JPH0624331B2 - Data relay satellite system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data relay satellite system, and more particularly to an improvement in user satellite tracking technology in a data relay satellite system in which a beacon transmitter is not mounted on a user satellite.

(Prior Art) A data relay satellite system relays the transmission signals of a plurality of user satellites placed on an orbit whose orbit around the earth is different from the earth rotation period by a data relay satellite placed on a geostationary orbit. It is a system for transmitting to the earth station. Therefore, in this data relay satellite system, a tracking technique in which an antenna for receiving a radio wave transmitted from a user satellite of the data relay satellite is used as a tracking antenna and the tracking antenna is directed toward the transmission antenna of the user satellite is essential. A method of mounting a beacon transmitter on the user satellite has been proposed for the purpose of facilitating tracking of the user satellite, but the data relay satellite system targeted by the present invention does not mount the beacon transmitter on the user satellite. Conventionally, a system shown in FIG. 4 is known.

In FIG. 4, this data relay satellite system includes a data relay satellite A, a user satellite B having a data relay satellite tracking antenna 24, and an earth station C. The data relay satellite A includes a receiving antenna 11, a command receiver 1, a command decoder 2, a command transmitter 14,
Attitude control processor 25 and antenna pointing control circuit 3
, Antenna pointing control mechanism 4, user satellite tracking antenna 12, relay receiver 7, power amplifier 9, free-running clock generator 26, telemetry encoder 6, telemetry transmitter 8, and multiplexer 10. And a transmitting antenna 13 are basically provided. The earth station C also includes a transmitting antenna 15, a receiving antenna 16, a command transmitter 17, a data processor 18, and a time / frequency system 2.
0, the computer 21, the telemetry receiver 23,
Integrator 27, error signal processor 28, A / D converter 2
9, the bandwidth setting device 19, the receiver 30, and the coupler 4
0 and basically are provided.

Next, the operation of the earth station C for collecting data from the user satellite B, that is, a conventional method for tracking the user satellite B will be outlined.

The tracking of the user satellite B is performed first by prediction (program tracking) and then by automatic tracking (automatic tracking). First, program tracking is performed as follows.
In the earth station C, the computer 21 creates a user satellite program tracking signal and a data relay satellite program tracking signal. The user satellite program tracking signal is for the data relay satellite A. The six satellite orbits of the data relay satellite and the user satellite, the data relay satellite A, respectively.
Is calculated from the posture of the robot, the reference time acquired from the time / frequency system 20, and the like. The data relay satellite program tracking signal is for the user satellite B, and is calculated from the six orbits of each satellite, the attitude of the user satellite, the reference time acquired from the time / frequency system 20, and the like. These program tracking signals are converted into a predetermined command signal format by the data processor 18, and the command transmitter 17
And is transmitted toward the data relay satellite A via the transmitting antenna 15.

In the data relay satellite A, the user satellite program tracking signal and the data relay satellite program tracking signal are separated and extracted from the command signal in the command decoder 2 via the receiving antenna 11 and the command receiver 1, and the user satellite program tracking signal is the attitude control processor. 25, the data relay satellite program tracking signal is output to the command transmitter 14, respectively.

The attitude control processor 25 receives a user satellite program tracking signal, which is a command from the ground, and outputs a control signal for pointing control of the user satellite tracking antenna 12 from the current attitude of the data relay satellite A and the attitude predicted on the ground. It is created and given to the antenna pointing control circuit 3. The antenna pointing control circuit 3 creates an antenna drive signal based on the input control signal and gives it to the antenna pointing control mechanism 4. As a result, the pointing direction of the user satellite tracking antenna 12 is controlled.

On the other hand, the command transmitter 14 transmits a data relay satellite program tracking signal, which is a command from the ground, from the user satellite tracking antenna 12 to the user satellite B. As a result, the user satellite B receives and demodulates the data relay satellite program tracking signal, and the data relay satellite tracking antenna 2
The directional control of No. 4 is performed to start transmitting data to the data relay satellite.

