JP2959541B2 - Earth sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth sensor mounted on an artificial satellite and used for attitude control, and more particularly to an earth sensor device requiring stability and high accuracy.

[0002]

2. Description of the Related Art In an infrared detector of a conventional earth sensor,
In order to remove the fluctuation of the threshold value when detecting the infrared signal, a configuration in which the spot beam is divided into east and west has been adopted. By scanning such a spot beam from the west to the east on the earth, pitch pulses in both the east and west directions of the earth are generated. If these pitch pulses are specified, the bitch angle can be obtained from the angle with the center of the viewing direction by the angle encoder. Such a scan type earth sensor is disclosed in Japanese Patent Application Laid-Open No. 61-20009.
9 or JP-A-6-331346, or
PIE Vol.1157 Infrared Technology XV (1989)
Is disclosed.

[0003]

However, in the conventional earth sensor, when the spot beam divided into two is scanned, the higher the latitude of the scanning position, the larger the intersection angle between the earth end and the end of the spot beam. The end face of the earth enters the spot field of view with a different shape. For this reason, the output signal waveform of each spot beam has a gentle rise and fall, which makes it easy to pick up external and internal noises, making it impossible to obtain a high-precision pitch pulse.

[0004] It is an object of the present invention to provide an earth sensor device capable of obtaining a sensor output having a sharp rise and fall.

Another object of the present invention is to provide an earth sensor device capable of making the same sensor output waveform on the east and west edges of the earth.

[0006]

An earth sensor device according to the present invention has a sensor surface divided into four parts, an edge of each sensor surface having a first direction and a second direction, and the first direction being a beam. A light detecting means that matches the angle of the first end of the earth when the spot is scanned and the second direction matches the angle of the second end of the earth when the beam spot is scanned; An operation for combining the sensor outputs of the sensor surface divided into four parts depending on whether it is located on the first end side or the second end side of the earth so that the first direction and the second direction coincide with each end of the earth. And means. Since the light receiving surface of the light detecting means is divided into the first and second directions corresponding to the direction of the end face of the earth, when scanning the beam spot, the sensor output changes sharply at the end face of the earth and becomes stable. It is possible to specify a highly reliable and highly accurate position.

[0007]

FIG. 1A is a plan view showing a split configuration of an infrared sensor unit in an embodiment of the earth sensor device according to the present invention, and FIG. 1B is a plan view showing the relationship between a spot beam and a scan latitude on the earth. It is a schematic diagram which shows a relationship.

In the infrared sensor section 10 of the present embodiment, the sensor surface is divided into four by two dividing lines 11 and 12, and the divided sensor portions are hereinafter referred to as A, B, C, and D, respectively, as shown in the drawing. The description will be made as a beam spot input to the infrared sensor. The dividing lines 11 and 12 are determined as follows.

As shown in FIG. 1B, when the spot beam 10 is scanned from west to east at the latitude θ of the earth 20, the spot beam 10 is scanned so as to coincide with the tangent of the earth 20 at the western latitude θ. A dividing line 11 is set, and similarly, a dividing line 12 of the spot beam 10 is set so as to coincide with the tangent of the earth 20 at the latitude θ on the east side. The normal 13 running from north to south perpendicular to the scan direction from simple geometry
Are + θ and −θ, respectively.

The combination of the sensor outputs of the infrared sensor divided into four parts is switched between the west side and the east side.
That is, on the west side as shown in FIG.
Divides (AB / CD) into sensor portions A and B and sensor portions C and D to generate two added outputs A + B and C + D. On the east side, parting line 1
2 divides the sensor part into D and A and two sensor parts B and C (DA / BC) to generate two added outputs of D + A and B + C. The details will be described below.

FIG. 2 is a block diagram showing a circuit configuration in the present embodiment. The adder 101 has sensor parts A and B
Input the sensor output output from the
02 inputs and adds the sensor outputs output from the sensor portions B and C, an adder 103 inputs and adds the sensor outputs output from the sensor portions C and D, and an adder 104 outputs the sensor portion D And the sensor output output from A is input and added. The addition results output from the adders 101 to 104 are respectively differentiators 105 to 108.
, And differentiated signals S _{1 to} S ₄ are generated.

