RU2625171C2 - System for measuring spacecraft distance - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: system for measuring the spacecraft (SC) distance consists of a spacecraft transceiver and a ground control complex (GCC) comprising a personal computer operator, a multiplexer/encoder, a transmitter, an antenna post, a receiver, a time-measuring unit, a reference generator, a permanent memory unit of commands and a permanent memory unit of ranging sequences, an OR gate, a search correlator and an averaging circuit unit, the output of which is the output of the system, wherein the first operator's PC output is connected to the permanent memory unit of commands and the first input of the OR gate, the second operator's PC output is connected to permanent memory unit of ranging sequences and the second input of the OR gate, the first correlator input with a search pattern is connected to the output of the multiplexer/encoder, the second correlator input with a search pattern is connected to the receiver output, the correlator output with a search pattern is connected to the second input of the time-measuring unit, the third input of the time measuring unit is connected to the output of the element OR, the output of the measuring unit is connected to the input of the averaging unit, the output of the multiplexer/encoder is connected to the input of the transmitter, the output of which is connected to the input of the antenna post, the output of which is connected to the receiver, the CA receiver is connected by two links to the antenna post, the reference generator is connected to the first input of the time-measuring unit.

EFFECT: increasing the accuracy of measuring the spacecraft distance.

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Description

The present technical solution relates to the field of measuring distance by radio engineering means and, more specifically, to measuring the range of a spacecraft (SC) located in a geostationary orbit.

The spacecraft range is measured in the Ground Control Complex (GCC). The personnel of the NKU carries out operations for the remote control of subsystems and nodes of the spacecraft, monitors the performance, parameters and functions of the spacecraft, also in remote mode.

The well-known "On-board relay of a communication system (options) and a method for relaying broadband signals", RF patent No. 2292117, publ. 01/20/2007. The analogue contains a synchronization error highlighting unit, a digital information transmitter control unit, a reference signal generator, a signal generation block, a series-connected receiving AFU, a signal processing block, a signal extraction block, a time-division multiplexer, a modulator, a group signal transmitter and a transmitting antenna, as well as a series connected unit for extracting command information, a unit for generating a command signal, a transmitter for command information and a transmitting AFU with a headlamp, and the unit for allocating synchronization errors according to the first the input is connected to the second output of the ШПС processing unit, the second input of the synchronization error allocation block is connected to the first output of the reference ШПС generator, the output of the synchronization error allocation block is connected to the second input of the temporary compression unit, the reference ШПС generator is connected to the second modulator input at the second output, the input the digital control unit of the information transmitter is connected to the second output of the command information allocation unit, the first output of the digital control unit is in parallel connected to the second inputs of the the command information transmitter and the transmitting AFU with the HEADLIGHT, the first input of the radio data generation unit is connected to the second output of the digital information transmitter control unit, the third output of the reference signal generator is connected to the second input of the taxiway formation unit, and the output of the radio data generation unit is connected to the second input of the command signal generation unit . The device is intended for relaying communication and control signals, which means command and rangefinder signals in the form of broadband signals. The expansion of the number and range of broadband signals requires a corresponding expansion of the occupied bandwidth. This leads to known difficulties, first of all, to a decrease in the signal-to-noise ratio, which has a decisive influence on the error in measuring the range. This is the most significant drawback of the analogue.

The closest is the system described in US Patent 6864838, March, 8, 2005 “Ranging system and method for satellites” by Harles et al. A well-known system in the spacecraft and GCC containing a time-measuring unit , a reference generator and series-connected digital signal multiplexer / encoder S1, S2, etc., QPSK modulator, upconverter, antenna post, downconverter, first receiver, first demodulator, first decoder, first processor unit, connected to first in a time-measuring unit, as well as a second receiver connected in series, connected to the QPSK modulator output, a second demodulator, a second decoder and a second processor unit, connected to the second input of the time-measuring unit, the output of the reference generator connected to the third time input -measurement unit.

Further, we assume that the restrictive part of the claims includes the personal computer of the operator, which is not described in the prototype, but is implied. Combine the QPSK modulator and the step-up frequency converter under the general name "transmitter" and under this name we will include these blocks in the restrictive part of the formula. We will also combine a step-down frequency converter, a first receiver, a first demodulator, a first decoder under the general name a receiver and under this name we will include these blocks in the restrictive part of the formula.

