RU2477836C1 - Method for ephemeral provisioning of process for controlling global navigation satellite system spacecraft - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention can be used for ephemeral provisioning of a process for controlling global navigation satellite system (GNSS) spacecraft. A low-orbiting spacecraft fitted with apparatus for synchronising the on-board time scale with the system time scale, apparatus for determining orbit parameters from ground-based radio beacons and consumer navigation equipment is taken to an orbit. During orbit flight thereof, the on-board time scale is synchronised with the system time scale of the GNSS; orbit parameters are determined from radio beacon signals; a GNSS spacecraft navigation message signal is received; Doppler frequency shift of the message signal is measured. Orbit parameters of the low-orbiting spacecraft and the measured values of the Doppler frequency shift of the message signal on-board the low-orbiting spacecraft are used to determine the orbit of navigation GNSS spacecraft and then transmitted for reception thereof at the GNSS spacecraft.

EFFECT: high measurement accuracy.

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Description

The invention relates to space navigation and can be used to calculate the ephemeris of spacecraft (SC) of the global navigation satellite system (GNSS).

The level of technology.

A known method of ephemeris support the control process of the GNSS spacecraft, in which the parameters of the orbits and ephemeris of each spacecraft is determined using an extensive network of ground-based monitoring measuring stations [1, p.16-17]. Under ephemeris support is understood the definition and prediction of the motion parameters of all GNSS spacecraft with the aim of subsequent transmission of this information by spacecraft in a navigation message to consumers [1, p.15]. The motion parameters of the GNSS spacecraft transmitted in the navigation message are called ephemeris information [1, p.14].

The network of ground stations does not provide constant interaction of the GNSS spacecraft with the ground-based GNSS control complex, therefore updating (clarification) of the ephemeris information on board the GNSS spacecraft is carried out periodically. So, in GNSS GLONASS, the technology of ephemeris support is used, in which the ephemeris information is updated once or twice a day, and the duration of the forecasted flight interval is about two turns, i.e. about one day [1, p.303]. The initial information for calculating the ephemeris information is the values of the current navigation parameters of the spacecraft motion, measured by ground control stations and transferred to the GNSS coordination and computing center, in which the orbits are determined and the ephemeris information is calculated. Moreover, for high-precision calculations of ephemeris information, 10 ... 12 measurement sessions are performed daily for each GNSS spacecraft [1, p.302].

The disadvantages of the described method are:

- a large number of daily measurements of current navigation parameters performed by ground-based monitoring measuring stations and necessary to calculate ephemeris information with the required accuracy (for 24 GNSS spacecraft, about 240 measurement sessions of current navigation parameters are required);

- the appearance of an error in the GNSS spacecraft ephemeris arising due to the difference in the predicted physical state of the space environment from the actual state in the interval of spacecraft prediction and calculation of ephemeris, due to the fact that the duration of the ephemeris forecast interval is about one day [1, p.303].

The known method of ephemeris support, which allows to increase the accuracy of the ephemeris, in which on-board equipment for inter-satellite measurements (BAMI) is used to measure the parameters of the mutual motion of the GNSS spacecraft, determine (refine) the parameters of their orbits [1, p. 48-458], designed to solve the following problems : measurement of parameters of mutual motion of the GNSS spacecraft transmitting ephemeris and time-frequency corrections to the GNSS spacecraft network. The parameters of mutual motion are measured by measuring the pseudorange and pseudo velocity of some GNSS spacecraft relative to others. The method allows to reduce the error of the ephemeris due to the frequent refinement of the parameters of the orbits using BAMI and the subsequent calculation of the ephemeris by the onboard control system of each GNSS spacecraft.

The method provides the determination of the parameters of the mutual position of the spacecraft of the GNSS orbital group. However, for high-precision navigation definitions of GNSS navigation information consumers, it is necessary to determine the parameters of the spacecraft orbits in the coordinate system associated with the rotating Earth, in other words, to bind the parameters of the GNSS orbital constellation to the coordinate system of the navigation information consumer. Binding is achieved by determining the orbit of one or more spacecraft using ground control measuring stations. After transferring on board some spacecraft of ephemeris information calculated from measurements of ground stations, the method allows you to refine the parameters of the orbits and ephemeris of all the spacecraft of the GNSS orbital group relative to this spacecraft. Such a spacecraft can essentially be considered as a spacecraft reference, with respect to which the GNSS spacecraft orbits are directly refined. To ensure the continuous maintenance of high accuracy of the GNSS spacecraft ephemeris relative to the Earth-related coordinate systems, it is necessary to maintain the high accuracy of the ephemeris of one or several spacecraft standards, which necessitates the measurement of the current navigation parameters of their orbits using ground control measuring stations.

