RU2526401C1 - Method for radar doppler angular measurements of spacecraft and system for realising said method - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: group of inventions relates to methods and means of taking spacecraft trajectory measurements using radio links. The method employs three spaced-apart ground-based measurement stations and a spacecraft transponder. The measurement stations measure radial velocity of the spacecraft relative to the measurement stations. One main measurement station operates in query mode of measuring said velocity and range to the spacecraft. The other two slave measurement stations operate in non-query mode. The latter are used to measure said velocity of a signal generated by the spacecraft transponder from the query frequency of the main measurement station. The measured Doppler frequency shifts from the main and slave measurement stations are transmitted to a ballistic centre where the differences between said shifts, which are equivalent to measurements of radio interferometer with bases corresponding to distances between the measurement stations, are calculated. Based on the measurements of said velocities and range, the ballistic centre calculates the trajectory of the spacecraft.

EFFECT: high-precision and high-speed trajectory measurement system with a simple design and easy operation of equipment thereof.

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Description

Technical field

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

State of the art

It is known that to determine the trajectory of the spacecraft (SC) and predict its further motion, the results of trajectory measurements performed by ground-based measuring stations (IS) and the onboard transponder of the spacecraft are used [1].

, угол места КА (β) и скорость изменения этого угла $$\left(\dot{\beta }\right)$$

и азимутальный угол положения КА относительно ИС (α) и скорость изменения этого угла $$\left(\dot{\alpha }\right)$$

. ИС, которая сможет измерять все шесть параметров движения КА, является весьма сложным и дорогостоящим устройством.In the general case, to determine the spacecraft motion path, it is necessary to measure six spacecraft motion parameters: the inclined range from the IS to the spacecraft (R), the radial component of the spacecraft’s speed relative to the IS $$(\dot{R})$$

, space elevation angle (β) and rate of change of this angle $$\left(\dot{\beta }\right)$$

and the azimuthal angle of the spacecraft relative to the IS (α) and the rate of change of this angle $$\left(\dot{\alpha }\right)$$

. The IC, which can measure all six parameters of the spacecraft motion, is a very complex and expensive device.

, которые последовательно измеряются несколькими ИС, разнесенными в долготном направлении. При такой схеме измерений погрешности определения траектории движения КА оказываются в пределах, достаточных для решения задач управления КА.In practice, when conducting trajectory measurements, only two spacecraft motion parameters, R and $$\dot{R}$$

, which are successively measured by several IP spaced in the longitudinal direction. With such a measurement scheme, the errors in determining the spacecraft trajectory are within the limits sufficient to solve the spacecraft control problems.

There are two main methods for conducting Doppler measurements of the radial component of the spacecraft velocity. The first method is the interrogation one, in which the IC emits a frequency-stable signal received by the airborne transponder and re-emitted to the Earth after coherent conversion to another frequency. This signal received by the IS has a total Doppler frequency shift due to the passage of the signal to the spacecraft and back. Measurement of this displacement allows one to determine the radial component of the spacecraft velocity relative to the IS. In this case, the radial component of the velocity is determined by a simplified expression:

где $$\dot{R}=\frac{\Delta f_{\text{additional}\text{.}}\times c}{f_0},$$

Where

Δf _add. - measured one-way Doppler frequency offset;

f ₀ is the value of the frequency radiated from the spacecraft; where c is the speed of light.

The second method is non-demanding, in which the spacecraft on-board transmitter operating in self-propelled mode emits a signal to the IS. On the IS, the Doppler frequency offset of the received signal is determined relative to the reference signal, the frequency of which is equal to the frequency of the signal emitted from the spacecraft.

With a non-demanding method of measuring Doppler frequency displacement, measurement errors are determined by the errors in the frequency values of the onboard and reference generators, as well as the frequency instability of the onboard generator. In the general case, the errors of the non-query method of measurement are significantly higher than when using the query method.

