JPS61200099A - Mirror scanning type biaxial earth sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is installed on an artificial satellite in orbit around the earth, and uses an infrared pencil beam field of view (hereinafter referred to as "infrared pencil beam FOVJ, !: when") The present invention relates to a mirror scan type two-axis earth sensor that can detect with high precision the two-dimensional deviation angle of a predetermined axis (yaw axis) of an artificial satellite from the direction of the earth's center by scanning the earth direction.

(Prior Art) First, the concepts of "light" and "reflected light" used in the description of the present invention include infrared rays.

Conventionally, two-axis earth sensors that two-dimensionally detect the deviation angle of a predetermined axis of an artificial satellite from the center of the earth direction include a mirror scan type, a static thermal radiation balance type, a conical scan type, and a mechanical chopping type. Three types of methods were considered. Among these, static thermal radiation balanced type sensors are sensitive to subtle fluctuations in the amount of infrared radiation from the earth, which tends to cause deterioration in detection accuracy, and it is necessary to precisely control the heat of the detector part. Therefore, there is a drawback that a large burden is placed on the thermal control system. The conical scan type requires bearings, so it has the disadvantage that there remains a problem with the service life for missions that require a long service life. Furthermore, the mechanical chopping type has the disadvantage that it is difficult to achieve high accuracy because it responds sensitively to fluctuations in the earth's infrared radiation.

For these reasons, especially for geostationary three-axis satellites that require long life and high-precision attitude measurement, the above three types of systems are not used, and mirror scan type two-axis earth sensors are often used.

A conventional mirror scan type two-axis earth sensor is shown in FIGS. 2 and 3.

FIG. 2(a) shows a mirror scan type using two infrared detecting elements, and FIG. 3(a) uses four infrared detecting elements. In both figures, 1 is a sensor housing, and inside this is a scan mirror 4 that is reciprocated by a torsion bar 5, an infrared lens system 3 that condenses the scanning light from the scan mirror 4, and an infrared lens system 3.
An infrared detection element 2 is arranged to detect infrared rays of the infrared pencil beam FOV emitted from the infrared pencil beam FOV.

Figure 2 (b) and Figure 3 (b3
are shown respectively. In both figures, 7 is the Earth disk;
9 is the pitch axis direction, and 10 is the roll axis direction. The sensor faces toward the earth, and in the case of Fig. 2(b), an infrared pencil beam FOV 6a scanned left and right over the northern half of the earth's disk by a scanning mirror 4 is detected by an infrared detection element 2a placed at the bottom of the housing. , an infrared pencil beam FOVab that scans the southern half of the Earth's disk left and right is placed at the top of the housing, and the former infrared detection element 2b
are detected respectively.

In the case of Fig. 3(b), an infrared pencil beam FOV 6at scanned left and right on the northern left half of the earth disk by the scanning mirror 4 is transmitted to the left and right on the north right half of the earth disk by an infrared detection element 2al arranged at the bottom of the housing. The infrared pencil beam 6az scanned by the infrared detecting element 2az is transmitted by the infrared detecting element 2az, and the infrared pencil beam 6bx which scanned the southern left half of the Earth's disk left and right is transmitted by the infrared detecting element 2bt. Infrared pencil beam 6bz scanning the southern right half of the Earth's disk from side to side
are respectively detected by the infrared detection element 2b2.

As a result, the four corners 11, 12, 13, and 14 of the earth are scanned, and the error angle Δθ around the secondary axis (roll axis and pitch axis) is calculated by the following equations (1) and (2).

Δθp can be measured.

ΔθR−−(Δθ3+Δθ4−Δθ1−Δθ2)...
...(1) 4tanγ Δθ,, An (Δθ2−Δθl) or i(Δθ4−Δ
θsu・・・・・・(2) However, Δθ1. Δθ2. Δθ3. Δθ4: Angle of increase from the nominal angle of the earth edge detection angle at scan points 1.2 and 3.4 γ: Half apex angle of the scan point (problem to be solved by the invention) These sensors are described above. As is clear from the explanation, since two or four infrared detection elements are used, two or four corresponding signal processing systems are required, which increases the complexity of the system, increases weight, and reduces reliability. It had the disadvantage of causing a decline in sexuality. In addition, since it is necessary to use an aspherical lens in the infrared lens system, a lot of effort is required to design and manufacture it, and variations in characteristics between each element and signal processing system may cause error angles. There was a drawback that detection accuracy deteriorated.

The purpose of the present invention is to eliminate these drawbacks, and to measure the error angle of rotation around two axes υ using only one infrared detection element and the corresponding infrared optical system and signal processing system. The object of the present invention is to provide a mirror scan type two-axis earth sensor.

