JPH0511586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning star detection device mounted on a spin-type artificial satellite. In particular, a bright star in a direction almost perpendicular to the spin axis according to its spin is determined as the target star, and the target star is observed through a fixed field of view, and the timing when the target star enters the field of view and the image formation of the target star are determined. This invention relates to a scanning star detection device (star scanner) used to detect the direction and amount of inclination of an artificial satellite's spin axis from its position.

〔overview〕

The present invention is a scanning star detection device fixedly mounted on the main body of a spin-type artificial satellite, in which a CCD is placed on the imaging plane of the target star, and pixel charges are accumulated in a register along the scanning direction of the target star. This improves sensitivity, reduces the influence of unnecessary stars other than the target star, and enables accurate detection of the angle of the spin axis.

[Conventional technology]

In spin-type artificial satellites, there are
It is important to determine the inclination of the satellite's spin axis. In that case, the direction of the star is used as a reference for direction.

As such an apparatus, a scanning star detection apparatus has conventionally been used in which a V-slit type light receiving element (such as a photodiode) is arranged on the imaging plane. An example is shown in FIG. 3, FIG. 4 shows the arrangement on the satellite, and FIG. 5 shows the positional relationship between the spin axis and the star direction.

As shown in FIG. 4, when focusing on a certain star, each time the satellite 41 rotates once around the spin axis 42, the light from that star crosses (scans) the light receiving section 43 provided on the side of the satellite 41. ). This direction is hereinafter referred to as the "horizontal direction." As shown in FIG. 5, the light receiving section 43 is provided with a lens 51, and the light receiving elements 1 and 2 are arranged at the focal point (image forming plane) of the lens 51.

When the starlight crosses the light receiving section 43 in the horizontal direction due to the spin of the satellite 41, the starlight scans the light receiving elements 1 and 2 as indicated by reference numeral 5 in the drawing, as shown in FIG. At this time, signal waveforms such as those indicated by reference numerals 3 and 4 in the drawing are obtained as detection signals,
If the time interval between the detection signals is short, it can be determined that the starlight scans the lower side in FIG. 3, and if the time interval is long, it can be determined that the starlight scans the upper side.

The scanned position of starlight depends on the perpendicular angle of the star to a reference direction that is at a constant angle to a plane perpendicular to the satellite's spin axis, or conversely, the inclination angle of the satellite's spin axis. Therefore, the inclination angle of the spin axis of the satellite can be determined from the interval between the two detection signals. In practice, the reference direction is set in a plane perpendicular to the spin axis, and a slight deviation from that direction is detected as a perpendicular angle.

[Problem that the invention seeks to solve]

However, in such a device, the area of the photodetector needs to be very large compared to the imaging area of the star, so the influence of the dark current of the entire photodetector cannot be ignored, making it difficult to obtain a sufficient S/N ratio. . Therefore, we were able to detect only about second magnitude stars.

Another disadvantage was that it was susceptible to the effects of unwanted stars and galactic light.

The present invention solves the above problems,
It is an object of the present invention to provide a scanning star detection device that has a sufficiently large S/N ratio, can eliminate the influence of unnecessary stars and galactic light, and can accurately determine the direction of stars.

[Means for solving problems]

The present invention provides an imaging surface that is fixedly attached to the main body of a spinning artificial satellite and that focuses the starlight of a target star on a star that is approximately perpendicular to the spin axis of the satellite; In this scanning star detection device, the imaging plane is equipped with a means for detecting the deviation of the spin axis of the satellite from the scanning locus generated by the starlight. Equipped with a charge storage device (CCD) in which M pixels are arranged in a direction perpendicular to the charge storage device, the charge stored in each pixel is cumulatively integrated and stored in each stage. The means for detecting
The present invention is characterized in that it includes means for detecting which step on the charge storage element the starlight from the target star has passed through, based on the cumulative amount of charge accumulated in the vertical register, and determining the direction of the target star.

It is preferable that the image forming apparatus further includes a control signal generating section that controls the timing of the start and end of light reception of the charge storage element so that the accumulated charge amount of the vertical register is maximized.

Further, the apparatus may further include means for outputting angle information about the spin axis in the direction of the target star based on the control timing by the control signal generator.