The user satellite tracking antenna 12 is composed of, for example, a horn for taking the sum signal Σ, two horns for taking the azimuth angle error signal ΔA _Z, and two horns for taking the elevation error signal ΔE _L. Of the multi-horn type, and these signals (Σ, ΔE _L , ΔA _Z ) are formed according to the reception intensity of the transmission radio wave of the user satellite B, and a multiplexer 10 is provided via a relay receiver 7 and a power amplifier 9. To enter. On the other hand, the telemetry encoder 6 creates various telemetry signals at a predetermined timing based on the output clock of the free-running clock generator 26.

The telemetry signal is subjected to a predetermined modulation process by the telemetry transmitter 8 and input to the multiplexer 10. as a result,
The multiplexer 10 outputs the sum signal Σ as it is,
The error signals (ΔE _L , ΔA _Z ) are superimposed on the output of the telemetry transmitter 8 and output. The output of the multiplexer 10 is transmitted to the earth station C via the transmitting antenna 13.

In the earth station C, the received signal received by the receiving antenna 16 is branched into two in the coupler 40 and input to the receiver 30 and the telemetry receiver 23, respectively. Telemetry receiver 23 the error signal from the received signal (Delta] E _L, .DELTA.A _Z) extracts and the synchronization signal (a signal related to the free-running clock), and outputs it to the telemetry demodulator 22. In the telemetry demodulator 22, the input error signal (ΔE _L , ΔA _Z )
Is demodulated based on the synchronization signal and is output to the error signal processor 28 and the integrator 27. On the other hand, the receiver 30
Is subjected to reception processing according to the pass band width designated and input from the bandwidth setting device 19, demodulates and forms the sum signal Σ, and
The data is output to the error signal processor 28 via the / D converter 29 and is also output to the outside as reception data. The bandwidth setting unit 19 is for allowing the data from the target user satellite B to be received in an optimum state in view of the fact that the data transmission rate of the user satellite B differs for each satellite. The bandwidth setting may be a manual setting.

The sum signal Σ and the error signal (ΔE _L , ΔA _Z ) demodulated as described above are subjected to constant processing such as level comparison and waveform shaping in the error signal processor 28, and C / N (in the integrator 27. The carrier wave-to-noise ratio) is improved and the data processor 18 is entered, where the error signals (ΔE _L , ΔA _Z )
It is determined whether or not the level of is within a certain range.
At the beginning of tracking, the user satellite tracking antenna 1
The pointing direction of 2 is the direction of the angle θ _E , and therefore the level value of the error signal is also a considerably large value.

This is detected by the data processor 18, and the computer 21
The computer 21 recreates the program tracking signal based on the detected content. That is,
When the program tracking is repeatedly performed by the closed loop described above, the user satellite tracking antenna 12 is correctly directed in the direction of the user satellite B, and the error signal level at the angle θ _B is within a certain range, this time the automatic tracking by the closed loop is performed. Move to tracking.

In the automatic tracking, the error signal (ΔE _L , ΔA _Z ) formed and output by the user satellite tracking antenna 12 as described above is received from the data relay satellite A, and the earth station C creates an automatic tracking signal and outputs it. A command is transmitted to the relay satellite A, and the user satellite tracking antenna 12 of the data relay satellite is controlled.
This automatic tracking is also repeated by the closed loop.

(Problems to be Solved by the Invention) However, in the above-described conventional data relay satellite system, when tracking a user satellite, a closed loop including the earth station is always formed, and therefore the following problems occur. is there.

First, the error signal received and acquired by the earth station in automatic tracking is a weaker signal than that in program tracking, and the noise level during reception is considerably high. Therefore, the earth station must perform high-level signal processing in order to accurately execute the automatic tracking, which causes the circuit configuration to be complicated and causes the system reliability to decrease.

