JPS6031241B2 - Satellite attitude determination device - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the attitude determination of a spin-stabilized or triaxially stabilized artificial satellite (hereinafter referred to as a satellite) flying in space, and more specifically relates to an optical image plane electronic scanning imager (hereinafter referred to as a TV camera) mounted on a satellite. The present invention aims to provide a method for determining the attitude of a satellite based on the orbit information of the satellite determined by the following methods (for example, the Ran Bag & Range Rate method or the optical side range method). Conventionally, the attitude of a satellite is determined by detecting the horizon on board the satellite.
A computer on the ground processed and determined the measured values of the earth detector, the sun detector that detects the direction of the sun, and the star detector that detects the direction of stars whose coordinates are known on the satellite sphere. These methods assume the position of the satellite, the position of the sun, and the position of stars in the geocentric coordinate system, and their positional accuracy cannot be said to be sufficiently good, and the detection of the earth's horizon is difficult. The system detects the spectrum emitted by the carbon dioxide (C02) layer on the earth's surface, and the CO2 layer changes depending on time and location.Furthermore, the sun has a finite interior, and stellar detection is based on electromagnetic fluctuations in outer space. to be influenced. Therefore, there is a limit to highly accurate attitude determination using conventional methods. However, with the recent development of earth sensing from satellites and moat sensing, a huge amount of image information has been acquired by satellite-mounted imaging devices, and the resolution has also made great strides. As a result, highly accurate processing technology for image information and highly accurate control of satellite attitude during imaging are required, and highly accurate attitude determination using image information is lacking in both of these requirements. It has become a long-awaited technology that is impossible to achieve. FIG. 1 is a conceptual diagram of an image taken by a TV camera 3 guided by a satellite 2 flying in an orbit 1. At a certain point on the orbit 1, the TV camera 3 receives incident light 6 from a region 5 on the earth's surface 4 and images it. The ground area 5 to be imaged is centered on the point ○ directly below the satellite 2, and the TV camera 3
It is determined by the viewing angle af of the satellite 2 and the altitude h of the satellite 2. FIG. 2 shows a schematic configuration diagram of the TV camera 3. The incident light 6 passes through the lens 7 and reaches the photoconductive surface 1 of the image pickup tube 9 when the shirt is momentarily opened.
0' image is formed, stored and subsequently retrieved by scanning of the electron beam 11 to produce an analog video signal 12 or A/
The PCM digital signal 13 is then transmitted to the ground through the FM transmitter 14 or PCM transmitter 15 of the satellite 2. FIG. 3 shows a configuration diagram of the photoconductive surface 10. The photoconductive surface 10 has a rectangular shape with side lengths a and b, and photoelectric conversion elements 16 are closely arranged parallel to sides a and b.
The incident light 6 is stored in each photoelectric conversion element 16 according to the location on the photoconductive surface 10 where the image is formed, and is stored in the order of scanning lines 1, 2, . . . n parallel to side b (or side a). Each scan line i
The information stored in each conversion element 16 is successively read out by the electron beam 11 scanned along (f=1, 2, . . . n). At the start of the green image, each scan line i? i=1,2,...,n)
A synchronizing signal, such as when the electron beam 11 starts scanning, is attached, so that a unique correspondence can be established between the image analog video signal and the information imaged on each photoelectric conversion element 16. When the position of the satellite on the geocentric coordinates is given, the geographic latitude, longitude and degree of the satellite's point directly below the earth's surface can be determined by a generally well-known method. Figure 4 shows the total geographic degree o and longitude of satellite 2 and the point directly below the satellite. shows the geometric relationship between In Figure 4a, the geocentric inertial coordinate system (
X, Y, Z) to Greenwich coordinate system (X., Yc, ZG
) is given by the following equation. ×GniX's S80YS
in8 (1) YG:XSin
80YCOS8

[2}Zo=Z
B} Here is the Greenwich side real time at Kawabataji time. Using (XG, YG, ZG), the geocentric latitude 6 in the geocentric inertial coordinate system of satellite 2 is 6=Si'・(Z2G+Chapter 10#G
〉 Given by ■. The earth's rotation axis is Z. Since it is a spheroid that is rotationally symmetrical around , the geographical longitude of the point directly below the satellite ○ is . = Ne n - (Beautiful) It is given by ■, but as shown in Figure 3b, the geographical latitude of the point ○ is the radius. For places other than =oo or ±90o, it is the geocentric latitude of the direct point ○. different from. If the earth's oblateness is d, then the geocentric stripe of the point ○ directly below. As is generally well known, the calculation formula for calculating the geographical fringe degree o from the following side~'9
' can be given using the expression.ノ 1-other ■ rC=re ・One (2d-d2) COS 2 swords. 'the law of nature. Sting n {crocodile poison} h=ノ〆−r2CSi
〆(sword. -sword'.) 1 rccos (ri. -ri'.) (8) △ri'. =Sin-・{kiin(Ri.-Katana'.)} side Here, re is the earth's equatorial radius, and r is the magnitude of the earth position vector r, r=lrl. To find o using equations 6i to 5, first enter . = 6, calculate the {7th} formula, and further calculate the {8th} formula.
