CN102207614A - Deep space optical communication tracking and aiming system and method - Google Patents

Abstract

The invention discloses a deep-space optical communication tracking and aiming system and method. The system has an internal inertial reference light source and two area array cameras. The internal inertial reference light source and the external target beacon light have different wavelengths. The area array camera images the inertial reference light source inside the system, and close-loop controls the fast tilting mirror according to the position deviation of the image point to stabilize the optical axis of the system optical path; the large area array camera images the external target beacon light, and adjusts the above small The tracking center of the area array camera achieves the purpose of stable and accurate tracking. The invention can greatly reduce the power requirement of the target terminal beacon light laser in the deep space optical communication, and provides a feasibility guarantee for system realization.

Description

A deep space optical communication tracking and targeting system and method

Technical field:

The invention relates to space optical communication tracking and targeting technology, in particular to a deep space optical communication tracking and targeting system and tracking method, which can be applied to deep space optical communication.

Background technique:

Compared with other classical communication methods, space optical communication has the advantages of small system size, high communication rate and good confidentiality. However, in order to improve the communication distance and reduce the system resources, the divergence angle of communication light is generally close to the emission diffraction limit (less than 10urad). In order to achieve the alignment of communication light with extremely narrow divergence angle at long distances, an acquisition tracking and targeting system (ATP system) is required. The ATP system is used to establish and maintain optical links between communication terminals, and the tracking accuracy can reach the urad level.

ATP technology has been developed simultaneously with the research of space laser communication, and has been successfully applied in the SILEX inter-satellite optical communication program of the European Space Agency and the OICETS inter-satellite laser communication program of Japan. At present, the ATP system generally adopts the composite axis control mode of the coarse tracking ring nested with the fine tracking ring. The tracking detectors of each loop use the beacon light or signal light sent by the other terminal as the light source, and the frame rate of the fine tracking detector reaches several KHz, so the integration time is very short. Due to the limited antenna aperture, the requirements for beacon lasers are getting higher and higher as the communication distance increases. For example, in the Mars deep space optical communication, if the mode of tracking the beacon light of the other party is still used alone, the required power of the beacon laser will reach more than 1KW, which is unrealistic in the system design.

If the interference factors to the ATP system in the space satellite platform are divided into three parts: low frequency, intermediate frequency and high frequency, the high frequency part is eliminated by the system mechanical vibration isolation, and the low and intermediate frequency part needs to be suppressed by ATP itself. The inertial reference unit is a miniaturized self-stabilizing platform, which has a good ability to suppress the middle and low frequency bands, and can provide a high-stability reference light source for the ATP system that is basically not affected by the vibration of the satellite platform.

Invention content:

The purpose of the present invention is to provide a novel tracking and aiming system and method applied to deep space optical communication, which adopts the combination detection method of internal inertial reference light source and external target beacon light, which reduces the detection frame rate of external beacon light, Therefore, the problem of excessively high requirements on the beacon optical power in the current system is solved.

The system structure of the present invention is shown in accompanying drawing 1, comprises: coarse tracking mechanism 1, optical telescope 2, inertial reference unit 3, reference laser source 4, mirror assembly 5, fast tilting mirror 6, small array camera 7, large area array camera 8, light splitting assembly 9.

The described rough tracking mechanism 1 is a two-dimensional turntable structure; the described optical telescope 2 is a transmissive or reflective telescope system; the described inertial reference unit 3 is a miniaturized self-stabilizing platform; the described reference laser source 4 The wavelength is in the visible light band, which differs from the wavelength of the external target beacon light by more than 50nm; the fast tilting mirror 6 is a fast tilting mirror driven by piezoelectric ceramics; the small area array camera 7 uses a CMOS or CCD detector, and the frame The frequency is greater than 2KHz; the large area array camera 8 adopts CMOS or CCD detectors, and the frame frequency is 2-5Hz.

