JPS60226399A - Solar 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 The present invention relates to a solar sensor used for attitude control of, for example, an artificial satellite.

[Prior art]

Figure 1 is a perspective view of a solar sensor installed on a conventional spin satellite. In Figure 0, fil is a silicon solar cell, (2) is a mask installed in front of this silicon solar cell, and (3) is this A cover glass provided in front of the mask, (4) is an entrance hole made in this cover glass, (
5) is the spin angle of the satellite, (6) is the spin plane of the satellite, (7
) is the solar angle α with respect to the satellite's spin plane, (8) is the sunlight, (9) is the apparent movement of 1·Ll due to the satellite's spin, 011 is the sun, and (111 is the satellite's spin axis.

(12 is the lead wire for the output signal of the silicon solar cell, and country 0 is the outer box of the solar sensor. Also, Figure 2 is an output waveform diagram obtained from the above configuration. In Figure 0, Q41 is the solar sensor outer box. The output waveform is one spin period of the A!9/RI satellite, and QG is the sun sensor output signal pulse width. It passes through the entrance hole (41) according to the spin.

Silicon solar cell (1) masked by mask (2)
) is scanned with a spot light. At this time, since the mask is designed so that the relationship between the solar angle (7) and the satellite spin angle (5) is linear, the output signal pulse of the silicon solar cell (1) is proportional to the satellite spin angle (5). Width+IG is also proportional to solar angle (7).

As described above, conventional solar sensors do not directly detect the solar angle, but indirectly measure the solar angle (7) relative to the satellite spin plane by measuring the solar sensor output signal pulse width (te). (Attitude and antenna control electronics) Internally, a complex circuit is required to convert the sun sensor output signal pulse width aQ into the solar angle (7) with respect to the satellite spin plane, and also the satellite spin rate and the silicon solar cell (1). Since the measurement accuracy depends on the size, the mechanical accuracy of the mask (21), the mechanical accuracy of the entrance hole drilled in the cover glass (3), etc., there was a drawback that there was a limit to the improvement of measurement accuracy. Furthermore, since the solar radiation 81 is directly irradiated onto the silicon solar cell (1), there is also the drawback that the silicon solar cell (1) deteriorates due to radiation from the sun.

[Summary of the invention]

This invention was made with the purpose of improving such drawbacks, and it involves directly using sunlight to measure the solar angle, passing it through an optical fiber placed on the light receiving surface, and detecting the obtained signal with an optical semiconductor. This project proposes a snowmaking method that calculates the solar angle with extremely high precision from the positional information.

[Embodiments of the invention]

FIG. 3 is a conceptual diagram of an embodiment of the present invention. In the figure, (3) is the cover glass, (7) is the solar angle α with respect to the satellite reference plane, (8) is the sunlight, (IG is the sun, aη is A monochromatic light passing optical filter or an aplanatic lens for aberration correction, Ql is the optical axis of this lens parallel to the satellite reference plane, ■ is the moving distance y of the spot focused by the lens, and Qυ is the lens The focal length is F.

In the conceptual diagram of the present invention configured as described above, sunlight 18
1 passes through the cover glass (3) and the monochromatic light passing optical filter a, enters the aberration correcting aplanat lens 0υ, and is focused on its pointless surface.The diameter of this focused spot is: Incoming sunlight (8) If the light is completely coherent, that is, a continuous wave with a single frequency, and when expressed as a 91-frequency spectrum, it corresponds to a single line spectrum. It can be expressed as

1) = o, s1 - λ... (1) However, F
is the focal length of the lens, A is the effective diameter of the lens, and λ is the wavelength of the incident light.Even an aberration-free lens cannot condense any more light than this at °C. In reality, sunlight is produced by waves of many short wave packets overlapping randomly, even if the wave fronts of light emitted from various parts of the sun overlap, even if it is as close as the Earth's geosynchronous orbit. It is incoherent light. Therefore, the light should not be focused on an extremely small spot of several times the wavelength expressed by equation (1). Cohy + and -tL, which are close to waves, are also incident on the $ -b uv Wanpei Shita Brannert lens.In addition, the convergent lens has the most significant of Seidel's five aberrations, which are aberrations for monochromatic light of the lens. Affects the focused spot area.

