CN114061594A - Multi-view-field starry sky observation satellite target attitude planning method - Google Patents

Abstract

A method for planning a target attitude of a multi-field-of-view starry sky observation satellite, comprising: step 1, acquiring the season or month, satellite orbit height, and stray light suppression angle of an imaging optical device for starry sky observation by the satellite; step 2, selecting a field of view according to the optical device The projection relationship with the observable sky area gives the optional sky area of each optical device; step 3, according to the distribution of stars in the optional sky area, select the set of observation points, and obtain the celestial coordinate system of each optical device under the observation point. To determine whether it is in the available sky area, delete the unavailable observation points; step 4, count the number of stars in the camera's field of view under the available observation points, and optimize the available observation points; step 5, repeat step 3, Fourth, until a satisfactory set of observation points is found, output the right ascension, declination and satellite attitude transformation matrix of the optimal observation point. The invention provides an ideal observation sky area and target attitude when remote sensing satellites and astronomical observation satellites perform multi-field starry sky imaging.

Description

A target attitude planning method for a multi-field starry sky observation satellite

technical field

The invention relates to a multi-field-of-view starry sky observation satellite target attitude planning method, which belongs to the field of satellite target attitude planning and is applied to imaging area selection and attitude planning when remote sensing satellites and astronomical observation satellites perform multi-field-of-view starry sky imaging.

Background technique

When the payload of a remote sensing satellite is a camera, it can perform radiometric calibration or geometric calibration on star imaging, requiring multiple cameras or star sensors to image the sky at the same time.

Since remote sensing satellites are designed for the needs of ground imaging, there are some problems when imaging the starry sky. For example, the small field of view of the camera leads to a limited number of observed celestial objects, and optical equipment (cameras, star sensors, etc.) At present, there is still a lack of corresponding observation sky area and target attitude planning methods in related fields.

In addition to remote sensing satellites imaging the starry sky, some astronomical observation space science satellites need to image specific sky areas due to the needs of their detection tasks. In the current literature on astronomical observation satellite mission planning, more consideration is given to adding fixed-point targets. Issues such as the number of visits, prolonging the observation time, minimizing energy consumption, and starry sky coverage are rarely involved in the attitude planning problem of simultaneous imaging of the starry sky by multiple field-of-view cameras.

SUMMARY OF THE INVENTION

The technical solution of the present invention is: overcoming the deficiencies of the prior art, providing a multi-field-of-view starry sky observation satellite target attitude planning method, and providing an ideal observation sky area for remote sensing satellites and astronomical observation satellites to perform multi-field starry sky imaging and target attitude, so that all imaging optical devices (such as cameras, star cameras and star sensors, the number is greater than or equal to 1, that is, multiple fields of view) during the observation process are not disturbed by sunlight and atmospheric light, and enter the camera. The number of stars in the field of view is as large as possible to ensure the validity of the observation and improve the quality of the observation.

The technical solution of the present invention is:

A multi-field of view starry sky observation satellite target attitude planning method, the steps are as follows:

Step 1: Obtain the season or month of starry sky observation by the satellite, the satellite orbit height, and the stray light suppression angle of the imaging optical equipment;

Step 2: According to the projection relationship between the optional field of view of the optical equipment and the observable sky area, the optional sky area of each optical device is given;

Step 3: Select a set of observation points according to the distribution of stars in the optional sky area, obtain the pointing of each optical device under the observation point in the celestial coordinate system, determine whether it is in its available sky area, and delete the unavailable observation point;

Step 4: Count the number of stars in the camera's field of view under the available observation points, and optimize the available observation points;

Step 5: Repeat steps 3 and 4 until a satisfactory set of observation points is found, and output the right ascension, declination and satellite attitude transformation matrix of the optimal observation point.

Further, the stray light suppression angle specifically refers to: the optical device is affected by external stray light, resulting in a decrease in imaging effect or even failure, and the optical device is constrained by the stray light suppression angle when imaging, when the stray light is outside the stray light suppression angle. When the optical device is working normally, the imaging effect of the optical device is degraded or cannot work normally; the stray light includes sunlight and atmospheric light.