Further, the data relay satellite essentially relays between a plurality of user satellites and the earth station, but a user satellite tracking antenna must be provided for each user satellite. Then,
The data relay satellite receives the command signal from the earth station to form the antenna drive signal, and the command reception is required to correctly transmit the antenna drive signal to the corresponding one of the plurality of user satellite tracking antennas. It is necessary to further reduce the noise of the machine, and it is necessary to increase the output of the telemetry transmitter in order to correctly transmit a plurality of error signals to the earth station. These improvements in performance lead to an increase in the weight and power consumption of the data relay satellite, resulting in a larger satellite.

Further, the C / N is lowered due to the deterioration of the line condition due to the rapid increase of the rainfall between the data relay satellite and the earth station, and the fidelity of the tracking signal of the closed loop including the earth station is lowered and the user satellite The tracking accuracy for

In addition, the earth station must always be involved in tracking control as a cornerstone of tracking control, which complicates the work of the operator.

The present invention has been made in view of such conventional problems, the object is to reduce the involvement of the earth station for tracking control by generating an antenna drive signal during automatic tracking in the data relay satellite, Therefore, it is intended to provide a data relay satellite system capable of improving tracking accuracy and system reliability.

(Means for Solving the Problems) In order to achieve the above object, the data relay satellite system of the present invention has the following configuration.

That is, the data relay satellite system of the present invention includes a plurality of user satellites that transmit data at different data transmission rates;
Earth station; Each user satellite has a tracking antenna, receives a program tracking signal from the earth station and directs the corresponding tracking antenna toward the corresponding user satellite, and starts data transmission to the user satellite. A data relay satellite that controls the pointing direction of the corresponding tracking antenna according to the reception state of the transmitted signal to track the corresponding user satellite, and relays the data transmitted by the user satellite to the earth station. In the data relay satellite system, the earth station includes command signal forming means for performing an operation of including a passband width setting signal in the program tracking signal transmitted for the first time; and from the data relay satellite after the first program tracking signal is transmitted. Whether to monitor the reception status of the user satellite capture signal and determine whether to retransmit the program tracking signal Monitoring means; and the data relay satellite receives the first program tracking signal, and also receives an antenna tracking error signal input thereafter as an automatic tracking signal, and drives the corresponding tracking antenna according to them. Antenna pointing control means for generating a user satellite capture signal when the received output level of the tracking antenna whose pointing direction is changed according to the drive signal is equal to or higher than a predetermined value, and transmits it to the earth station. User satellite capture signal generating means, the bandwidth of a band pass filter arranged on a pass path of a received output signal of the corresponding tracking antenna and an error signal regarding an antenna pointing direction according to the pass band width setting signal from the earth station. Automatic tracking data for generating the antenna tracking error signal based on the output of the bandpass filter that is set And it is characterized in that it comprises a; and management means.

(Operation) Next, the operation of the data relay satellite system of the present invention configured as described above will be described.

First, the earth station transmits the created program tracking signal to the data relay satellite. It is well known that the program tracking signal comprises a user satellite program tracking signal for the data relay satellite to track the user satellite and a data relay satellite program tracking signal for the user satellite to track the data relay satellite. . In the present invention, the user satellite program tracking signal includes a pass bandwidth setting signal. After transmitting the first program tracking signal, the earth station waits for the reception of the user satellite acquisition signal, which is a telemetry signal from the data relay satellite, and if there is no reception of the user satellite acquisition signal, transmits the program tracking signal again. Send. If there is a reception, the reception state is continuously monitored thereafter.

Next, when the data relay satellite receives the program tracking signal, it controls the pointing direction of the corresponding tracking antenna according to the user satellite program tracking signal to direct it toward the corresponding user satellite, and sends the data relay satellite program tracking signal to the user satellite. Send. In response to this, the user satellite starts data transmission. Although the above is the same as the conventional one, in the present invention, the following operation is performed subsequent to the above operation.