(Means for Solving the Problems) In order to achieve the above object, the mirror sugikin type two-axis earth sensor according to the present invention includes a divided mirror arranged so as to be able to scan the upper half and the lower half of the earth disk, respectively;
a scanning mirror that receives the reflected light from the split mirror and scans the upper and lower halves of the earth disk back and forth from side to side;
an infrared lens system that collects the light scanned by the scan mirror and provides an infrared pencil beam FOVI; and an infrared pencil beam FO that is emitted from the infrared lens system.
It is configured to include one infrared detection element that detects Vi, and a signal processing circuit that processes the output signal of the infrared detection element.

(Function) According to the above configuration, since the infrared detection element is only one year old, the system can be simplified and reliability can be improved, and a spherical lens can be used in the infrared lens system, so
The design and manufacture of the device does not require the same effort as in the past, and the variations that exist between each element and the signal processing system can be reduced.

(Example) Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 3 is a schematic diagram for explaining the present invention in detail.
Figure 3(a) shows the sensor housing, and Figure 3(b) shows the scanning state of the infrared pencil beam FOV on the earth disk. In the figure, 18 is a sensor housing, 22 is an infrared detection element, 19 is a scan mirror, 20 is a torsion bar, 6 is an infrared pencil beam FOV, 7 is an earth disk, 8 is a scan path of the infrared pencil beam FOV, and 9 is a satellite roll axis direction, 10 is pitch axis direction,
11 is a scan point -1112 is a scan point -2, 13 is a scan point -3, 14 is a scan point -4, 15 is a split mirror, 16 is a signal processing section, and 17 is a signal output.

The infrared pencil beam FOV is scanned onto the split mirror 15 by swinging the scan mirror 19 around the shaft 2o.

The split mirror 15 is a mirror 15a that is split into two left and right parts,
15b, with scan mirror 19 as one mirror 1
5b, the northern hemisphere side of the earth disk is scanned east-west, and when scanning the other mirror 15a, the southern hemisphere side is tilted and fixed so as to be scanned east-west.

Therefore, the infrared pencil beam F scans the southern hemisphere and the northern hemisphere of the earth disk alternately by the scanning mirror 19 that vibrates back and forth around the torsion bar axis 20.
The OV is emitted from the infrared lens system 21. With this structure, one infrared detection element 22, one infrared lens system 21, and one infrared signal processing circuit 16 can scan four scanning points 11, 12, 13, 14 on the earth disk 7. 't' scan, and by substituting deviation angles Δθ1 to Δθ4 from the nominal value of the earth edge scan angle at these scan points into equations (1) and (2), the roll and pitch errors of the satellite can be calculated. The angles Δθa and Δθp? can be generated.A series of these signal processings is performed in the sensor signal processing section 16, and the resulting roll and pitch error angles are outputted from the sensor output terminal 17.

(Effects of the Invention) As described above, according to the present invention, by using one infrared detection element, one system of infrared lens systems, and one system of infrared signal processing system, the error angle of roll and pitch axis rotation can be reduced. The system is simplified because it can generate
Leads to improved reliability. Furthermore, since a spherical lens can be used in the infrared lens system, design and manufacturing can be simplified.

Furthermore, it has various advantages in that it is possible to prevent deterioration of measurement accuracy due to variations in characteristics of a plurality of elements and a signal processing system.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a mirror scan type two-axis earth sensor according to the present invention, and FIGS. 2 and 3 are schematic diagrams for explaining the configuration of a conventional mirror scan type two-axis earth sensor. Figure 2 shows that when there are two infrared detection elements, the third
The figures each show a case where there are four infrared detecting elements. 1.18...Sensor housing 2.22...Infrared detection element 3, 21...Infrared lens system 4.19...Scan mirror 5.20...Torsion bar 6...Infrared pencil beam FOV 7...Earth disk as seen from the satellite 8...Infrared pencil beam FOV scan path 9.
...Satellite roll axis direction 10...Satellite-pitch axis direction 11...Earth edge scan point -1 12...Earth edge scan point -2 13...Earth edge scan point -3 14...Earth Edge scan point -4 15... Divided mirror 16... Signal processing section 17.
...Sensor output patent applicant NEC Co., Ltd. agent Patent attorney Hisashi Inoro" trl m

Claims (1)

[Claims] a split mirror disposed so as to be able to scan the upper and lower halves of the earth disk, respectively; a scanning mirror that receives reflected light from the split mirror and scans the upper and lower halves of the earth disk back and forth from side to side; Infrared pencil beam FOV by concentrating the light scanned by a scan mirror
an infrared lens system that provides an infrared lens system, one infrared detection element that detects an infrared pencil beam FOV emitted from the infrared lens system, and a signal processing circuit that processes an output signal of the infrared detection element. A mirror scan type two-axis earth sensor.