[Effect]

N stages and M columns of charge storage elements each having M pixels in the horizontal direction parallel to the spin direction of the satellite and N pixels in the direction perpendicular thereto are arranged on the imaging plane of the light receiving section. When the starlight horizontally scans a given stage, each pixel in that stage generates a photodiode charge sequentially along the trajectory. The photodiode charges are immediately transferred to corresponding pixel registers, and are then accumulated and stored in vertical registers for each horizontal stage. As a result, a large amount of charge is stored in the vertical register at the position of the step scanned by the starlight. Therefore, the vertical angle of the direction of the star can be determined from the position on the vertical register where a large amount of charge is stored. The vertical angle resolution at this time is determined approximately by the pixel size. Furthermore, since the charges of pixels in the horizontal direction are accumulated, a large signal-to-noise ratio can be obtained even for weak starlight.

Furthermore, the charge storage element can control the timing of light reception. That is, it becomes possible to receive light only after the charge in each pixel is cleared, and the light receiving state is maintained until the accumulated charge is transferred. Setting the light receiving state in this manner is called "opening the gate." Therefore, the gate can be closed when there is no need to capture starlight, and the influence of unnecessary star and galaxy light can be removed.

Furthermore, by adjusting the opening and closing timing of the gate, the horizontal angle of the star's direction can be determined.
To do this, first, at the start of the operation, the position of the gate is sequentially changed to search for starlight, and once the starlight is captured, the position of the gate is adjusted to match the timing of the starlight. At this time, the position of the gate coincides with the position of the starlight, and the timing of the gate position indicates the horizontal angle of the starlight with respect to the reference direction. Conversely, it is possible to determine the position of the satellite in the spin direction relative to the position of the star.

〔Example〕

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

A charge storage element 6 is arranged on the imaging surface that receives starlight from the target star. This charge storage element 6 is N
Contains M columns of pixels, each N stages in the direction of the spin axis of the satellite, and M rows in the direction (horizontal direction) perpendicular to it.
Each pixel is placed. Therefore, as the satellite spins, starlight passes through any stage of the charge storage element 6. In FIG. 1, reference numeral 5 indicates a state in which the starlight scans M pixels of the n-th stage.

The charge storage element 6 is also provided with a vertical register 61 that cumulatively integrates and stores the charges stored in each pixel for each stage. The output of this vertical register 61 is supplied to the output signal processing section 8 as a charge storage element output signal 12.

The output signal processing unit 8 is a circuit that detects the deviation of the spin axis of the satellite from the scanning trajectory generated by the starlight, and determines which stage on the charge storage element 6 the starlight from the target star passes through from the charge storage element output signal 12. The direction of the target star is determined by detecting the direction of the target star, and outputs it as a vertical angle signal 14. The output signal processing section 8 also outputs the charge level when the vertical angle signal 14 is obtained as a level signal 15, and feeds it back to the control signal generation section 7.

The control signal generator 7 controls the timing of the start and end of light reception of the charge storage element 6 so that the accumulated charge amount of the vertical register 61 becomes maximum, that is, the level signal 15 becomes the maximum.
A pixel register control signal 9, which is a control signal for transferring the photodiode charge of 1 to each pixel register, is generated, and a timing signal 13 is outputted to the output signal processing section 8 in synchronization with the timing.

The output signal processing unit 8 uses this timing signal 13
angular information about the spin axis in the direction of the target star is obtained from and outputted as a horizontal angle signal 16.

The control signal generation unit 7 also outputs a horizontal register transfer control signal 10 for transferring the charge of the pixel register to the vertical register 61 in the row direction, and a charge storage element output signal 12 for the charge accumulated in the vertical register 61 to the outside. A vertical register transfer control signal 11, which is a strobe signal for reading, is generated and input to the charge storage element 6. The vertical register transfer control signal 11 is also input to the output signal processing section 8 for synchronous operation with the vertical register 61.

FIG. 6 shows the arrangement and angle of the charge storage element 6 on the satellite. The scanning star detection device of this embodiment is fixedly attached to the main body of a spinning artificial satellite, and is used to form an image of the starlight of the target star as a target star located approximately perpendicular to the spin axis of the satellite. A charge storage element 6 is attached to the image plane. The direction of the star is determined by the vertical angle, which is the deviation angle from a plane almost perpendicular to the spin axis (the reference direction in Figure 5), and the direction in which a given part of the satellite should be facing at a certain timing (as shown in Figure 6). horizontal angle, which is the rotation angle with respect to the indicated reference direction).

