) at a center of the main reflector <NUM> and on a side on which the subreflector <NUM> of the main body <NUM> is disposed. As an example, the hub <NUM> is formed in a substantially columnar shape and formed of a dielectric such as plastic or a metal such as titanium or stainless. The hub <NUM> has a central axis X as a center, and a plurality of the ribs <NUM> are radially arranged at predetermined intervals on an outer circumferential surface of the hub <NUM>. That is, a cross sectional shape of the hub <NUM> (cross sectional shape when viewed from a direction along the central axis X) is circular, but the shape may be formed in either an elliptical shape or a polygonal shape.

The rib <NUM> includes a plurality of ribs. Each of the ribs <NUM> is radially arranged on an outer circumference of the hub <NUM> at predetermined intervals around the hub <NUM>. An upper surface of each of the ribs <NUM> on a side serving as a reflection mirror surface is formed in a parabolic shape. The planar body <NUM> is provided on the upper surface formed in the parabolic shape. As an example, the rib <NUM> is a spring member formed of stainless spring steel or a composite material such as glass fiber reinforced plastics (GFRP) or carbon fiber reinforced plastics (CFRP), and has elasticity.

Additionally, in the present embodiment, the rib <NUM> includes a total of <NUM> ribs. However, the number of the ribs <NUM> can be changed, regardless of an even number or an odd number, according to an area of the deployable antenna at the time of deployment, a material and strength of the ribs to be used, and the like. Furthermore, in the present embodiment, the ribs <NUM> are disposed at predetermined intervals. However, all of the ribs <NUM> may be disposed at constant intervals, and may be disposed at partially dense intervals, or may be disposed at irregular intervals.

The planar body <NUM> forming the main reflector <NUM> together with the ribs <NUM> is provided between a pair of the ribs <NUM> adjacent to each other. The planar body <NUM> is formed of a material capable of reflecting the radio wave and has a parabolic shape as a whole. As an example, the planar body <NUM> is formed by a metal network (metal mesh) formed of molybdenum, gold, or a combination thereof. In the present embodiment, in the planar body <NUM>, substantially triangular metal meshes are prepared according to the number of the ribs <NUM>, and the metal meshes are coupled to be provided on upper surfaces of the ribs <NUM> formed in the parabolic shape.

The subreflector <NUM> is disposed to face the main reflector <NUM>, and a lower surface side of the subreflector <NUM> (side corresponding to the main reflector <NUM>) is supported by the support rod <NUM>. The subreflector <NUM> is disposed to be spaced from the radiator <NUM> disposed on a line of the central axis X by a predetermined distance with the support rod <NUM>. Similarly to the planar body <NUM> of the main reflector <NUM>, the subreflector <NUM> is made of a material capable of reflecting the radio wave and has a quadratic surface shape as a whole toward the surface of the main reflector <NUM>. The subreflector <NUM> reflects the radio wave radiated from the radiator <NUM> toward the main reflector <NUM>. Therefore, the subreflector <NUM> is disposed to be spaced from the radiator <NUM> and the main reflector <NUM> by a predetermined distance.

The support rod <NUM> is disposed in order to dispose the subreflector <NUM> to be spaced from the radiator <NUM> and the main reflector <NUM> by a predetermined distance. The support rod <NUM> includes a first support rod <NUM> having one end connected to the subreflector <NUM> and the other end connected to a joint <NUM>, and a second support rod <NUM> having one end connected to the joint <NUM> and the other end connected to the main body. The subreflector <NUM> connected to one end of the first support rod <NUM> is supported by the first support rod <NUM> and the second support rod <NUM>. The support rod <NUM> includes one or more rods to support the subreflector <NUM>. In the example of <FIG>, three pairs of the support rods <NUM> (one is covered on the back surface and is not illustrated) are arranged at equal intervals. In the example of <FIG>, it has been described that the first support rod <NUM> and the second support rod <NUM> form a pair. However, the present disclosure is not limited to this, and the number of the second support rods <NUM> may be reduced or increased with respect to the first support rod <NUM>.

In the present embodiment, as the spacecraft <NUM>, a small SAR satellite having a Cassegrain antenna of which the main reflector <NUM> is formed in a parabolic shape will be described. However, the present disclosure is not limited to this, and other parabolic antennas such as a Gregorian antenna or a planar antenna may be provided.

<FIG> is a block diagram illustrating a configuration of the spacecraft <NUM> according to the first embodiment of the present disclosure. The spacecraft <NUM> does not need to comprise all of the constituent elements illustrated in <FIG>, and can have a configuration in which a part of the spacecraft <NUM> is omitted, or other constituent elements can be added. For example, the spacecraft <NUM> can also be provided with a plurality of the power supply units <NUM> and/or a plurality of the communication units <NUM>.

