JPH01214713A - Punch-through scan type earth sensor - Google Patents

Abstract

PURPOSE:To enable the correct switching control of a measurement mode, by comparing a signal level of an infrared detection signal with a reference level and by detecting therefrom that a signal due to solar scan is contained therein. CONSTITUTION:A scanning mirror driving circuit 11 supplies an exciting current to a driving coil 10 to drive mirrors of two infrared detectors 1 and 2, and detecting beams of the detectors 1 and 2 scan different parts of the earth in a parallel and reciprocating manner with a larger scanning width than a visual width of the earth. The attitude of a space craft to the earth is measured on the basis of both or either of two detection signals obtained. When the sun is present within a scanning range of one detecting beams on the occasion, a detection signal level thereof is larger considerably than an earth detection signal level. An appropriate reference value being set, therefore, the detector judges to have scanned the sun when the detection signal level exceeds the reference value, and switching is made over to the measurement by the other detector. According to this method, a switching control of a measurement mode can be implemented correctly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a punch-through scanning earth sensor, and more particularly to a punch-through scanning earth sensor that is mounted on a spacecraft and measures its attitude with respect to the earth.

(Prior Art) As is well known, a piercing scanning earth sensor mounted on a spacecraft has two infrared detectors, and each of these two infrared detectors detects a different part of the earth with a detection beam. The pitch angle of the spacecraft with respect to the Earth or This device measures at least one of the roll angles. Below, Figures 3 and 4
The operating principle will be explained with reference to the drawings.

Figure 3 shows the scanning orbit (Ll, L2) of the detection beam (hereinafter referred to as the "field beam") of the infrared detector when scanning the earth in an orbit that moves from west to east on the earth's equator and the earth disk ( Et”E2), the third
In the figure, Ll is the channel on the northern hemisphere side of the earth (hereinafter referred to as “
L2 is the scanning trajectory of the earth's southern hemisphere side channel (hereinafter referred to as "S channel") beam. Further, the earth disk E1 indicates a case where the earth is within the scanning range of the field beam of the sensor and the scanning trajectories th and t2 both pass through.

On the other hand, in the earth disks E2 to E5, the earth is shifted toward the edge of the scanning range of the field beam of the sensor, and the scanning trajectory Ll+
This shows a case where t2 does not pass through.

Next, FIG. 4 shows the detection signal of the infrared detector/device.

In FIG. 4, FIG. 4(1) is a scanning pulse P, which provides a time reference for scanning. , tl is one round-trip scanning period, and the first half, t2, is one-sided scanning period from west to east,
The second half, 1S, is a one-sided scanning period from east to west. Further, the reference pulse p r@ shown in FIG. 4(2) is a pulse representing the timing when the beam is at the center of each one-sided scan.

On the other hand, the detection signal of the infrared detector is the analog detection signal (Figure 4 (4) (6) (10)) and the digital detection signal generated based on this (Figure 4 (3) (5) (7) (11)). )
), but in Figure 4 (3) and (4), the pitch angle and roll angle are both 0, and the Earth's disk is E as shown in Figure 3.
! In other words, each pulse of the digital detection signal (Fig. 4 (3)) is at a symmetrical position at the change point of the reference pulse P, and the pulse width of each pulse is It is equal for the n channel and the S channel.

When the pitch angle is no longer O, each pulse of the digital detection signal becomes asymmetric with respect to the reference pulse pre, so the pitch angle can be determined from what angular relationship between the digital detection signal and the reference pulse Pr. Further, when the roll angle is no longer 0, the pulse width of each pulse of the digital detection signal differs between the n channel and the S channel, so the roll angle can be determined from these pulse widths. By the way, if the spacecraft carrying the sensor is in a geostationary orbit, for example, depending on the time of year, the field of view beam of the earth sensor may scan the sun due to the positional relationship between the sun, the earth, and the spacecraft.

In such a case, the digital detection signal is, for example, as shown by reference numeral 201 in FIG. 4(5).

Since extra pulses from scanning the sun (hereinafter referred to as "solar interference") are included, the measured data also contains many errors and causes the attitude of the spacecraft to be disturbed.

