RU2671921C2 - Method for determining error in trajectory measurements of interplanetary spacecraft due to propagation of radio signals in earth's ionosphere and interplanetary plasma - Google Patents

Abstract

FIELD: astronautics.SUBSTANCE: invention relates to the tracking of the flight of interplanetary spacecrafts (2), in case of errors introduced by the passage of radio signals from the interplanetary spacecraft (at f01 frequency) and quasar (1) close to it on the celestial sphere (at f01 and f02 frequencies) through ionized medium (8). Using Δf1 = f01- fpr1 displacement of the fpr1 frequency received from the quasar and the two-frequency method, the error in measuring the speed of the interplanetary spacecraft is determined, as well as the integral electronic concentration of medium (8) and, by its magnitude, the time delay of the signal with f01 frequency. Receiving points (9) are arranged at the vertices of a rectangular triangle-interferometer with three extra-long bases: in the azimuthal, angle and hypotenuse planes. Signals received by the interferometer, emitted by the quasar at f02 frequency, are processed using adjustable delay blocks and correlation functions. As a result, the location of quasar (1) is determined exactly and unambiguously.EFFECT: technical result of the invention is an increase in the reliability of the determination of the errors of the trajectory measurements of interplanetary spacecrafts.1 cl, 3 dwg

Description

The proposed method relates to the field of astronautics, and in particular to systems of trajectory measurements of interplanetary spacecraft.

Known methods for determining errors in trajectory measurements of interplanetary spacecraft (RF patents Nos. 2.107.306, 2.578.003 C1, 31663 U1; US patent No. 7.197.381; US application No. 2.010.012.4895; Yakovlev OI Space radiophysics, M .: 1998, 432 p. And others).

Of the closest to the proposed one is the "Method for determining errors in trajectory measurements of interplanetary spacecraft due to the propagation of radio signals in the Earth's ionosphere and interplanetary plasma" (RF patent No. 2.578.003, B64G 3/00, 2016), which is chosen as a prototype .

It is known that in practice, when conducting trajectory measurements of interplanetary spacecraft (MCA), they use the measurement of two motion parameters of the spacecraft — the inclined range to the spacecraft R and the radial velocity component of the spacecraft relative to the measuring station R, which are sequentially measured by several geographically spaced measuring stations (IS) [4 ].

входят погрешности, вызываемые распространением радиоволн в ионосфере Земли и ионизированной межпланетной плазме.The composition of the measurement error R and

Includes errors caused by the propagation of radio waves in the Earth’s ionosphere and ionized interplanetary plasma.

уменьшаются и по мере их уменьшения доля погрешностей за счет распространения радиоволн в суммарных погрешностях траекторных измерений увеличивается. Погрешности распространения становятся сравнимыми по величине с аппаратурными погрешностями и даже превышают их.With the improvement of space technology, instrument errors of measurements of R and

decrease and as they decrease, the share of errors due to the propagation of radio waves in the total errors of the trajectory measurements increases. Propagation errors become comparable in magnitude with the hardware errors and even exceed them.

Inaccuracy of trajectory measurements due to the propagation of radio waves in practice is carried out by calculation. The accuracy of the results is very low. Therefore, an urgent task is the real measurement of errors due to the propagation of radio waves by objective methods with the necessary accuracy. For these purposes, the two-frequency method is used in ultra-long base radio interferometry (VLBI) [3].

As a result of the correlation processing of radio signals received from the MCA and the reference quasar, located at a minimum angular distance from it with precisely known coordinates, which serves as an information basis for determining the relative angular position of the MCA and the quasar in the celestial sphere. The exact positions of the quasars used in the measurements are given by the corresponding catalogs of quasars [5].

The difference in the position of a quasar taken from the catalog and measured by a super-long base radio interferometer (VLBI) is caused by measurement errors due to the propagation of radio signals through the interplanetary plasma and the Earth’s ionosphere.

An object of the invention is to increase the reliability in measuring the errors of trajectory measurements of the MCA caused by the propagation of measuring radio signals through an ionized medium, by accurately and unambiguously determining the location of the nearest reference quasar.