FIG. 2 shows an operation time chart.

When the starlight scans the charge storage element 6 like a scanning locus 5, the photodiodes of M pixels in the n-th stage in the horizontal direction of the charge storage element 6 receive the light as indicated by reference numerals 21a to 24a in the drawing, respectively. Drawing code 21a is the first pixel of the n-th stage, 24
a is the light reception timing of the Mth pixel.

However, the charge storage element 6 enters the light-receiving state with pulse A of the pixel register control signal 9, and transfers the accumulated charge to the pixel register for each photodiode with the next pulse B, and enters the non-light-receiving state. That is, pulse A opens the gate of charge storage element 6, and pulse B closes the gate. Therefore, if the photodiode charges were zeroed by pulse A of the pixel register control signal 9, they are accumulated after pulse A as indicated by numerals 21b to 24b in the drawing.

The charge of each pixel is transferred to the register at timing B of the pixel register control signal 9. That is, the starlight signal to be transferred is one received during the pulse time width from A to B of the pixel register control signal 9. Thereafter, each minute charge is transferred to the charge storage element 6 by the horizontal register transfer control signal 10.
The data is transferred to the vertical register 61 and accumulated there. Therefore, the charge in the n-th stage of the vertical register 61 is multiplied by the number of horizontal pixels of the charge storage element 6 (M times in this embodiment).

The charge in the vertical register 61 is transferred to the charge storage element output signal 12 by the vertical register transfer control signal 11.
The signal is read out to the output signal processing section 8 as a signal. As shown in FIG. 2, the charge storage element output signal 12 has a high level when the n-th register charge scanned by the starlight is output, so by observing this charge storage element output signal 12, , it is possible to identify which pixel of the charge storage element 6 is scanned by the starlight. The resolution at this time is determined by the number of pixel stages (N in this embodiment) of the charge storage element 6. The output signal processing unit 8 determines the vertical angle of the target star from this identification result and outputs it as a vertical angle signal 14.

The interval between pulses A and B of the pixel register control signal 9 is set as the time required for the starlight to scan the charge storage element 6 from end to end. Therefore, if the timing of this pixel register control signal 9 lags behind the starlight scanning, starlight charges are accumulated in the left side of the horizontal pixels of the charge storage element 6, that is, in the pixels on the smaller number side. Later, pulse A is input and the charge is cleared. Therefore, when pulse B is transferred to each pixel's register, the left pixel remains at zero charge. Therefore, the accumulated charge amount of the n-th horizontal pixel decreases. In addition, if the timing of the pixel register control signal 9 is too early than the scanning of the starlight, the pulse B is applied to the register before the starlight charge is accumulated in the right side of the horizontal pixel of the charge storage element 6, that is, the pixel on the larger number side. It will be transferred. Therefore, the accumulated charge amount of the horizontal pixels also decreases. Therefore, the level signal 15 representing the accumulated charge amount is fed back from the output signal processing section 8 to the control signal generating section 7, and the timing of the pixel register control signal 9 is controlled so that the level signal 15 becomes maximum.

Furthermore, the timing of the pixel register control signal 9 indicates the timing of starlight scanning. Therefore, a timing signal 13 synchronized with the pixel register control signal 9 is input from the control signal generator 7 to the output signal processor 8, and the angle in the spin rotation direction of the starlight is measured and output as a horizontal angle signal 16. Since the timing of the pixel register control signal 9 is controlled with high time resolution, the horizontal angle of the star can be measured with high precision.

To set the scanning of the starlight to occur between the gates of pulses A and B of the pixel register control signal 9, the feedback by the level signal 15 is canceled and a plurality of temporally consecutive gates are generated, and the spin Observe the entire circumference of the star and decide which gate the starlight enters should be the target star. Once you have decided on the gate,
Inhibits output signals coming into other gates. At this time, the output signal processing section 8 measures the level of the charge storage element output signal 12 which has become a single pulse, and feeds back the level signal 15 to the control signal generation section 7 . The control signal generating section 7 controls the output timing of each control signal based on this level signal 15 so that the level signal 15 is always at the maximum level.

