Method for accessing deep space spacecraft to Beidou inter-satellite link system

Abstract

The invention discloses a method for accessing a deep space spacecraft to a Big Dipper inter-satellite link system, which comprises the following steps: injecting a group of virtual orbits for the Big Dipper and the deep space spacecraft by using a pseudo target deception method, making a pre-compensation strategy for the sending frequency and the sending time of the deep space spacecraft according to the virtual orbits, therefore, Ka inter-satellite link signal bidirectional capture is carried out with a Beidou global navigation system satellite running in orbit, an inter-satellite link is established, and a current Beidou inter-satellite link transceiving system does not need to be changed.

Description

Technical Field

[0001] The technology of the present invention is applicable to inter-satellite communication, lunar exploration, deep space exploration, etc. in the aerospace field. In particular, it is applicable to the scenario where a spacecraft equipped with a Ka (Ka-band, which is a part of the microwave band of the electromagnetic spectrum. This band is directly above the K-band, so it is called Ka (K-above). The frequency range of the Ka-band is 26.5 - 40 GHz and is usually used for satellite communication) inter-satellite link payload in deep space needs to access the Beidou inter-satellite link system. Background Art

[0002] In the prior art, signal acquisition between two satellites of different constellations often requires both parties to modify the transceiver mechanism simultaneously, especially in the scenario where the distance between the two parties is relatively far. However, the technical difficulty of modifying the transceiver system simultaneously is relatively high, the influence range is relatively wide, and the risk to the satellites already in orbit is huge. Summary of the Invention

[0003] The present invention provides a method for a deep space spacecraft to access the Beidou inter-satellite link system. The method uses a pseudo-target deception method to inject a set of virtual orbits for Beidou and the deep space spacecraft. The virtual orbits satisfy the current system of Beidou, and based on this, a transmission frequency and transmission time pre-compensation strategy for the deep space spacecraft is formulated, so as to perform two-way acquisition of Ka inter-satellite link signals with the satellites of the Beidou Global Navigation Satellite System in orbit and establish an inter-satellite link without changing the current transceiver system of the Beidou inter-satellite link.

[0004] The technical solution of the present invention is: a method for a deep space spacecraft to access the Beidou inter-satellite link system, which injects the orbital parameters of a pseudo-target into the Beidou satellite through the ground inter-satellite link operation and management center, so that for the Beidou satellite, the signal characteristics of the pseudo-target are consistent with those of the deep space spacecraft, thereby solving the problem of receiving and transmitting signals by the Beidou satellite under the existing system; the signal characteristics include the signal arrival time and signal Doppler.

[0005] The method for fitting the orbital parameters of the pseudo-target is as follows: the signal transmission distance of the Beidou satellite is less than 75,000 kilometers, while the deep space spacecraft far exceeds this distance limit. Therefore, consider selecting a point less than 75,000 kilometers away from the Beidou satellite on the signal transmission path between the Beidou satellite and the deep space spacecraft at each moment, and find a set of suitable orbital parameters through simulation to fit these points, so as to obtain the pseudo-target and its orbit.

[0006] For the Beidou satellite, only the time and frequency delays caused by the distance to the pseudo-target need to be considered when receiving and transmitting signals; for the deep space spacecraft, when transmitting signals, it is necessary to make the arrival time and frequency of the signal at the Beidou satellite the same as the arrival time and frequency of the signal transmitted by the pseudo-target to the Beidou satellite, and when receiving signals, capture them at the time and frequency when the signal sent by the Beidou satellite to the pseudo-target reaches the deep space spacecraft.

[0007] Furthermore, the motion characteristics of the virtual pseudo-target orbit meet the following requirements:

[0008] (1) The expression method of the pseudo-target position meets the requirements of the current Beidou satellite parameter expression range;

[0009] (2) The relative velocity / acceleration between the pseudo-target and the Beidou satellite is the same as that between the deep-space spacecraft and the Beidou satellite;

[0010] (3) The signal frequency received by the pseudo-target from the Beidou satellite is sufficient to be transmitted to the deep-space spacecraft;

[0011] According to the access requirements of the deep-space spacecraft, the ground inter-satellite link operation and management center searches for suitable pseudo-target points at different times, and based on a series of obtained pseudo-target points, fits to obtain the pseudo-target orbit and injects it into the Beidou satellite. When the orbit cannot be obtained by fitting, the pseudo-target motion trajectory can be directly expressed in the form of coordinate points.