Therefore, in this type of piercing-scanning earth sensor, the arrangement of the two infrared detectors is determined so that they do not scan the sun at the same time, so that measurements can be taken only on channels that are not scanning the other sun. It has become.

In other words, solar interference is detected and the measurement mode is switched.
For example, a method of detecting solar interference by mounting a special sensor such as a solar sensor, or a method of detecting a pulse 201 due to solar interference as shown in FIG. 4 (5), etc., have been adopted.

Note that this type of piercing scanning earth sensor may measure both the pitch angle and the roll angle, or may measure either one of them. Also, one of the n-channel and S-channel detection signals is replaced with a reference signal,
It is customary to also allow measurements to be taken only with the other.

(Problems to be Solved by the Invention) However, when a special sensor is used to detect solar interference, there is a problem that the system becomes complicated and the weight increases.

In addition, in the method of detecting extra pulses in the digital detection signal of the earth sensor, if the images of the sun and the earth are sufficiently separated, the digital detection signal will be
5), solar interference can be detected by detecting the extra pulse 201. However, there is a problem in that when the images of the sun and the earth come close to each other, accurate detection may not be possible, or there may be cases where no detection is possible. That is, when the images of the sun and the earth are close enough that they do not overlap, the analog detection signal is as shown in FIG. 4 (6), for example, and the sun detection signal 202 and the earth detection signal (earth edge detection)
exists in an identifiable manner.

However, in this case, since the detection level of the sun detection signal 202 is very high, it influences the earth detection signal 203, and when this digital detection signal is formed, solar interference occurs as shown at 204 in FIG. 4 (7). If the images of the sun and the earth approach each other to such an extent that they overlap, the analog detection signal will become as shown in Figure 4 (10), making it difficult to detect the earth. In this case, a part of the signal disappears, and the digital detection signal in this case becomes as shown in Figure 4 (11).It does not contain any extra pulses and cannot detect solar interference, as shown in Figure 4 (11).
Although the digital detection signal shown in 1) appears to be correct at first glance, the pulse width is wide and it is an incorrect detection signal.

The present invention was made in view of these conventional problems, and its purpose is to provide a piercing scanning earth sensor that can reliably detect the scanning of the sun with a simple circuit configuration and that can control the measurement mode correctly. It is about providing.

(Means for Solving the Problems) In order to achieve the above object, the punch-through scanning earth sensor of the present invention has the following configuration.

That is, the punch-through scanning earth sensor of the present invention uses the detection beams of two infrared detectors to reciprocate different parts of the earth in parallel with scanning widths that are wider than the visual angle width of the earth. In a punch-through scanning earth sensor that measures the attitude of a spacecraft with respect to the earth based on a signal obtained by digitizing both or one of two detection signals; detection is based on the magnitude relationship between the signal level of the detection signal and a reference level. a detection means for detecting that the signal includes a signal caused by solar scanning; and a detection means for detecting that the signal includes a signal due to solar scanning; The present invention is characterized by comprising: a control means for controlling the switching so that the switching is performed.

(Function) Next, the function of the punch-through scanning earth sensor of the present invention configured as described above will be explained.

When the sun is within the scanning range of an infrared detector's detection beam, the signal level of its detection signal will be significantly greater than the earth detection signal level.

Therefore, the reference level is set to an appropriate value that also has a large earth detection signal level, and when the detection signal level exceeds this reference level, it is determined that the infrared detector has scanned the sun, and has not scanned the sun. The measurement is then switched to the output signal from the other infrared detector.

Therefore, even if the original earth detection signal is affected and there is no earth pulse in the digital detection signal, it can be reliably determined that the sun has been scanned, and the measurement mode switching control can be performed correctly.

Furthermore, since the detection means can be constructed using a known comparator, the construction can be simple.

In other words, since the sun is not detected using a special sensor such as a sun sensor as in the past, problems such as increased weight do not occur.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a piercing scanning earth sensor according to an embodiment of the present invention. This piercing scanning earth sensor includes an n-channel infrared detector 1, an S-channel infrared detector 2, and an n-channel analog signal processing circuit. 3, an S channel analog signal processing circuit 4, a solar interference determination circuit 5, a mode control circuit 6, a pitch/roll measurement circuit 7, an optical encoder 8, an encoder processing circuit 9, and a drive coil 10. , and a scanning mirror drive circuit 11.