A disadvantage of the known system is the low accuracy of measuring the range of the spacecraft due to interruption of the range measurement caused by the transfer of commands, because the same uplink radio channel is used to transmit commands and one of the range-finding sequences (of which there may be several). Teams and rangefinding sequences are transmitted alternately with priority in favor of the teams. Therefore, the measurement of the range in the known system can be intermittently caused by the transfer of commands, which reduces the accuracy of the range measurement, since it is difficult to average the results of private measurements, which is widely used in practice. Transmission in a known system of one of the range-finding sequences is performed with the NKU automatically during the absence of a command. The ranging signal emitted from the antenna post and received by the spacecraft receiver is re-emitted by the spacecraft transmitter towards the NKU. The range is determined by the delay of the ranging signal for the duration of the NKU - KA - NKU route. If the command is transmitted, the transmission of the rangefinder signal is interrupted and the spacecraft range is not measured.

The objective of the proposed technical solution is to increase the accuracy of measuring the range of the spacecraft by increasing the accuracy of measuring the time interval between the signal emission and the reception of the re-emitted spacecraft, either rangefinder or command signals, which provides distance measurement without interruptions caused by the need to transmit commands. The measurement of the delay time caused by the propagation of a rangefinder or command signal along the path noted above allows one to ensure effective averaging of the results of private measurements, which is a prerequisite for increasing the accuracy of measuring the range of the spacecraft.

In the known ranging system, the Ground Control Complex contains an operator’s personal computer, a multiplexer / encoder, a transmitter, an antenna post, a receiver, as well as a time-measuring unit and a reference generator, the output of the multiplexer / encoder connected to the transmitter input, the output of which is connected to the antenna input the post, the output of which is connected to the receiver, the transceiver of the spacecraft is connected by two radio links to the antenna post, the reference generator is connected to the first input of the time-measuring unit. The problem is solved by the fact that in the known system for measuring the range of the spacecraft, an additional node for the constant memory of commands and a node for the constant memory of range-finding sequences, an OR element, a correlator with a search circuit and an averaging node, the output of which is the output of the system, are additionally introduced. The first output of the operator’s personal computer is connected to the permanent memory node of the commands and the first input of the OR element, the second output of the operator’s personal computer is connected to the permanent memory node of the range-finding sequences and the second input of the OR element. The first input of the correlator with the search circuit is connected to the output of the multiplexer / encoder, the second input of the correlator with the search circuit is connected to the output of the receiver, the output of the correlator with the search circuit is connected to the second input of the time-measuring unit, the third input of the time-measuring unit is connected to the output of the OR element, the output of the measuring unit is connected to the input of the averaging unit.

In FIG. 1 shows a structural diagram of the proposed technical solution. The essence of the proposal is that the range measurement is not interrupted for the time the command is transmitted.

The system contains a personal computer of operator 1, a node for read-only memory of commands 2, a multiplexer / encoder 3, a transmitter 4, an antenna post 5, a transceiver KA 6, a read-only memory node for range-finding sequences 7, a correlator with a search circuit 8, receiver 9, OR 10, time measuring unit 11, the reference generator 12 and the averaging unit 13.

The system works as follows.

From the operator’s personal computer 1, an impulse is transmitted occasionally in automatic or manual mode to read commands from the read-only memory node 2. The command sequence from the read-only memory node 2 is sent to transmitter 4 in the form of a bit signal via multiplexer / encoder 3 and in the form of a sequence of radio pulses to the carrier frequency of the radio line “up” through the antenna post 5 it arrives at the transceiver KA 6. At the time of the absence of commands from the personal computer of the operator 1 is automatically regularly received by them Pulse rangefinder reading sequence of the permanent memory unit 7. ranging sequences ranging sequence also in bit form is supplied to the signal transmitter 4 through multiplexer 3, and is emitted toward the spacecraft 6 through the transceiver antenna post 5.

Therefore, either a command or a ranging sequence is emitted to the transceiver KA 6 without interruptions.

The accepted and identified command sequence on board the spacecraft is sent for execution by the nodes and subsystems of the spacecraft (not considered here). In addition, on the downlink from the spacecraft, the received command is relayed completely to the NKU. The rangefinder sequence received on board the spacecraft is also relayed downlink.

