JPH08261788A - Earth sensor - Google Patents

Abstract

PURPOSE: To prevent the occurrence of trouble when an attitude is controlled, by setting a comparison device and, short-circuiting and discharging a capacitor not to overflow when an infrared output is larger than a certain value. CONSTITUTION: The infrared output of an infrared detection device 11 is sent to a differentiation device 12 and also to a comparison device 16. The infrared output of the detection device 11 is compared with a reference voltage at the comparison device 16. When a visual field of the infrared detector 11 enters the sun, the output of the detector 11 becomes larger than when the detector is faced to an earth image. The comparison device 16 subsequently outputs a signal. The output signal of the comparison device 16 is sent to selection devices 14A-14D, closing a discharge switch 17 connected in parallel to a capacitor C of an integration circuit IN, with both ends of the capacitor being short- circuited and discharged. The discharge switch 17 is closed for a short time and returned to be opened immediately afterwards.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth sensor used for attitude control of a spacecraft.

[0002]

2. Description of the Related Art An earth sensor is a device mounted on a spacecraft or the like and detects the direction of the earth and controls the attitude of the spacecraft.

FIG. 2 shows a conventional earth sensor.
Will be described with reference to.

Reference numeral 11 denotes an infrared detecting device. The infrared detecting device 11 comprises an infrared detector for detecting infrared rays generated by the earth, an optical system for sweeping the visual field of the infrared detecting device 11, and the like. The field of view of the infrared detection device 11 is swept by the optical system so as to draw an ellipse, for example. When the earth image is E in FIG. 3, the field of view of the infrared detection device 11 is substantially elliptic from P to Q, and Q to P as indicated by the arrow Y, and the earth image is formed in a direction crossing the earth image. It is swept so that the position across it is different.

At this time, the position where the field of view of the infrared detector 11 crosses the earth image, and therefore the length across which the earth image crosses, differs depending on the attitude of the spacecraft. The attitude of the spacecraft is controlled by utilizing such a relationship. In the following description, P to Q will be described as a forward path, and Q to P will be described as a return path.

By the way, while the field of view of the infrared detector 11 crosses the earth image, infrared rays are detected by the infrared detector 11. In addition, in FIG.
Φ1 and φ2 are the timings at which the field of view crosses the edge of the Earth image on the outward path, and φ at the return path.
3 and φ4. In this case, the infrared output detected by the infrared detection device 11 is as shown in FIG. Note that in FIG. 4, the horizontal axis represents time t. Further, the detected infrared output is differentiated by the differentiator 12 (FIG. 2).
Therefore, the differentiated signals are b1, b in FIG.
2, b3, b4.

Then, the outputs b1, b2 of the differentiator 12 are
Based on b3 and b4, the length of the field of view of the infrared detection device 11 that crosses the earth image on the outward path is obtained from the value of (φ2-φ1), and the earth edge angle is measured. In addition, the crossing length on the return path is obtained from the value of (φ4-φ3), and the earth edge angle is measured. Then, the direction of the earth is detected from the earth edge angles measured on the outward and return paths.

However, if noise N1, N2, ... Is superimposed on the infrared output as shown in FIG.
A differential output (not shown) is also generated by 1, N2, .... In this case, there is a risk that the differential output due to the noises N1, N2, ... Is erroneously determined as the edge portion of the earth and the earth edge angle is measured based on this value. In order to prevent such an error, the output of the differentiator 12 (FIG. 2) is divided into, for example, four groups and processed by the sorter 13. For example, it is determined whether the timing at which the output of the differentiator 12 is obtained is the outward path from P to Q or the return path from Q to P. Then, it is divided into four groups A, B, C, and D based on the combination of the timing and the polarity of the differential output.

For example, the differential output b1 is output on the outward path and has a positive polarity, so that the differential output b1 is output to the group A. The differential output b2 is output on the outward path and has a negative polarity, which is output to the group B.
3 is output on the return path and has a positive polarity, so it is divided into a group C, and the differential output b4 is output on the return path and is divided into a group D because it is negative and has a negative polarity. It should be noted that whether the differential output is output on the outward path or on the return path is determined based on information obtained from the optical system of the infrared detection device 11.