The detection beams of the two infrared detectors (1, 2) are scanned back and forth by a mirror, but the drive coil 10
is a coil for driving this mirror, and its excitation current is supplied from the scanning mirror drive circuit 11. That is,
The scanning mirror drive circuit is a circuit that manages scanning, and the scanning pulse P. Create pitch/roll measurement circuit 7
give to

Further, the optical encoder 8 optically detects the increment in the scanning angle, converts it into an electrical signal, and supplies it to the encoder processing circuit 9. In response to this, the encoder processing circuit 9 creates an angle clock (such as the reference pulse Pr0) necessary for pitch and roll measurement, and supplies it to the pitch and roll measurement circuit 7. Then, the pitch/roll measurement circuit 7 selects both or one output of the two analog signal processing circuits (3, 4) according to instructions from the mode control circuit 6, and measures the pitch/roll angle.

By the way, the two analog signal processing circuits (3°4) are
For example, as shown in FIG. 2, there is a preamplifier 31 that amplifies the weak output signal of the infrared detector, and the output is processed as a filtrate to generate an analog detection signal V as shown in FIG. 4 (4). A bandpass filter 32 to output, and a comparator 33 that receives the analog detection signal V in parallel at one input.
It basically consists of 36. The comparators 33 and 34 are for forming a digital detection signal, and the comparator 33 has the positive side comparison voltage v8 applied to the other input, and the positive side signal level of the analog detection signal V (for example, as shown in FIG. (4)) outputs an earth pulse (a) for the period when the voltage exceeds the comparison voltage VE+. Further, the comparator 34 has a negative side comparison voltage v8- applied to its other input, so that the negative side signal level of the analog detection signal V is set to the comparison voltage V8-.
Outputs the earth pulse (b) for the period exceeding B-.

These two earth pulses (a) and (b) are input to the pitch/roll measurement circuit 7, where a digital detection signal as shown in FIG. 4(3), for example, is formed.

On the other hand, the comparators 35 and 36 detect solar interference when the analog detection signal V is as shown in FIG. 4 (6), and communicate it to the solar interference determination circuit 5. That is, the positive side comparison voltage V, + is applied to the other input of the comparator 35, and the negative side comparison voltage V, - is applied to the other input of the comparator 36. The comparison voltages V, + are set to an appropriate level higher than the maximum value of the earth detection signal, and the comparison voltages V, - are set to an appropriate level lower than the minimum value of the earth detection signal. As a result, the comparator 35 outputs a solar interference presence (+) signal (c) for the period in which the positive side signal level of the analog detection signal V exceeds the comparison voltage v3° (Fig.
8)), and the comparator 36 outputs a solar interference presence (-) signal (d) for the period in which the negative side signal level of the analog detection signal V exceeds the comparison voltage V, - (Fig.
9)).

Therefore, the comparators 35 and 36 constitute a detection means.

The solar interference presence/absence determination circuit 5 includes both analog signal processing circuits (
The output states of the comparators 35 and 36 in 3 and 4) are checked during one reciprocating scanning period to determine whether there is solar interference (
If there is a comparator that outputs the +) signal (c), the presence of solar interference (-) signal (d), or both, it will be determined that the infrared detector corresponding to that analog signal processing circuit has scanned the sun, and a signal to that effect will be sent. The mode control circuit 6 is notified.

Therefore, this solar interference presence/absence determination circuit 5 constitutes a control means, and when it is determined that there is solar interference, the output level is set to "1", for example, and when it is not, the output level is set to "1". 0” respectively.

The mode control circuit 6 receives a command given from the outside.
When "enabled", the output contents of the solar interference presence/absence determination circuit 5 are notified to the pitch/roll measurement circuit 7 and the scanning mirror drive circuit 11.