[0012] Furthermore, the signal transmission time compensation and signal reception time compensation of the deep-space spacecraft include the following steps:

[0013] It is known that the signal time delay caused by the space distance between the deep-space spacecraft and the pseudo-target is ΔT, ΔT > 250 ms, and the signal time delay caused by the space distance between the pseudo-target and the Beidou satellite is Δt, Δt < 250 ms;

[0014] When the deep-space spacecraft transmits a signal - the Beidou satellite receives the signal:

[0015] (a) The deep-space spacecraft does not transmit a signal at 1.5 s of Beidou time during the planned inter-satellite link signal transmission time slot, but instead transmits the signal at a time ΔT before 1.5 s of Beidou time, so that the time when the signal reaches the pseudo-target is 1.5 s of Beidou time;

[0016] (b) The signal arrival time calculated by the Beidou satellite according to the position of the pseudo-target is Δt. Since the signal transmitted by the deep-space spacecraft at 1.5 s just passes through the pseudo-target, the Beidou satellite can directly control signal acquisition according to the signal arrival time Δt;

[0017] (c) When the inter-satellite link signal transmitted by the deep-space spacecraft reaches the Beidou satellite, it is exactly at a time Δt after 1.5 s of the planned Beidou satellite reception time slot and Δt < 250 ms. Therefore, the Beidou satellite can directly acquire the inter-satellite link signal transmitted by the deep-space spacecraft under its current signal reception system;

[0018] When the Beidou satellite transmits a signal - the deep-space spacecraft receives the signal:

[0019] (a)The Beidou satellite normally transmits the inter-satellite link signal at the planned transmission time of 1.5 s according to the Beidou time rhythm;

[0020] (b)The deep space spacecraft calculates the signal arrival time as ΔT + Δt according to the real position of the Beidou satellite, and controls the inter-satellite link terminal to perform signal acquisition around the time of ΔT + Δt after 1.5 s of transmission;

[0021] The inter-satellite link signal transmitted by the Beidou satellite reaches the deep space spacecraft after a time of ΔT + Δt. The delay caused by the space distance is offset by the deep space spacecraft adjusting the signal acquisition time, so that the Beidou satellite can maintain the current signal transmission system unchanged.

[0022] According to the above methods and steps, the Beidou satellite can establish a link with the deep space spacecraft within the original designed transceiver time slots, without affecting the operation of other time slots of the Beidou satellite, and without any changes to the Beidou transceiver system. Only the deep space spacecraft needs to have the functions of signal pre-transmission and lagged reception.

[0023] Furthermore, the signal frequency compensation for transmission by the deep space spacecraft and the signal frequency compensation for reception include the following steps:

[0024] It is known that the relative motion between deep space spacecrafts will cause Doppler frequency shift of the signal. The Beidou inter-satellite link considers the Doppler caused by the relative motion between MEO, IGSO, and GEO satellites and leaves a certain margin. The maximum signal Doppler frequency shift that the inter-satellite link terminal of the Beidou satellite can tolerate is ±ΔDOP0;

[0025] It is also known that the signal Doppler frequency shift caused by the relative motion between the deep space spacecraft and the pseudo-target is ΔDOP1, and the signal Doppler frequency shift caused by the relative motion between the pseudo-target and the Beidou satellite is ΔDOP2, where the absolute value of ΔDOP1 is not greater than 2 times ΔDOP0, and the absolute value of ΔDOP2 is not greater than ΔDOP0;

[0026] And it is known that the center frequency of the inter-satellite link between the Beidou satellite and the deep space spacecraft is H;

[0027] When the deep space spacecraft transmits a signal - the Beidou satellite receives the signal:

[0028] (a)During the planned signal transmission time slot, the deep space spacecraft calculates the relative motion speed ΔDOP1 between it and the pseudo-target, and the relative motion speed ΔDOP2 between the pseudo-target and the Beidou satellite; when the two are approaching each other, the center frequency H is negatively offset by |ΔDOP1|, that is, the signal is transmitted at the frequency corresponding to H - |ΔDOP1|; when the signal reaches the pseudo-target, the frequency is H, then the Beidou satellite calculates the Doppler of the signal when it arrives according to the relative speed with the pseudo-target, and controls the inter-satellite link terminal to perform signal acquisition with a signal Doppler of |ΔDOP2|;