When the transmission signal of the user satellite is received by the corresponding tracking antenna, the reception level is monitored, and when it is equal to or higher than a predetermined value, a user satellite acquisition signal is generated and transmitted to the earth station. Then, once the user satellite capture signal is generated once, automatic tracking is performed by the closed loop of the tracking data processing means and the antenna pointing direction control means. That is, when the transmission signal of the user satellite is received by the corresponding tracking antenna,
The corresponding tracking antenna forms and outputs a received output signal and an error signal related to the antenna pointing direction. Conventionally, these were transmitted to the earth station, but in the present invention, these signals are input to the tracking data processing means, where an antenna tracking error signal as an automatic tracking signal is generated and automatic tracking is started. To be done. At this time, the tracking data processing means
A bandpass filter is arranged in a passage path of the reception output signal of the corresponding tracking antenna and an error signal related to the antenna pointing direction, and the bandwidth of the bandpass filter is included in the user satellite program tracking signal. It is set according to the bandwidth setting signal. That is, the antenna tracking error signal can be generated with high accuracy.

In short, according to the data relay satellite system of the present invention, the tracking error signal of the tracking antenna of the data relay satellite is processed in the data relay satellite to execute automatic tracking, so that a closed loop including the earth station is formed. You do n’t have to
The system can be simplified. In particular, the influence of rain attenuation can be ignored, and tracking accuracy and system reliability can be improved.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.

FIG. 1 shows a data relay satellite system according to an embodiment of the present invention. In FIG. 1, in the earth station C, the portion that processed the error signal of the tracking antenna in the conventional example (see the fourth example)
The part from the integrator 27 to the A / D converter 29 in the figure) is omitted, and the data processor 18 'includes a telemetry demodulator 22'.
And the output of the bandwidth setter 19 '. On the other hand, in the data relay satellite A, the conventional example (4th
The attitude control processor 25 and the free-running clock generator 26 in the figure) are omitted, and the tracking receiver 5 is newly installed. The output of the command decoder 2'is the command receiver 14
And the antenna pointing control circuit 3'and the tracking receiver 5, respectively. Further, the sum signal Σ and the error signals (ΔE _L , ΔA _Z ) output from the user satellite tracking antenna 12 are given to the tracking receiver 5, and the sum signal Σ is given to the relay receiver 7. Further, of the two outputs of the tracking receiver 5, the output a (antenna tracking error signal) is given to the antenna pointing control circuit 3 ', and the output b (user satellite capture signal) is given to the telemetry encoder 6. In addition,
Attitude data that gives the reference attitude of the data relay satellite A is supplied to the antenna pointing control circuit 3 '.

The operation of the part according to the present invention will be described below. In the earth station C, when the computer 21 outputs the program tracking signal to the data processor 18 ', the data processor 18' outputs the user satellite program tracking signal to the output from the bandwidth setting device 19 '(pass band width). A setting signal) is included (operation of command signal forming means). Here, the bandwidth setting signal is, for example, 150 MHz, 50 MHz, 15 MHz, 1 MH
It is a signal that specifies a bandwidth such as z and is determined in consideration of the data transmission rate of the target user satellite B. In addition, in most cases, the setting contents are different from those for the receiver 30.

And the data relay satellite A that received the program tracking signal
In the command decoder 2 ', the user satellite program tracking signal is output to the antenna pointing control circuit 3', the data relay satellite program tracking signal is output to the command transmitter 14, and the pass band width setting signal c is output to the tracking receiver 5. .

Upon receiving the user satellite program tracking signal, the antenna pointing control circuit 3'creates a driving signal for the user satellite tracking antenna 12 from the reference attitude of the data relay satellite A and the attitude predicted on the ground, and controls the antenna pointing control. It is given to the mechanism 4.

As a result, as in the conventional case, the user satellite tracking antenna 12
Is controlled, the transmission signal of the user satellite B is received, and the tracking receiver 5 from the user satellite tracking antenna 12 is received.
The sum signal Σ and the error signal (ΔE _L , ΔA _Z ) are supplied to.
The sum signal Σ is also supplied to the relay receiver 7.