According to <FIG>, the spacecraft <NUM> comprises a control unit including a memory <NUM>, a processor <NUM>, and a sensor <NUM>, the power supply unit <NUM> including a power supply control circuit <NUM>, the battery <NUM>, and the solar panel <NUM>, and the communication unit <NUM> including the communication control circuit <NUM>, the transmitter <NUM>, a receiver <NUM>, the radiator <NUM>, and a reflection unit <NUM>. These constituent elements are electrically connected to each other via a control line and a data line.

The memory <NUM> includes a RAM, a ROM, a nonvolatile memory, an HDD, and the like, and functions as a storage unit. The memory <NUM> stores, as a program, instruction commands for controlling the spacecraft <NUM> according to the present embodiment in various manners. As an example, the memory <NUM> appropriately stores an image of an outside of the spacecraft <NUM>, which is captured by a camera (not illustrated), an observation value obtained by using the communication unit <NUM> as a radar, information received from the ground station via the communication unit <NUM> or information transmitted to the ground station via the communication unit <NUM>, detection information obtained by the sensor <NUM> necessary for controlling the orientation and travel of the spacecraft <NUM>, and the like.

The processor <NUM> functions as the control unit that controls the spacecraft <NUM> based on the program stored in the memory <NUM>. Specifically, the power supply unit <NUM>, the communication unit <NUM>, the sensor <NUM>, and the like are controlled based on the program stored in the memory <NUM>. As an example, generation of information for performing transmission to the ground station or other spacecraft via the communication unit <NUM>, and control related to the observation performed by emitting the radio wave to an observation target to receive the radio wave reflected from the observation target by using the communication unit <NUM> as a radar are performed.

As an example, the sensor <NUM> can include a gyro sensor, an acceleration sensor, a position sensor, a velocity sensor, a fixed star sensor, and the like, which are necessary for controlling the travel and orientation of the spacecraft <NUM>, a temperature sensor, an illuminance sensor, an infrared sensor, and the like, which are for observing an external environment of the spacecraft <NUM>, and a temperature sensor and an illuminance sensor, and the like, which are for measuring an internal environment of the spacecraft <NUM>. The detected information and data are appropriately stored in the memory <NUM>, used for control by the processor <NUM>, and transmitted to a base station on the ground via the communication unit <NUM>.

The actuator <NUM> can include, for example, a magnetic torquer, a reaction wheel, a control moment gyro (CMG), and the like. The actuator <NUM> is used to obtain torque and thrust for controlling the orientation of the spacecraft <NUM> in response to an instruction command from the processor <NUM>, and functions as a propulsion unit.

The power supply unit <NUM> includes the power supply control circuit <NUM>, the battery <NUM>, and the solar panel <NUM>, and functions as a power supply unit. The power supply control circuit <NUM> is connected to the battery <NUM> and controls charging and discharging of electric power of the battery <NUM>. Under the control by the power supply control circuit <NUM>, the battery <NUM> charges electric power generated by the solar panel <NUM> and accumulates the electric power to be supplied to each of drive systems such as the computer <NUM> and the communication unit <NUM> in the main body <NUM>.

The communication unit <NUM> includes the communication control circuit <NUM>, the transmitter <NUM>, the receiver <NUM>, the radiator <NUM>, and the reflection unit <NUM>, and functions as a communication unit. The communication control circuit <NUM> performs processing such as encoding/decoding of information and signals in order to transmit and receive information to and from the ground station or other spacecraft via the radiator <NUM> connected to the communication control circuit <NUM>. The transmitter <NUM> includes an oscillator, an amplifier, and the like, and amplifies a radio wave having a frequency of a predetermined frequency band, which is generated by the oscillator, with the amplifier. The amplified radio wave is emitted to the reflection surface of the reflection unit <NUM> via the radiator <NUM>. In the present embodiment, the communication unit <NUM> is used for performing the observation by using the radio wave emitted to the observation target and reflected from the observation target. Accordingly, the radio wave emitted from the radiator <NUM> is once reflected by the subreflector <NUM> forming the reflection unit <NUM> and emitted to the outside by the main reflector <NUM>. On the other hand, the reflected radio wave received from the outside is received by the receiver <NUM> through a reverse path.