The problem is solved in that the method for determining errors in trajectory measurements of interplanetary spacecraft arising from the passage of a radio signal through the Earth’s ionosphere and interplanetary plasma, which consists, in accordance with the closest analogue, in the process of conducting trajectory measurements of the range and radial velocity component MCA, in addition to measuring signals from MCA at a frequency f _o1 , receive signals from a quasar at a frequency f ₀₁ emitted by it and a frequency f ₀₂ , significantly different from frequency f ₀₁ while providing a minimum time shift between measurements from the MCA and the quasar, choose the angular position of the quasar so that the projection of its position on the celestial sphere is as close as possible to the position of the MCA during trajectory measurements so that the signal paths from the MCA and the quasar to the measuring station practically coincided by the measured values of the frequencies f _CR1 and f _CR2 received from the quasar, determined by the two-frequency method, the offset of the frequency f _CR1 relative to the frequency f ₀₁ equal to Δf ₁ , as measured the values of the frequencies f _CR1 and f _CR2 received from the quasar, _{which is} equal to the error in the MCA speed measurements due to the practical coincidence of the signal paths from the MCA and the quasar, in addition, the integral electron concentration of the quasar - measuring station path is determined by the frequency offset Δf ₁ , and by its magnitude calculated time delay Δt ₀₁ of the signal f which is substantially equal to the distance measurement error Δt, where C - velocity of light, when the ICA trajectory measurements obtained data is transmitted to the ballistic tse Tp together with the results of trajectory ICA measurements to calculate the trajectory of the ICA is different from the closest analog by the fact that collection points arranged in a rectangular triangle is formed radiointerferometer three VLB in azimuth, elevation and hypotenuse planes, respectively, receive signals from the quasar to f ₀₂ frequency measure the phase difference between them:

where d ₁ , d ₂ , d ₃ - ultra-long measuring base;

λ is the wavelength with a frequency f ₀₂ ;

α, β, γ - azimuth, elevation and orientation angle of the quasar,

form phase scales of readings of the angular coordinates α, β, γ: accurate, but ambiguous, multiply the signal received by the second point with the signal received by the first point and passed through the first block of adjustable delay, a low-frequency voltage proportional to the first correlation function R ₁ (τ) where the τ-bearing time delay, the time delay is changed until the maximum value of the first correlation function R ₁ (τ) is obtained, which corresponds to the equality τ = τ _z1 , and the azimuth of the quasar is determined

multiply the signal received by the third point with the signal received by the first point and passed through the second adjustable delay unit, select a low-frequency voltage proportional to the second correlation function R ₂ (τ), change the time delay τ to obtain the maximum value of the second correlation function R ₂ (τ), which corresponds to the equality τ = τ _З2 , and determine the elevation angle of the quasar

multiply the signal received by the second point, with the signal received by the third point and passed through the third adjustable delay unit, select a low-frequency voltage proportional to the third correlation function R ₃ (τ), change the time delay τ to obtain the maximum value of the third correlation function R ₃ (τ ), which corresponds to the equality τ = τ _s2 , and determine the orientation angle of the quasar

form the time scales for reading the angular coordinates α, β and γ: rough, but unambiguous, from the measured values of the angular coordinates α, β and γ precisely and unambiguously determine the location of the quasar.

The mutual arrangement of receiving points 3, 4, 5, quasar 1 and MCA 2 is shown in FIG. 1. The relative position of the measuring station 9, ionized space 8, quasar 1 and MCA 2 is shown in FIG. 2. The structural diagram of a device that implements the proposed method is presented in FIG. 3.

The device contains three receiving points, each of which consists of a series-connected receiving antenna 11 (12, 13), a band-pass filter 14 (15, 16) and a phase meter 17 (18, 19), the output of which is connected to computer 7. To the output of the second of filter 15, a first multiplier 22.1 is connected in series, the second input of which is connected through the first block 21.1 of adjustable delay to the output of the first band-pass filter 14, the first low-pass filter 23.1 and the first extreme controller 24.1, the output of which is connected to the second input of the first block 21.1 a delay, the second input of which through the azimuth indicator 25 is connected to the fourth input of the computer 7. A second multiplier 22.2 is connected in series to the output of the third band-pass filter 16, the second input of which is connected to the output of the first band-pass filter 14 to the output of the first band-pass filter 14, the second lower filter 23.2 frequency and the second extreme controller 24.2, the output of which is connected to the second input of the second adjustable delay unit 21.2, the second output through the elevation angle indicator 26 is connected to the fifth input of computer 7. K the output of the second band-pass filter 15 is connected in series with a third multiplier 22.3, the second input of which is connected through the third block 21.3 of the adjustable delay to the output of the third band-pass filter 16, the third low-pass filter 23.3 and the third extreme controller 24.3, the output of which is connected to the second input of the third block 21.3 of the adjustable delay , the second output of which through the indicator 27 of the angle of orientation is connected to the sixth input of the computer 7. The first block 21.1 adjustable delay, the first multiplier 22.1, the first lower filter 23.1 often and a first controller 24.1 extreme form a first correlator 20.1.

The second adjustable delay unit 21.1, the second multiplier 22.2, the second low-pass filter 23.2 and the second extreme controller 24.2. form the second correlator 20.2.