}, calculate the formula [9}. As a result, △ri′o generally does not become zero. =6−△katana′. Totoe {6th
} ~ [Repeat the calculation of formula 91. This repeated calculation is △
the law of nature'. Repeat until it falls within a certain tolerance. becomes the geographical latitude of the point directly below 0. Also, h at that time is the altitude from the direct point ○ to satellite 2. FIG. 5 shows a definition diagram of the line-of-sight vector P when viewing an arbitrary point P on the earth's surface 4 within the viewing angle of the TV camera from the satellite 2. Now, the mechanical axes x, y, and z with the center of mass S of satellite 2 as the origin are defined as follows. The photoconductive surface 1 is perpendicular to the optical axis 17, with the orientation of the ground surface 4 being the z-axis in the direction of the optical axis 17 of the TV camera.
If the x-axis is parallel to side a of 0 and the direction of travel of the satellite 2, the optical axis 17 and the photoconductive surface 10 are orthogonal, so the x-axis,
The z-axes are orthogonal. Right-handed orthogonal system (x,
y, z) is the y axis, the x-y plane is parallel to the photoconductive surface 10, and the sides a and b are orthogonal, so the y
The axis is parallel to side b. Here, as shown in FIG. 5, a ball is defined with an axis parallel to side a and opposite to the x-axis, and a y-axis parallel to side b. Since each point on the photoconductive surface 10 can be defined as a point with f-coordinates, the coordinates of the point Q on the photoconductive surface 10 on which the incident light 6 from the point P on the ground surface 4 forms an image can be expressed as (g, k). ), and the point where the optical axis 17 intersects with the photoconductive surface 10 is C(
f. , Kio), the satellite center of mass S is the origin, and S
A field of view vector P directed toward P is defined, and x, y, z
The direction cosines PX, Py, and P2 of P in the coordinate system are -f.) 20 (Kisa. A ten - f (12) Pz=ノ
It is given by fr (r. 10s), where f is the focal length of the TV camera (in Fig. 5, SC = f). Generally, a satellite in orbit has a rotation angle around the satellite center of mass. The relative relationship between the satellite mechanical axis system and the earth is changing. Figure 6 shows the satellite mechanical axis system x,
The relative relationship between y, z and the ground surface 4 is shown. In FIG. 6a, the orbital reference coordinate system (roll axis, pitch axis, and yaw axis) with the satellite center of mass S as the origin is defined as follows. If the direction of the point ○ directly below the satellite from S is the yaw axis 18, and the direction of the velocity vector V of S is the roll axis 19, then generally the yaw axis 18
The pitch axis 20 is defined to be perpendicular to the roll axis 19 and the roll axis 19, and to be perpendicular to the roll axis 19 and the jaw axis 18, and to form a right-handed system in the order of the roll axis 19, pitch axis 20, and jaw axis 19. Generally speaking, while the satellite is being imaged by a TV camera, the satellite mechanical axis, x axis and roll axis 19, y axis and pitch axis 2, as shown in Figure 6M.
It is controlled by a mounting attitude control device so that the 0 and z axes and the yaw axis 18 coincide with each other. However, in reality, due to control errors, the satellite mechanical axis system x, y, z
are rotated by small angles ◇, x, and J around the roll axis 19, pitch axis 20, and jaw axis 18, respectively. At this time, the coordinate transformation matrix ■ from the x, y, z coordinate system to the roll, pitch, and yaw coordinate system is, as is generally well known,
If x and J are minute, it is given by. If the direction cosines of the line-of-sight vector P in the roll, pitch, and yaw coordinate systems are PR, PP, and PY, a Q relationship is established between them and Px, Py, and Pz. FIG. 7 shows the geometric relationship between the geographical angle and longitude of point P and the line-of-sight vector P. Let the angle formed by the meridian 21 passing through the point ○ directly below the satellite and the locus 22 on the earth's surface 4 of the point ○ directly below the satellite as it moves in the orbit. If the center of curvature near the point 0 directly below the earth's surface 4 is ○, and the radius of curvature is C'○3r'e, then ○ is the virtual center of the earth and SO is orthogonal to the earth's surface 4, so SOG' is a straight line. Become. A plane 23 and S that is orthogonal to the straight line S〇 and passes through the point P
The intersection with G' is ○', and it is on a straight line connecting the meridian 21, the intersection of the satellite nadir trajectory 22, and the plane 23 with point 0', and with ○' as the origin, the north N direction and the satellite mass Let ln and lx be the axes in which the direction of the velocity vector V of the center S is positive. is on the plane 23 and has the axis lxln
If the axes that are orthogonal to each other and have positive directions toward the left and west W toward the direction of travel of the satellite are ly and lw, respectively, then the two-dimensional orthogonal system (]x, iy) on the plane 23 is an orthogonal system. (ln, lw) around ○' at an angle of (-180o)
It is rotated by 180 degrees. At this time,
Rotate the ln axis from north N to east E so that the direction is >0. Therefore, the coordinate transformation matrix from the (1n, IW) system to the (lx, ly) system is given by: Next, two OGP three Q (O
If SQ<oo), the geographical latitude and longitude of point ○ are (T., In.), so the vectors G'○, 〇○ in the Greenwich coordinate system (the origin of the Greenwich coordinate system is set at point G') From the inner product of ), COSQ±COS is calculated.
