KR20010011662A - Three axis stellar sensor using electric optical shutter - Google Patents

Abstract

PURPOSE: A star sensor for controlling a three-shaft posture using shutters is provided to reduce the size of the star sensor to be driven by a low power consumption and expand the star observation range by using electro-optical shutters. CONSTITUTION: A star sensor for controlling a three-shaft posture using shutters includes a telephoto lens(51) for receiving light information provided via a first line of sight for observing a first light source, a beam splitter(34) for transmitting and reflecting light information of a second light source provided via a second line of sight perpendicular to the first line of sight toward the telephoto lens, beam detector(CCD;33) for detecting light information provided to the telephoto lens via the first and second lines of sight, first and second electro-optical shutters(52-1,52-2) for respectively controlling shutoff and transmission of light provided via the first and the second lines of sight, a shutter switching part(53) for controlling power supply provided to the first and second electro-optical shutters, and a central processing unit(54) for analyzing information provided via the CCD and outputting control signals for controlling the posture of a satellite and the shutter switching part according to the information.

Description

Three axis stellar sensor using electric optical shutter

The present invention relates to a sensor for satellite attitude control, and more particularly, to a precision control device in which an observation range is enlarged using an electro-optic shutter.

In general, a star sensor or a star tracker is used as a position control sensor of a satellite used in space. In order to accurately control the attitude of the satellite, it is necessary to accurately measure the position of the satellite around a fixed object. According to the prior art, a region having an observation range of more than 20 parts (hereinafter referred to as FOV) is observed for precise posture control. In the currently used star detector, it has an observation range of 10 ° or less to perform two-axis control, and an observation range of 20 ° or more (FOV) to perform three-axis control. In the case of 3-axis control, even if it has a field of view (FOV) of more than 20 °, in order to obtain the information on the 3rd axis corresponding to the rotation, a star as far as possible from the center of the star detector can be detected to obtain more accurate data. If not, only the phenomenon can be detected, but it is difficult to detect the exact movement. Therefore, in the case of three-axis control, the observation range (FOV) was greatly expanded or two star detectors 1 were mounted as shown in FIG. 1.

In order to solve this inconvenience, as shown in FIG. 2, an improvement scheme in which only one star detector 2 is used has been disclosed in US Pat. No. 4,159,419. The main contents of this technique are outlined as follows.

As shown in FIG. 3, the light information provided from the first light source body 31 and the second light source body 32 is divided into a single star detector 33 and a beam splitter or beam splitter 34. I use it. The light information provided from the first light source body 31 is transmitted to the star detector 33 via a first line of sight, and the light information provided from the second light source body 32 is the first line of sight. It is transmitted to the star detector 33 via a second line of sight perpendicular to the second detector. In this case, the light information provided from the second light source body 32 is reflected and provided by the beam splitter 34, and a portion of the surface of the beam splitter 34 is coated with silver to reflect light. It is. In addition, the beam splitter 34 is installed to form an angle of 45 degrees with respect to the plane of the star detector 23.

4 is a partial detailed view of FIG. 3, provided from a first line of sight and a second line of sight by a beam splitter 34 that rotates as the motor 37 is driven. The light information is selectively transmitted to the star detector 33. Reference numeral 35 denotes a bearing for smoothing the rotation of the motor 37, and 36 denotes a goniometer for measuring the rotation angle of the beam splitter 34.

However, even in this improvement technique, a large amount of power is required to drive the motor 37, and a problem remains in precise control of the satellite position due to an error in the value provided from the goniometer 36.

An object of the present invention is to provide a star sensing device that can perform three-axis control of the satellite by using a single star detector.

Another object of the present invention is to provide a star sensing device driven at low power.

Another object of the present invention is to reduce the installation volume of the star sensing device.

The present invention for achieving the above object is a telephoto lens that receives optical information provided through a first line of sight for observing the first light source, and a second line perpendicular to the first line of sight. a beam splitter for transmitting and reflecting light information of a second light source provided through the sight to the telephoto lens, and provided to the telephoto lens through a first line of sight and a second line of sight A beam detector (CCD) for detecting light information, a first electro-optical-shutter for controlling the blocking and transmission of light provided through the first line of sight, and a second line of sight A second electro-optical shutter for controlling the blocking and transmission of light provided through the shutter, a shutter switching unit for controlling a power provided to the first / second electro-optical shutter, and a beam detector (CCD) ) Analyze the information provided and Parts of the switching control signal and a shutter for controlling the sex position, including a central processing unit for outputting a control signal for controlling characterized by the configured.