The inertial reference unit 3, the reference laser source 4, and the mirror assembly 5 are all fixed on the optical telescope 2, and deflect along with the rough tracking mechanism 1; On the optical path, the beam splitting assembly 9 divides the laser light of the reference laser source 4 and the beacon light into two different image planes on the imaging plane of the optical telescope 2, the small area array camera 7 is placed on the laser imaging plane of the reference laser source 4, and the large area array The camera 8 is placed on the imaging surface of the beacon light, and the centers of their receiving fields of view keep coincident. The system works as follows:

The inertial reference unit 3 provides a highly stable platform for the reference laser source 4. The small area array camera 7 and the fast tilting mirror 6 form a closed-loop control system. The deviation is controlled by a high-bandwidth closed-loop control to control the deflection of the fast tilting mirror 6, so that the position of the image point is stabilized on the tracking point, and the purpose of stabilizing the optical axis of the rear optical path is achieved.

The external target beacon light enters the large area array camera 8, and the detection frame rate of the large area array camera 8 is low, so the power requirement for the beacon light is low. First, according to the deviation of the target beacon light image point 11 (accompanying drawing 2) on the camera relative to the tracking center 12, the rough tracking mechanism 1 is controlled to move, and the target beacon light image point 11 is introduced into the fine tracking field of view area 10; then the The deviation is used to adjust the tracking center of the small area array detector 7 in real time, and indirectly control the action of the fast tilting mirror 6 so that the target beacon light image point 11 is stabilized near the tracking center 12 of the large area array camera 8, and finally achieves the purpose of precise tracking.

The complete closed-loop control block diagram of the fast tilting mirror 6 is shown in Figure 3 .

The present invention has following beneficial effect:

By reducing the detection frame rate of the target beacon light, the power demand for the beacon light laser can be greatly reduced, and at the same time, the tracking accuracy can be guaranteed, which is very suitable for applications in deep space optical communication.

Description of drawings:

Fig. 1 is a structural diagram of the novel deep space optical communication tracking and targeting system of the present invention.

Fig. 2 is a schematic diagram of the position of the light image point of the target terminal beacon in the large area array camera.

Figure 3 is a closed-loop control block diagram of a fast tilting mirror.

In the figure 1. Coarse tracking mechanism, 2. Optical telescope, 3. Inertial reference unit, 4. Reference laser source, 5. Mirror assembly, 6. Fast tilting mirror, 7. Small area array camera, 8. Large area array camera , 9. Spectroscope assembly, 10. Fine tracking field of view area, 11. Target beacon light image point, 12. Large area array camera tracking center.

Detailed ways:

The specific embodiment of the present invention is described in further detail below in conjunction with accompanying drawing:

Taking the ATP application of a deep space optical communication as an example, the functions of the ATP system are divided into two parts: optical axis stabilization and absolute deviation adjustment. The optical axis stabilization is to overcome the vibration of the satellite platform, and the internal inertial reference light source is used to close the loop; the absolute deviation adjustment is to correct the deviation between the system optical axis and the target beacon optical axis, and the external beacon light source is used to close the loop.

(1) The wavelength of the reference laser source 4 is selected to be 532nm, and the wavelength of the external target beacon light is 671nm. After passing through the beam splitter assembly 9, the reference laser light enters the small area array camera 7, and the external target beacon light enters the large area array camera 9. The small area detector 7 is a CMOS detector, the window size is 64×64, and the frame frequency can reach above 2.5KHz. Using the detector and the fast tilting mirror 6 for closed-loop control, and using the PID control algorithm, the control bandwidth above 200Hz can be achieved, thereby effectively suppressing the medium and low frequency vibration interference of the satellite platform, so that the jitter of the optical axis of the rear optical path is in the order of μrad. The control block diagram is shown in the inner ring part in Fig. 3 .

(2) In order to accurately align the target position, the beacon light from the target terminal is detected. After the telescope 2 and the beam splitter assembly 5, the target beacon light enters the large area array camera 8. The detector adopts a CMOS detector with a window size of 1000×1000 and a frame frequency of less than 5Hz, so that the target beacon light has a longer integration time. Compared with the method of directly detecting the beacon light with a high frame rate camera, the power requirement for the beacon light is reduced by 400 times. The large area array camera 8 and the small area array camera 7 need to be strictly registered at the center of the field of view, and the field of view of the small area array camera 7 corresponds to the fine tracking field of view area 10 in FIG. 2 .