COS Ri・C. S one entry. ) 10SInrigainri (1
6) holds true. Using this Q, altitude S○3h, GO'=GP=re, so SO'=h+r'e (1-cosQ), (
lx, ly component l of vector ○'P in lx, ly) system
xp, lyp are IXp ni {h+ and C(1-cosQ
)}tan8× (17) IXpe {h+r′e(
11 coso)} tanay (18) Here, ox
, 8y is the foot of the perpendicular line drawn lm ly from point P as A,A
′, 0SA38x, 20SA18y (when A and A' are lx>○, ly>○, respectively, 8x>○, 8y>○). On the other hand, the component lnp in the (ln, lw) system of vector ○'P
, IWp are given as follows. ln, lw from point P
Let the legs of the perpendicular drawn to .
), ku○′G′B=(入一入.) cosri. Since it is given by lnp=rec. sQ・tan (Reli.) (1 rule IWp=r'e
C○SQ. tan {(^-^.). C○Sri. }
(20) holds true. Therefore, if we use the coordinate transformation matrix G in equation (15), (lxM
lyp) is given by (ln”lwp).
17), tan8x, nay in equations (18) are the components PR, PP' of the line-of-sight vector P given in equation (14).
PR with Py (2
2) Leg 8X=Hei-PP
(23) Since it is given by
, (18) is IXp={h+r'e(1-COSQ)
}A long time ago (2-heart IW Ko {hten r'e (1-COSQ)}
It can be rewritten as sheep (25). From the above, the {1st, (11), (12), (13), (
14), (15), (16), (19), (20), (
21), (24), and (25), we can calculate the geographical latitude and longitude of point P, and the coordinates of the image of point P on the photocathode (f
, ki) can be connected. No.

[1■, (11), (12), (13), (14),
From equations (24) and (25), Xp = {h + r'e (11 cosQ)} (ff.
)×-(Kisa.)gujuflyp={hten
osQ)} -(gi-;.)yamaju(;- sa.)juf? (27)-(f-
f. )×−(Kisa.)○10f is derived, and the (15th),
From equations (19), (20), and (21), IXp=reC○
SQ. [tan (Katana Ichiri.) C○S Rene n {(Entertainment.) C○S Rene. } ． Si
nre] (28) 1yp=reC○SQ. [tan (liri.) Sinri tenne n {(iriiiri.) cosri. }
．． cozy] (29) is derived. h ten r'e (1-c
osQ)3h' and expand equations (26) and (27) for the satellite's minute rotation angle ◇, x, J, IXp
(Kisa.)・guten {IXp (giichiyo.) tenh'f}x tenh'(;
one;. ) Shinichi 1Xpf 10th (Ma-f.) = 0
(3 no {lyp (gi-;.) ten days f
}◇10lypkuru-many〇)X-hくff-f. )shi-1yp ten days;-;. )=0
(31), (30)×ly
Organized by p-(30)×lxp, the (28), (2
In 9), MX nine n(ri-ri.) cos le-tan {ku^ichi^^. ) C○Sri. } ． Sm le (32) MyE is n (lily.) sin le tenmatsu n {(entering one entering.). C○Sri. }C○S Ri (33), skin x・◇
‐fMy・x−{MX(Tagi.) 10My(Kisa.)}Shinju{MX(Kisa.)−My(Gima.)}=. (It becomes 3 less. No. (32)
, In equation (33), the geographical fringe degree o and the longitude of the point immediately below are entered. and the angle between the locus on the earth's surface of the point directly below it and the meridian〃[
If the satellite's orbital position in geocentric inertial coordinates and the imaging time are given, it can be found using formulas m to '9'. ) can be given by referring to On the other hand, in equation (34), the coordinates (f, ki) of the imaging point of point P on the photoconductive surface are:
It is given by comparing the acquired image with a reference map and detecting the pixel number of point P on the image. Furthermore, since the coordinates (f., kio) of the point on the photoconductive surface that intersects with the optical sea bream are generally set at the center point a on the photoconductive surface, f as shown in FIG. =back, ki=object, and f is given to the parameters of the imaging device itself. Therefore, equation (34) is the roll, pitch, and minute rotation angle of the satellite machine koji x'y'z around the axis, and is an equation with x and the center as unknowns, and the geographical latitude of point P, If three different combinations of longitude and image point coordinates (ri, iri, f, ki) are given, that is, three different points P within the imaging range are given for one image.
