JP2970261B2 - Solar synchronous satellite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sun-synchronous satellite, and more particularly, to a sun-synchronous earth-oriented three-axis stably used for earth observation.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sun-synchronous satellite in which an attitude control satellite optimizes a distribution of a solar absorption area and eliminates a change in an orbital heat input which is a sum of heat amounts due to sunlight and albedo (heat reflection from the ground surface).

[0002]

2. Description of the Related Art In general, the navigation orbit of an artificial satellite orbiting a sun-synchronous orbit, as shown in FIG. Is normally maintained at around 20 degrees, and is set to pass through the solar eclipse area 14. The attitude of this artificial satellite 14 is shown in FIG.
As shown in FIG. 3, one axis (+ X in FIG.
In general, three-axis control is used in which the first axis (the + Y axis in FIG. 3) is directed in the direction of the track surface, and the third axis (the + Z axis in FIG. 3) is directed in the ground-center direction. At this time, the sun trajectory 11 with respect to the artificial satellite has a conical shape centered on the −Y axis as shown in FIG. The surface of the satellite is provided with a radiation surface 2 for radiating the internal heat of the satellite, and the other parts are insulated. Since the + Z-axis surface of the satellite faces the earth at room temperature, the heat radiation efficiency is poor, so the heat radiation surface 2 is usually provided on the other five surfaces. The heat radiation surface 2 receives terrestrial infrared radiation, sunlight, and albedo, which are reflections of sunlight from the earth's surface, as external heat input.

Under the above-mentioned conditions, the conventional satellite sets the position angle of the satellite 10 in the sun-synchronous orbit 12 with the passage of time as α, as shown in FIG.
Then, the time change of the amount of incidence on the five surfaces of the satellite 1 is shown in FIG.
(B). The amount of light incident on each surface is β angle and solar irradiance μ
(Ratio of sunshine duration during one round of orbit). The sunshine factor μ is a function of the β angle as shown in FIG. The incident amount of albedo is almost proportional to cosβ. The incident amount of the terrestrial infrared radiation is independent of the sun, and thus is constant without depending on the β angle.

[0004]

However, the β angle of the above-mentioned conventional sun-synchronous orbit has an allowable range of about 15 degrees because the allowable range of the satellite launch time is usually about one hour. In addition, there is a seasonal fluctuation range of about 10 degrees per year due to deviation from the spherical shape of the earth shape and deviation from the true circle of the earth orbit. In total, the annual fluctuation range of the β angle is about 25 degrees. As described above, the orbital heat input to the five surfaces of the artificial satellite due to sunlight and albedo depends on this β angle. It is a major disturbance factor. That is, in order to reduce the fluctuation of the orbital heat to the satellite, control by a heat control element such as a heater or a thermal louver of the satellite is required, so that there is a disadvantage that the thermal design of the satellite is complicated.

[0005]

SUMMARY OF THE INVENTION A sun-synchronous satellite according to the present invention travels in a circular orbit around the earth synchronously with the sun.
In a solar-synchronous satellite that is earth-oriented and performs three-axis stable attitude control, the total value Q of the heat absorption of sunlight and the albedo at the end of the minimum and maximum fluctuation range of the angle β between the orbital surface and the sunlight direction is to be equal, anti-earth face of the sun-synchronous satellite, the satellite traveling direction plane, satellite anti traveling direction plane, track parallel surface of the anti-sun side, a portion of each side of the track parallel surface of the sun side
Absorb the sunlight and the albedo provided
Select the size of the heat absorption area .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing the β angle dependence of the total absorption Q of sunlight and albedo according to one embodiment of the present invention. In FIG. 1, the relative ratio of the absorption area of each surface of the satellite is set so that Q is equal at both ends of the variation range of the β angle. As shown in FIGS. 5 and 6, the β angle dependence of each surface of the satellite is about 20%.
Since the β angle variation range of about 30 degrees is substantially linear, if the Qs at both ends of the β angle variation range are matched, as shown in FIG. Gender almost disappears. The absorption area for each satellite
The setting will be described with reference to FIGS. 3 (a) and 3 (b).
3 (a) and 3 (b) show artificial satellites in orbit 12 of the sun-synchronous satellite.
FIG. 3 is an explanatory diagram in which the satellite 1 orbits as an orbiting satellite of the earth 15.
You. Since the artificial satellite 1 is a three-axis stable attitude control satellite,
15 with respect to the ground-centered directional surface (see FIG. 3 (b))
In FIG.
The anti-earth surface 25 (-Z) in which the -Z axis shown in FIG.
Surface). In addition, as shown in Fig. 3 (b),
Surface 21 in the direction of satellite travel with the normal to the + X axis in the same direction as the surface
(+ X plane) and the opposite surface 22 (−X
Plane) and the sun whose normal is the -Y axis which is the normal direction of the orbital plane.
Orbit parallel surface 23 (-Y surface) on the side and the opposite surface
And a track parallel surface 24 (+ Y surface). Sun direction 10
As described in FIG. 2, the angle with respect to the plane of the sun-synchronous orbit 12
f varies along the sun trajectory 11. Here artificial
The satellite 1 has five planes excluding the geocentric plane, -Z plane, + X plane,
Heat absorbing surface on part of each of -X, -Y, and + Y surfaces
Sunlight and Al provided with product _{A -Z, A + X, A} -X, A -Y, A + Y
It absorbs and dissipates heat from the bed.

