JPH02263112A - Fixed star sensor - Google Patents

Abstract

PURPOSE:To securely control the attitude of an artificial satellite by finding time variation of each picture element of image data within a specified range. CONSTITUTION:First and second image data within the specific range which are obtained by picking up an image each at different time are stored in 1st and 2nd storage means 26 and 27 respectively and the time variation of the image is detected according to image data on the difference between the 1st and 2nd image data stored in the 1st and 2nd storage means 26 and 27 to detect the attitude variation. Therefore, even when such image data that a specially bright star is not present in the visual field or that a nebula is present in the visual field while all the data are utilized effectively, the attitude variation can easily and securely be detected. Consequently, the attitude of the artificial satellite can be controlled effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a stellar sensor for detecting azimuth data for attitude control of an artificial satellite, for example.

(Prior Art) In order to control the attitude of an artificial satellite flying in outer space, it is necessary to observe the positions of stars existing in outer space and measure its attitude and orientation. A stellar sensor is used to control the attitude of such an artificial satellite, and as shown in FIG. .

First, the sensor head section 11 includes a light receiving section 111 using COD.
The light receiving unit 111 captures images of outer space, particularly stars, through an optical system 112 and converts them into image data. The light receiving section 111 is cooled by a cooling system 113 and is driven by an electronics section 114 of a COD drive.

The electronic circuit section 12 also includes a signal processing section 121 that performs A/D conversion processing, etc., and a CCD control section 12 of the image receiving section ill.
2. A data processing unit 123 that performs processing, etc., and an interface 124 for various data are set for each group to be described later.

In the star sensor configured in this way, the optical system 11
2 detects an image of a star, and converts it into image data in the CCD light receiving section 11. However, in order to function as a star sensor, the focal length of the optical system 112 is first shifted as shown in FIG. The star image transferred to the CCD light receiving element of the light receiving section 111 is greatly blurred.

Once a largely blurred star image has been projected onto the surface of the CCD light receiving element in this way, the data of each pixel is weighted using the X and Y coordinates of each pixel of the CCD light receiving element. Based on the obtained data, find the center of gravity of this star image. This center of gravity is the direction in which the stars can be seen, and the attitude angle of the satellite can be determined based on this direction.

In a method based on such an operating principle, when multiple stars exist in the field of view of the optical system, the output of each pixel of the CCD image receiving element containing images of the multiple stars is transmitted for each corner star. After grouping, it is necessary to perform processing to find the center of gravity of the star images.

The process of dividing into loops as described above requires a complicated procedure, and as a result, bright stars that can be clearly imaged may not be within the field of view, or images that are widely spread out like nebulae may be in the field of view. If you have entered the
This star sensor cannot clearly confirm the orientation, making it difficult to control the satellite's attitude with high precision.

(Problems to be Solved by the Invention) As described above, in the conventional star sensor, highly accurate attitude control is difficult depending on the state of the image of the star that enters the field of view of the optical system.

Therefore, the present invention was made in view of the above points, and even if the image received by the light receiving element does not only show bright stars, it is possible to easily and reliably detect changes in orientation based on data within a specified range. The objective is to provide a star sensor that can be used in directions where there are no bright stars or where there are nebulae, etc., so that, for example, the attitude control of an artificial satellite can be reliably executed. be.

[Structure of the Invention] (Means for Solving the Problems) In the stellar sensor according to the present invention, first and second image data of a specific range captured at different times are first and second image data, respectively. The image is stored in the second storage means, and temporal changes in the image are detected based on the image data of the difference between the first and second images stored in the first and second storage means. Allow changes to be detected.

(Function) The above-mentioned stellar sensor calculates temporal changes in each pixel of image data in a specified range, and does not require data grouping or selection processing as in the past. There's no need to do it. Therefore, even when using image data with no particularly bright stars in the field of view or with nebulae in the field of view, with a simple procedure and with effective use of all data,
This makes it possible to detect attitude changes easily and reliably, and for example, enables effective control of the attitude of an artificial satellite.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows its configuration, in which a CCD light receiving section 21 receives an image obtained through an optical system 22. Light receiving part 2
1 is appropriately cooled by a cooling system 23,
It is also driven by the CCD drive electronics section 24.

The image data of the video image received by the CCD light receiving section 21 is A.
The image data is converted into digital data by the /D converter 25, and this image digital data is written and stored in the first or second frame memory 26, 27. The frame memories 26 and 27 each constitute a storage device for storing digital data of one screen, and one of them is selected to store and hold the image data from the A/D converter 25.

The image data stored in the first and second frame memories 26 and 27, respectively, is processed by the image processor 28 and processed by the data processing section 29, and this processed data is sent to the I10 port 30. will be output from.

The operation of such a sensor configuration will first be briefly explained in terms of dimensions.

Now, assume that image data as shown in (A) in Figure 2 is obtained at a certain time t1, and that image data as shown in (B) in Figure 2 is obtained at time t2 following this time t1. do. Then, the difference between the image data at times t1 and t2 becomes as shown in (C) of FIG. Here, time t1
In the field of view of the screen, image data exists in the range of pixel numbers i to i+6 of the CCD image receiving element, and at time t2, the field of view changes from time t1, and the image data exists in the range of pixel numbers i+4 to i+10. Pigs are now present.