The disadvantages of the method are:

- the energy costs of the GNSS spacecraft during inter-satellite measurements;

- the need for measurements of the current navigation parameters of the GNSS spacecraft using an extensive network of ground-based monitoring measuring stations.

The need to measure ground stations leads to resource costs, firstly, directly for the ground complex to measure current navigation parameters, calculate the ephemeris and transfer them onboard the spacecraft, and secondly, to maintain an extensive network of ground station measuring stations in an operational state. Since measuring stations are expensive technical systems, the cost of resources is significant. In addition, not all spacecraft of the GNSS orbital group can be visible simultaneously by one spacecraft-standard. So, when surveying from any spacecraft of the GNSS orbital group, some of them are covered by the Earth, therefore it is impossible to calculate the ephemeris of all the spacecraft of the GNSS orbital group directly with respect to one spacecraft-standard. It causes:

- or the need to clarify the ephemeris of those GNSS satellites that are invisible to the CA standard by inter-satellite measurements relative to other spacecraft whose ephemeris are calculated directly relative to the CA standard, which leads to the accumulation of the error in the calculation of ephemeris during inter-satellite measurements;

- or the need to use several spacecraft standards, which leads to an increase in the cost of resources of the GNSS ground-based control complex for calculating the ephemeris of several spacecraft-standards.

A known prototype method of the ephemeris support of the GNSS spacecraft control process, in which the spacecraft timeline of each spacecraft is synchronized with the system timeline, pseudorange and spacecraft pseudo-velocities are measured using the onboard inter-satellite measurement equipment, in which the low-orbit spacecraft is put into orbit with forward or reverse inclination the apparatus on which the equipment for synchronizing the on-board time scale with the GNSS system time scale, the measuring equipment for current navigation parameters of motion of terrestrial stationary television radio stations on the basis of terrestrial television signals and determining from them the parameters of the orbit of the low-orbit spacecraft, the on-board equipment for inter-satellite measurements, during orbital flight, the on-board time scale of the low-orbit spacecraft is synchronized with the GNSS system time scale, the orbits of the low-orbit television spacecraft are determined from the signals radio stations, conduct inter-satellite measurements of space motion parameters of the navigation system of a relatively low-orbit spacecraft, a navigation message is formed on board the low-orbit spacecraft containing its orbit parameters measured by television signals, which are transmitted and received on board the spacecraft of the navigation system, and their orbits and parameters are determined onboard GNSS spacecraft control systems ephemeris according to inter-satellite measurements and orbital parameters of a low-orbit spacecraft.

In the prototype method, the orbit of a low-orbit spacecraft is determined by measuring the signal parameters of some terrestrial radio stations, which are hereinafter referred to as terrestrial beacons.

The disadvantage of the prototype method is the need for inter-satellite measurements between GNSS spacecraft and low-orbit spacecraft to determine the parameters of the GNSS spacecraft orbits. This leads, firstly, to the necessity of installing on-board equipment of inter-satellite measurements on low-orbit spacecraft, and secondly, to the cost of GNSS spacecraft energy resources for carrying out inter-satellite measurements.

Disclosure of the invention.

The problem to which the claimed invention is directed, is to ensure high accuracy of the GNSS spacecraft ephemeris due to the frequent refinement of the GNSS spacecraft orbits without inter-satellite measurements and measurements of the current GNSS spacecraft navigation parameters by ground-based measuring stations.

The main technical result achieved by the claimed invention is to continuously maintain high accuracy of the ephemeris of the spacecraft of the navigation system by continuously updating the parameters of their orbits from the measured values of the signal parameters of the navigation message.

The essence of the invention lies in the fact that for the ephemeris support of the process of controlling the spacecraft of the global navigation satellite system, the on-board time scale of each spacecraft is synchronized with the system time scale, the on-board control systems of the spacecraft of the navigation system calculate the ephemeris according to their orbit, in orbit with direct or by reverse inclination they bring out a low-orbit spacecraft on which the board synchronization equipment is placed the time scale with the system time scale of the global navigation satellite system, the equipment for measuring the current navigation parameters of motion from the signals of terrestrial beacons and determine the parameters of the orbit of the low-orbit spacecraft from them, during its orbital flight, the on-board time scale of the low-orbit spacecraft is synchronized with the system time scale of the global navigation satellite systems that determine the orbit parameters of a low-orbit spacecraft based on the signals of radio beacons according to the invention, consumer navigation equipment is installed on the low-orbit spacecraft, with which the navigation message of the spacecraft of the global navigation satellite system is received, the Doppler frequency shift of the navigation message signal is measured, on-board low-orbit spacecraft the orbit parameters of the navigation spacecraft are calculated from the measured values Doppler frequency shift and low-orbit parameters nogo spacecraft broadcast calculated orbital parameters and take them on board spacecraft navigation system.