The differential signal S ₁ is input to the inverting input terminal of the differential amplifier 109, and the differential signal S ₃ is input to its non-inverting input terminal. Further, the differential signal S ₂ is input to the non-inverting input terminal of the differential amplifier 110, the differential signal S ₄ is input to an inverting input terminal. Further, the differential signals S ₁ and S ₃ are output from the comparator 11
1 and 112 and each is compared to a predetermined threshold. The comparison results are input to the AND gate 113 as a pulse signal, and a west window pulse WIN _W is generated. Similarly, the differential signals S ₂ and S ₄ are output from the comparator 11
4 and 115, and each is compared with a predetermined threshold. The comparison results are input to the AND gate 116 as a pulse signal, and an east window pulse WIN _E is generated.

[0013] The differential output S ₅ of the differential amplifier 109 is input to zero cross comparator 117, it is generated a pulse which rises at the zero-crossing point, and inputs to the AND gate 118 together with the window pulse WIN _W. Thus western pitch pulse P ₁ is generated. Similarly, the differential amplifier 110
The differential output S ₆ of input to zero cross comparator 119, it is generated a pulse which rises at the zero-crossing point, and inputs to the AND gate 120 together with the window pulse WIN _E.
Thus the east pitch pulse P ₂ is generated. The west pitch pulse P ₁ and the east pitch pulse P ₂ are
And one of them is selected and output according to the pulse signal W / E. The selection signal W / E is a signal indicating whether the scan is on the west side or on the east side, and its rise indicates the center of the viewing direction by the angle encoder.

FIG. 3 is a schematic diagram showing an example of a scan operation on the earth, and FIG. 4 is a waveform diagram for explaining the operation of the present embodiment when the scan shown in FIG. 3 is performed. The scanning of the spot beam 10 is performed from west to east. Therefore, the waveform diagram of FIG. 4 shows the waveform of the differentiated signal generated at the western end of the earth and the eastern end of the earth, and its processed waveform.

[0015] As shown in FIG. 4 (a), the sensor output of the sensor portions A and B are added by the adder 101 is differentiated by the differentiator 105, the differential signals S ₁ indicating the west side of the earth terminal can be obtained. Similarly, the sensor outputs of the sensor parts D and A added by the adder 104 are differentiator 10
8 and a differential signal S ₄ indicating the eastern edge of the earth
Is obtained. Since the differential signal S ₁ indicates a rising portion and the differential signal S ₄ indicates a falling portion, their polarities are reversed. As shown in FIG. 4 (b), the sensor output of the sensor portions C and D are added by the adder 103 is differentiated by differentiator 107 west of the differential signal S ₃ is obtained. Similarly, the sensor output of the sensor portions are added by the adder 102 B and C is a differential signal S ₂ on the east side is obtained is differentiated by differentiator 106. The polarities of these differential signals are also reversed.

As shown in FIG. 4C, the differential amplifier 10
9 outputs the sum of the inverted signal of the differential signal S ₁ and the differential signal S _{3, so} that the west-side zero-cross signal S ₅ is obtained. The differential amplifier 110 outputs the inverted signal of the differential signal S ₄ and the differential signal S ₂ . Since the sum is output, the east-side zero-cross signal S ₆ is obtained.

As shown in FIG. 4E, the differential signals S ₁ and S ₃ are inputted to comparators 111 and 112 and compared with a predetermined threshold value.
, A west window pulse WIN _W is generated. Similarly, as shown in FIG.
₂ and S ₄ are compared with a predetermined threshold value is input to the comparator 114 and 115, they compare the result AND gate 11
6, an east window pulse WIN _E is generated.

[0018] As shown in FIG. 4 (g), the differential output S ₅ inputted to zero cross comparator 117, a pulse rising at the zero-cross point is generated, the window pulse WIN _W and logical product is taken of the West pitch pulse P ₁ is generated. Similarly, the differential output S ₆ of the differential amplifier 110 is input to the zero-cross comparator 119, where a pulse rising at the zero-cross point is generated, and an east-side pitch pulse P ₂ is generated by a logical product with the window pulse WIN _E. And
When the selection signal W / E is at low level, the west pitch pulse P
₁ is selected, when the high level east pitch pulse P ₂ is selected. The differences θ ₁ and θ ₂ between the west pitch pulse P ₁ and the east pitch pulse P ₂ thus obtained and the rising timing of the selection signal W / E are calculated, respectively, and the pitch angle θp = (θ ₁ −θ ₂ ) / 2. Can be obtained.