The third adjustable delay unit 21.3, the third multiplier 22.3, the third low-pass filter 23.3 and the third extremal regulator 24.3 form the third correlator 20.3.

The proposed method is implemented as follows.

Reception points 3,4 and 5 are placed in the form of a right-angled triangle, forming three ultra-long measuring bases d ₁ , d ₂ and d ₃ in the azimuthal, rectangular and hypotenuse planes, respectively (Fig. 1). Received Signals

u ₁ (t) = U ₁ cos (2πf ₀₂ t + ϕ ₁ ),

u ₂ (t) = U ₂ cos (2πf _o2 t + ϕ ₂ ),

u ₃ (t) = U ₃ cos (2πf _o2 t + ϕ ₃ ),

from quasar 1 at a frequency f ₀₂ are allocated by band-pass filters 14, 15 and 16, respectively, and fed to the inputs of phase meters 17, 18 and 19. The latter measure the following phase differences:

where d ₁ , d ₂ and d ₃ are extra-long measuring bases,

λ is the wavelength with a frequency f ₀₂ ;

α, β, and γ are the azimuth, elevation angle, and orientation angle of the quasar,

which are fixed by computer 7. This is how the phase scales of the angular coordinates α, β and γ of the quasar are formed: accurate, but ambiguous.

The received signals u ₁ (t), u ₂ (t) and u ₃ (t) are simultaneously fed to two inputs of the correlators 20.1, 20.2 and 20.3. The correlation functions R ₁ (τ), R ₂ (τ), and R ₃ (τ) obtained at the output of filters 23.1, 23.2, and 23.3 have a maximum for the value of the introduced adjustable delay:

τ = τ _s1 , τ = τ _s2 , τ = τ _s3 .

The maximum values of the correlation functions R ₁ (τ), R ₂ (τ), and R ₃ (τ) are automatically supported using the extreme controllers 24.1, 24.3, and 24.3, which act on the control inputs of the adjustable delay blocks 21.1, 21.2, and 21.3. Indicators 25, 26 m 27 are graded directly in the values of the angular coordinates α, β and γ of the quasar:

The values of the angular coordinates α, β, and γ are fixed by computer 7. Thus, the formed time scales for reading the angular coordinates α, β, and γ of the quasar are rough, but unambiguous.

From the measured values of the angular coordinates α, β, and γ, the location of the quasar is determined. In the proposed method for measuring the errors of trajectory measurements of the MCA, cosmic radiation sources (quasars) are used located on the celestial sphere near the MCA due to the passage of radio signals through the ionizing medium by measuring two changes in the frequencies emitted by the quasar when they are received by the ground-based measuring station (Fig. 2).

Frequency ratios are determined by two expressions:

where f ₀₁ and f ₀₂ are the frequencies of the signals emitted by the quasar.

In this case, one frequency f ₀₁ coincides with the frequency at which the trajectory measurements of the MCA are carried out, and the other frequency f ₀₂ is chosen with a significant difference from f ₀₁ . To ensure coherence of the frequencies received from the quasar of signals, the local oscillators of the receivers of the measuring station 9 should be coherent.

Δf ₁ and Δf ₂ - changes in the values of the emitted frequencies due to the passage of signals through ionized regions of outer space;

f _CR1 and f _CR2 - the values of the frequencies of the signals received by ground measuring stations;

- соотношение частот, излучаемых квазаром;

- ratio of frequencies emitted by a quasar;

- (2) соотношение величины изменения частот, за счет

- (2) the ratio of the magnitude of the change in frequency due to

the passage of signals through ionized space.

Equation (2) can be converted

Having solved equations (1) and (2) with respect to Δf ₁ , we obtain the magnitude of the change in frequency f ₀₁ through the values of the received frequencies f _CR1 and f _CR2

if m> 2-3, the unit in the denominator can be neglected. Then

Due to the small value of the angle ψ (Fig. 2), the line of passage of the signals of the quasar L ₁ and MCA L ₂ pass through the ionized plasma 8 at a close distance and we can assume that the integral electron concentration of the ionosphere and interplanetary plasma along the lines L ₁ and L ₂ are close .

Therefore, the measured value along the line L _{1 the} frequency shift of the signal f ₀₁ will have the same value as when the signal passes along the line L ₂ , i.e. the measured value Δf ₁ will be the error value when measuring the radial velocity of the MCA.

To determine the error in measuring the range of the MCA, it is necessary to solve the inverse problem, i.e. the measured value of the frequency shift Δf _{1 to} determine the integral electron concentration of the ionosphere along the line L ₂ , and from it to determine the delay of the radio signal Δt along the line L ₂ , which will actually be the error in measuring the distance to the MCA along the line L ₂ , Δt c = ΔR.

