# Method of orientation of spacecraft

FIELD: programmed positioning and orientation of mobile objects; angular orientation or positioning of spacecraft.

SUBSTANCE: proposed method includes measurement of angles of position of optical axes of astro-visual units tracking the stars relative to body-axis coordinate system. For determination of orientation of mobile object, use is made of coordinates of its center of mass in geocentric coordinate system which are determined by means of high-precision global navigation satellite system.

EFFECT: enhanced accuracy of orientation of mobile objects.

2 dwg

The proposed invention relates to the field of control angular motion of the SPACECRAFT). The basis for such management is the process of determining the angular orientation of the SPACECRAFT relative to any basis.

For most targets in space is most often used in practice, the orientation of the SPACECRAFT in the mobile orbital coordinate system (PQS), which has its beginning (point a) is combined with the center of mass of the SPACECRAFT, one of the axes (τ) lies in the orbit plane and perpendicular to the current radius-vector in the direction of movement, the other axis (b) collinear to the vector of the angular momentum of the orbital motion of the SPACECRAFT, the third axis (n) is directed along the radius vector, the Angular position of the SPACECRAFT relative to its center of mass is uniquely determined by the angles associated with the case SPACECRAFT coordinate system Ax_{1}y_{1}z_{1}relatively PQS, i.e. the pitch angles ϑ, yaw ψ roll γ (figure 1).

The accuracy of determination of orientation angles in this approach depends not only on the errors in angular measurements, but from the errors of determination of the position of the center of mass of the SPACECRAFT in space, i.e. from the errors of the navigation channel.

There are ways to control angular movement [1-4]based on the determination of the orientation of the SPACECRAFT using a gyro-stabilized platform (GSP) or through free thormania inertial systems using astronomical correction. However, the unavoidable errors of onboard measurements and other sources of interference lead to significant errors in the solutions as the problems of navigation SPACECRAFT and, therefore, the task orientation of the SPACECRAFT.

Closest to the proposed composition measurement is a method for determining motion parameters of the center of mass of the SPACECRAFT [5], which consists in measuring Zenith distances of two stars and the flight altitude above the planet's surface. Under Zenith distance refers to the angle between the direction of the center of the Earth and the direction of the star. The measurement of altitude of the SPACECRAFT and the determination of the direction to the center of the planet by using local Builder vertical - radioterminal-altimeter (RVV). The main stars are determined by two astrovision devices (AVA). The disadvantage of this method is the low precision of the translational and angular motion of the SPACECRAFT, where the marginal errors correspond to the following values:

- channel navigation [5]:

on the flight altitude of 150 m;

- on the distance (along the orbit) 6000 m;

- on a lateral coordinate (normal to the orbit plane) 1500 m;

- channel orientation [2]:

- pitch 25 minutes of arc;

- yaw 10 minutes of arc;

- roll 15 angular minutes.

The aim of the invention is to improve the accuracy of the orientation of the SPACECRAFT.

The goal has been reached is carried out using equipment of high precision global navigation satellite system (SNA) type “GLONASS” to determine the coordinates of the center of mass of the SPACECRAFT in geocentric Equatorial coordinate system (GASC).

The invention consists in the following. The angles of deflection of the associated coordinate system relative to the PQS are determined by:

the measurements of the angles of the optical axes of the two AVA, watching the stars, relative to the body of the SPACECRAFT;

- calculate the guides of the cosines vizireanu stars in GASK;

- determine the current coordinates of the center of mass of the SPACECRAFT using the equipment of the consumer global SNA type “GLONASS”;

mathematical processing of the information received by the algorithms given in [8].

Since the error in the determination of the coordinates of the center of mass of the SPACECRAFT using SNA type “GLONASS” is 10 m [6, 7], the component of error orientation of the SPACECRAFT as a consequence, will not exceed fractional angular seconds. Let us consider this in more detail.

To simplify the proof we assume that a task orientation system is the combination of the axes of the associated coordinate system X_{1}, Y_{1}, Z_{1}with the axes PQS τ, b, n, respectively, i.e. in maintaining zero values of the orientation angles.

Consider “flat” problem, when the movement is in the XY plane (figure 2).

Let_{p}- design point location KA with coordinates X_{p}, Y_{p};_{f}the actual point location with coordinates X_{f},_{f}. Position is the moving axes τ
n in the calculation point With_{p}set the measurement Zenith angle β_{p}star S (known). At point C_{f}the actual location of the SPACECRAFT appears error Δϑ≠0 pitch angle, the value of which is determined by the errors of the coordinates of the center of mass:

ΔX=X_{f}-X_{p};

ΔY=Y_{p}-U_{f}.

The calculated value of the Zenith angle β_{1}is determined by the formula [3]:

wheremodule radius-vector, and^{0}b^{0}c^{0}well - known direction cosines ORT visiwave stars.

Compatible to simplify the calculations, the Y-axis with the direction of the star S. Then

a^{0}=c^{0}=0, b^{0}=1.

You will receive:

Assuming sufficient smallness of the deviations ΔX, ΔY, Δβ, Δϑ get:

For the flight altitude H≈200 km:

r=R_{3}+N=6570 km, where R_{3}the radius of the Earth;

When β_{1}=0, X=0, Y=r received

or as Δβ=Δhave finally

If the equipment of the consumer SNA “GLONASS” determines the location error ΔX=10 m, Δ=1,5·10^{-6}happy = 0,3 corner sec.

While the orientation error of the prototype by the angle of pitch is 25 arc min [2].

Thus, the proposed method significantly improves the accuracy of the orientation of the SPACECRAFT through the use when solving navigation tasks more precise measurements of the coordinates of the center of mass of the SPACECRAFT using SNA “GLONASS”.

Sources of information

1. Apertures. The basics of flight control spacecraft. - M.: Mashinostroenie, 1990.

2. Kinetics And Ask, Upominki. Fundamentals of Autonomous navigation of spacecraft. M: the USSR Ministry of defense, 1982.

3. Lpparam, Kinetics And Vijasnitsa. Analytical assessment of the accuracy of the offline methods of orbit determination. M.: Mashinostroenie, 1987.

4. Weekececif. System of astronomical orientation of the spacecraft. - M.: Mashinostroenie, 1980.

5. Mathematical and software systems Autonomous navigation KA “amber”. M: the USSR Ministry of defense, 1986.

6. Umounting, VScan. MEO satellite radio navigation system “GLONASS” and “GPS”. M: Petropavlovsk-Kamchatsky, 2002.

7. EAACI, Vffaluv. Satellite navigation system. M: the USSR Ministry of defense, 1990.

Way Oriental and spacecraft, consisting in the calculation of the Zenith distances of two stars on the basis of measurements of the angles of the optical axes Astrovirus devices, watching the stars, relative to the associated coordinate system, characterized in that for calculations using the coordinates of the center of mass of the spacecraft in geocentric Equatorial coordinate system, which is determined using high-precision global navigation satellite system.

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