[0019]

As described above in detail, according to the present invention, the sensor surface is divided into four parts by two dividing lines in accordance with the scanning latitude, and the sensor outputs are appropriately combined, whereby a steep sensor is obtained. Output can be obtained, and even if the scanning latitude becomes high, it is hardly affected by changes in the state of the earth's cloud, gas, atmosphere, etc., and furthermore, various fluctuations such as temperature fluctuation inside and outside the device, noise, or fluctuation of power supply voltage A high-precision bitch pulse that is stable against drift can be generated.

[Brief description of the drawings]

FIG. 1A is a plan view showing a divided configuration of an infrared sensor unit in an embodiment of the earth sensor device according to the present invention, and FIG. 1B is a schematic diagram showing a relationship between a spot beam and a scan latitude on the earth. FIG.

FIG. 2 is a block diagram illustrating a circuit configuration according to the embodiment.

FIG. 3 is a schematic diagram illustrating an example of a scanning operation on the earth.

FIG. 4 is a waveform chart for explaining the operation of the present embodiment.

[Explanation of symbols]

 Reference Signs List 10 spot beam (split sensor surface) 11 first split line 12 second split line 20 earth 101-104 adder 105-108 differentiator 109, 110 differential amplifier 111, 112 comparator 113 AND gate 114, 115 comparison Unit 116 AND gate 117, 119 Zero cross comparator 118, 120 AND gate 121 Selector

Claims (6)

(57) [Claims] 1. An earth sensor device for scanning a beam spot in a direction traversing the earth, wherein a sensor surface is divided into four parts, and edges of each sensor surface have a first direction and a second direction. One direction matches the angle of the first end of the earth when scanning the beam spot, and the second direction matches the angle of the second end of the earth when scanning the beam spot. A light detection unit that outputs the sensor outputs of the four divided sensor surfaces in the first direction and the second direction, depending on whether the beam spot is located on the first end side or the second end side of the earth. And an arithmetic means for combining directions of the earth so as to coincide with each end of the earth. 2. The arithmetic means combines the sensor outputs so that when the beam spot is located on the first end side of the earth, two sets of sensor surfaces divided by the first direction are formed. , The beam spot is on the second of the earth
2. The earth sensor device according to claim 1, wherein the sensor outputs are combined so as to form another two sets of sensor surfaces divided by the second direction when located at the end side. 3. The computing means further comprises: first and second sensors from two sets of sensor surfaces divided by the first direction when the beam spot is located at a first end of the earth. The output difference is calculated, and the position of the first end of the earth is specified by detecting the zero crossing point of the difference signal. When the beam spot is located on the second end side of the earth, the second end is detected. Calculating the difference between the third and fourth sensor outputs from the two sets of sensor surfaces divided by direction and detecting the zero-cross point of the difference signal to determine the position of the second end of the earth. The earth sensor device according to claim 2, wherein: 4. An earth sensor device for scanning a beam spot in a direction crossing the earth, wherein a sensor surface is divided into four parts, edges of each sensor surface have a first direction and a second direction, and The first direction is tilted by an angle corresponding to the latitude of the earth traversed by the beam spot with respect to a normal direction orthogonal to the scan direction of the beam spot, and the second direction is the latitude relative to the normal direction. A light detecting means inclined in a direction opposite to the first direction by a corresponding angle of, and each of the four-divided sensor surfaces depending on whether the beam spot is located on the west or east side of the earth. An arithmetic means for combining a sensor output so that the first direction and the second direction coincide with each end of the earth. 5. The arithmetic means combines the sensor outputs so as to form two sets of sensor surfaces divided by the first direction when the beam spot is located on the west side of the earth. 5. The earth sensor device according to claim 4, wherein when the spot is located on the east side of the earth, the sensor outputs are combined so as to form another two sets of sensor surfaces divided by the second direction. . 6. The computing means further comprises: when the beam spot is located west of the earth, the difference between the first and second sensor outputs from the two sets of sensor planes divided by the first direction. Is calculated, and the position of the west end of the earth is specified by detecting the zero-cross point of the difference signal. When the beam spot is located on the east side of the earth, two sets of the beam spot are divided by the second direction. 6. The earth sensor according to claim 5, wherein a difference between the third and fourth sensor outputs from the sensor surface is calculated, and a position of the eastern end of the earth is specified by detecting a zero cross point of the difference signal. apparatus.