In the large area array camera, the tracking center 12 corresponds to the optical axis of the optical communication signal light, and the action of the rough tracking mechanism or the fast mirror is selected and controlled according to the deviation between the target terminal beacon position 11 and the tracking center 12 . When the beacon position 11 is outside the fine tracking field of view area 10 , the deviation is used to control the rough tracking mechanism to bring the image point into the fine tracking field of view area 10 according to the closed-loop feedback. Then enter the fine tracking adjustment stage, that is, the outer ring part in the accompanying drawing 3 of the specification, at this time, the deviation between the beacon position 11 and the tracking center 12 is used to calculate and adjust the tracking center of the inner ring. The change of the tracking center of the inner ring corresponds to the change of the position of the beacon image point in the large area array camera. Finally, the light image point 11 of the target beacon is stabilized near the tracking center 12 of the large area array camera, and the deviation between the two is the tracking error of the entire tracking system.

(3) When the large area array camera 7 is used for the closed-loop control of the fast tilting mirror 6, in order to prevent the long-term and large-scale drift of the target position relative to the on-board terminal beyond the limit of the movement range of the fast tilting mirror 6, the rough tracking mechanism needs to reverse towards open loop compensation. The angle sensor inside the fast tilt mirror 6 detects the current deflection angle value of the mirror, and when it exceeds a certain value, the rough tracking mechanism deflects by an equal angle in the same direction, thereby releasing the deflection space of the fast tilt mirror 6 .

Claims (2)

1. A deep-space optical communication tracking and targeting system, which includes: a rough tracking mechanism (1), an optical telescope (2), an inertial reference unit (3), a reference laser source (4), a mirror assembly (5), a fast Tilting mirror (6), small area array camera (7), large area array camera (8), light splitting assembly (9), is characterized in that: The described coarse tracking mechanism (1) is a two-dimensional turntable structure; the described optical telescope (2) is a transmissive or reflective telescope system; the described inertial reference unit (3) is a miniaturized self-stabilizing platform; the The wavelength of the reference laser source (4) is in the visible light band, which is more than 50nm different from the external target beacon light; the fast tilt mirror (6) is a fast tilt mirror driven by piezoelectric ceramics; the small area array camera (7) adopt CMOS or CCD detector, frame frequency is greater than 2KHz; Described large area array camera (8) adopts CMOS or CCD detector, frame frequency 2～5Hz; The inertial reference unit (3), the reference laser source (4), and the mirror assembly (5) are all fixed on the optical telescope (2), and deflect along with the rough tracking mechanism (1); the fast tilting mirror (6) The beam splitting assembly (9) is installed on the image square optical path of the optical telescope (2), and the beam splitting assembly (9) divides the laser light of the reference laser source (4) and the beacon light into two different beams on the imaging surface of the optical telescope (2). On the imaging surface, the small area array camera (7) is placed on the laser imaging surface of the reference laser source (4), and the large area array camera 8 is placed on the imaging surface of the beacon light, and the centers of their receiving fields of view keep coincident. 2. An optical communication tracking and aiming method based on the system according to claim 1, characterized in that it comprises the following steps: 1) Turn on the reference laser source (4), and the small area array camera (7) receives the reference laser emitted by the reference laser source (4) in real time, and performs high-bandwidth closed-loop control according to the deviation between the image point centroid position and the tracking point position of the reference laser , to control the deflection of the fast tilting mirror (6), so that the position of the image point is stabilized on the tracking point, and the optical axis of the rear optical path is stabilized; 2) When the external target beacon light enters the large area array camera (8), firstly, the movement of the rough tracking mechanism (1) is controlled according to the deviation between the target beacon light image point (11) on the camera and the relative tracking center (12), and the The target beacon light image point (11) is introduced into the fine tracking field of view area (10); then the deviation is used to adjust the tracking center of the small area detector (7) in real time, and indirectly control the action of the fast tilting mirror (6) The light image point (11) of the target beacon is stabilized near the tracking center (12) of the large area array camera (8), thereby realizing precise tracking and aiming.

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