In the present embodiment, only the communication unit <NUM> including a pair of the subreflector <NUM> and the main reflector <NUM> will be described. The communication unit <NUM> can adjust a frequency of a microwave band such as a frequency band of <NUM> or less, an <NUM> to <NUM> band (so-called X band), and a <NUM> to <NUM> band (so-called Ku band), a frequency of a millimeter wave band of <NUM> or more, a frequency of a sub-millimeter wave band of <NUM> or more, and the like as desired.

<FIG> is a block diagram illustrating a configuration of the transmitter <NUM> according to the first embodiment of the present disclosure. Specifically, <FIG> is a diagram functionally illustrating an internal configuration of the transmitter <NUM> illustrated in <FIG>. According to <FIG>, the transmitter <NUM> includes an oscillator <NUM>, an amplifier <NUM>, a synthesizer <NUM>, and a low-pass filter <NUM>.

As an example, the oscillator <NUM> is disposed inside the main body <NUM> in <FIG>. The oscillator <NUM> outputs a high frequency signal serving as a radio wave for transmitting a signal or the like. In the present embodiment, the oscillator <NUM> outputs a radio wave including at least any of frequencies of a microwave band such as a frequency band of <NUM> or less, an <NUM> to <NUM> band (so-called X band), and a <NUM> to <NUM> band (so-called Ku band), a frequency of a millimeter wave band of <NUM> or more, or a frequency of a submillimeter wave band of <NUM> or more, preferably at least any of frequencies of a microwave band such as frequency band of <NUM> or less, an <NUM> to <NUM> band (so-called X band), and a <NUM> to <NUM> band (so-called Ku band), and more preferably at least any of frequencies of an <NUM> to <NUM> band (so-called X band).

The amplifier <NUM> is electrically connected to the oscillator <NUM> and amplifies electric power of the radio wave output from the oscillator <NUM>. In the present embodiment, as an example, data of the observation target is observed by emitting a radio wave toward the observation target and receiving the radio wave reflected from the observation target. Therefore, significantly high transmit electric power is required. In the present embodiment, the amplifier <NUM> amplifies the transmit electric power so as to be <NUM> W to <NUM>,<NUM> W, preferably <NUM> W to <NUM>,500W, and more preferably <NUM>,<NUM> W to <NUM>,<NUM> W. The amplifier <NUM> according to the invention is configured by combining four or more amplifiers in accordance with output capability of the amplifier. A specific configuration of the amplifier <NUM> comprising four amplifiers will be described later. Additionally, the output capability of the amplifier is merely an example. For example, an upper limit and a lower limit of each range merely define the electric power required at the present time, and it is possible to obtain a desired effect such as a heat dissipation effect by applying the configuration according to the present embodiment as a matter of course even when the output capability exceeds the upper limit or the output capability is lower than the lower limit.

In a case where the amplifier <NUM> is configured by combining a plurality of the amplifiers, the synthesizer <NUM> is electrically connected to the amplifier <NUM> and synthesizes the radio waves output from the respective amplifiers into one carrier wave. The low-pass filter <NUM> is electrically connected to the synthesizer <NUM>, and is used to extract only a low-frequency component from the radio wave output from the synthesizer <NUM> and remove the low-frequency component. For example, this is for removing the radio wave of a frequency band, of which use is restricted by the Radio Act. The radio wave which has passed through the low-pass filter <NUM> is output to the radiator <NUM> illustrated in <FIG> and emitted to the outside via the radiator <NUM>.

Here, as the amplifier <NUM> included in the transmitter <NUM>, a high output electric power amplifier is used as described above. Therefore, the amplifier <NUM> dissipates heat when operating, and adversely affects surrounding electronic devices. Moreover, when a temperature of the amplifier <NUM> is high, risk such as the damage of the element itself constituting the amplifier <NUM> is increased. Accordingly, in the present embodiment, the amplifier <NUM> is disposed on an exterior portion of the main body <NUM> and exposed to space. In this configuration, the amplifier <NUM> can be isolated from other electronic devices such as the processor <NUM>, which are accommodated in the accommodation space inside the main body <NUM>, and adverse effects on other electronic devices can be reduced. Furthermore, in a case where the spacecraft <NUM> is going around a satellite orbit, it is also possible to efficiently cool the amplifier <NUM> by exposing the amplifier <NUM> to space.

<FIG> is a side view illustrating an outline of a configuration of the spacecraft <NUM> according to the first embodiment of the present disclosure. Specifically, <FIG> is a view in which a partial configuration of the main reflector <NUM> is omitted in order to illustrate the arrangement position of the amplifier <NUM>. Furthermore, <FIG> is a top view illustrating an outline of a configuration of the spacecraft <NUM> according to the first embodiment of the present disclosure. Specifically, <FIG> is a view in which a partial configuration of the subreflector <NUM> is omitted in order to illustrate the arrangement position of the amplifier <NUM>.