A detailed feature of the present invention resides in the use of ferroelectric liquid crystal devices as electro-optic shutters.

1 is an example of three-axis attitude control using two star detector according to the prior art,

2 illustrates an example of three-axis attitude control using one star detector according to an improved technique.

3 is a block diagram showing the concept of the improved technology,

4 is a detailed view of the main part of FIG. 3;

Figure 5 is a block diagram showing the configuration of a three-axis attitude control star detection apparatus according to the present invention.

Hereinafter, the configuration of the present invention and its operation will be described with reference to the accompanying drawings. Figure 5 is a block diagram showing the configuration of a three-axis attitude control star detection apparatus according to the present invention. Provided through a telephoto lens 51 receiving optical information provided through a first line of sight for observing a first light source, and a second line of sight perpendicular to the first line of sight. A beam splitter 34 for transmitting and reflecting light information of a second light source to be transmitted to the telephoto lens 51, and a telephoto lens 51 through the first and second eyes. A beam detector (CCD) 33 for detecting light information provided to the light source, and a first electro-optical device for controlling the blocking and transmission of light provided through the first line of sight. shutter (52-1), a second electro-optical-shutter (52-2) for controlling the blocking and transmission of light provided through the second line of sight, and the first and second 2 The shutter switching unit 53 for controlling the power supplied to the electro-optic shutters 52-1 and 52-2, and the information provided through the beam detector (CCD) 33 are divided. It consists of: (CPU Central Processing Unit) (54) and a control signal and a central processing unit for outputting a control signal for controlling the switching shutter unit 53 for controlling the attitude of the satellite according to the information.

The retina is a kind of surface sensor. The imaging technique in the camera is a technique of converting this surface information into time information by sampling. The high speed imaging technique is to increase the sampling frequency to obtain a high speed image. In general, about 200 to 10,000 coma / sec is defined as high speed and more than ultra high speed in high speed imaging.

When observing a star from an astronomical telescope, the light from the star is affected by atmospheric changes and the refractive index changes from time to time so that the image itself is severely shaken. This problem is inevitable unless the telescope is installed outside the atmosphere. In addition, since the temporal frequency characteristic of the shaking has a cut-off at 500 to 1000 Hz, a long exposure CCD camera used for ordinary astronomical observation observes the shape of a star spread wider than it actually is. Therefore, in order to observe the actual star shape, a camera for ultra-high sensitivity and high speed imaging is required.

The present invention is possible because there is a beam detector (CCD) having a high reading speed, a processing unit (CPU) having a fast data processing capability, and a mirror that transmits or reflects light without movement.

Electro-optical-shutters 52-1 and 52-2 used in the present invention are made of ferroelectric liquid crystal elements, and are converted into a transmission mode and a non-transmission mode by applying electricity to the electrodes. It is an element that repeats. Each electro-optic shutter is triggered according to the output signal of the shutter switching unit 53 which is operated by a control signal provided from the central processing unit (CPU).

The light provided from the first light source and the second light source is selectively transmitted by the beam splitter 34 to the beam detector 33 through the lens 51 to be converted into an image. However, unlike the prior art, there is no need for a motor for rotating the beam splitter 34 or a goniometer for measuring the rotation angle of the beam splitter, and a pulse applied by a circuit operated using less power. In some cases, an electro-optical-shutter is used to repeat light transmission or blocking. Therefore, the problem of power consumption for driving the motor can be solved, and it is possible to prevent the decrease in precision due to the error of the goniometer.

As described above, the present invention can reduce the size of the star sensing device, it has the effect that can be driven at low power.

Claims (3)

A telephoto lens receiving optical information provided through a first line of sight for observing a first light source; A beam splitter for transmitting and reflecting light information of a second light source provided through a second line of sight perpendicular to the first line of sight to the telephoto lens; A beam detector (CCD) for detecting light information provided to the telephoto lens through the first eye and the second eye; A first electro-optical-shutter for controlling the blocking and transmission of light provided through the first line of sight; A second electro-optical-shutter for controlling the blocking and transmission of light provided through the second line of sight; Shutter switching unit for controlling the power supplied to the first, second electro-optic shutter, And a central processing unit for analyzing the information provided through the beam detector (CCD) and outputting a control signal for controlling the attitude of the satellite according to the corresponding information and a control signal for controlling the shutter switching unit. Star detector for 3-axis attitude control. The method of claim 1; The beam splitter is a three-axis attitude control star sensing device, characterized in that installed to form 45 ° with the telephoto lens. The method of claim 1; And the first and second electro-optic shutters use a ferroelectric liquid crystal device.