,, Regarding P2, P3 (rii, entering i, mai, kii)
(i = 1, 2, 3), the attitude of the satellite is g, x, J
can be uniquely determined. A configuration diagram of this invention is shown in FIG. The PCM image signal 13 acquired by the TV camera 3 and the reference diagram 25 corresponding to the acquired image extracted from the standard map file 24 are input to the reference point measurement unit 26, and at least three predetermined reference points are inputted. Measure the degree of fringe, longitude, and pixel position on the image of point V on the map. In addition, the geocentric inertial coordinate system component (Xo,
Yo, Yo) and imaging time T, the first calculation unit 27 calculates the geocentric inertial coordinate system component (X,
Y, Z) and side real time 8, and based on the results, the second arithmetic unit 28 calculates the azimuth degree o and longitude ^ of the point just below the earth's surface of the satellite at the time of imaging. and the angle y between the orbital plane of the satellite and the meridian. At this time, the reference map 25 corresponding to the acquired image is extracted based on the latitude and longitude values. Finally, the latitude, longitude, image position (f, x), latitude, longitude, and angle y are input to the determination unit 29, and the attitude angle of the satellite (0 , x, mind). With the above configuration, the satellite attitude at the time of imaging can be determined. Since the present invention is configured as described above, it is possible to determine the attitude of a spin-stabilized or triaxially-stabilized artificial satellite at the time of imaging.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the image taken by a TV camera mounted on a satellite in orbit, Figure 2 is a schematic configuration diagram of the TV camera, Figure 3 is an explanatory diagram showing image acquisition using a photoconductive surface and an electron beam, 4
The figure is a geometric relationship diagram of the geographical latitude and longitude of the point directly below the satellite, Figure 5 is a definition of the line-of-sight vector that looks at any point on the earth's surface from the TV camera on the satellite, and Figure 6 is the mechanical track of the satellite. Fig. 7 is an explanatory diagram showing the geometrical relationship between the earth surface and the geographical latitude and longitude of any point on the earth's surface, and the line-of-sight vector; Fig. 8 is an illustration of the artificial satellite of the present invention. 1 is a configuration diagram showing the attitude determination device of
Camera, 4 is the ground surface, 5 is the ground area to be photographed, 6 is the incident light, 7 is the radiation, 8 is the camera, 9 is the image pickup tube, 1 is the photoconductive surface, 11 is the electron beam, 12 is the image video signal, 1
3 is an image PCM signal, 14 is an FM transmitter, and 15 is a PCM
16 is a photoelectric conversion element, 17 is an optical axis, 18 is a transmitter, and 16 is a photoelectric conversion element.
axis, 19 is the oar axis, 20 is the pitch axis, 21 is the meridian,
22 is a direct point locus, 23 is a plane passing through point P and facing SG', 24 is a standard map file, 25 is a reference map, 26
is the reference V point measurement unit, 27 is the first calculation unit, 28 is the second calculation unit, 29 is the determination unit, Xo, Yo, Zo are the geocentric inertial coordinate system components of the satellite initial position, and T is the imaging time. be. Note that the same or corresponding parts in the figures are indicated by the same reference numerals. Figure 3 Figure 1 Figure 2 Figure 7 Figure 4 Figure 5 Figure 8 Figure 6

Claims (1)

[Claims] 1 Comparing an image signal captured by an imaging device that images the ground surface with a reference map in an attitude determination device for an artificial satellite equipped with an optical image plane electronic scanning type imaging device with a shutter, etc. a reference point measuring means for measuring the latitude and longitude on a map of an arbitrary reference point on an acquired image and the pixel position on the image; and a geocentric inertial coordinate system component of the position of the satellite at the imaging time of the imaging device. and calculation means for calculating the latitude and longitude of a point directly below the surface of the earth of the satellite at the imaging time based on the side real time, and the angle formed between the locus of the point directly below the surface of the earth and the meridian according to the orbital movement of the satellite;
An apparatus for determining the attitude of an artificial satellite, comprising: the reference point measuring means; and means for determining an attitude angle of the satellite based on the orbital reference coordinate system of the satellite based on the output of the calculating means.