Relay communication system and method suitable for planetary exploration

Abstract

The invention provides a relay communication system and method suitable for planet exploration, and the system comprises a spacecraft which comprises two communication relay satellites, the communication relay satellites are located on the heliocentric orbit of a golden star, and the two communication relay satellites are located at the Lagrange L4 and L5 points of a golden star-sun system respectively; the golden star detector transmits data to a communication relay satellite close to the earth, and then the communication relay satellite transmits the data to a ground station. The communication satellite system provided by the invention can provide communication relay service for the detector on the astronomical body when the astronomical body such as the astronomical body is shielded by the sun and cannot directly communicate with the earth. According to the invention, complete or partial relay communication service can be provided for deep space detectors, such as water stars, mars, solar detectors, solar-earth system L3 point detectors and the like, which are also faced with the problem of communication obstruction at the same time.

Description

Technical Field

[0001] The present invention relates to the field of aerospace communication technology, and in particular to a relay communication system and method suitable for planetary exploration. Background Art

[0002] Since the launch of the first artificial satellite on October 4, 1957, humans have never stopped their curiosity about exploring the entire solar system. So far, more than 160 probes have been sent into deep space to explore the solar system. However, due to distance and other reasons, we have only explored a small part of the solar system so far.

[0003] One of the main problems hindering the development of deep space exploration is the communication and tracking problem. The current spacecraft communication and tracking functions are heavily dependent on the traditional deep space tracking network composed of large antennas located on the ground. For most celestial bodies in the solar system, the communication environment between the celestial body and the earth is not stable due to orbital reasons. When the detection celestial body and the earth are at both ends of the sun and close to a straight line, due to the long distance and the obstruction of the sun, the communication between the detector located at the target celestial body and the earth will be difficult to carry out, and the closer the target celestial body is to the sun, the more serious this situation will be. Taking Venus as an example, every about 1.5 years, the angle between Venus, the sun and the earth will be greater than 160° and last for about 3 months. At this time, the distance between Venus and the earth will reach nearly 1.7 astronomical units, and the communication radio waves will be severely interfered because the path is too close to the sun. Summary of the invention

[0004] In view of the defects in the prior art, an object of the present invention is to provide a relay communication system and method suitable for planetary exploration.

[0005] According to the present invention, a relay communication system suitable for planetary exploration includes: a spacecraft, wherein the spacecraft includes two communication relay satellites, wherein the communication relay satellites are located on the heliocentric orbit of Venus, and the two communication relay satellites are respectively located at the Lagrange L4 and L5 points of the Venus-Sun system; the Venus probe transmits data to a communication relay satellite close to the earth, and the communication relay satellite then sends the data to a ground station.

[0006] Preferably, a communication relay satellite close to the earth acquires control information from a ground station and sends the control information to the Venus probe.

[0007] Preferably, the two communication relay satellites are located on the orbit of Venus, leading and lagging Venus by 60° in phase respectively; a rectangular coordinate system is established with the sun as the origin and the orbital plane of Venus as the plane, wherein the position of Venus is (R, 0), and the coordinates of the two communication satellites are respectively

[0008]

[0009] Among them, R is the distance between Venus and the Sun, M1 is the mass of the Sun, and M2 is the mass of Venus.

[0010] Preferably, the communication relay satellite is provided with an X-band amplifier, an X-band transceiver, an S-band amplifier and an S-band transceiver; the X-band amplifier and the X-band transceiver are connected to form an X-band link, and the S-band amplifier and the S-band transceiver are connected to form an S-band link;

[0011] Scientific data are transmitted via S-band links;

[0012] Engineering data is transmitted via X-band links, or S-band links are used as a supplement.

[0013] Preferably, the communication relay satellite is provided with an S-band movable high-gain Yagi antenna array and an S-band fixed high-gain Yagi antenna array; the S-band movable high-gain Yagi antenna array is arranged on the top of the communication relay satellite, and the S-band movable high-gain Yagi antenna array is arranged pointing in the direction of the earth; the S-band fixed high-gain Yagi antenna array is arranged on the side of the communication relay satellite, and the S-band fixed high-gain Yagi antenna array is arranged toward the Venus probe.