The tracking receiver 5 is configured, for example, as shown in FIG. FIG. 2 shows the configuration including the user satellite tracking antenna 12. In FIG. 2, 52 is a coupler, 53 is a low noise amplifier, 54 is a down converter, 55 is a hybrid, 56 is a variable band pass filter, 57 is an AM detector,
58 is a low-pass filter, 59 is a PN code remover, 60
Is a switch, 61a and 61b are integrators, 62a and 62b
Is a hybrid, 63 is a modulator, 64 is a PN code generator, 65 is a clock generator, and 66 is a signal detector.

The clock generator 65 has a high speed clock and a low speed clock.
It generates the clock signal of the seed, and the high-speed clock is P
The low-speed clock is output to the N (pseudo random code) code generator 64 and to the modulator 63 and the switch 60, respectively. The PN code generator 64 generates a predetermined PN code according to the high speed clock, and outputs it to the modulator 63 and the PN code remover 59, respectively.

The modulator 63 includes error signals ΔE _L and ΔA _Z from the hybrids 62a and 62b of the user satellite tracking antenna 12, respectively.
, Respectively, are subjected to modulation processing by the PN code and the low-speed clock, and output to one input of the coupler 52. In the coupler 52, since the sum signal Σ from the user satellite tracking antenna 12 is given to the other input, the signals of both inputs are combined and output. Coupler 52
The output of the down converter 5 via the low noise amplifier 53
At 4, the frequency is converted into an intermediate frequency signal, for example, and is distributed from the hybrid 55 to the signal detector 66 and the variable band pass filter 56.

The signal detector 66 generates a user satellite acquisition signal when the input signal level exceeds a predetermined threshold value.

This is output to the telemetry encoder 6 and transmitted to the earth station C. In the earth station C, the data processor 18 'monitors whether the user satellite acquisition signal is input from the telemetry demodulator 22', and if the user satellite acquisition signal is not input after the first program tracking signal transmission, The computer 21 is made to generate the program tracking signal again. The same operation is performed when the user satellite capture signal is relatively continuously input and then interrupted (operation of the monitoring means).

On the other hand, the variable band pass filter 56 has a command decoder 2 '.
The input signal is filtered with the bandwidth specified by the passband width setting signal from. That is, the received signal from the user satellite B has the maximum S / N (signal-to-noise ratio) at the output of the variable band pass filter 56, enters the AM detector 57 in that state, is subjected to envelope detection, and has a low level. It is input to the PN code remover 59 via the pass filter 58.
As a result, the PN code remover 59 performs the inverse modulation processing, and the output thereof is the elevation angle error component to the integrator 61a and the azimuth angle error component to the integrator 61 by the switching operation of the switch 60.
and the antenna tracking error signals (ΔE _LO , ΔA _ZO ) are output from the integrators 61a and 61b to the antenna pointing control circuit 3 '.

Thus, the antenna pointing control circuit 3'creates an antenna drive signal from the input antenna tracking error signal (ΔE _LO , ΔA _ZO ) and the attitude data of the data relay satellite A,
Output to the antenna pointing control mechanism 4.

That is, after the user satellite acquisition signal is generated, a closed loop of the user satellite tracking antenna 12, the tracking receiver 5, the antenna pointing control circuit 3 ', the antenna pointing control mechanism 4 and the user satellite tracking antenna 12 is formed, and the user satellite B The automatic tracking of is achieved. Therefore, the tracking receiver 5
Constitutes a user satellite acquisition signal generation means and a tracking data processing means.

FIG. 3 is a conceptual diagram of tracking of the user satellite described above.
As shown in the figure, the fluctuation of the tracking error bias when the automatic tracking is started from the program tracking approaches the true trajectory of the user satellite B as much as possible, and the automatic tracking is favorably performed.

Although the tracking receiver 5 was newly installed in the data relay satellite, this can be made smaller and lighter by using an LSI, and can be realized without significantly increasing the weight or power consumption of the data relay satellite. Is.