оказывается недостаточно для решения некоторых задач, например обеспечения посадки на поверхность Луны спускаемого аппарата с высокой точностью, в дополнение к измерениям R и $$\dot{R}$$

используют измерение угловых параметров движения КА (а, $$\dot{\alpha }$$

, β, $$\dot{\beta }$$

).In those cases when the obtained accuracy of determining the trajectory of the spacecraft motion only when measuring R and $$\dot{R}$$

it turns out to be insufficient to solve some problems, for example, to ensure the descent vehicle landing on the lunar surface with high accuracy, in addition to measurements of R and $$\dot{R}$$

use the measurement of the angular parameters of the spacecraft motion (a, $$\dot{\alpha }$$

, β, $$\dot{\beta }$$

)

) сигналов, принимаемых несколькими ИС, которые эквивалентны угловым измерениям радиоинтерферометра с базами, соответствующими расстояниям между ИС.During the spacecraft flight to the moon, landing on the moon, take-off from the moon and docking with an orbital ship in orbit around the moon, flight to the Earth and landing on the Earth, a number of trajectory corrections are necessary. At the same time, a very short time is allotted for the preparation (conducting trajectory measurements) and for making corrections to the trajectory, but at the same time, high accuracy in determining the orbit must be ensured. To meet these requirements, the system of measuring the difference in radial velocities (Δ $$\dot{R}$$

) signals received by several ICs, which are equivalent to the angular measurements of the radio interferometer with bases corresponding to the distances between the ICs.

The principle of measuring the difference in radial velocities was as follows ([1, section 3, 4], figure 1):

- on-board transponder (22) and three geographically separated ICs with known coordinates (23, 28, 33) participate in the measurements;

- one of the IS - the main (GIS), two other slaves (VIS1 and VIS2), - the GIS signal received on board (16.4) coherently converts to the response frequency (5) and re-radiates to the ground (1.17);

- the signal f ₀ [1, Fig. 17] is received simultaneously by GIS (6), VIS1 (24) and VIS2 (29);

- on VIS1 and VIS2, this signal is converted into a response frequency (20, 21) and re-emitted to the spacecraft (27, 32, 20, 21);

VIS1 (20, 2) and VIS2 (21, 3) response signals received on board are converted into response frequencies (5) and re-emitted to the Earth together with the GIS response signal (1, 17, 18, 19);

- A GIS receives all three signals transmitted at different frequencies (17, 18, 19, 6, 7, 8), determines the Doppler frequency shift of each signal (9, 10, 11), calculates the differences of the Doppler frequency shift between GIS signals and VIS1 signals and VIS2 (12);

передаются в баллистический центр, где они используются для точного определения траектории движения КА.- received data

transmitted to the ballistic center, where they are used to accurately determine the trajectory of the spacecraft.

The described system has several disadvantages, the main of which are:

- the availability of special equipment as part of a GIS (6, 7, 9, 10, 11) and VIS 1, 2 (25, 30), which provides a measurement of the difference in radial velocities;

- VIS operation in transceiver mode;

- complication of the onboard transponder of the spacecraft for receiving and relaying simultaneously three signals (1, 2, 3).

The described radial velocity difference measurement system [1] is selected as an analog of the described invention.

Disclosure of invention

The claimed method and system is aimed at eliminating the disadvantages of the analogue.

The technical result of the claimed invention is to simplify the design and operation of the system of trajectory measurements of the difference in the radial speeds of the spacecraft.

The technical result is achieved by the fact that the method of radio-technical Doppler goniometric measurements of the spacecraft consists in generating a request signal from the main ground-based measuring station, transmitting a signal to the on-board transponder of the spacecraft, generating a highly stable response signal from the request signal in the on-board transponder, and simultaneously relaying it using the on-board spacecraft transponder highly stable response signal to the main ground measuring station June and the first and second conducted ground-based measuring stations, geographically spaced among themselves, simultaneously measure the radial velocity components of the spacecraft by measuring the Doppler frequency offset of the received highly stable signal, all measuring stations in the receiving mode use the same highly stable signal generated by the onboard transponder of the spacecraft from the request signal of the main measuring station, the difference of the measured Doppler frequency shifts of the signals the main ground measuring station and the first and second slave ground measuring stations, equivalent to the goniometric measurements of the radio interferometer with bases corresponding to the distances between the measuring stations involved in the measurements, are transmitted to the ballistic center, where the trajectories of the spacecraft are determined.