Spherical aberration and coma aberration do not occur (・Front Kerr ellipsoid surface.

The rear surface is a spherical surface centered at the focal point F, and by using an ellipsoidal aplanat lens of °C, the area of the focused spot is made as small as possible. This focused spot moves on the return point of the aplanato lens QB due to the elongation of the sunlight (8) that enters the aplanato lens 1 second with respect to the reference plane +61, that is, the change in the solar angle α (7). do. At this time, the following relational expression is established between the focal length FC11 of the aplanat lens of 0 seconds, the pointless movement distance y■, and the solar angle α(7).

α＝ tan”'−'□・・・・・・・・・・・・・・・
・(2) This formula is not an abbreviation, but an exact value.

Based on the above concept, an embodiment of the invention is shown in FIGS. 4 and 5. FIG. 4 is a perspective view showing an embodiment of the present invention. From the figure, (3) is glass (-glass, (611
Ii satellite reference plane, (7) is the solar angle α with respect to the satellite reference plane
, (8) is sunlight, aυ is the sun, (+71 is a monochromatic light passing optical filter, brocade is an aberration correction aplanat lens,
a is the optical axis of the lens parallel to the satellite reference plane (6), and ■ is the distance y that the spot focused by the lens moves on the elongated point plane due to the change in the solar angle α (71).

a'1lFi Cornes focal length P, (to) is an optical fiber placed in the focal plane of the lens, (c) is an avalanche photodiode that converts the light incident through this optical fiber into an electrical signal and multiplies it, ) is a photodetector that detects the position of the sys-pot using this avalanche photodiode, (c) is a calculator that calculates the solar angle α (7) from the device information signal composed of this photodetector, and (b) is a Computer output signal cable, @ is the solar sensor outer box, @
is a cylinder whose inner surface is painted black. Further, FIG. 5 is a sectional view showing an embodiment of the present invention. (3) ~ (to)
is exactly the same as the above conceptual diagram and perspective diagram.

configured as above. In solar sensors.

Sunlight (81tri) emitted from the sun 11CI passes through a cover glass (3) and further passes through a monochromatic light passing optical filter +17. At this time, incoherent sunlight (8) with many spectral components becomes coherent light with slight amplitude fluctuations and phase fluctuations. As this monochromatic light passing optical filter aη, an interference filter that transmits only bright yellow-green visible light with a wavelength of 0.546074 x 10-6 m called e-line, which is currently most widely and commonly used in the lens industry, is used. is the most suitable option from the point of view of zero cost, from the point of view of blocking infrared rays and suppressing the heat rise at the focal plane, and from the point of view that the avalanche photodiode (2) is effective in the wavelength band of 0.9 x 10-6 m or less. The coherent light that has passed through the filter enters the aberration correcting aplanat lens, which eliminates 0 spherical aberration and comatic aberration, and focuses it on a very small spot. It is detected by the avalanche photodiode (c) in the photodetector.

The moving distance y of the spot from the optical axis 0 is output from the photodetector (incorporated) to the computer (c) as a position information signal.
The calculator (c) uses the focal length F2+1 of the lens brocade and the position information signal output from the photodetector@9 as explained in FIG. 3, which is a conceptual diagram of the present invention (according to equation 21).

Calculate the solar angle α(7). The calculated solar angle α is.

The sun sensor signal passes through the computer output signal cable@AAOB (Attitude and Antenna Control Electronics)
is output to. With conventional solar sensors.

The solar angle measurement accuracy was about ±0.5°, and it was impossible to detect even small changes in the solar angle α(7). However, as artificial satellites become larger in size or become multi-beam in the future, it is desired to establish highly accurate attitude control technology4, and even more highly accurate solar sensors are required. The present invention fully satisfies that need. Focal length 100 on aberration corrected aplanat lens A8
When using a chestnut lens, the optical fibers are arranged on a pointless surface.