[0014] Preferably, the communication relay satellite has four working modes:

[0015] Orbit transfer mode: the working mode of the satellite before entering the working orbit;

[0016] Attitude adjustment mode: orbit maintenance, target alignment and desaturation of momentum wheels for communication relay satellites in operating orbit;

[0017] Relay communication mode: the nominal operating mode of a communication relay satellite;

[0018] Safety / Standby Mode: A risk avoidance mode for dealing with extreme space environments such as solar magnetic storms and a standby mode for non-relay communication missions.

[0019] Preferably, the communication relay satellite includes a propulsion system, which includes a main thruster and an attitude control thruster; the main thruster is used for orbit insertion when reaching the Lagrange point, and the attitude control thruster provides momentum unloading, attitude maintenance and control for the communication relay satellite.

[0020] Preferably, the communication relay satellite includes an attitude determination and control system; the satellite attitude confirmation is determined by a three-axis star sensor arranged on the Z+ direction panel, two precision sun sensors arranged on the X+ direction panel and the Y+ direction panel respectively, and two three-axis inertial measurement units;

[0021] Satellite attitude control is achieved through four momentum wheels, which are arranged in the shape of an isosceles right triangle tetrahedron inside the satellite. Three of the momentum wheels are parallel to the X, Y, and Z planes, respectively, and the fourth momentum wheel serves as a redundant supplement.

[0022] According to the present invention, a relay communication method suitable for planetary exploration includes: setting two communication relay satellites on the heliocentric orbit of Venus, wherein the communication relay satellites are located at the Lagrange L4 and L5 points of the Venus-Sun system, and the Venus probe transmits data to a communication relay satellite close to the earth, and the communication relay satellite then sends the data to a ground station.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Since the L4 and L5 points of the Sun-Venus system are visible to Venus at any time of the year and there must be at least one point visible to the Earth and any other celestial body, the communication satellite system of the present invention can provide communication relay services for probes on Venus and other celestial bodies when they are blocked by the Sun and cannot communicate directly with the Earth. The present invention can also provide full or partial relay communication services for other deep space probes that also face communication obstacles, such as Mercury, Mars, solar probes, and L3 point probes of the Sun-Earth system;

[0025] 2. The communication relay satellite system of the present invention can effectively reduce the demand for communication systems of deep space probes. Taking Venus as an example, without considering the shielding situation, the maximum communication distance of the Venus probe is reduced from 1.7Au when Venus and the Earth are located on both sides of the sun to 0.7Au from Venus to L4 or L5 points. Since the loss of electromagnetic waves in free space is proportional to the cube of the distance, this solution reduces the free space loss of communication signals by 93%, so the probe can release more power and quality budget from the communication system. At the same time, due to the shortening of the communication distance, the demand for pointing accuracy is also greatly reduced.

[0026] 3. The communication relay satellite one-rocket two-satellite launch and separation deployment scheme of the present invention can achieve the purpose of consistent fuel carried by the two satellites, thereby reducing production costs and launch costs and improving the feasibility of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0028] Figure 1 A schematic diagram of the relay communication service provided by the present invention with the Venus probe as the service object;

[0029] Figure 2 It is a schematic diagram of the architecture of the relay communication system of the present invention;

[0030] Figure 3 This is a schematic diagram of the phase difference between the orbits of Venus and the Earth;

[0031] Figure 4 The phase difference between the three points and the Earth when a communication satellite is deployed at the L4 and L5 points of the Sun-Venus system respectively;

[0032] Figure 5 The figure is a graph showing the change of the earth communication capability of two communication satellites of the present invention over time;

[0033] Figure 6 This is a deep space coverage diagram of the relay communication system of the present invention;

[0034] Figure 7 This is a chart showing the launch capability of the Long March 3B rocket;

[0035] Figure 8 A side view of the communication relay satellite provided by the present invention after it is fully deployed