The system of radio-technical Doppler goniometric measurements of the spacecraft includes an on-board transponder, a main measurement station (GIS), a first slave measuring station (VIS1), a second slave measuring station (VIS2), a ballistic center, and a GIS equipped with a second transceiver antenna, transmitter, and the first coherent synthesizer frequency shift, the first exact frequency generator, the first output of which is connected to the first inputs of the transmitter and the first coherent frequency shift synthesizer, the output of the transmitter Ika is connected to the input of the second transceiver antenna, also the first receiver of the response signal f _resp. GIS, the first unit for measuring Doppler frequency offset f _add. GIS, the input of which is connected to the output of the first receiver of the response signal f _resp. GIS, the input of which is connected to the output of the second transceiver antenna, the first output of the first unit for measuring the Doppler frequency offset f _add. The GIS is connected to the second input of the first coherent frequency shift synthesizer, the output of which is connected to the second input of the transmitter, the third input of the first coherent frequency shift synthesizer is connected to the second output of the first exact frequency generator, the second output of the first Doppler frequency shift measurement unit f _add. A GIS is connected to a ballistic center, VIS 1 includes a first receiving antenna, the output of which is connected to the first input of the second receiver of the response signal f _resp. GIS, the second unit for measuring Doppler frequency offset f _add. GIS, the first input of which is connected to the output of the second receiver of the response signal f _resp. GIS, and the output is connected to a ballistic center, the second exact frequency generator, the output of which is connected to the second inputs of the second receiver of the response signal f _resp. GIS and the second unit for measuring Doppler frequency offset f _add. GIS, respectively, VIS2 includes a second receiving antenna, the output of which is connected to the first input of the third receiver of the response signal f _resp. GIS, the third unit for measuring Doppler frequency f _add. GIS, the first input of which is connected to the output of the third receiver of the response signal f _resp. GIS, and the output is connected to a ballistic center, the third exact frequency generator, the output of which is connected to the second inputs of the third receiver of the response signal f _resp. GIS and the third unit for measuring Doppler frequency offset f _add. GIS, respectively, the structure of the airborne transponder includes a first transceiver antenna, series-connected receiver of the request signal f _app. GIS, frequency converter, on-board transmitter, the output of which is connected to the input of the first transceiver antenna, the input of the receiver of the request signal f _app. The GIS is connected to the output of the transceiver antenna, the transceiver antenna is connected via radio channels to the GIS through the second transceiver antenna, and also to VIS1 and VIS2 through the first and second receiving antennas, respectively.

An analogue of the claimed method and system is presented in figure 1, where:

1. On-board three-channel transmitter;

2. The receiver of the request signal f _app. VIS1;

3. The receiver of the request signal f _app. VIS2;

4. The receiver of the request signal f _app. GIS

5. The frequency converter;

6. The first receiver of the response signal f _resp. GIS

7. The receiver of the response signal f _resp. VIS1;

8. The receiver of the response signal f _resp. VIS2;

9. The meter Doppler frequency offset f _add. GIS

10. The meter Doppler frequency offset f _add. VIS1;

11. The meter Doppler frequency offset f _add. VIS2;

,12. The meter of the difference of Doppler frequency shifts $$\Delta f_{d\mathrm{about}P.}G\mathrm{AND}\mathrm{FROM}=f_{d\mathrm{about}P.}\mathrm{AT}\mathrm{AND}\mathrm{FROM}\mathrm{one}=\Delta {\dot{R}}_{\mathrm{one}}$$

,

13. The first generator of exact frequencies;

14. The first coherent frequency shift synthesizer;

15. Transmitter

16. Request signal f app _. GIS

17. The response signal f _resp. GIS

18. The response signal f _resp. VIS1;

19. The response signal f _resp. VIS2;

20. The request signal f app _. VIS1;

21. The request signal f app _. VIS2;

22. On-board transponder;

23. The first slave measuring station (VIS1);

24. The second receiver of the response signal f _resp. GIS

25. The second generator of exact frequencies;

26. The second coherent frequency shift synthesizer;

27. The second transmitter;

28. The second slave measuring station (VIS2);

29. The third receiver of the response signal f _resp. GIS

30. The third generator of exact frequencies;

31. Third coherent frequency shift synthesizer;

32. Third transmitter;

33. The main measuring station (GIS);

34. The first transceiver antenna;

35. The second transceiver antenna;

36. Third transceiver antenna;

37. Fourth transceiver antenna;

The inventive radio system of Doppler goniometric measurements is presented in figure 2, where:

38. Onboard transponder;

39. Airborne transmitter;

40. The receiver of the request signal f _app. GIS

41. Frequency converter;

42. Request signal f app _. GIS

43. The response signal f _resp. GIS

44. The main measuring station (GIS);

45. The first receiver of the response signal f _resp. GIS

46. The first unit for measuring Doppler frequency shift f _add. GIS

47. The first generator of exact frequencies;

48. Coherent frequency shift synthesizer;

49. Transmitter;

50. The first slave measuring station (VIS1);

51. The second receiver of the response signal f _resp. GIS

52. The second unit for measuring the Doppler frequency shift f _add. GIS

53. The second generator of exact frequencies;

54. The second slave measuring station (VIS2);

55. The third receiver of the response signal f _resp. GIS

56. The third unit for measuring Doppler frequency offset f _add. GIS

57. The third generator of exact frequencies;

58. The first transceiver antenna;

59. The second transceiver antenna;

60. The first receiving antenna;

61. The second receiving antenna.

The calculation algorithm in the ballistic center is presented in figure 3.