Further, according to the mission planning of the satellite, select the month or specific date for starry sky imaging, and choose to perform multi-field starry sky imaging in the shadow area, obtain satellite orbit data through satellite-ground measurement and control, and extrapolate to obtain the satellite orbit height on the starry sky observation day. , when the satellite is in a circular orbit, the satellite orbit height directly uses the nominal orbit height.

Further, the step 2 provides the optional sky area of each optical device according to the projection relationship between the optional field of view of the optical device and the observable sky area, specifically:

After obtaining the satellite orbit height H and the stray light suppression angle B of the imaging optical device, the angle A between the XOY plane of the orbital coordinate system and the edge of the earth and atmosphere is

The available cone C of the field of view of the optical device is

where p is the thickness of the atmosphere and _Re is the radius of the earth;

The observation sky area is analyzed in the celestial coordinate system, and the projection of the available conical field of view of the optical device's field of view on the celestial sphere is recorded as the optional sky area of the optical device. When the optical axis of the optical device points in the direction of R _Z When it is any direction within the conical range of the generatrix, it will not be disturbed by the air and air, α ₀ is the right ascension center point of the optional sky area of the optical equipment, and α ₀ is related to the specific season/month of the observation; The optional observation center points of the sky area for the vernal equinox, summer solstice, autumn equinox, and winter solstice are:

Spring Equinox α ₀ = 180°

Summer Solstice α ₀ = 270°

Autumnal Equinox α ₀ =0°

Winter Solstice α ₀ =90°

The optional sky area set is

S={α,δ:cos ² (α-α ₀ )cos ² δ+sin ² δ≤sin ² C}

If B>A, then C<90°, δ _e ∈(-C,C), the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

If B<A, then C>90°, δ _e ∈ [-90°, 90°], the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

Further, in the step 3, select a set of observation points, specifically:

When selecting observation points, each observation point contains two celestial sphere coordinate points, one coordinate point is the satellite + Z-axis pointing point, and the coordinates are marked as (α ₁ ,δ ₁ ), and the other coordinate point is located in the XOZ plane of the satellite system. , the pointing point of the vector with a certain positive angle between the +X axis and the +Z axis, and the coordinates are marked as (α ₂ ,δ ₂ );

When selecting the observation point set, follow the principles from wide to narrow and from sparse to dense. When selecting the observation point set for the first time, the optical equipment with the largest coverage is selected, and the density is sparse; after one calculation, the observation point is selected for the second time. When collecting, the observation point is selected near the first available observation point, and the density is more encrypted than the last time, and so on;

According to the conversion relationship between the celestial coordinate system and the inertial coordinate system, the attitude transformation matrix C _ib from the inertial coordinate system of the satellite J2000 to the satellite system is calculated by the following formula:

in,

X^T＝Y^T×Z^T

X ^T =Y ^T ×Z ^T

According to the installation orientation of each optical device on the satellite, calculate the orientation of each optical device in the celestial coordinate system; set the installation array of the optical device in the satellite system as C _bCam , then the attitude matrix of the optical device in the J2000 inertial system is :

为光学设备光轴在惯性系下的矢量表示，z₁、z₂、z₃为矢量的三个分量；in,

is the vector representation of the optical axis of the optical device in the inertial frame, and z ₁ , z ₂ , and z ₃ are the three components of the vector;

在天球坐标系下的坐标(α,δ)为The optical axis of the optical device

The coordinates (α, δ) in the celestial coordinate system are

δ=arcsin(z ₃ ),

Next, determine whether the coordinates (α, δ) of the optical device in the celestial coordinate system are in the available sky area obtained in step 2:

This observation point is available when all optics are in their respective optional sky zones;

When the optical axis of one or two optical devices is not in the optional sky area and cannot meet the mission requirements, the observation point is unavailable;

Delete unavailable observations to obtain available observations.