[0029] (b)During the planned signal transmission time slot of the deep-space spacecraft, calculate the relative motion speed ΔDOP1 between the spacecraft and the pseudo-target, and the relative motion speed ΔDOP2 between the pseudo-target and the Beidou satellite. When the two are moving away from each other, correct |ΔDOP1| with a positive offset from the center frequency H, that is, transmit the signal at the frequency corresponding to H + |ΔDOP1|. When the signal reaches the pseudo-target, its frequency is H. Then, the Beidou satellite calculates the Doppler effect of the signal when it arrives according to the relative speed with the pseudo-target, and controls the inter-satellite link terminal to capture the signal with a signal Doppler of -|ΔDOP2|.

[0030] (c)When the inter-satellite link signal sent by the deep-space spacecraft reaches the Beidou satellite, the signal Doppler of the signal meets the signal Doppler requirements of the maximum ΔDOP0 of the Beidou navigation satellite, and the capture of the inter-satellite link signal sent by the deep-space spacecraft can be completed without changing the existing receiving system of the Beidou satellite.

[0031] When the Beidou satellite sends a signal and the deep-space spacecraft receives the signal:

[0032] (a)The Beidou satellite sends the inter-satellite link signal at the center frequency H according to the Beidou time rhythm at the planned transmission time of 1.5 s.

[0033] (b)The deep-space spacecraft calculates the Doppler effect of the signal when it arrives according to the true relative speed with the Beidou satellite to control the inter-satellite link terminal to capture the signal. When the two are approaching each other, the deep-space spacecraft captures the signal with a signal Doppler of |ΔDOP1| + |ΔDOP2|. When the two are moving away from each other, the deep-space spacecraft captures the signal with a signal Doppler of -|ΔDOP1| - |ΔDOP2|.

[0034] (c)When the inter-satellite link signal sent by the Beidou satellite reaches the deep-space spacecraft, the capture of the inter-satellite link signal sent by the Beidou satellite can be completed.

[0035] According to the above methods and steps, the Beidou satellite can establish a link with the deep-space spacecraft within the signal Doppler capture capability range of the original design without any changes to the existing Beidou transceiver system, and only the deep-space spacecraft needs to have a signal frequency transmission compensation function.

[0036] The beneficial effects of the present invention are as follows: A method for a deep-space spacecraft to access the Beidou inter-satellite link system is provided. The spacecraft operating in deep space, through equipping with dedicated or dual-purpose inter-satellite link terminal payloads, according to the capabilities and characteristics of the on-orbit Beidou inter-satellite link system, by introducing pseudo-targets and implementing adaptive designs in aspects such as the antenna terminal equipment of the deep-space spacecraft, signal transceiver modes, transmission frequency parameter compensation, and signal propagation time compensation, enables it to smoothly access the Beidou inter-satellite link system. This method can enable the deep-space spacecraft to perform two-way TT&C by utilizing the surplus time slot resources of the Beidou inter-satellite link communication without changing the existing signal transceiver mechanism of the Beidou inter-satellite link, and realize that any ground station can conduct TT&C support for the deep-space spacecraft through the globally covering Beidou inter-satellite link system at any time.

[0037] The deep-space spacecraft is configured with dedicated or dual-purpose inter-satellite link terminal payloads to perform time delay compensation and frequency compensation for received and transmitted signals. At the same time, pseudo-targets are set to deceive Beidou satellites, solving the problems of large propagation time delay during ultra-long-distance signal transmission and the Doppler effect of signals caused by high relative motion speed exceeding the capture ability of the Beidou inter-satellite link mechanism, and realizing two-way capture of signals between Beidou satellites and deep-space spacecraft. This method can connect the deep-space spacecraft to the Beidou inter-satellite link system without changing the Beidou inter-satellite link mechanism, thereby providing a new method for TT&C of deep-space spacecraft. Brief Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the working mode of the Beidou inter-satellite link system;

[0039] Figure 2 It is a schematic diagram of the relationship between the pseudo-target, Beidou satellites, and deep-space spacecraft;

[0040] Figure 3 It is a schematic diagram of the time compensation for the signals transmitted by the deep-space spacecraft and the time compensation for the received signals;

[0041] Figure 4 It is a schematic diagram of the frequency compensation for the signals transmitted by the deep-space spacecraft and the frequency compensation for the received signals. Detailed Embodiment

[0042] The following further describes the present invention with reference to the drawings.

[0043] The Beidou inter-satellite link system is mainly composed of Ka inter-satellite link terminal payloads equipped on each satellite, and its working mode is as Figure 1: ① The Beidou inter-satellite link system transmits and receives signals based on Beidou Time. Each minimum working time unit of 3 seconds is called a "time slot". Each time slot is further divided into the first half time slot of 1.5 seconds for signal transmission / reception and the second half time slot of 1.5 seconds for signal reception / transmission. The first 250 ms of the 1.5-second signal reception is the signal guiding and capturing time, corresponding to the signal propagation delay within a distance of 75,000 km. The signal needs to reach the receiving antenna within this time. ② The Ka-band inter-satellite link terminal payload uses a phased array antenna, which can continuously switch the signal direction according to the time slot sequence planned by the ground, and establish an inter-satellite link with different satellites.

[0044] To achieve the purpose of communicating with deep space spacecraft without changing the existing Beidou inter-satellite link system, the present invention provides a method of pseudo-target deception. On the one hand, the orbit parameters of the pseudo-target are injected into the BD satellites (Beidou satellites) through the ground inter-satellite link operation and management center, so that for the BD satellites, the signal characteristics of the pseudo-target are consistent with those of the deep space extended users, including the signal arrival time and signal Doppler, thus solving the problem of the BD satellites receiving and sending signals under the existing system. On the other hand, the deep space spacecraft needs to perform time delay compensation and frequency compensation on the transmitted / received signals according to the transmission / reception mechanism between the Beidou satellites and the pseudo-target.

[0045] The pseudo-target refers to that in order to adapt to the existing Beidou system, the signal transmission distance needs to be less than 75,000 km, while the deep space spacecraft far exceeds this distance limit. Therefore, a point less than 75,000 km from the Beidou satellite is selected on the signal transmission path between the Beidou satellite and the deep space spacecraft at each moment, and a suitable set of orbit parameters is found through simulation to fit these points, so as to obtain the pseudo-target and its orbit. For the Beidou satellite, only the time and frequency delays caused by the distance to the pseudo-target need to be considered during signal transmission / reception; for the deep space spacecraft, when sending a signal, the arrival time and frequency of the signal at the Beidou satellite should be the same as those of the pseudo-target sending a signal to the Beidou satellite, and when receiving a signal, it is captured at the time and frequency when the signal sent by the Beidou satellite to the pseudo-target reaches the deep space spacecraft.

[0046] The time delay compensation for the transmitted / received signals of the deep space spacecraft means that when the deep space spacecraft inter-satellite link terminal payload sends a signal to the Beidou satellite, the signal sending time is offset and compensated according to the agreed strategy, so that the arrival time of the signal at the Beidou satellite is the same as that of the pseudo-target sending a signal to the Beidou satellite; when the deep space spacecraft inter-satellite link terminal payload receives the Beidou satellite signal, it needs to calculate the time when the signal sent by the Beidou satellite to the pseudo-target reaches the deep space spacecraft for capture.

[0047] The frequency compensation for signal transmission and reception of the deep space spacecraft refers to that when the terminal payload of the inter-satellite link of the deep space spacecraft sends a signal to the Beidou satellite, the frequency of the transmitted signal is offset and compensated according to a pre-agreed strategy, so that the frequency of the signal reaching the Beidou satellite is the same as that of the signal sent by the pseudo-target to the Beidou satellite; when the terminal payload of the inter-satellite link of the deep space spacecraft receives the Beidou satellite signal, it is necessary to calculate the frequency of the signal sent by the Beidou satellite to the pseudo-target when it reaches the deep space spacecraft, so as to perform capture.