〔Effect of the invention〕

As explained above, the present invention utilizes the high pixel resolution and charge accumulation property of charge storage elements,
It is possible to obtain a signal with a high signal-to-noise ratio for weak starlight. This has the advantage that it is possible to measure the starlight incident angle in the direction perpendicular to the spin and in the horizontal direction, which is necessary for a star scanner, with high accuracy even in the case of a faint star with a large luminosity magnitude. Furthermore, since it is no longer affected by other stars, there is no need to perform complex signal processing.
In particular, the detection of the angle perpendicular to the spin is a direct measurement, which improves accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.
FIG. 2 is a waveform diagram of each part of the embodiment shown in FIG. 1. FIG. 3 is a diagram showing a sensor section of a conventional star scanner and its output waveform. FIG. 4 is a diagram showing the arrangement on a conventional satellite. FIG. 5 is a diagram showing the positional relationship between the spin axis and the star direction. FIG. 6 is a diagram showing the arrangement of the embodiment shown in FIG. 1 on a satellite. DESCRIPTION OF SYMBOLS 1, 2... Light receiving element, 3, 4... Photodiode output signal, 5... Scanning locus of starlight, 6... Charge storage element, 7... Control signal generating section, 8... Output signal processing section,
9... Pixel register control signal, 10... Horizontal register transfer control signal, 11... Vertical register transfer control signal, 12... Charge storage element output signal, 13... Timing signal, 14... Vertical angle signal, 15... Level signal, 16... Horizontal Angle signal, 21a to 24a...Photodiode light reception signal of each pixel, 21b to
24b...Photodiode accumulated charge of each pixel, M...Number of horizontal pixels, N...Number of pixel stages.

Claims (1)

[Claims] 1. Imaging that is fixedly attached to the main body of a spinning artificial satellite, and that images the starlight of the target star with a star located approximately perpendicular to the spin axis of the satellite as the target star. A scanning star detection device comprising: a plane; and means for detecting a deviation of the spin axis of the satellite from a scanning trajectory generated by the starlight on the imaging plane, A charge storage device (CCD) is equipped with a charge storage device (CCD) in which M pixels are arranged in each N stage and in a direction perpendicular to the CCD. The detecting means includes a vertical register that integrates and accumulates, and the detecting means detects which step on the charge storage element the starlight from the target star has passed, based on the cumulative amount of charge accumulated in the vertical register. A scanning star detection device comprising means for determining the direction of the target star. 2. An imaging surface that is fixedly attached to the main body of a spinning artificial satellite and that images the starlight of the target star with a star located approximately perpendicular to the spin axis of the satellite as the target star; In a scanning star detection device comprising means for detecting a deviation of the spin axis of the satellite from the scanning locus generated by the starlight on the imaging plane, N stages are arranged on the imaging plane in the direction of the spin axis of the satellite, orthogonal thereto. The charge storage device (CCD) is equipped with a charge storage device (CCD) in which M pixels are arranged in each direction. The detecting means includes a register, and the detecting means detects which step on the charge storage element the starlight from the target star has passed through, based on the accumulated charge accumulated in the vertical register, and determines the direction of the target star. , and further comprising a control signal generator for controlling the timing of the start and end of light reception of the charge storage element so that the accumulated charge amount of the vertical register is maximized. Detection device. 3. An imaging surface that is fixedly attached to the main body of a spinning artificial satellite and that images the starlight of the target star with a star located approximately perpendicular to the spin axis of the satellite as the target star; In a scanning star detection device, the scanning star detection device is equipped with a means for detecting the deviation of the spin axis of the satellite from the scanning locus generated by the starlight on the imaging plane, and on the imaging plane, N steps are arranged in the direction of the spin axis of the satellite, perpendicular thereto. The charge storage device (CCD) is equipped with a charge storage device (CCD) in which M pixels are arranged in each direction. The detecting means includes a register, and the detecting means detects which step on the charge storage element the starlight from the target star has passed through, based on the accumulated charge accumulated in the vertical register, and determines the direction of the target star. a control signal generating section that controls the timing of the start and end of light reception of the charge storage element so that the accumulated charge amount of the vertical register is maximized; 1. A scanning star detection device comprising: means for outputting angular information about a spin axis regarding the direction of a star.