Next, in this embodiment, Q at both ends of the β angle variation range
The following describes a specific method for equalizing. Earth-oriented plane (+ Z
Assuming that the five surfaces except the surface) are heat radiation surfaces, the orbital circle average value Q of the sum of the absorbed heat amounts of sunlight and albedo of the entire satellite is expressed by equation (1).

[0008]

[0009] Here, P _S Viewfacter solar constant, beta is beta angle (see FIG. 2), mu is sunshine rate, a is the solar reflectance of the ground surface, F _E saw ground from ± Y plane, A _{+ X to} A
_-Z is the absorption area of the + X plane to the Z plane (area x absorption rate)
It is.

When the absorption area of each surface is normalized by (A _{+ X} + A _-X ) as follows and transformed, the following expression is obtained.

[0011]

[0012]

(Β, Q,
μ) to (β ₁ , Q ₁ , μ ₁ ), (β ₂ , Q ₂ ,
μ ₂ ), in order to make Q ₁ = Q ₂ , the absorption area ratios q and r of each surface should satisfy the expression (3).

[0014]

By rearranging equation (3), C = (cos β ₁ -c
osβ ₂ ), D = π (μ ₁ sinβ ₁ −μ ₂ sin
β ₂ ) gives equation (4).

[0016]

Β ₁ , μ ₁ , β ₂ , μ ₂ are values that are uniquely determined from the orbital conditions.
An equation of a straight line representing the relationship between q and r is obtained. What is necessary is just to select q and r on the straight line.

[0018]

As described above, according to the present invention, the five areas of the satellite are selected so that the total absorption amount Q of sunlight and albedo becomes equal at the ends of the minimum and maximum fluctuation ranges of the β angle. The orbital heat input of the entire satellite
Since the fluctuation due to the angle is almost eliminated, there is an effect that a heat control element such as a heater or a thermal louver used for suppressing a fluctuation in the satellite temperature caused by a fluctuation in the amount of orbital heat input becomes unnecessary.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of characteristics of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a general sun-synchronous orbit.

FIG. 3 is an explanatory diagram of a definition of each surface of a satellite and a sun trajectory for each surface according to the embodiment.

FIG. 4 is an explanatory diagram of a temporal change in the amount of sunlight incident on each surface of a satellite in a conventional example.

FIG. 5 is an explanatory diagram showing a change in a general solar irradiance μ due to a β angle.

FIG. 6 is an explanatory diagram showing a change in the amount of solar albedo absorbed by each surface of the satellite according to the β angle in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Artificial satellite 2 Heat dissipation surface 10 Sun direction 11 Sun trajectory 12 Sun synchronous orbit 13 β angle 14 Solar eclipse area 15 Earth

Claims (2)

(57) [Claims] 1. A sun-synchronous satellite that sails in a circular orbit around the earth in a sun-synchronous manner and performs earth-oriented and three-axis stable attitude control.
Sum Q as equal to the minimum and sunlight at the end of the maximum variation range and albedo of the heat absorption amount, the thickness
Anti-earth face of the positive synchronization satellite, the satellite traveling direction plane, satellite anti traveling direction plane, track parallel surface of the anti-sun side, the sunlight and the albedo provided at a part of each side of the track parallel surface of the sun side
A solar-synchronous satellite characterized by selecting the size of a heat absorption area for absorbing heat . 2. The anti-earth surface of the sun-synchronous satellite, satellite travel
Direction plane, satellite anti-progress direction plane, orbit parallel plane on the anti-sun side,
The heat absorption areas provided on the five parallel orbital planes on the positive side
Each _{A -Z, A + X, A} -X, A + Y, and the A _-Y wherein the sum
Arithmetic expression Q is the sum of the A _-X and the A _{+ X} A _{+ X +}
First for setting A- _Z and A _{+ Y} based on A- _X
A- _Y is set based on the coefficient of A _{+ X} + A- _X
2. The solar synchronous satellite according to claim 1 , further comprising a second coefficient .