The correlator with the search circuit 8 compares the received and the local sequence coming from the output of the multiplexer 3. The search circuit of the correlator 8 provides a search for the maximum correlation function, which is achieved at the moment of coincidence of the radiated and the received sequences. The “Start” pulse from the output of the OR element 10 starts the time-measuring unit 11 each time a command or rangefinder sequence is launched. The pulse "Stop" from the output of the correlator with the search circuit 8, the work of the time-measuring unit 11 is terminated. The duration of the time interval between the “Start” and “Stop” pulses is proportional to the range of the spacecraft. The measurement of the duration of this time interval is made by counting the number of pulses of the reference generator 12 for the time interval between the pulses "Start" and "Stop".

Therefore, at the output of the time-measuring unit 11 regularly there are digital equivalents of the duration of the measured time interval without interruptions characteristic of the prototype. The results of private measurements are averaged in the averaging unit 13.

The effectiveness of the proposed technical solution can be shown in the following way. Let us denote the result of measuring the duration of the time interval

.

.

Here the index “and” denotes the true value of x _{and the} duration of the time interval, Δ _{i the} error in measuring the true value in the i-th cycle. It is understood that x _and , like the spacecraft range, during the measurement period vary within less than the measurement error. The most significant distortion caused by noise in the path of the received signal.

If teams are sent often enough, which is typical for a non-oriented flight of the spacecraft, then measuring the range according to the prototype becomes impossible. In this case, only one-time measurements are possible, in which the measurement error is Δ _i . Since in the proposed system the range measurements are performed continuously using both command and ranging signals, it is possible to efficiently average the results of k measurements, i∈ (1 ... k), performed at the averaging node 13. Assuming the individual Δ _i are uncorrelated, we obtain:

.

.

- среднее значение погрешности при k измерениях и

.Here

- the average value of the error in k measurements and

.

М - символ математического ожидания.This expression is based on the well-known position of probability theory:

M is a symbol of mathematical expectation.

It is widely known from the theory of measurements (ES Wentzel. Probability Theory. M .: - Higher School, 1999) that

Here, D _p is the variance of the averaged measurement result, and D _in is the variance Δ _i . For k >> 1, the variance of the resulting error D _p tends to zero. This allows one to significantly reduce the random component of the measurement error of the spacecraft range caused by noise. The situation is different when repeated transmission of commands is necessary. Moreover, according to the prototype, the averaging efficiency decreases until the loss of information on the spacecraft range. In accordance with the proposed technical solution, the spacecraft range is measured not only by the range-finding sequence, but also by the command sequence, i.e. without interruptions caused by sending a command. The ranging sequence is a pseudo-random sequence (Pseudo-Noise (PN) Ranging Systems. Issue 2. Recommendation for Space Data Standards (Blue Book), CCSDS 414.1-B-2. Washington, DC: CCSDS, January, 2014). The greatest efficiency of the proposed spacecraft range measuring system is achieved when encoding instructions with a pseudo-random sequence with a bit capacity equal to the bit depth of the rangefinding SRP.

Claims (1)

A spacecraft range measuring system consisting of a spacecraft transceiver and a ground control complex containing an operator’s personal computer, a multiplexer / encoder, a transmitter, an antenna post, a receiver, as well as a time-measuring unit and a reference generator, the output of the multiplexer / encoder being connected to the input the transmitter, the output of which is connected to the input of the antenna post, the output of which is connected to the receiver, the transceiver of the spacecraft is connected by two radio links to the antenna post, the pore generator is connected to the first input of the time-measuring unit, characterized in that it also includes a read-only memory node and a read-only memory node of the ranging sequences, an OR element, a correlator with a search circuit and an averaging node, the output of which is the output of the system, the first output the operator’s personal computer is connected to the read-only memory node of the commands and the first input of the OR element, the second output of the operator’s personal computer is connected to the read-only memory node of the ranging sequences and the second input of the OR element, the first input of the correlator with the search circuit is connected to the output of the multiplexer / encoder, the second input of the correlator with the search circuit is connected to the output of the receiver, the output of the correlator with the search circuit is connected to the second input of the time-measuring unit, the third input is time-measuring node is connected to the output of the OR element, the output of the measuring node is connected to the input of the averaging node.

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