[0036] Fig. 9 A side view of the communication relay satellite provided by the present invention in a folded state;

[0037] Fig.10 A bottom view of the communication relay satellite provided by the present invention in a folded state;

[0038] Fig.11 A top view of the internal payload of the communication relay satellite provided by the present invention (excluding the Z+ panel);

[0039] Fig.12 A schematic diagram of the internal load of the Z+ panel of the communication relay satellite provided by the present invention;

[0040] Description of reference numerals:

[0041] DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0043] The present invention proposes a relay communication system suitable for planetary exploration, the system comprising: a spacecraft and a ground station, the spacecraft comprising two communication relay satellites, the communication relay satellites being located on the heliocentric orbit of Venus, respectively located at the Lagrange L4 and L5 points of the Venus-Sun system. When the Venus probe and other deep space probes are in a communication blind spot or weak signal area with the Earth, the data will be transferred to the communication relay satellite closer to the Earth, and then the communication relay satellite will send the detection data to the ground station. In a preferred embodiment, the ground station can also forward the control instructions and mission data of the ground station to the deep space probe via a specific band through the communication relay satellite.

[0044] The two communication relay satellites are located in the orbit of Venus and maintain their position through their own propulsion systems. They lead and lag Venus by 60° in phase respectively. A rectangular coordinate system is established with the sun as the origin and the orbital plane of Venus as the plane, where the position of Venus is (R, 0). At this time, the coordinates of the two communication satellites are

[0045]

[0046] Among them, R is the distance between Venus and the Sun, M1 is the mass of the Sun, and M2 is the mass of Venus.

[0047] For users of deep space probes such as the Venus probe, the communication distance with the relay satellite is shown in Table 1:

[0048] Table 1

[0049] User detector Relay communication distance Direct ground communication distance Solar Probe 0.72Au 1Au Mercury Probe 0.32Au~0.82Au 0.6Au~1.4Au Venus probe 0.72Au 0.28Au~1.72Au Mars Rover 0.8Au~1.67Au 0.5Au~2.5Au

[0050] Through the relay communication system disclosed in the present invention, small deep space probes do not need to carry large antennas and high-power transmitters, but only need to carry low-power, low-cost communication payloads. Scientific data, signals, images, and remote control commands can all be relayed through the present invention.

[0051] The two communication relay satellites in the present invention have equal mass and are symmetrical about the YZ plane in overall structure. The two satellites can be launched simultaneously and decelerate after arriving at predetermined points respectively. They orbit the corresponding Lagrange points through a Lissajous orbit or a halo orbit, with the X+ plane facing quasi-Venus and the Y+ plane normal forming an angle of 30 degrees with the sunlight.

[0052] In a preferred embodiment, when two communication relay satellites are launched together, the launch mass is no more than 900 kg, and the launch energy C3 provided by the Long March 3B rocket exceeds 36 km 2 / s 2 , which is sufficient to support the simultaneous orbital transfer of the two stars.

[0053] The two communication relay satellites are designed as pure plate structures, consisting of six external structural plates with an envelope of 1.1×1×0.8m. 3 The interior of the cube is composed of 4 composite panels to supplement the load-bearing structure and frame. Except for the propellant tank, all payloads and equipment of the communication relay satellite are placed on 6 outer panels.

[0054] Specifically, the communication relay satellite includes an X-band amplifier, an S-band amplifier, an X-band transceiver, an S-band transceiver, a 2×4 array of S-band movable high-gain Yagi antenna arrays, a 5×4 array of S-band fixed high-gain Yagi antenna arrays, and an X-band omnidirectional antenna. The S-band movable high-gain Yagi antenna array is arranged on the Z+ plane of the relay satellite and can rotate 360° around the Z axis and pitch ±10° along the antenna direction. It is kept pointing to the earth through a motor-controlled universal joint for data transmission. The S-band fixed high-gain Yagi antenna array is kept pointing to the user spacecraft (such as the Venus probe) through satellite attitude control and is used to receive scientific data sent by the user probe. The X-band omnidirectional antenna is used to exchange engineering data and assist the satellite in orientation. Scientific data is transmitted through the S-band link, and engineering data is generally transmitted through the X-band link, which can be supplemented through the S-band link when necessary.