[0048] Reference Figure 2 , the relationship between the pseudo-target, the Beidou satellite and the deep space spacecraft in the present invention includes the following steps:

[0049] The deep space extended user and the BD satellite plan to establish a link at times T1, T2, and T3. At time T1, the position of the deep space extended user is Dm1 and the position of the BD satellite is DBD1. Therefore, the signal propagation delay is (Dm1 - DBD1) / c and the signal Doppler is MOA1. At this time, a virtual pseudo-target Df1 can be set on the line connecting Dm1 and DBD1; at time T2, the position of the deep space extended user is Dm2 and the position of the BD satellite is DBD2. According to the same method above, a virtual pseudo-target Df2 can be set; at time T3, the position of the deep space extended user is Dm3 and the position of the BD satellite is DBD3. According to the same method above, a virtual pseudo-target Df3 can be set.

[0050] The motion characteristics of the virtual pseudo-target orbit meet the following requirements:

[0051] 1. Its position expression meets the requirements of the current BD parameter expression range;

[0052] 2. Its relative velocity / acceleration with the BD satellite is the same as that of the deep space extended user and the BD satellite;

[0053] 3. The frequency of the signal it receives from the BD is sufficient to be transmitted to the deep space user.

[0054] The ground operation and management center searches for suitable pseudo-target points at different times according to the access requirements of the deep space extended user, and fits the obtained series of pseudo-target points to obtain the pseudo-target orbit, which is injected into the BD satellite. When the orbit cannot be obtained by fitting, the motion trajectory of the pseudo-target can be directly expressed in the form of coordinate points.

[0055] Reference Figure 3 , the time compensation for signal transmission and reception of the deep space spacecraft in the present invention includes the following steps:

[0056] It is known that the signal time delay caused by the spatial distance between a deep space spacecraft and a false target is ΔT (>250 ms), and the signal time delay caused by the spatial distance between the false target and a Beidou satellite is Δt (<250 ms).

[0057] When the deep space spacecraft sends a signal and the Beidou satellite receives the signal:

[0058] 1) When the deep space spacecraft sends a signal in the planned inter-satellite link signal transmission time slot, instead of sending the signal at the moment of 1.5 s in Beidou time, it changes to send the signal at the moment of ΔT before this 1.5 s, so that the moment when the signal reaches the false target is 1.5 s in Beidou time;

[0059] 2) The signal arrival time calculated by the Beidou satellite according to the position of the false target is Δt. Since the signal sent by the deep space spacecraft at the moment of 1.5 s just passes through the false target, the Beidou satellite can directly control signal acquisition according to the signal arrival time Δt;

[0060] 3) When the inter-satellite link signal sent by the deep space spacecraft reaches the Beidou satellite, it is exactly at the moment of Δt after the planned Beidou satellite receiving time slot of 1.5 s and Δt < 250 ms. Therefore, it is possible to realize that the Beidou satellite directly acquires the inter-satellite link signal sent by the deep space spacecraft under its current signal receiving system.

[0061] When the Beidou satellite sends a signal and the deep space spacecraft receives the signal:

[0062] 1) The Beidou satellite normally sends an inter-satellite link signal at the planned sending moment of 1.5 s according to the Beidou time rhythm;

[0063] 2) The deep space spacecraft calculates the signal arrival time as ΔT + Δt according to the real position of the Beidou satellite, and controls the inter-satellite link terminal to perform signal acquisition around the moment of ΔT + Δt after the sending moment of 1.5 s;

[0064] The inter-satellite link signal sent by the Beidou satellite reaches the deep space spacecraft after a time of ΔT + Δt. The time delay caused by the spatial distance is offset by the deep space spacecraft adjusting the signal acquisition time, so that the Beidou satellite can keep its current signal sending system unchanged.

[0065] According to the above methods and steps, the Beidou satellite can complete the link establishment with the deep space spacecraft within the originally designed sending and receiving time slots, without affecting the operation of other time slot services of the Beidou satellite. Without any change to the Beidou sending and receiving system, only the deep space spacecraft needs to have the functions of sending signals in advance and receiving signals with a delay.

[0066] Reference Figure 4 , the frequency compensation for the signal sent by the deep space spacecraft and the frequency compensation for the received signal described in the present invention include the following steps:

[0067] It is known that the relative motion between spacecraft will cause Doppler shift of signals. The Beidou inter-satellite link takes into account the Doppler effect caused by the relative motion between MEO, IGSO, and GEO satellites and leaves a certain margin. The maximum signal Doppler shift that the Beidou satellite inter-satellite link terminal can tolerate for signal acquisition is ±ΔDOP0;

[0068] It is also known that the signal Doppler shift caused by the relative motion between deep space spacecraft and the pseudo-target is ΔDOP1, and the signal Doppler shift caused by the relative motion between the pseudo-target and the Beidou satellite is ΔDOP2. Among them, the absolute value of ΔDOP1 is not greater than 2 times ΔDOP0, and the absolute value of ΔDOP2 is not greater than ΔDOP0;

[0069] And it is known that the center frequency of the inter-satellite link between the Beidou satellite and the deep space spacecraft is H.