First, according to <FIG>, on the upper surface of the main body <NUM> formed by an octahedron having a hexagonal upper surface and a hexagonal bottom surface, the hub <NUM>, which is formed in a substantially columnar shape and on which the ribs <NUM> forming the main reflector <NUM> are radially disposed at equal intervals on the outer circumference, is disposed. The hub <NUM> has, as an example, a substantially circular shape when viewed from a direction along the central axis X in cross section. The amplifier <NUM> is disposed at a substantially central position of the hub <NUM> formed in a circular shape and on the same surface (that is, the upper surface) as the main body <NUM> on which the hub <NUM> is disposed. Therefore, the amplifier <NUM> is not accommodated in the accommodation space inside the main body <NUM>, but is disposed on a surface exposed to space.

Furthermore, in the present embodiment, the radiator <NUM> is of course not limited to this configuration, but is configured as a horn type radiator as an example. Furthermore, the subreflector <NUM> is disposed to be spaced from the horn type radiator <NUM> by a predetermined interval by using the support rod <NUM> including the first support rod <NUM>, the second support rod <NUM>, and the joint <NUM>. In the present embodiment, the amplifier <NUM> is disposed at a position close to the radiator <NUM> and on a line (that is, on the line of the central axis X) connecting the radiator <NUM> with the subreflector <NUM>.

In general, the radio wave amplified by the amplifier <NUM> is electrically transmitted via a coaxial cable and/or a waveguide until reaching the radiator <NUM> via various electronic components electrically connected to each other. In this transmission process, electric power loss occurs when the radio wave passes through each electronic component and the coaxial cable, and the transmission efficiency thereof is reduced. Therefore, as in the present embodiment, by disposing the amplifier <NUM> at a position close to the radiator <NUM> and on a line (that is, on the line of the central axis X) connecting the radiator <NUM> with the subreflector <NUM>, it is possible to minimize a wiring distance by using the coaxial cable and/or the waveguide, and to reduce the electric power loss.

Next, according to <FIG>, the hub <NUM> is formed in a substantially circular shape in a top view, and is disposed on the upper surface of the main body <NUM> formed in a hexagonal shape. Furthermore, the center of the hub <NUM> is disposed so as to pass through the central axis X. On the outer circumferential surface of the hub <NUM>, a plurality of the ribs <NUM> forming the main reflector <NUM> are disposed at equal intervals. In the present embodiment, it is not illustrated in <FIG>, but the subreflector <NUM> is disposed so that the center of the subreflector <NUM> is positioned on the central axis X of the hub <NUM>. Therefore, the radiator <NUM> that emits the radio wave to the subreflector <NUM> is also disposed on the central axis of the hub <NUM>.

Furthermore, in the present embodiment, the amplifier <NUM> is disposed on the upper surface of the main body <NUM> formed in a hexagonal shape and immediately below the radiator <NUM> for the purpose of reducing the wiring distance to the radiator <NUM>. Therefore, the amplifier <NUM> is disposed so as to be positioned substantially at the center of the hub <NUM>.

<FIG> is a top view illustrating an outline of a configuration of the spacecraft <NUM> according to the first embodiment of the present disclosure. Furthermore, <FIG> is a side view illustrating an outline of a configuration of the amplifier <NUM> according to the first embodiment of the present disclosure. According to <FIG> and <FIG>, the amplifier <NUM> includes four amplifiers <NUM>-1a to <NUM>-1d. In the examples of <FIG> and <FIG>, the four amplifiers <NUM>-1a to <NUM>-1d are disposed so as to form side surfaces of a rectangular parallelepiped respectively. These amplifiers <NUM>-1a to <NUM>-1d are supported by a frame <NUM>-<NUM> disposed so as to connect the amplifiers. That is, it is not illustrated in <FIG> and <FIG>, but the amplifiers <NUM>-1a to <NUM>-1d are fixed to the upper surface of the main body <NUM> via the frame <NUM>-<NUM>. In the examples of <FIG> and <FIG>, the four amplifiers are disposed so as to form the side surfaces of the rectangular parallelepiped, but the number of amplifiers to be used may be more than four. It is possible to appropriately adjust the number of amplifiers in accordance with the desired electric power.