The Doppler frequency shift of the navigation message signal, measured on board the low-orbit spacecraft, is essentially the current navigation parameter used in the calculation of the GNSS spacecraft orbit parameters.

The essential features characterizing the invention

1. Measurement of the current navigation parameters of the GNSS spacecraft motion on a low-orbit spacecraft based on the received signal of the GNSS spacecraft navigation message.

2. The following set of sequential steps to calculate the ephemeris of the GNSS satellite:

- synchronization of the onboard time scale of a low-orbit spacecraft with the GNSS system timeline by using standard ground stations used to synchronize the GNSS spacecraft on-board timelines with the system timeline;

- determination of the orbit parameters of the low-orbit spacecraft from the current navigation parameters, measured by signals from ground-based radio beacons;

- receiving a GNSS satellite navigation message signal and measuring the Doppler frequency shift of the message signal by the low-orbit spacecraft onboard equipment;

- determination of the GNSS spacecraft orbit parameters aboard a low-orbit spacecraft from measurements of the Doppler frequency shift of the navigation message signal and the low-orbit spacecraft orbit parameters;

- translation of the calculated parameters of the GNSS spacecraft orbit from the low-orbit spacecraft and their reception onboard the GNSS spacecraft;

- calculation of the ephemeris of the navigation spacecraft onboard control systems according to the orbit parameters calculated on the low-orbit spacecraft.

Signs that distinguish the claimed method from the prototype method:

1) measurement of the current navigation parameters of the GNSS spacecraft motion on a low-orbit spacecraft by the received signal of the navigation message without inter-satellite measurements;

2) determination of the orbit parameters of the GNSS spacecraft on board the low-orbit spacecraft.

GNSS satellite navigation emits continuously. The claimed method allows to clarify onboard a low-orbit spacecraft the orbit parameters of the navigation spacecraft after receiving each navigation message transmitted to it. It can be argued that the claimed method allows you to specify the parameters of the orbits of the GNSS spacecraft located in the radio-visibility zone of the low-orbit spacecraft, continuously. Due to the continuity of the refinement of the orbit parameters of the GNSS spacecraft, the claimed method allows to maintain high accuracy of the ephemeris continuously.

For the implementation of the reception and processing of navigation messages of the GNSS spacecraft, necessary for the implementation of the claimed method, the energy costs of the low-orbit spacecraft are small.

The prototype method provides the ability to refine the ephemeris after inter-satellite measurements between the low-orbit spacecraft and the GNSS spacecraft. Since airborne energy resources are limited, inter-satellite measurements and refinement of the ephemeris in accordance with the prototype method can be carried out periodically. The claimed method provides the ability to continuously refine the parameters of the orbit of the GNSS spacecraft, which improves the accuracy of the ephemeris in comparison with the prototype method.

The advantages of the claimed invention are:

- improving the accuracy of the GNSS spacecraft ephemeris located in the radio-visibility zone of a low-orbit spacecraft by continuously measuring the current navigation parameters of their motion and determining the orbits from the emitted navigation signals;

- the ability to continuously maintain high accuracy of the GNSS satellite ephemeris due to the continuous measurement of the current GNSS satellite navigation parameters by the signal of the navigation message;

- the absence of the need for energy costs of GNSS spacecraft to ensure continuous maintenance of high accuracy of GNSS spacecraft ephemeris.

A block diagram of a device intended for installation on board a low-orbit spacecraft and the implementation of the proposed method is presented in the drawing.

The device comprises an antenna 1 directed toward the center of the Earth, a transceiver 2, an on-board digital computer (BTSC) 3, equipment for synchronizing the on-board timeline with the system timeline of the global navigation satellite system 4, equipment 5 for measuring current navigation parameters of movement from the signals of beacons and determining from them the orbit parameters of the low-orbit spacecraft, consumer navigation equipment 6, receiving antenna 7 and transmitting antenna 8, both directed towards nomic space opposite the center of the Earth.