(Effects of the Invention) As described in detail above, according to the data relay satellite system of the present invention, the tracking error signal of the tracking antenna of the data relay satellite is processed in the data relay satellite to perform automatic tracking. , It is not necessary to form a closed loop including the earth station, and the system can be simplified. In particular, the influence of rain attenuation can be ignored, and tracking accuracy and system reliability can be improved. In addition, since data processing is performed within the data relay satellite, the amount of data transmission between earth stations is greatly reduced. Therefore, even if the number of user satellite tracking antennas increases, there is no need for significant performance improvement such as an increase in the output of the transmission output of the telemetry transmitter and a reduction in the noise of the command receiver. In addition, 1 user satellite
Once it is captured, closed-loop automatic tracking between the data relay satellite and the user satellite is achieved, so even if the line between the data relay satellite and the earth station deteriorates, the tracking accuracy with respect to the user satellite is completely lost. Not affected. In addition, the operation for user satellite tracking has various effects such as once the automatic tracking is started, the operator's work on the earth station side can be simplified as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a block diagram of a data relay satellite system according to an embodiment of the present invention, FIG. 2 is a block diagram of a tracking receiver, FIG. 3 is a conceptual diagram of tracking of a user satellite, and FIG. It is a block diagram of a data relay satellite system. 1 ... Command receiver, 2, 2 '... Command decoder, 3, 3' ... Antenna pointing control circuit, 4 ... Antenna pointing control mechanism, 5 ... Tracking receiver, 6 ... Telemetry encoder, 7 ... ... Relay receiver, 8 ... Telemetry transmitter, 9 ... Power amplifier, 10 ... Multiplexer, 1
1 ... Receiving antenna, 12 ... User satellite tracking antenna, 13 ... Transmitting antenna, 14 ... Command transmitter,
15 ... Transmission antenna, 16 ... Transmission antenna, 17 ...
... Command transmitter, 18, 18 '... Data processor, 1
9, 19 '... Bandwidth setting device, 20 ... Time / frequency system, 21 ... Computer, 22, 22' ... Telemetry demodulator, 23 ... Telemetry receiver, 24 ... Data relay satellite tracking antenna , 25 ... Attitude control processor, 26 ... Free-running clock generator, 27 ... Integrator,
28 ... Error signal processor, 29 ... A / D converter, 30
...... Receiver, 40 …… Coupler.

Claims (1)

[Claims] 1. A plurality of user satellites that transmit data at different data transmission rates; an earth station; a tracking antenna for each user satellite, and a corresponding tracking antenna that receives a program tracking signal which is a command from the earth station. Point the user satellite in the corresponding direction and start data transmission to that user satellite, and control the pointing direction of the corresponding tracking antenna according to the reception state of the transmitted signal to track the corresponding user satellite. A data relay satellite for relaying and transmitting data transmitted by the earth station to an earth station; in the data relay satellite system, the earth station operates to include a pass band width setting signal in the program tracking signal to be transmitted for the first time. Command signal forming means; a user satellite acquisition signal from the data relay satellite after the first program tracking signal is transmitted. Monitoring means for observing the reception status of the program and determining whether or not to transmit the program tracking signal again; and, the data relay satellite receives the first program tracking signal and inputs after that. Antenna pointing control means for receiving an antenna tracking error signal as an automatic tracking signal and generating a drive signal for the corresponding tracking antenna in accordance therewith; a reception output level of the corresponding tracking antenna whose pointing direction is changed according to the drive signal is a predetermined value or more And a user satellite capture signal generating means for generating the user satellite capture signal and transmitting the user satellite capture signal to the earth station; arranged in the passage of the received output signal of the tracking antenna and the error signal relating to the antenna pointing direction. The bandwidth of the band pass filter is set according to the pass band setting signal from the earth station, and the band pass filter is A data relay satellite system comprising: an automatic tracking data processing means for generating the antenna tracking error signal based on the output of the wave device.