Here, in the image pig shown in FIG. 2 (C) above, weighting is performed using the address of each CCD pixel as a weighting function, and the result of calculating the sum is S, and the (
Let A be the sum of the signal levels for each pixel of the image data of A) and (B). Assuming that there is no random error in the sensor, (A) and (B) in Figure 2
) The total value of each signal level is theoretically equal. Then, the moving distance δ of the image between time t1 and t2 is given by the following equation.

δ−S+A ・・・・・・・・・(1
) Similarly, if we extend the above method to two-dimensional images, we get the following.

The sum of signal levels of image data obtained at time t1 is A
Let B be the sum total of the signal levels of the image data obtained at time t2. If a star disappears from the field of view of the screen or a new star enters between the above times t1 and t2, the difference between the above sums A and B will appear large, and such a difference will appear. In such a case, adjust the range of the screen to be calculated so that there are no stars entering or exiting, and select “A′
.

B”.

Next, take the difference between the two screens at times t1 and t2, set the sum of the data weighted by the X coordinate address of the CCD screen as Sx, and set the sum of the data similarly weighted by the Y coordinate address as Sy.
Then, the screen movement amount δx1 in the X-axis direction and the screen movement amount δy in the Y-axis direction are each expressed by the following equations.

δx = Sx +A ・・・・・・・・・
(2) δy=δy +A ・・・・・・・・・
(3) Then, from the above δx and δy, the posture rate around the X axis and around the X axis can be determined.

FIG. 3 shows the flow of the above-mentioned processing. First, in step 100, image data at time t1 captured by the CCD image receiving element is stored in the first frame memory 26. Further, the image data at time t2 is also stored in the second frame memory 27 as shown in step 101. Then, in the next step 102, the image processing processor 28 obtains a screen of the difference between the image data stored in the first and second frame memories 26 and 27, respectively, and the difference image data produced by the processor 28 is , for example, stored in the second frame memory 27.

In this manner, with the image data at time t1 stored in the first frame memory 2G and the image data of the difference described above stored in the second frame memory 27, step 10
3, the sum A of the signal levels of the image data stored in the first frame memory 26 is determined.

That is, as shown in FIG. 4(A), the sum of data aij corresponding to each pixel is determined.

In steps 104 and 105, the difference image data stored in the second frame memory 27 is weighted by X-axis and Y-axis coordinates,
The purpose is to find the sum Sx and δy, and (B
), the total sum S
x and δy are each expressed as follows.

However, X represents the X coordinate and y represents the X coordinate.

Here, (A) in FIG. 5 schematically shows a specific example of image data at time t1 that is stored in the first frame memory 2B, and (B) shows a concrete example of the image data that is initially stored in the second frame memory 2B. The image data at time t2 stored in the frame memory 27 is shown in a simulated manner in the same way as above. In this example, the first
Comparing the image data at time t2 with the second image data at time t2, the second image is “
+22, moving "-1" in the Y direction. And the first
The sum A of the image data of the screen is calculated as follows.

= (1+6+2+5+10+4+4+1)=33 Furthermore, the image data of the difference between the first and second image data at time tl and time t2 shown in (A) and (B) above is shown in (C) in FIG. Sx
and δy are calculated as follows.

-[(-2) X (-1) +(-1) X (-B
) 10X(-2)+・・・・・・・・・・・・-8+3
0+22+6-66 − (-1) + (-2) + (-if) +(-
18)+(-G) --33 In steps 106 and 107, the amounts of movement δx and δy are determined based on Sx and yl determined as above, and the total sum A, respectively, corresponding to the above example. It is calculated as follows.

δx-66÷33-2 δy--33÷33--1 The travel amounts δx and δy thus determined are output in step 108, and attitude control is executed based on the travel amounts δx and δy. It becomes like this.

[Effects of the Invention] As described above, according to the stellar sensor according to the present invention, the attitude rate of the artificial satellite can be easily and reliably adjusted, for example, based on the amount of movement of the field of view of the screen used in the artificial satellite to image stars. It is assumed that the accuracy is highly reliable. Therefore, it is possible to provide an attitude rate sensor that is used for high-precision pointing control over a long period of time, particularly for use in astronomical observation satellites and the like.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram for explaining a stellar sensor according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the state of time data obtained by the stellar sensor, and FIG. 3 is a processing diagram of the stellar sensor. 4 is a flow chart explaining the flow of the above process, FIG. 5 is a diagram explaining the state of the image data in the same simulated example, and FIG. 6 is a diagram explaining the state of the image data in the above process flow. Block diagram explaining the sensor, No. 7
The figure is a diagram illustrating the state of a star image. 21... COD light receiving section, 22... Optical system, 25...
・A/D converter, 26.27...first and second
frame memory (image data storage means), 28...
Image processing processor. Applicant's representative Patent attorney Takehiko Suzue CCD Pirin Lua #-A Figure 3 (A) (B) Figure 4 N-plate plate (A) (B) (C) Figure

Claims (1)

[Scope of Claims] CCD optical image receiving means for capturing a star image; first storage means for storing image data of a first image captured by the image receiving means at a first time; a second storage means for storing image data of a second video imaged by the image receiving means at a second time different from the time of the image data stored in the first and second storage means, respectively; difference screen formation storage means for creating and storing difference screen data for each pixel of the first and second image data; Weighting is performed on each pixel of the X coordinate and Y coordinate of the difference screen stored in the calculating means and the difference screen formation storage means, respectively.
and means for determining the summation Sx and Sy of the coordinates, and based on the summation A and Sx and Sy, the posture change δ
A stellar sensor characterized by determining x and δy.