Such measurements of errors due to the propagation of radio signals in the ionized space using quasar 1 must be carried out in each session of the trajectory measurements of the MCA 2, and the results should be transferred to the ballistic center to take these errors into account when calculating the trajectory of the MCA.

Thus, the proposed method in comparison with the prototype and other technical solutions for a similar purpose provides increased reliability in measuring the errors of the trajectory measurements of the MCA caused by the propagation of the measuring radio signals through the ionized medium. This is achieved by accurately and unambiguously determining the location of the nearest quasar.

It should be noted that the location of the reception points in the form of a right-angled triangle is dictated by the new ideology of phase direction finding of radio emission sources in space, which provides a passive method for determining the location of a quasar. Moreover, for accurate and unambiguous determination of the location of the quasar, phase scales of reading the angular coordinates α, β and γ are used: accurate, but ambiguous, and time scales of reading the angular coordinates α, β, and γ: rough but unambiguous, obtained due to the correlation processing of the received signals.

Ultra-long base radio interferometers that implement the right-angled triangle method are novel, original and can be widely used for accurate and unambiguous determination of the location of quasars and MCAs.

Literature

1. RF patent No. 2.578.003, B64 G 3/00, 2016.

2. Yakovlev O.I. Space radiophysics. M .: "Scientific book", 1998.

3. Radio systems of interplanetary spacecraft. / Ed. A.S. Vinnitsa. - M .: Radio and communications, 1993.

4. Molotov EP Terrestrial radio control systems for spacecraft. - M .: FIZMATLIT, 2004 - 256 p.

5. ICRF quasar catalog - International celestial reference system.

Claims (14)

The method for determining errors in trajectory measurements of interplanetary spacecraft (MCA) due to the propagation of radio signals in the Earth's ionosphere and interplanetary plasma, which consists in the fact that during trajectory measurements of the range and radial velocity component of the MCA, in addition to measuring signals from the MCA at a frequency f ₀₁ , receive signals from the quasar emitted by it at a frequency f ₀₁ and a frequency f ₀₂ , significantly different from the frequency f ₀₁ , while providing a minimum time shift between measurements with MCA and qua Zara, choose the angular position of the quasar so that the projection of its position on the celestial sphere is as close as possible to the position of the MCA during trajectory measurements, while the signal paths from the MCA and the quasar to the measuring station practically coincide, according to the measured values of the frequencies f received from the quasar _pr1 and f _np2 determined by dual frequency offset Δf ₁ received from the frequency f quasar _{pr1 01} relative to the frequency f, which is considered equal to the error in the ICA velocity measurements because practical coincidence tra with the passage of signals from the ICA and the quasar, moreover, the magnitude of the frequency shift Δf ₁ define integral electron density along the track quasar - measuring station being and its magnitude calculated time delay Δt of the signal with the frequency f ₀₁ that is substantially equal to the measurement error range Δt C where C is the speed of light, during trajectory measurements of the MCA, the obtained data is transmitted to the ballistic center together with the results of trajectory measurements of the MCA to calculate the trajectory of the MCA, characterized in that the receiving The items are placed in the form of a right triangle is formed with three radiointerferometer VLB in azimuth, elevation and hypotenuse planes receive signals from the quasar ₀₂ at a frequency f, measure a phase difference between them

where d ₁ , d ₂ and d ₃ are extra-long measuring bases, λ is the wavelength with a frequency f ₀₂ , α, β, and γ are the azimuth, elevation angle, and orientation angle of the quasar, form phase scales of readings of the angular coordinates α, β and γ: accurate, but ambiguous, multiply the signal received by the second point, with the signal received by the first and the point passed through the first block of adjustable delay, a low-frequency voltage proportional to the first correlation function R ₁ ( τ), where τ is the current time delay, the time delay is changed until the maximum value of the first correlation function R ₁ (τ) is obtained, which corresponds to the equality τ = τ _З1 , and the azimuth of the quasar is determined

multiply the signal received by the third point, with the signal received by the first point and passed through the second adjustable delay unit, select a low-frequency voltage proportional to the second correlation function R ₂ (τ), change the time delay τ to obtain the maximum value of the second correlation function R ₂ (τ ) corresponding to the equality τ = τ _s2 , and determine the elevation angle of the quasar

multiply the signal received by the second point, with the signal received by the third point and passed through the third adjustable delay unit, select a low-frequency voltage proportional to the third correlation function R ₃ (τ), change the time delay τ to obtain the maximum value of the third correlation function R ₃ (τ ) corresponding to the equality τ = τ _s3 , and determine the orientation angle of the quasar

form coarse, but unambiguous time scales for reading the angular coordinates α, β and γ, from the measured values of the angular coordinates α, β and γ precisely and unambiguously determine the location of the quasar.

Images