[0070] When the deep space spacecraft sends a signal and the Beidou satellite receives the signal:

[0071] 1) During the planned signal transmission time slot of the deep space spacecraft, calculate the relative motion speed ΔDOP1 between the deep space spacecraft and the pseudo-target, and the relative motion speed ΔDOP2 between the pseudo-target and the Beidou satellite. When the two are approaching each other, correct |ΔDOP1| with a negative offset from the center frequency H, that is, send the signal at the frequency corresponding to H - |ΔDOP1|; when the signal reaches the pseudo-target, the frequency is H, then the Beidou satellite calculates the Doppler of the signal when it arrives according to the relative speed with the pseudo-target, and controls the inter-satellite link terminal to perform signal acquisition with the signal Doppler of |ΔDOP2|;

[0072] 2) During the planned signal transmission time slot of the deep space spacecraft, calculate the relative motion speed ΔDOP1 between the deep space spacecraft and the pseudo-target, and the relative motion speed ΔDOP2 between the pseudo-target and the Beidou satellite. When the two are moving away from each other, correct |ΔDOP1| with a positive offset from the center frequency H, that is, send the signal at the frequency corresponding to H + |ΔDOP1|; when the signal reaches the pseudo-target, the frequency is H, then the Beidou satellite calculates the Doppler of the signal when it arrives according to the relative speed with the pseudo-target, and controls the inter-satellite link terminal to perform signal acquisition with the signal Doppler of -|ΔDOP2|;

[0073] 3) When the inter-satellite link signal sent by the deep space spacecraft reaches the Beidou satellite, the signal Doppler meets the signal Doppler requirements of the maximum ΔDOP0 of the Beidou navigation satellite, and the acquisition of the inter-satellite link signal sent by the deep space spacecraft can be completed without changing the existing receiving system of the Beidou satellite.

[0074] When the Beidou satellite sends a signal and the deep space spacecraft receives the signal:

[0075] 1) The Beidou satellite sends the inter-satellite link signal at the center frequency H according to the Beidou time rhythm at the planned 1.5s transmission moment;

[0076] 2) The deep-space spacecraft calculates the Doppler effect when the signal arrives based on the true relative velocity of the Beidou satellites to control the signal capture of the inter-satellite link terminal. When the two are approaching each other, the deep-space spacecraft captures the signal with a Doppler effect of |ΔDOP1| + |ΔDOP2|; when the two are moving away from each other, the deep-space spacecraft captures the signal with a Doppler effect of -|ΔDOP1| - |ΔDOP2|.

[0077] 3) When the inter-satellite link signal sent by the Beidou satellite reaches the deep-space spacecraft, the capture of the inter-satellite link signal sent by the Beidou satellite can be completed.

[0078] According to the above methods and steps, the Beidou satellite can establish a link with the deep-space spacecraft within the signal Doppler capture capability of the original design without any modification to the existing Beidou transceiver system. Only the deep-space spacecraft needs to have a signal frequency transmission compensation function.

[0079] The deep-space spacecraft is equipped with a dedicated or shared inter-satellite link terminal payload to compensate for the time delay and frequency of the received and transmitted signals. At the same time, a false target is set to deceive the Beidou satellite, solving the problems of large propagation time delay during ultra-long-distance signal transmission and the signal Doppler exceeding the capture capability of the Beidou inter-satellite link system caused by high relative motion speed, and realizing the two-way capture of signals between the Beidou satellite and the deep-space spacecraft. This method can connect the deep-space spacecraft to the Beidou inter-satellite link system without changing the Beidou inter-satellite link system, thus providing a new method for deep-space spacecraft measurement and control.