When a single mode quartz fiber with a diameter of 100 x 10'm is used, (from equation 21, 0.1 solar angle α = jan-1-: 0.0513° ± 0 in the knee)
．． A solar angle measurement accuracy of 0573° is obtained. this is.

The accuracy is approximately 88 times higher than that of conventional solar sensors, and it is fully usable as a solar sensor for use on a 6-multibeam satellite. If a lens with a longer pointless distance than this is used, an even more precise solar sensor can be realized. ,t. Optical semiconductor (diameter 100 x 10-
By using the current optical integrated circuit technology and using an avalanche photodiode (150 x 10-6 m), it is possible to realize a photodetector that is sufficiently small and lightweight for use on a satellite and has no optical system instability. As a result, the solar sensor of the present invention has a much simpler structure than a conventional solar sensor using a large silicon solar cell and requiring a complicated circuit, and is also smaller and lighter. Furthermore, by using an aplanat lens consisting of an interference filter and a single lens that allows only monochromatic light to pass through the optical system, and a cylinder with a matte black coating on the inside to suppress the generation of ghosts due to internal reflection, lens aberrations can be reduced. Since the method detects light that has passed through a quartz glass fiber that has excellent transmission characteristics by minimizing measurement errors caused by internal reflection, there is no need to consider deterioration of photoelectric conversion elements due to radiation from the sun. By invention. It goes without saying that the solar sensor can be used with both spin satellites and three-axis attitude control satellites.

〔Effect of the invention〕

As explained above, this invention moves a spot focused by a lens on a pointless surface.

A photodetector detects this through a glass fiber, and a computer processes the position information, making it possible to measure the solar angle with extremely high precision. Furthermore, by using an optical semiconductor for the photodetector and making it into an optical integrated circuit, it is possible to make the structure smaller, lighter, and simpler. Furthermore, by using a monochromatic light-passing optical filter and an aberration-correcting aplanat lens in the optical system, measurement errors due to lens aberrations can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a conventional sun sensor, Fig. 2 is an output waveform diagram of a conventional sun sensor, Fig. 3 is a conceptual diagram of an embodiment of the present invention, and Fig. 4 is an illustration of an embodiment of the present invention. FIG. 5 is a perspective view showing an embodiment of the present invention, and FIG. 5 is a sectional view showing an embodiment of the present invention. In the figure, (1) is a silicon thick battery,
Mask, (3) is cover glass, (4) is entrance hole, (5
) is the spin angle of the satellite, (6) is the spin plane of the satellite, (7)
is the solar angle α, (8) is the sunlight, (9) is the apparent movement of the sun due to the spin of the satellite, 01 is the sun, αD is the spin axis of the satellite, Q3 is the output signal lead wire of the silicon solar cell, Q3 is the sun sensor outer box, Q41 is the conventional sun sensor output waveform, and aS is one spin period of the satellite. aS is the conventional solar sensor output signal pulse width, (171
is a monochromatic light passing optical filter, Q16 is an aplanato lens for aberration correction, optical axis of +1lfd lens, ■ is for lens. The moving distance y of the more focused spot, Q11 is the hot spot distance F of the lens, (2) is the optical fiber (to) placed at the focal plane of the lens is the avalanche photodiode, @
is a photodetector, (c) is a computer, (b) is a cable for the output signal of the computer, @ is the outer box of the solar sensor, and @ is a cylinder whose inner surface is painted black. In Figure 1, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa Figure 2 Figure 3

Claims (3)

[Claims] (1) A cylinder whose inner surface was painted black, a protective cover glass provided at the tip of the cylinder, a monochromatic light-passing optical filter attached to the rear of the cover glass, and further placed at the rear of the filter. Equipped with an aplanat lens for aberration correction, a photodetector detects the optical signal on the focal point of the lens via a glass fiber, and the position information is processed by a computer to calculate the solar angle, which is then sent as a sensor signal. A solar sensor characterized by output. (2) The solar sensor according to claim (1), characterized in that an optical semiconductor is used for the photodetector. (3) A sun sensor according to claim (1), characterized in that a monochromatic light passing optical filter and an aplanatic lens are combined to reduce measurement errors due to aberrations.