[0055] The uplink frequency of S-band communication is 2050-2150MHz, the downlink frequency is 2200-2300MHz, it is BPSK coded, and the maximum transmission power is 400W. Other relevant calculation data values ​​are shown in Table 2:

[0056] Table 2 Link calculation parameters

[0057]

[0058] According to the link budget inequality:

[0059]

[0060] Where c is the speed of light and k is the Boltzmann constant 1.38×10 -23 J / K, is the normalized signal-to-noise ratio, which is calculated by the modulation mode of the modulator. p , A d , A S They are polarization mismatch attenuation, misadaptation attenuation and additional attenuation. In an ideal state, there is no attenuation, so A is taken p =A d =A S =1, and finally the communication rate B can be obtained r for:

[0061]

[0062] For BPSK modulation mode, The calculation method is:

[0063]

[0064] Where inverfc is the inverse of erfc function.

[0065] When the communication satellite is at the farthest distance from the earth (the orbital phase angle difference is 120°), the maximum downlink communication rate is about 2.4Mbps; when the communication satellite is at the closest distance from the earth (the orbital phase angle difference is 0), the downlink communication rate is about 1933Mbps.

[0066] The power system of the communication relay satellite consists of the following parts: solar panel array, battery, and power management unit. The solar panel consists of a movable solar wing placed on the Z-panel and a solar panel fixed on the Y+ panel, which is used to generate electricity; the battery is used to store energy; the power management unit adjusts the overall working mode of the communication relay satellite according to the instructions of the onboard computer, and then controls and distributes the generated power, provides power lines for all equipment and instruments, controls battery charging and discharging, provides TM / TC interfaces for subsystem operation and performance evaluation, and provides redundancy and protection for the circuit.

[0067] The propulsion system of the communication relay satellite consists of the following parts: 1 100N thruster, 6 1.5N attitude control thrusters, AND-based propellant tanks, high-pressure nitrogen tanks, and fuel supply and distribution systems. All thrusters are AND-based monopropellant thrusters and share a propellant tank. The 100N thruster is mainly used for orbit insertion when arriving at the Lagrange point, and the 1.5N attitude control thruster is mainly used to provide momentum unloading for the spacecraft momentum wheels, and to provide additional attitude maintenance and control when necessary.

[0068] The attitude determination and control system (ADCS) of the communication relay satellite consists of the following parts: first, determining the flight attitude and orientation of the satellite throughout its life cycle; second, providing attitude control for the satellite in different working modes. Attitude determination is mainly composed of a three-axis star sensor arranged on the Z+ panel, two precision sun sensors arranged on the X+ panel and the Y+ panel respectively, and two three-axis inertial measurement units (IMUs). The precision sun sensor is the main component of attitude determination. It determines the current attitude of the spacecraft by the relative attitude and position with the sun. Each precision sun sensor has a ±60° field of view. The combination of two sun sensors enables the satellite of the present invention to have a 210° capture field of view of the sun on the XY plane. In all conventional working modes, the sun should be within the field of view of the sun sensor. The star sensor and IMU will provide relative star observation images and motion parameters to assist in the determination of the attitude of Venus, and also serve as system redundancy when the sun is out of view due to unexpected circumstances and the sun sensor cannot work.

[0069] The satellite's attitude control is mainly completed through four momentum wheels, each of which can provide an angular momentum of no less than 0.5Nms. The four momentum wheels are arranged in an isosceles right triangle tetrahedron inside the satellite, three of which are parallel to the X, Y, and Z planes, respectively, and the fourth momentum wheel is used as a redundant supplement. This arrangement can ensure that the satellite still has full attitude control capabilities after one of the momentum wheels fails to work.