[0080] The moon is the best test bed for the preliminary exploration of deep-space research. When a lunar spacecraft needs to be connected to the Beidou-3 inter-satellite link system, in order not to modify the existing signal transceiver system of the Beidou inter-satellite link, first, a false target needs to be found whose orbit satisfies a distance less than 75,000 kilometers from the Beidou. Then, this virtual orbit is injected into both the Beidou satellite and the lunar spacecraft. When the Beidou satellite receives and transmits signals, it calculates the frequency and time of signal capture and transmission according to the position of the false target. The lunar spacecraft designs the time and frequency compensation mechanism for signal reception and transmission accordingly.

[0081] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for a deep-space spacecraft to access the Beidou inter-satellite link system, characterized in that: Inject the orbital parameters of the pseudo-target to the Beidou satellite through the ground inter-satellite link operation and management center, so that for the Beidou satellite, the signal characteristics of the pseudo-target are consistent with those of the deep space spacecraft, thus solving the problem of the Beidou satellite receiving and sending signals under the existing system; the signal characteristics include the signal arrival time and signal Doppler; The orbital parameter fitting method of the pseudo-target is as follows: the signal transmission distance of the Beidou satellite is less than 75,000 km, while the deep space spacecraft far exceeds this distance limit. Therefore, consider selecting a point less than 75,000 km from the Beidou satellite on the signal transmission path between the Beidou satellite and the deep space spacecraft at each moment, and find a set of suitable orbital parameters through simulation to fit these points, so as to obtain the pseudo-target and its orbit; For the Beidou satellite, only the time and frequency delays caused by the distance to the pseudo-target need to be considered when receiving and sending signals; for the deep space spacecraft, when sending signals, it is necessary to make the arrival time and frequency of the signal at the Beidou satellite the same as the time and frequency when the pseudo-target sends signals to the Beidou satellite, and when receiving signals, capture them at the time and frequency when the signal sent by the Beidou satellite to the pseudo-target reaches the deep space spacecraft.

2. The method for a deep space spacecraft to access the Beidou inter-satellite link system according to claim 1, characterized in that, The motion characteristics of the virtual pseudo-target orbit meet the following requirements: (1) The expression method of the pseudo-target position meets the current Beidou satellite parameter expression range requirements; (2) The relative velocity / acceleration between the pseudo-target and the Beidou satellite is the same as the relative velocity / acceleration between the deep space spacecraft and the Beidou satellite; (3) The signal frequency received by the pseudo-target from the Beidou satellite is sufficient to be transmitted to the deep space spacecraft; The ground inter-satellite link operation and management center searches for suitable pseudo-target points at different times according to the access requirements of the deep space spacecraft, and fits the pseudo-target orbit according to the obtained series of pseudo-target points, and injects it into the Beidou satellite. When the orbit cannot be obtained through fitting, the motion trajectory of the pseudo-target can be directly expressed in the form of coordinate points.

3. A method for a deep space spacecraft to access the Beidou inter-satellite link system according to claim 1, characterized in that, The time compensation for the deep space spacecraft to send signals and the time compensation for receiving signals include the following steps: It is known that the signal time delay caused by the space distance between the deep space spacecraft and the pseudo-target is ΔT, ΔT>250ms, and the signal time delay caused by the space distance between the pseudo-target and the Beidou satellite is Δt, Δt<250ms; When the deep space spacecraft sends a signal - the Beidou satellite receives a signal: (a) The deep space spacecraft does not send a signal at 1.5 s of Beidou time during the planned inter-satellite link signal transmission time slot, but instead sends a signal at a time ΔT before 1.5 s of Beidou time, so that the arrival time of the signal at the pseudo-target is 1.5 s of Beidou time; (b) The signal arrival time calculated by the Beidou satellite according to the position of the pseudo-target is Δt. Since the signal sent by the deep space spacecraft at 1.5 s just passes through the pseudo-target, the Beidou satellite can directly control signal capture according to the signal arrival time Δt; (c) When the inter-satellite link signal sent by the deep space spacecraft reaches the Beidou satellite, it is exactly Δt after 1.5 s of the planned Beidou satellite receiving time slot and Δt < 250ms. Therefore, the Beidou satellite can directly capture the inter-satellite link signal sent by the deep space spacecraft under its current signal receiving system; When the Beidou satellite sends a signal and the deep-space spacecraft receives the signal: (a)The Beidou satellite normally sends the inter-satellite link signal at the planned transmission time of 1.5 s according to the Beidou time rhythm; (b)The deep-space spacecraft calculates the signal arrival time as ΔT + Δt based on the real position of the Beidou satellite, and controls the inter-satellite link terminal to perform signal acquisition around the time of ΔT + Δt after the 1.5 s transmission time; The inter-satellite link signal sent by the Beidou satellite arrives at the deep-space spacecraft after a time of ΔT + Δt. The delay caused by the space distance is offset by the deep-space spacecraft adjusting the signal acquisition time, so that the Beidou satellite can maintain the current signal transmission system unchanged.