The differential outputs b1, b2, b3, b4 (FIG. 4b) divided by the sorting device 13 are added to the selecting devices 14A-14D, respectively. The selection device 14A
14D have the same configuration, the configuration is shown for one selection device 14A and the other selection devices 14B-
The configuration of 14D is omitted. The selection device 14A includes a switch SW and an integration circuit IN, and the integration circuit IN
Is composed of an amplifier A and a capacitor C.

The differential output b1 is input to the integrating circuit IN,
An integrated waveform as shown in FIG. 4C is obtained. Further, the integrated waveforms of FIGS. 4D to 4F are obtained from the differential outputs b2 to b4, respectively. The integral waveform rises at the input of the differential output and then gradually decreases. Since the cycle of crossing the earth edge in the forward and backward paths can be predicted, the integral output is set to 0 before the next differential output. Then, when the integrated waveform rises and then its value drops to, for example, 50%, the switches S of the selection devices 14A to 14D are
Close W. Therefore, the differential output that is input from the sorting device 13 after the switch SW is closed is measured by the measuring device 1.
Added to 5. Then, the measuring device 15 measures the earth edge angle and detects the earth direction.

[0012]

According to the above-mentioned structure, the switch SW of the selection device is opened until a fixed time elapses after the differential output is input. Therefore,
Even if a differential output is generated due to a noise component in the meantime, the differential output can be blocked by the selection device so as not to be sent to the measuring device 15. Therefore, the problem of measuring the earth edge angle by the differential output due to the noise component can be prevented.

However, an integrating circuit is used in the selecting device. Therefore, when the field of view of the infrared detection device enters the sun, a large infrared output is input to the integrating circuit, and the capacitor of the integrating circuit overflows. When the capacitor overflows, it takes ten and several seconds for the capacitor of the integrating circuit to discharge and return to its original state, during which the earth sensor does not function. As a result, the attitude control of the spacecraft may be disturbed and the correct attitude may not be restored.

In order to avoid such a problem, when sunlight is expected to enter in advance, the field of view of the infrared detection device is masked while the sunlight is incident so that the condenser of the integrating circuit does not overflow. I have to.
However, since the position of the sun cannot be predicted during the initial attitude control of the spacecraft, the field of view of the infrared detection device cannot be masked, and the overflow of the integration circuit cannot be prevented.

The present invention solves the above-mentioned drawbacks by providing an earth sensor which does not hinder attitude control by forcibly discharging the capacitor of the integrating circuit when the field of view of the infrared detector goes into the sun. The purpose is to provide.

[0016]

The earth sensor of the present invention comprises:
An infrared detector whose field of view is swept across the earth image, a differentiator that differentiates the infrared output detected when the field of view of this infrared detector crosses the earth image, and a differential output differentiated by this differentiator. , According to the timing of sweeping the field of view of the infrared detection device and the polarity of the differential output, the dividing device that divides into a plurality of groups and the differential output divided by this dividing device are integrated, and the integrated output becomes smaller than a certain value. After that, a selection device that passes the differential output that is output from the sorting device, a measurement device that measures the edge angle of the earth image from the differential output that passed this selection device, and an infrared output that is detected by the infrared detection device Is larger than a certain value, and a comparator for short-circuiting and discharging the capacitor forming the integrating circuit of the selecting device is provided.

[0017]

When the field of view of the infrared detection device enters the sun, the infrared detection output increases. Therefore, if this large infrared ray detection output is directly applied to the selection device, the capacitor of the integration circuit constituting the selection device overflows, and the function of the earth sensor stops. This invention utilizes the fact that the infrared detection output increases when the field of view of the infrared detection device enters the sun, and the comparison device detects that the field of view of the infrared detection device has entered the sun. Then, the capacitor of the integrating circuit that constitutes the selecting device is short-circuited and discharged by the output of the comparing device so that the earth sensor does not stop functioning.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and parts different from those in FIG. 1 will be mainly described.