[0070] The control and data handling system (C&DH) of the communication relay satellite consists of the following parts: processing, storing and forwarding the corresponding scientific data and engineering instructions; controlling the communication relay satellite itself. Therefore, the main component of C&DH is an on-board computer (OBC) equipped with an additional 8TB storage hard disk. It should be noted that the management units of the thermal control system and the power system are not included in the C&DH. The on-board computer delivers the requirements of different stages to the management units of the two systems for adjustment.

[0071] The thermal control system of the communication relay satellite includes: multi-layer insulation coating (Multi-layerInsulation, MLI), heat pipe, refrigerant, refrigerant pump, coating, flexible heating sheet, thermal control management unit. The heat pipe is used to build a conductive connection between the internal structure and the radiator, using R134a as the refrigerant and driven by the refrigerant pump. Two heat sinks are placed on the Y-plane and Z-plane respectively. The flexible heating sheet is independently pasted on the outer shell of each component according to the needs of different electronic components to avoid component failure caused by low temperature. A separate thermal control management unit controls the heating sheet and the heat dissipation system to ensure that the temperature of all components is maintained within the corresponding operating temperature range. Quality and power budget.

[0072] Table 3 Quality budget

[0073]

[0074] The communication relay satellite of the present invention is a standard small satellite with a total mass of about 384 kg, of which the propellant is about 140 kg.

[0075] Table 4 Power budget

[0076]

[0077] The communication relay satellite of the present invention mainly has four working modes, namely orbit transfer mode, attitude adjustment mode, relay communication mode and safety / standby mode.

[0078] The orbit transfer mode refers to the working mode of the satellite of the present invention before entering the working orbit.

[0079] The attitude adjustment mode includes orbit maintenance, target alignment, and momentum wheel desaturation of the communication relay satellite on the working orbit.

[0080] The relay communication mode is the nominal working mode of the communication relay satellite of the present invention.

[0081] The safety / standby mode includes a risk avoidance mode for dealing with extreme space environments such as solar magnetic storms and a standby mode for non-relay communication tasks.

[0082] Table 3 Actual power budget for different working modes

[0083] Working Mode Orbital transfer Posture Adjustment Relay communication Safety / Standby Subsystem Power(W) Power(W) Power(W) Power(W) Communication System 60 60 430 60 Power System 12 12 12 12 Propulsion system 160 60 0 0 Attitude determination and control system 23 23 12.5 12.5 Structural system 15 5 0 0 Control and data processing system 10 10 40 5 Thermal Control System 150 60 40 150 System Redundancy 42 30 55.5 24.5 total 474 260 590 264

[0084] For the Venus probe, the present invention uses traditional S-band and X-band wireless transmission, which is compatible with the deep space probes that have been launched and are planned to carry the corresponding frequency band communication system. For the Venus orbit probe, the net transmission gain (power amplifier gain + antenna gain) required to maintain the minimum transmission rate (~2Kbps) between the probe and the relay satellite should not be less than 40dB; for the Venus lander, the required net transmission gain should not be less than 60dB.

[0085] In addition to the Venus probe, the solar probe, Mercury probe and other probes located within the Earth's orbit can also use the relay communication service provided by the present invention. The coverage rate of the present invention for the space within the Earth's orbit reaches 100%, and it can provide uninterrupted relay communication services throughout the year; the coverage rate for the Mars orbit reaches 80%, and it can provide basic communication relay services for most of the year. In this embodiment, when the distance between all the communication relay satellites and a certain point in space exceeds 1.5Au, it is considered that the present invention cannot cover this point to provide relay services.

[0086] The present invention does not require the construction of additional dedicated ground communication units. Any ground / orbital communication base station equipped with an S-band feed can obtain downlink scientific data from the communication relay satellite, but the transmission rate is affected by the antenna gain of the receiving end. Taking the transmission rate of 327Kbps-290Mbps as an example, the net gain of the base station's receiving system needs to be no less than 60dB.

[0087] A base station equipped with an X-band feed can also communicate and exchange data with the relay satellite of the present invention, but due to the limitation of antenna performance, only engineering data and instructions can be transmitted via the X-band.