The inventive radio engineering system of Doppler goniometric measurements includes an on-board transponder 22, three ground-based diversity measuring stations (44, 50, 54) with known coordinates, but differs from the prototype [1] as follows (see Figure 2):

- of the three ISs, only one - the GIS (44) operates in the interrogation mode of measuring Doppler frequency offset, and the other two VIS1 (50) and VIS2 (54) operate in non-query mode.

Form a request signal f _app. GIS (42) by the first reference frequency generator (47), then this signal is transmitted from the transmitter (49) to the airborne transponder (38).

The airborne transponder relays to the Earth a highly stable frequency signal f _resp. GIS (43) from the airborne transmitter (38), formed from the GIS request signal (42), arriving at the signal receiver f _app. GIS (40), then to the frequency converter (41) and then to the on-board transmitter (39).

- relayed signal f _resp. GIS (43) simultaneously receive the first receiver of the signal f _resp. GIS (45), which is part of the GIS, the second receiver of the signal f _resp. VIS1 (51) and the third signal receiver f _resp. VIS2 (55), which are part of VIS 1 and VIS 2, then these signals are fed to the first, second and third units of measuring the Doppler frequency offset f _add. GIS (46, 52, 56), which are part of GIS, VIS1 and VIS2, respectively, also on the second and third measurement units f _add. GIS receives accurate frequency signals from the second and third exact frequency generators (53, 57), which are part of VIS 1 and VIS 2. The obtained values of the Doppler frequency shift of the received signal from the outputs of the first, second and third units of the Doppler frequency shift measurement f _add. GIS (46, 52, 56), as well as the distance from the GIS to KA (R ₁ ) transmit to the ballistic center.

Although VIS1 and VIS2 measure the Doppler frequency offset in a non-request mode, however, the measurement errors at VIS1, VIS2 and GIS are the same, since the signal frequency stability is f _resp. A GIS (43) generated by an airborne transponder 38 is determined by the frequency stability of the GIS request signal (42), which is determined by the high frequency stability of the first GIS reference frequency generator (47).

The frequency standard of the second and third reference frequency generators (53, 57) used in VIS1 and VIS2 for measuring the Doppler frequency shift in unquestioned mode has the same high stability.

, ВИС1 $$\left({\dot{R}}_2\right)$$

, ВИС2 $$\left({\dot{R}}_3\right)$$

передают в баллистический центр, где определяют разность смещений частоты измеренных в ГИС и ВИС:Measurement results of Doppler frequency offset with GIS $$\left({\dot{R}}_{\mathrm{one}}\right)$$

, VIS1 $$\left({\dot{R}}_2\right)$$

, VIS2 $$\left({\dot{R}}_3\right)$$

transmit to the ballistic center, where they determine the difference between the frequency offsets measured in the GIS and VIS:

$$\Delta {\dot{R}}_{\mathrm{one}}={\dot{R}}_{\mathrm{one}}-{\dot{R}}_2=f_{d\mathrm{about}P.G\mathrm{AND}\mathrm{FROM}}-f_{d\mathrm{about}P.\mathrm{AT}\mathrm{AND}\mathrm{FROM}\mathrm{one}};$$

$$\Delta {\dot{R}}_2={\dot{R}}_{\mathrm{one}}-{\dot{R}}_3=f_{d\mathrm{about}P.G\mathrm{AND}\mathrm{FROM}}-f_{d\mathrm{about}P.\mathrm{AT}\mathrm{AND}\mathrm{FROM}2}.$$

The obtained data characterizing the angular parameters of the motion of the spacecraft, is used to accurately determine the orbit of the motion of the spacecraft (see Figure 3)

Due to the fact that with the claimed method of measuring angular coordinates, there is no need to use special equipment for measuring the difference of radial frequency offsets in the onboard transceiver and in the GIS, VIS1 and VIS2, and also because VIS1 and VIS2 work only in the receiving mode, the cost of creating and operation of the inventive system is much lower than the prototype system.