In this case, the first input of the transceiver 2 is connected to the output of the antenna 1, and the second input is connected to the first output of the digital computer 3, the first output of the device 2 is connected to the input of the antenna 8, the second output of the transceiver 2 is connected to the first input of the 3, second input of the digital computer 3 is connected to the output of the equipment 4, the third input of the computer 3 is connected to the output of the equipment 5, the fourth input of the computer 3 is connected to the output of the equipment 6, the second output of the computer 3 is connected to the input of the equipment 4, the third output of the computer 3 is connected to the input of the equipment 5, the fourth output of the computer 3 connection n with the first input of the equipment 6, the second input of the equipment 6 is connected to the output of the antenna 7.

The device operates as follows.

The equipment 4 synchronizes the on-board time scale with the system time scale. In this case, the signals corresponding to the time values of the on-board scale, necessary for calculating the corrections of the on-board scale to the system time scale, are received from the output of the equipment 4 to the second input of the digital computer 3, which generates a radio signal, which then comes from the first output of the digital computer 3 to the second input of the transceiver 2, then from the first output of the device 2 to the input of the antenna 1, which transmits a radio signal in the direction of the ground control station that performs synchronization. Antenna 1 receives signals of the corrections of the on-board scale to the system time scale, calculated and transmitted by the ground control station, which are received from the output of the antenna 1 to the first input of the transceiver 2, then from the second output of the device 2 to the first input of the digital computer 3, and then from the second output BTsVM 3 at the input of equipment 4.

The equipment 5 determines the orbit parameters of the low-orbit spacecraft based on the signals of radio beacons. In this case, the antenna 1 receives the signals of the beacons, which from the output of the antenna 1 go to the first input of the transceiver 2, then from the second output of the device 2 to the first input of the digital computer 3, then from the third output of the digital computer 3 to the input of the equipment 5, which measures the values of the current navigation parameters from signals and beacons determines the parameters of the orbit.

The navigation equipment of consumer 6 receives the signals of the navigation messages of the GNSS spacecraft coming from the output of the antenna 7, which then go to the fourth input of the digital computer 3. At the same time, the signals of the on-board time scale necessary for measuring the Doppler frequency shift of the signal of the navigation message come from the output of the equipment 4 to the second input of the digital computer 3, which measures the Doppler frequency shift of the signal of the navigation message.

BTsVM 3 calculates the orbit parameter of the navigation spacecraft from the measured values of the Doppler frequency offset and the orbit parameters of the low-orbit spacecraft, generates a message with the GNSS spacecraft orbit parameters. The digital computer 3 generates a message signal containing the orbit parameters of the GNSS spacecraft, which comes from the first output of the digital computer 3 to the second input of the transceiver 2, and then from the first output of the device 2 to the input of the antenna 8. Antenna 8 transmits a navigation message to receive it on the spacecraft GNSS spacecraft, the orbit parameters of which are calculated.

The digital computer 3 controls the operation and interaction of all subsystems of the device. The GNSS spacecraft orbit parameters are determined from the measured values of the Doppler frequency shift or the corresponding radial velocity values by the methods described in [2, p.145-185].

Literature

1. GLONASS. The principles of construction and operation. / Ed. A.I. Petrova, V.N. Kharisova. - M .: Radio engineering, 2005.

2. Patent No. 2390730 of the Russian Federation, IPC ³ G01C 21/24. Method of ephemeris support of the spacecraft control process of the global navigation satellite system. / Strelnikov S.V., claimed April 6, 2009, publ. 05/27/2010.

3. Ivanov N.M., Lysenko L.N. Ballistics and spacecraft navigation. - M.: Bustard, 2004.

Claims (1)

The ephemeris support method for the spacecraft control process of the global navigation satellite system is that for the ephemeris support spacecraft control process of the global navigation satellite system, the onboard time scale of each spacecraft is synchronized with the system time scale, the ephemeris are calculated in the onboard control systems of the spacecraft of the navigation system according to the parameters of their orbit, into orbit with a forward or reverse inclination they bring out a low-orbit spacecraft, on which the equipment for synchronizing the onboard time scale with the system time scale of the global navigation satellite system, the equipment for measuring the current navigation parameters of motion from the signals of ground-based beacons and determining the orbit parameters of the low-orbit spacecraft are placed on them, during their orbital flight the onboard scale is synchronized time of a low-orbit spacecraft with a system time scale of global navigation satellite of an infrared system, the orbit parameters of the low-orbit spacecraft are determined by signals from ground-level radio beacons, characterized in that the consumer’s navigation equipment is installed on the low-orbit spacecraft, by which the navigation message of the spacecraft of the global navigation satellite system is received, the Doppler frequency offset of the navigation message signal is measured, on board low-orbit spacecraft according to the measured values of the Doppler frequency shift and the parameters of the orbit of a low-orbit spacecraft broadcast calculated orbital parameters and take them on board spacecraft navigation system.