4. A method for a deep - space spacecraft to access the Beidou inter - satellite link system according to claim 1, characterized in that, The signal frequency compensation for the deep-space spacecraft to send signals and the signal frequency compensation for receiving signals include the following steps: It is known that the relative motion between deep-space spacecrafts will cause Doppler frequency shift of the signal. The Beidou inter-satellite link considers the Doppler caused by the relative motion between MEO, IGSO, and GEO satellites and leaves a certain margin. The maximum signal Doppler frequency shift allowable for signal acquisition by the Beidou satellite inter-satellite link terminal is ±ΔDOP0; It is also known that the signal Doppler frequency shift caused by the relative motion between the deep-space spacecraft and the pseudo-target is ΔDOP1, and the signal Doppler frequency shift caused by the relative motion between the pseudo-target and the Beidou satellite is ΔDOP2, where the absolute value of ΔDOP1 is not greater than 2 times ΔDOP0, and the absolute value of ΔDOP2 is not greater than ΔDOP0; And it is known that the center frequency of the inter-satellite link between the Beidou satellite and the deep-space spacecraft is H; When the deep-space spacecraft sends a signal and the Beidou satellite receives the signal: (a)During the planned signal transmission time slot of the deep-space spacecraft, calculate the relative motion speed ΔDOP1 between the deep-space spacecraft and the pseudo-target, and the relative motion speed ΔDOP2 between the pseudo-target and the Beidou satellite; when the two are approaching each other, correct |ΔDOP1| with a negative offset from the center frequency H, that is, send the signal at the frequency corresponding to H - |ΔDOP1|; when the signal arrives at the pseudo-target, the frequency is H, then the Beidou satellite calculates the Doppler at the time of signal arrival according to the relative speed with the pseudo-target, and controls the inter-satellite link terminal to perform signal acquisition with a signal Doppler of |ΔDOP2|; (b)During the planned signal transmission time slot of the deep-space spacecraft, calculate the relative motion speed ΔDOP1 between the deep-space spacecraft and the pseudo-target, and the relative motion speed ΔDOP2 between the pseudo-target and the Beidou satellite; when the two are moving away from each other, correct |ΔDOP1| with a positive offset from the center frequency H, that is, send the signal at the frequency corresponding to H + |ΔDOP1|; when the signal arrives at the pseudo-target, the frequency is H, then the Beidou satellite calculates the Doppler at the time of signal arrival according to the relative speed with the pseudo-target, and controls the inter-satellite link terminal to perform signal acquisition with a signal Doppler of -|ΔDOP2|; (c)When the inter-satellite link signal sent by the deep-space spacecraft arrives at the Beidou satellite, its signal Doppler meets the signal Doppler requirement of the maximum ΔDOP0 of the Beidou navigation satellite, and the acquisition of the inter-satellite link signal sent by the deep-space spacecraft can be completed without changing the existing receiving system of the Beidou satellite; When the Beidou satellite sends a signal and the deep-space spacecraft receives the signal: (a)The Beidou satellite sends the inter-satellite link signal at the center frequency H according to the Beidou time rhythm at the planned transmission time of 1.5 s. (b)The deep-space spacecraft calculates the Doppler effect at the time of signal arrival according to the true relative velocity of the Beidou satellite to control the signal acquisition of the inter-satellite link terminal. When the two are approaching each other, the deep-space spacecraft acquires the signal with the Doppler effect of |ΔDOP1| + |ΔDOP2|; when the two are moving away from each other, the deep-space spacecraft acquires the signal with the Doppler effect of -|ΔDOP1| - |ΔDOP2|. (c)When the inter-satellite link signal sent by the Beidou satellite reaches the deep-space spacecraft, the acquisition of the inter-satellite link signal sent by the Beidou satellite can be completed.

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