The described method and system for measuring the difference in radial velocities can most effectively be used for trajectory measurements of lunar spacecraft. But it is also advisable to use interplanetary spacecraft (MCA) for trajectory measurements.

The new method and system will give the best results for determining the angular parameters of the spacecraft’s motion at the initial stage of the spacecraft’s flight (up to 1-2 min), where the ratio of bases and range to the spacecraft, the orbit (trajectory) of which allows three geographically separated IS involved in the measurements.

Thus, the claimed method and system provide a simplification of the design and operation of the system of trajectory measurements of the difference in the radial speeds of the spacecraft.

Literature

1. Molotov EP Terrestrial radio control systems for spacecraft. M .: FIZMATLIT, 2004.

Claims (2)

1. A method of radio-technical Doppler goniometric measurements of a spacecraft, which consists in generating a request signal from a main ground-based measuring station, transmitting a signal to an on-board transponder of a spacecraft, generating a highly stable response signal from a request signal in an on-board transponder, and simultaneously relaying it using an on-board transponder of a spacecraft highly stable response signal to the main ground measuring station and the first and second slave ground and measuring stations, geographically separated, simultaneously measure the radial components of the spacecraft’s speed by measuring the Doppler frequency shifts of the received highly stable signal, and all measuring stations in the receiving mode use the same highly stable signal generated by the onboard transponder of the spacecraft from the interrogation signal of the main measuring station , differences of the measured Doppler frequency shifts of the signals of the main ground measuring Dancing and first and second driven ground-based measuring stations, equivalent goniometric measurements radiointerferometer with bases corresponding to the distances between the measuring stations involved in the measurements are transmitted to the ballistic center where the determined trajectory of the spacecraft. 2. A system of radio-technical Doppler goniometric measurements of a spacecraft, including an on-board transponder, a main measuring station (GIS), a first slave measuring station (VIS1), a second slave measuring station (VIS2) and a ballistic center, and the GIS is equipped with a second transceiver antenna, transmitter , the first coherent frequency shift synthesizer, the first exact frequency generator, the first output of which is connected to the first inputs of the transmitter and the first coherent frequency shift synthesizer, you the transmitter course is connected to the input of the second transceiver antenna, while the GIS includes the first receiver of the response signal f _resp. GIS, the first unit for measuring Doppler frequency offset f _add. GIS, the input of which is connected to the output of the first receiver of the response signal f _resp. GIS, the input of which is connected to the output of the second transceiver antenna, the first output of the first unit for measuring the Doppler frequency offset f _add. The GIS is connected to the second input of the first coherent frequency shift synthesizer, the output of which is connected to the second input of the transmitter, the third input of the first coherent frequency shift synthesizer is connected to the second output of the first exact frequency generator, the second output of the first Doppler frequency shift measurement unit f _add. GIS is connected to a ballistic center, VIS1 includes a first receiving antenna, the output of which is connected to the first input of the second receiver of the response signal f _resp. GIS, the second unit for measuring Doppler frequency offset f _add. GIS, the first input of which is connected to the output of the second receiver of the response signal f _resp. GIS, and the output is connected to a ballistic center, the second exact frequency generator, the output of which is connected to the second inputs of the second receiver of the response signal f _resp. GIS and the second unit for measuring Doppler frequency offset f _add. GIS, respectively, VIS2 includes a second receiving antenna, the output of which is connected to the first input of the third receiver of the response signal f _resp. GIS, the third unit for measuring Doppler frequency f _add. GIS, the first input of which is connected to the output of the third receiver of the response signal f _resp. GIS, and the output is connected to a ballistic center, the third exact frequency generator, the output of which is connected to the second inputs of the third receiver of the response signal f _resp. GIS and the third unit for measuring Doppler frequency offset f _add. GIS, respectively, with the structure of the airborne transponder includes a first transceiver antenna, series-connected receiver of the request signal f _app. GIS, frequency converter and airborne transmitter, the output of which is connected to the input of the first transceiver antenna, and the input of the receiver of the interrogation signal f _app. The GIS is connected to the output of the transceiver antenna, the transceiver antenna is connected via radio channels to the GIS through the second transceiver antenna, and also to VIS1 and VIS2 through the first and second receiving antennas, respectively.

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