JPS612086A - Posture determining system using star sensor - Google Patents

Abstract

PURPOSE:To remove interference due to solar light effectively by fitting plural sensors to the roll and yaw surfaces of a satellite and selecting a star sensor to be arranged on the shadow of a solar panel. CONSTITUTION:One of four star sensors 3 forms the image of the North Pole on a picture sensor surface. At that time, a sensor prevented from the influence of interference light of the solar padle is selected. A schedular 4 controls a star sensor to be selected at an optional time. On the other hand, a stationary satellite turns about one revolution in a day. Thereby, the schedular 4 controls so as to select a corresponding sensor by dividing about one day into four parts and storing information related to the sensors to be selected in respecrive time sections. A processor 5 determines the position of the North Pole from the picture of the selected sensor. Consequently, the roll angle and the posture angle of the yaw angle can be detected without receiving solar interference light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is directed to a system that uses a star sensor to determine posture with high precision.

[Background of the invention]

As the missions of recent satellites such as communication satellites have become more sophisticated, it has become necessary to detect and control their attitudes with high precision. On the other hand, in a geostationary satellite such as a communication satellite, as shown in FIG. 1, the pitch axis p of the three axes r+VtP of the satellite S always points north. Therefore, by tracking Polaris Po, it is possible to detect the attitude in the yaw angle direction and the roll angle direction from the difference between the planned position of Polaris Pa on the sensor surface and the actually observed position on the sensor surface. ing.

However, in order to always receive sunlight on the paddle, it is necessary to install the solar paddle on the pitch axis plane. However, as shown in Fig. 2, if there is only one star sensor 3, and the star sensor is located in front of the solar paddle 2, it will receive interference light from the sun, so the North Star will not be visible to the image sensor ( There was a problem in that it could not be detected due to

[Purpose of the invention]

An object of the present invention is to provide a new attitude determination system that can effectively avoid interference caused by sunlight.

[Summary of the invention]

Therefore, in the present invention, in order to solve the above-mentioned problem, a plurality of sensors are attached to the roll and yaw planes of the satellite, and a star sensor that is in the shadow of the solar paddle is selected, and from the image of the pole star reflected on this, the satellite By detecting posture changes,
Roll angle and yaw attitude angle can be constantly detected without being affected by solar interference light.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 3 shows the satellite viewed from due north. Here, four star sensors were installed on the roll and yaw planes. That is, four star sensors 3 are installed at 90° intervals. In this case, a star sensor that is not exposed to sunlight is selected to determine the attitude. FIG. 4 is a configuration diagram of an attitude determination system using a star sensor. The four star sensors form an image of the North Star E on the image sensor surface as shown in FIG. However, since there is interference light due to the influence of the solar paddle, it is necessary to select a sensor that is not affected by interference light. The scheduler 4 selects an arbitrary time T.
Controls which star sensor is selected for. A geostationary satellite rotates about once a day. Therefore, the scheduler 4 divides approximately one day into 1/4 equal parts, stores information on which sensor is to be selected at which time, and controls the sensor to be selected. The processing device 5 determines the position of the North Star (x+y) from the image of the selected sensor. (x
, y), the surrounding area of the image is 3×3.
The gray steel P(IIJ) of the pixel is taken and both Xy and y are calculated as the center of gravity of the image as follows. (X ljp
'j ij) represents the pixel position corresponding to P(i, j).

J −1 Next, the roll angle and pitch angle are calculated from XsV. The calculation algorithm is as follows.

Polaris is located at right ascension 31.8° and declination 89.9°.

If we approximate this to be located at 90° declination, that is, due north, then if the focal length of the star sensor is f, then the roll angle or
, yaw angle θy can be determined by or = −− θy” − respectively. However, it is assumed that the X direction of the sensor surface coincides with the yaw axis, and the X direction coincides with the roll axis.

In order to determine the attitude more accurately, it is necessary to take into account the deviation of the North Star from true north. That is, the azimuth vector of the pole star is (ε×eE'/+ε2), and the Greenwich angle of the satellite is calculated.

Above, we have explained the attitude determination method using multiple star sensors, but when there are two star sensors, 18
They may be arranged at 0' intervals. In the case of four star sensors, two star sensors will always be placed in the shadow of the solar paddle, which is also effective from a fail-safe point of view.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to solve the solar damage prevention problem that was a problem with star sensor attitude determination systems using pole star trackers.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram explaining the motion of the satellite, Fig. 2 is an overall view of the satellite, Fig. 3 is a roll and side plan view of the satellite, and Fig. 4 is a block diagram showing the configuration of an attitude determination system using a star sensor. , FIG. 5 is a schematic diagram showing an image of the North Star on the image sensor surface. 1... Satellite main body, 2... Solar paddle, 3... Starsen Figure 1'-14 Figure 2 Figure 3 4 Figure % 5 Figure

Claims (1)

[Claims] In a system that uses star sensors to track Polaris and detect attitude changes of satellites, multiple star sensors are installed at equal angular intervals in the direction of Polaris, a star sensor that is in the shadow of the solar paddle is selected, and the polar star of that sensor is A posture determination system using a star sensor that detects posture fluctuations from images.