[0088] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0089] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A relay communication system suitable for planetary exploration, characterized in that: include: The spacecraft includes two communication relay satellites, which are located in the heliocentric orbit of Venus. The two communication relay satellites are respectively located at the Lagrange L4 and L5 points of the Venus-Sun system; the Venus probe transmits data to a communication relay satellite close to the Earth, and the communication relay satellite then sends the data to a ground station.

2. The relay communication system suitable for new detection according to claim 1, characterized in that: A communication relay satellite close to the Earth acquires control information from the ground station and sends it to the Venus probe.

3. The relay communication system suitable for planetary exploration according to claim 1, characterized in that: The two communication relay satellites are located in the orbit of Venus, leading and lagging Venus by 60° in phase respectively. A rectangular coordinate system is established with the sun as the origin and the orbital plane of Venus as the plane, where the position of Venus is (R, 0). At this time, the coordinates of the two communication satellites are Among them, R is the distance between Venus and the Sun, M1 is the mass of the Sun, and M2 is the mass of Venus.

4. The relay communication system suitable for planetary exploration according to claim 1, characterized in that: The communication relay satellite is provided with an X-band amplifier, an X-band transceiver, an S-band amplifier and an S-band transceiver; the X-band amplifier and the X-band transceiver are connected to form an X-band link, and the S-band amplifier and the S-band transceiver are connected to form an S-band link; Scientific data are transmitted via S-band links; Engineering data is transmitted via X-band links, or S-band links are used as a supplement.

5. The relay communication system suitable for planetary exploration according to claim 1, characterized in that: The communication relay satellite is provided with an S-band movable high-gain Yagi antenna array and an S-band fixed high-gain Yagi antenna array; the S-band movable high-gain Yagi antenna array is arranged on the top of the communication relay satellite, and the S-band movable high-gain Yagi antenna array is arranged pointing in the direction of the earth; the S-band fixed high-gain Yagi antenna array is arranged on the side of the communication relay satellite, and the S-band fixed high-gain Yagi antenna array is arranged toward the Venus probe.

6. The relay communication system suitable for planetary exploration according to claim 1, characterized in that: The communication relay satellite has 4 working modes: Orbit transfer mode: the working mode of the satellite before entering the working orbit; Attitude adjustment mode: orbit maintenance, target alignment and desaturation of momentum wheels for communication relay satellites in operating orbit; Relay communication mode: the nominal operating mode of a communication relay satellite; Safety / Standby Mode: A risk avoidance mode for dealing with extreme space environments such as solar magnetic storms and a standby mode for non-relay communication missions.

7. The relay communication system suitable for planetary exploration according to claim 1, characterized in that: The communication relay satellite includes a propulsion system, which includes a main thruster and an attitude control thruster; the main thruster is used for orbit insertion when reaching a Lagrange point, and the attitude control thruster provides momentum unloading, attitude maintenance and control for the communication relay satellite.

8. The relay communication system suitable for planetary exploration according to claim 1, characterized in that: The communication relay satellite includes an attitude determination and control system; the satellite attitude confirmation is determined by a three-axis star sensor arranged on the Z+ direction panel, two precision sun sensors arranged on the X+ direction panel and the Y+ direction panel respectively, and two three-axis inertial measurement units; Satellite attitude control is achieved through four momentum wheels, which are arranged in the shape of an isosceles right triangle tetrahedron inside the satellite. Three of the momentum wheels are parallel to the X, Y, and Z planes, respectively, and the fourth momentum wheel serves as a redundant supplement.

9. A relay communication method suitable for planetary exploration, based on the relay communication system suitable for planetary exploration according to any one of claims 1 to 8, characterized in that: include: Two communication relay satellites are set up in the heliocentric orbit of Venus. The communication relay satellites are located at the Lagrange L4 and L5 points of the Venus-Sun system. The Venus probe transmits data to a communication relay satellite close to the earth, and the communication relay satellite then sends the data to the ground station.

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