In the examples of <FIG> and <FIG>, at least a part of the amplifier <NUM>, specifically, outer surfaces <NUM>-3a to <NUM>-3d on sides exposed to space is coated with silver-deposited Teflon, aluminum-deposited Teflon, indium oxide, indium tin oxide, white paint, black paint, or a combination thereof, and preferably the silver-deposited Teflon or the aluminum-deposited Teflon, in order to further increase the heat dissipation effect. This coating can be formed by any method as necessary, such as sticking a coating material formed in a sheet shape or spraying a coating agent formed in a liquid state. Furthermore, in the examples of <FIG> and <FIG>, only the surface exposed to space is coated, but the present disclosure is not limited to this, and the upper surface or the inner surface may be coated.

The four amplifiers <NUM>-1a to <NUM>-1d are connected to the synthesizer <NUM> by a coaxial cable and/or a waveguide (not illustrated) having one end connected to each of the amplifiers <NUM>-1a to <NUM>-1d and the other end connected to the synthesizer <NUM>. The radio waves power-amplified by the amplifiers <NUM>-1a to <NUM>-1d are synthesized by the synthesizer <NUM>. Here, in the examples of <FIG> and <FIG>, the horn type radiator <NUM> is disposed on the central axis X which is a center of the amplifiers <NUM>-1a to <NUM>-1d disposed so as to form the side surfaces of the rectangular parallelepiped. The synthesizer <NUM> and the radiator <NUM> are disposed on the upper surface side of the main body <NUM> by the frame <NUM>-<NUM> together with the amplifiers <NUM>-1a to <NUM>-1d.

Furthermore, in the present embodiment, the other communication unit <NUM> is adjacent to the radiator <NUM>, and also fixed to the frame <NUM>-<NUM>. The communication unit <NUM> includes the horn type radiator, and is used, for example, for communication in a frequency band of <NUM> to <NUM> band (so-called Ku band) used for data transmission from the spacecraft <NUM> to the ground station. In this case, unlike the communication unit <NUM> that needs to receive a reflected radio wave from the observation target for observation, since a radio wave only needs to be transmitted to the ground station, an amplifier having a higher output than that of the communication unit <NUM> is not required. Therefore, the communication unit <NUM> includes, for example, only a low power amplifier.

As described above, in the present embodiment, the amplifier <NUM> is disposed on the surface of the main body <NUM> exposed to space. According to this, not only the heat dissipation effect of the heat generated by the amplifier <NUM> can be enhanced, but also the amplifier <NUM> which is a heat generating source can be isolated from other electronic devices, so that the adverse effect can be reduced. Furthermore, by enhancing the heat dissipation effect of the amplifier <NUM>, the risk such as the damage of the element itself constituting the amplifier <NUM> can be reduced. Moreover, particularly in the small SAR satellite, the limited accommodation space of the main body <NUM> can be effectively used.

As per claim <NUM>, the amplifier <NUM> is disposed on the antenna arrangement surface side of the main body <NUM>. However, although not covered by the claims, the amplifier <NUM> can be disposed on the other surface of the main body <NUM>. For example, similarly to the first embodiment, it is possible to enhance the heat dissipation effect of the amplifier <NUM> by disposing the amplifier <NUM> on a lower surface of the main body <NUM>, the lower surface being exposed to space.

Claim 1:
A spacecraft (<NUM>) comprising:
a main body (<NUM>) that has an accommodation space for accommodating an electronic device therein;
an oscillator (<NUM>) configured to output a radio wave including a frequency of a predetermined frequency band;
at least four amplifiers (<NUM>-la, <NUM>-1b, <NUM>-1c, <NUM>-1d) that are disposed on an exterior portion of the main body (<NUM>) to be exposed to space and configured to amplify electric power of the radio wave output by the oscillator (<NUM>), each of the at least four amplifiers (<NUM>-la, <NUM>-1b, <NUM>-1c, <NUM>-1d) forming a side surface of a rectangular parallelepiped, each of the at least four amplifiers (<NUM>-la, <NUM>-1b, <NUM>-1c, <NUM>-1d) being supported by a frame (<NUM>-<NUM>) so as to connect the at least four amplifiers (<NUM>-la, <NUM>-1b, <NUM>-1c, <NUM>-1d); and
an antenna that is disposed on the exterior portion of the main body (<NUM>) and is for emitting the radio wave to an outside with the electric power amplified by the at least four amplifiers (<NUM>-la, <NUM>-1b, <NUM>-1c, <NUM>-1d),
wherein the at least four amplifiers (<NUM>-la, <NUM>-1b, <NUM>-1c, <NUM>-1d) and the antenna are fixed on a same surface side of the main body (<NUM>) to be arranged along a central axis (X) of the antenna.