As a result, for example, the output of the solar interference detection circuit 5 is
1” level, the pitch/roll measurement circuit 7
The digital detection signal shown in Figure (7) is not used and the fourth
The measurement operation is performed based on the digital detection signal shown in Figure (3). In other words, if the output signals of both analog signal processing circuits 3 and 4 are used, one is ignored and only the other is used. Also, if one of the output signals is used, the other output signal is used instead. In the latter case, since one of the two infrared detectors (1, 2) is in a dormant state, the scanning mirror drive circuit 11 starts scanning the detection beam of the infrared detector in the dormant state. It is. On the other hand, when the command is "disable", the mode control circuit 6 ignores the output of the solar interference detection circuit 5 and does not cause any change in the operation of the pitch/roll measurement circuit 7 or the scanning mirror drive circuit 11. do it like this.

That is, although measurement mode switching control can basically be performed by the output of the solar interference presence/absence determination circuit 5, cases in which it is not necessary to perform it all the time have also been considered.

Figure 4 (6) shows the case where the images of the sun and the earth are close enough that they do not overlap, but when the images of the sun and the earth are close enough that they overlap, the analog detection signal V is e.g. The digital detection signal generated by the earth pulse (a) and the earth pulse (b) based on this is shown in FIG. 4 (11). Figure 4 (1
In 1), there are no extra pulses as shown in Figure 4 (5) and (7), and it looks like a correct digital detection signal, but it is incorrect because the pulse width has expanded due to the influence of solar interference. This is a digital detection signal.

Conventionally, this could not be detected, but the present invention can correctly detect even such a case.

That is, when the analog detection signal V is as shown in FIG. 4 (10), the digital detection signal is as shown in FIG. 4 (11), but the comparator 35 is as shown in FIG. 4 (12). A presence (+) signal (c) is output, and the comparator 36 outputs a solar interference presence (-) signal (d) shown in FIG. 4 (13). As a result, the pitch/roll measuring circuit can obtain correct measurement values by using the correct digital detection signal shown in Figure 4 (3) without using the digital detection signal shown in Figure 4 (11). Become.

(Effects of the Invention) As explained above, according to the punch-through scanning earth sensor of the present invention, the presence or absence of solar interference can be detected at the analog detection signal stage, so solar interference that cannot be determined with digital detection signals alone can be detected. It is also possible to effectively determine whether the measurement mode is the same or not, and to control the switching of the measurement mode correctly.

Furthermore, since the detection means can be constructed using a known comparator, the construction can be simple.

In other words, since the sun is not detected using a special sensor such as a sun sensor as in the past, it is possible to provide a punch-through scanning earth sensor that does not cause problems such as increased weight.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the structure of a piercing scanning earth sensor according to an embodiment of the present invention, Fig. 2 is a block diagram of the structure of an analog signal processing circuit, and Fig. 3 shows the scanning locus of the detection beam of the infrared detector and the earth. FIG. 4, which is a diagram showing the relative relationship with the disk, is a time chart for explaining the operating principle and details of the present invention. 1...N-channel infrared detector, 2...
... S channel infrared detector, 3 ... N channel analog signal processing circuit, 4 ... S channel analog signal processing circuit, 5 ... Solar interference presence determination circuit, 6 ...Mode control circuit, 7...
...Pitch/roll measurement circuit, 8...Optical encoder, 9...-Encoder processing circuit, 10...Drive coil, 11...Scanning Mirror drive circuit, 31... Preamplifier,
32...Band pass filter, 33-36...
····comparator. Agent: Patent Attorney Yoshi Yahata, Takuaki Hiromoto, 11, 11 and a half
No Figure Analog Yu8 Immunity Recurrence 4? ]

Claims (1)

[Claims] The detection beams of two infrared detectors scan different parts of the earth back and forth in parallel with a scanning width wider than the viewing angle of the earth, and both or one of the two resulting detection signals are digitized. In a punch-through scanning earth sensor that measures the attitude of a spacecraft with respect to the earth based on a signal detected by the detection signal; based on the magnitude relationship between the signal level of the detection signal and a reference level, the detection signal includes a signal caused by solar scanning. and a control means that receives the output of the detection means and controls switching so that the measurement is performed based on the output signal of the infrared detector that does not include the sun within the scanning range; A breakthrough scanning earth sensor that is characterized by: