RU2580827C1 - Method for angular orientation of object - Google Patents

Abstract

FIELD: space industry.

SUBSTANCE: invention relates to space navigation and can be used in systems for obtaining information on navigation parameters of space vehicles (SV) at geostationary orbits (GSO) relative to the geocentric coordinate system (GCS). Specified result is achieved due to the fact that signals of inter-satellite measurements performed by the unmanned spacecraft (USC) on-board equipment are used as signals with Doppler frequency, while angular position of the object (SC) is determined within the time interval during which the object is in the area of radio-navigation field of on-board equipment signals from no less than four unmanned spacecrafts.

EFFECT: technical result consists in high-precision measurement of coordinates and angular orientation of spacecraft axes on geostationary orbit by signals from on-board equipment for inter-satellite measurements by navigation space vehicles (NSV) GLONASS.

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Description

The invention relates to space navigation and can be used in systems for obtaining information about the navigation parameters of spacecraft in geostationary orbits (hereinafter - SC) relative to the geocentric coordinate system (GCC).

There is a method of inertial navigation of the spacecraft, according to which the navigation parameters, namely the coordinates of the location of the spacecraft, as well as the components of the velocity and acceleration vectors are determined by integrating the components of the indicated navigation parameters measured during the spacecraft motion [1, 2]. In any device for implementing the inertial navigation method, as a rule, several measurements are carried out, for each of which certain devices are used: a) when measuring the angular direction, gyroscopic devices; b) when measuring linear acceleration - suspended inert masses in accelerometers; c) when measuring time - precision sources of a stabilized frequency [3]. The main disadvantage of this method is the error accumulating over time of determining the resulting data on the value of the vector of the navigation state of the spacecraft and the need for very accurate knowledge of the initial values of the coordinates of the spacecraft.

As a result of the foregoing, in order to correct the determination of the spacecraft’s location, one should periodically conduct sighting from the Earth by a radar or quantum-optical systems and determine its coordinates by calculation. However, as a result of navigational reconciliations from the Earth, the angular coordinates of the spacecraft are not determined and there is a great dependence on the infrastructures of ground-based control systems (GCC).

There is also a known method of geomagnetic navigation of a spacecraft, which includes comparing the physical parameters of the magnetic field measured by the sensors of geomagnetic information on board the object with similar parameters of the magnetic field, the distribution of which in space relative to the Earth is known in advance (a priori information). A priori information about the Earth's magnetic field is recorded on geographical maps taking into account the flight altitude, as well as in tables, in computer memory systems, or in an analytical form. A device for implementing this method (geomagnetic navigation system) includes geomagnetic information sensors, angle information sensors, systems of comparison, correction, calculation and output of output signals [4]. The disadvantage of the method of geomagnetic navigation is the presence of changes over a wide range of informational properties of the Earth’s magnetic field depending on the geographical latitude and distance from the planet and, therefore, the possible use of this method only with a small distance from the Earth.

There is also a method of calculating the zenith distances of two stars based on measurements of the angles of orientation of the spacecraft and the orientation of the optical axes of the astroizing devices relative to the associated coordinate system. The navigation parameters of the spacecraft are determined during the static processing of the measurement information for the measured section. In each cycle, the orientation angles are additionally specified. Based on the updated values of the angles and information on the orientation of the optical axes of the astroizing devices, the values of the zenith distances of the stars are specified. Use the adjusted values when solving a navigation problem in the current period.

A common drawback of solving the navigation problem using the above methods of autonomous navigation is the low accuracy of determining the motion parameters of the center of mass of the spacecraft, due to instrumental and methodological errors of onboard navigation measurements, incomplete consideration in the navigation algorithms of forces actually acting on the spacecraft in flight, errors of physical constants that determine the law movement [5].

Closest to the claimed is a method of angular orientation of the object on the radio navigation signals of navigation spacecraft (NSC), based on the reception of signals from n NSC two or more antenna-receiving devices located parallel to one or two axes of the object, the selection of the signal with Doppler frequency, determining the raid phases for the measurement time interval, determining the coordinates and angular position of the object [6].

The disadvantage of this method is the inability to determine the orientation of the spacecraft, because the scope of the radio navigation signals of the spacecraft is limited and aimed at consumers of the Earth's navigation information (the shape of the radiation pattern of the spacecraft's on-board antennas limits the coverage of global navigation satellite systems to near-Earth space).

The basis of the invention is the task of high-precision measurement of the coordinates and angular orientation of the axes of the spacecraft of the geostationary orbit, using signals from the onboard inter-satellite measurement equipment (BAM) of the GLONASS navigation spacecraft.

The problem is solved in that in the method of angular orientation of an object, according to which signals from n navigation spacecraft (NSC) are received by two or more antenna receivers located parallel to one or two axes of the object, signals with a Doppler frequency are extracted, phase shifts between pairs of antenna receivers and determine the angular position of the object for the measurement time interval, according to the invention, as signals with a Doppler frequency, signals of inter-satellite measurements of the sides are used equipment of the spacecraft, and the angular position of the object is determined for the time interval during which the object is in the radio navigation field of the signals of inter-satellite measurements of onboard equipment from at least four spacecraft.

In FIG. 1 shows the signal propagation area of BAMI NKA, in FIG. 2 shows an exemplary view of the radiation pattern of the antenna system BAM of the Glonass-M NSA; in FIG. 3 is a graph of the number of simultaneously observed spacecraft through the BAMI channel: GLONASS (solid) and GPS (intermittent).

The invention consists in the following.

Classical methods for determining position using global navigation satellite systems (GNSS) suggest the presence of simultaneous measurements from at least four satellite systems of one system (GLONASS or GPS), due to the number of unknowns - 3 coordinates X, Y, Z and time delay Δt. When using measurements from two GNSSs, the minimum number of NCA will be at least 5 (2 NCA of one and 3 NCA of the other system). The number of unknowns in this case increases to 5, i.e. 3 coordinates X, Y, Z and 2 time delays Δt ₁ and Δt ₂ , due to the fact that the time scales of different GNSS are not synchronized with each other.

In the general case, when determining the angular coordinates of an object, the results of measurements of the cosines of the angles between the base vector of the object and the direction vector at the i-th GNSS GNU are used. The phase shift of the satellite’s signal received by two separated antennas of the object, and the cosine of the angle between the base vector and the direction vector to the satellite are related by the expression:

where λ is the wavelength of the signal NKA,

φ is the phase shift of the NCA signals between the separated antennas (antenna-receiving devices) of the object,

B is the length of the base of the antenna-receiving devices of the object,

α is the angle between the base vector of the object and the direction vector to the satellite.

Expression (1) is the equation of interferometric methods (the use of spaced receiving antennas) and is widely used in the theory of phase direction finders, multi-base interferometers, and antenna arrays [7, 8].

When determining the angular coordinates of the spacecraft (object), the direction cosines of the vector base can be determined from the equation based on the scalar product of vectors:

where λ _i is the wavelength of the BAMI signal of the i-th spacecraft;

F is the phase shift of the BAMI signals of the spacecraft between the pairs of the antenna-receiving devices of the spacecraft;

ΔR is the difference in the signal path of BAMI NSA between pairs of antenna-receiving devices of the spacecraft;

X, Y, Z - coordinates of the vector-base of the spacecraft (object);

k _{xi, yi, zi} are the direction cosines of the direction vectors between the spacecraft and the ith spacecraft, equal to:

where x, y, z are the coordinates of KA in the GCC;

x _ci , y _ci , z _ci - coordinates of i-satellite in the HCC;

- расстояние между КА и i-m НКА;

- the distance between the spacecraft and im NKA;

i is the number of the navigation spacecraft, i = 1, 2, ..., n.

The coordinates of the spacecraft are determined on the basis of measurements of the delays of the BAMI signals received from the board of each satellite. To carry out such measurements, the BAMI signals of each satellite are modulated by pseudorandom sequences (PSP) and have a similar structure to radio navigation signals. The difference is the bit length of digital information, which is 1 ms in BAMI signals, and 20 ms in radio navigation signals.

BAMI NKA GLONASS uses frequency, code and time separation of signals. For the transmission of BAMI signals, 7 letter frequencies are used, and each letter frequency uses its own pseudo-random sequence. The duration of the session is 20 s, which is divided into 4 time intervals of 5 s. In each time interval, a signal is transmitted by two antipodal NSCs in each plane (6 NSCs, each with its own modulating SRP code) simultaneously transmit, the rest of the NSCs in this time interval receive a signal. BAMI works on a rigid cyclogram. On each satellite, 5 seconds - signal transmission in its own time interval, 15 seconds - reception. At each hourly interval BAMI works 15 minutes, the remaining 45 minutes - a break.

Thus, navigational measurements based on BAMI signals are not much different, in essence, from measurements on radio navigation signals. In structure, the receiver of the signals of the inter-satellite radio link has much in common with the receiver of the radio navigation signals, which is due to the similar structure of the signals and the functional purpose. In the part of the BAMI channel, the tasks of measuring the current navigation parameters should be solved taking into account the characteristics of the signal format in the BAMI channel.

Since the angular position of the spacecraft is determined for the time interval during which the spacecraft is located in the radio navigation field of the BAMI signals from at least four spacecraft, the possibility of angular orientation of the spacecraft is limited based on the calculation of the duration and number of simultaneously observed spacecraft. The antenna radiation pattern of the BAMI NKA is conical with a dip directed to the center of the Earth, which ensures the same power of signals received from all visible NKA. BAMI NKA GLONASS forms two maximums of the antenna radiation pattern in the range of angles from 18 ° to 70 ° (Fig. 2) from the normal each [9]. For the GPS satellite, it is assumed that the lower and upper boundaries of the radiation pattern of the antenna emitting BAMI signals are 16.2 ° and 32.5 °, respectively [10]. Based on the shapes of the radiation patterns of the BAMI antennas and the BAMI signal propagation region, this angular orientation method is effective for spacecraft whose orbit heights are close to geostationary and higher.

As an example, we consider the formation of a radio navigation field of BAMI signals for spacecraft of geostationary orbits, separately for each GNSS and their joint grouping. All calculations will be carried out in the geocentric coordinate system (GCC) OXYZ, the center of which is aligned with the center of mass of the Earth, the OZ axis is directed along the Earth's rotation axis toward the North Pole, the OX axis lies in the plane of the Earth's equator and is connected with the Greenwich meridian, the OY axis complements the system coordinates to the right (Fig. 1). In GNSS GLONASS, the geocentric mobile coordinate system is defined as PZ-90, and in GNSS GPS it is defined as WGS-84. In FIG. Figure 1 shows the relative positions of the spacecraft and spacecraft in geostationary orbits (the shaded area is the radiation pattern of the BAMI spacecraft). Given that the orbit of the GLONASS satellite in the geocentric coordinate system is 25478000 m, the GPS satellite is 26578000 m, the geostationary orbits are 42164000 m, the Earth's radius is 6378000 m and using elementary geometric constructions and the sine theorem, we find the duration and number of simultaneously observed spacecraft from BAMI channel. The position of the GLONASS and GPS in orbit are calculated on the basis of almanacs published in the public domain. Calculation algorithms are given in the corresponding Interface control documents.

The results of calculations of the duration and quantity simultaneously observed by the NCA along the BAMI channel in the eight-day interval are given in Table. 1 and in the graphs (Fig. 3), taking into account the intermittent nature of the radiation. The calculation was carried out on an eight-day interval (17 turns of the GLONASS satellite), since it is precisely this interval that is the repeatability interval of the orbit of the GLONASS satellite.

As can be seen from the calculation results presented in table. 1 and in FIG. 3, spacecraft navigation determinations from BAMI signals of the spacecraft are possible even according to one GLONASS system (the radio visibility of at least 4 spacecraft is 75.3% of eight days). In this case, the accuracy of determining the spatial orientation of the spacecraft will be no more than 20 angular minutes with an interferometer base of 0.7 m, and the error in measuring absolute coordinates is less than 10 m.

Based on the research results, it can be concluded that it is advisable to use BAMI signals for high-precision navigation of the spacecraft, which significantly increases the accuracy of determining the location and spatial orientation of the spacecraft using interferometric methods, especially in the conditions of its autonomous functioning without the support of the ground-based control complex.

Information sources

1. USSR Copyright Certificate No. 1098383, publ. 05/23/85

2. W. Wrigley, R. Woodbury, J. Govorka. Inertial navigation, per. with English, ed. G.O. Friedlander. - M .: Publishing house of foreign literature, 1958

3. Navigation, guidance and stabilization in space, count. authors (C.S. Draper, W. Wrigley, etc.), ed. J.E. Miller, per. from English., M.: Mechanical Engineering, 1970.

4. B.Z. Mikhlin, V.P. Seleznev, A.V. Seleznev. Geomagnetic navigation. - M.: Mechanical Engineering, 1976.

5. Patent RU 2171969, IPC ⁶ G01C 21/24. publ. 08/10/2001.

6. Patent RU 2122217, IPC ⁶ G01S 5/02. publ. 11/20/1998.

7. Belov V.I. Theory of phase measuring systems. / Ed. G.N. Glazov. - Tomsk: Tomsk State Academy of Control Systems and Radio Electronics, 1994. - 144 p.

8. Denisov V.P., Dubinin D.V. Phase direction finders: Monograph. - Tomsk: Tomsk State University of Control Systems and Radio Electronics, 2002. - 251 p.

9. GLONASS. The principles of construction and operation / Ed. A.I. Perova, V.N. Harisova. - Ed. 4th, rev. - M .: Radio engineering, 2010.

10. GNSS Satellite Autonomous Integrity Monitoring (SAIM) using inter-satellite measurements / Xu, H., Wang, J., Zhan, X. // Advancesin Space Search. - Vol. 47, Issue 7. - April 2011 .-- P. 1116-1126.

Claims (1)

A method of angular orientation of an object, according to which signals from n navigation spacecraft are received by two or more antenna-receiving devices located parallel to one or two axes of the object, signals with a Doppler frequency are extracted, phase shifts between pairs of antenna-receiving devices are measured, and the angular position of the object is determined for the measurement time interval, characterized in that as signals with a Doppler frequency, the signals of inter-satellite measurements of the onboard equipment of navigation space vehicles are used gates, and the angular position of the object is determined over the time interval during which the object is in the region of the radio navigation field of the signals of inter-satellite measurements of on-board equipment from at least four navigation spacecraft.

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