Reference numeral 11 is an infrared detecting device which constitutes an earth sensor. The infrared detector 11 includes an infrared detector that detects infrared rays generated by the earth, an optical system that sweeps the field of view of the infrared detector, and the like. The field of view of the infrared detection device 11 is swept by the optical system so as to draw an ellipse, and is set so as to cross the earth image during the sweep. As described above, for example, if the earth image is E in FIG. 3, P to Q is the forward path of the sweep, and Q to P is the backward path of the sweep, for example, the forward and backward paths of the sweep have different earth images. Sweeping across position.

Note that infrared rays are detected when the field of view of the infrared detection device 11 crosses the earth image. Infrared detector 11
, 1 and 2 when the field of view crosses the edge of the Earth image on the outward path, and φ 3 when it crosses on the return path.
Assuming φ4, the infrared output detected by the infrared detection device 11 is shown in FIG. The detected infrared output is differentiated by the differentiator 12. Therefore, the output of the differentiator 12 is represented by b1, b2, b3, b4 in FIG. 4 (b). The output of the differentiator 12 is the sorter 13
According to this, for example, the processing is divided into four groups A to D and processed. The differential output grouping is performed by the same method as described in the related art.

The grouped differential outputs are supplied to the selection devices 14A to 14D. Selectors 14A-14D
Then, the differential output due to the noise component is eliminated, and the normal differential output is sent to the measuring device 15. And the measuring device 1
In 5, the forward and backward earth edge angles are measured and the earth direction is detected.

The infrared output of the infrared detecting device 11 is sent to the differentiating device 12 and simultaneously to the comparing device 16. The other terminal of the comparison device 16 is set to the reference voltage, and the infrared output of the infrared detection device 11 is compared with the reference voltage by the comparison device 16. When the field of view of the infrared detector 11 enters the sun, the output of the infrared detector 11 becomes larger than that when it is directed toward the earth image, and at this time, the comparison device 16 outputs a signal. The output signal of the comparison device 16 is sent to the selection devices 14A to 14D, and the discharge switch 17 connected in parallel with the capacitor C of the integrating circuit IN is closed to short-circuit both ends of the capacitor to discharge. It should be noted that the discharge switch 17 is closed for a short time, and then immediately returns to the open state.

According to the above construction, even if the field of view of the infrared detector enters the sun, the overflow of the integrating circuit is immediately canceled, and the function of the earth sensor does not stop for a long time of ten and several seconds.

[0025]

According to the present invention, it is possible to realize an earth sensor capable of preventing the function stop even when the field of view of the infrared detecting device enters the sun.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing a conventional example.

FIG. 3 is a diagram illustrating a conventional example.

FIG. 4 is a diagram illustrating a conventional example.

[Explanation of symbols]

 11 ... Infrared detecting device 12 ... Differentiating device 13 ... Sorting device 14A-14D ... Selection device 15 ... Measuring device 16 ... Comparison device 17 ... Switch IN ... Integration circuit C ... Capacitor

Claims (1)

[Claims] 1. An infrared detector whose field of view is swept across the earth image, a differentiator for differentiating the infrared output detected when the field of view of this infrared detector crosses the earth image, and a derivative by this differentiator. The differentiated output is divided into a plurality of groups by the timing of sweeping the field of view of the infrared detection device and the polarity of the differential output, and the differential output divided by this dividing device is integrated, and the integrated output is After becoming smaller than a certain value, a selection device that passes the differential output output from the sorting device, a measuring device that measures the edge angle of the earth image from the differential output that passed this selection device, and the infrared detection device. An earth detector equipped with a comparator for detecting that the detected infrared output is larger than a certain value and short-circuiting and discharging the capacitor forming the integrating circuit of the selecting device. Nsa.