Further, the step 4 counts the number of stars in the field of view of the camera under the available observation points, and optimizes the available observation points, specifically:

First, according to the camera installation matrix, the field of view shape and the definition of the coordinate system, the camera field of view edge pointing vector array under the satellite system is established as

Among them, n is the number of edge points of the field of view, [z _1i z _2i z _3i ] ^T is the direction of the i-th edge vector in the satellite system, i=1,...,n;

The coordinate array Cam _ball of the edge vector of the camera's field of view under the celestial sphere system is obtained by the method described in step 3;

According to the field of view of the camera detector, determine whether a certain star point is within the field of view of the detector of the optical device, calculate the number of star points in the field of view of the camera, and select the observation point with the largest number of star points as the preferred observation point.

Further, when judging whether a certain star point is within the detector's field of view of the optical device, if the detector's field of view is a circular detector's field of view, the following methods are used:

Calculate the angle between the star point coordinates (α _Star , δ _Star ) and the camera optical axis coordinates (α _Cam , δ _Cam )

Ang=arccos(Z _Star · Z _Cam )

Among them, the coordinates of the star point are derived from the known star catalog information;

The semi-vertebral angle of the camera's circular field of view is D _r , then there are

If Ang≥D _r , the star point is not in the field of view of the camera detector;

If Ang<D _r , the star point is in the field of view of the camera detector.

Further, when judging whether a star point is in the detector field of view of the optical device, if the detector field of view is a circular detector field of view, it can also be judged by using the directionality of the cross product to determine whether a star point is in the detector field of view. The way in the rectangular field of view is carried out:

The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), construct vectors p ₁₂ (α ₂ -α ₁ ,δ ₂ -δ ₁ ), p ₂₃ (α ₃ -α ₂ ,δ ₃ -δ ₂ ), p ₃₄ (α ₄ -α ₃ ,δ ₄ -δ ₃ ), p ₄₁ (α ₁ -α ₄ ,δ ₁ -δ ₄ ), p _Star1 (α ₁ -α _Star ,δ ₁ -δ _Star ), p _Star2 (α ₂ -α _Star ,δ ₂ -δ _Star ) , p _Star3 (α ₃ -α _Star , δ ₃ -δ _Star ), p _Star4 (α ₄ -α _Star ,δ ₄ -δ _Star );

If (p ₁₂ ×p _Star1 )*(p ₃₄ ×p _Star3 )≥0 and (p ₂₃ ×p _Star2 )*(p ₄₁ ×p _Star4 )≥0, then the star point is within the field of view of the camera detector; otherwise , the star point is not in the field of view of the camera detector.

Further, when judging whether a certain star point is within the field of view of the detector of the optical device, if the field of view of the detector is a rectangular field of view of the detector, the following methods are used:

Calculate the area of the rectangular field of view. The star point and the four points of the rectangular field of view form four spherical triangles. The sum of the areas of the four spherical triangles is compared with the rectangular area. If they are equal, the star point is in the field of view. outside the field of view;

The calculation method of the area of a spherical triangle is as follows: the area of a spherical triangle P _A P _B P _C with a radius of 1 is

S=P _A +P _B +P _C -π

和

分别为点P_B和点P_C到直线OP_A的垂线，则球面角P_A为矢量

和

的夹角，则Among them, P _A , P _B , P _C are spherical angles, and the spherical angle is measured by the angle formed by the two planes, that is, the spherical angle P _A is the angle between the plane P _A OP _B and the plane P _A OP _C ,

and

are the perpendiculars from point P _B and point P _C to the straight line OP _A , respectively, then the spherical angle P _A is a vector

and

the included angle, then

分别为点O到点P_A、点P_B、点P_C的矢量；则Among them, then

are the vectors from point O to point _{P A} , point P _B , and point PC respectively; then

计算其构成的球面三角形面积的函数为

则有Note through the vector inside the sphere

The function to calculate the area of the spherical triangle formed by it is

then there are

The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), the corresponding vector coordinates in the inertial frame are Z _star , Z ₁ , Z ₂ , Z ₃ , Z ₄ , then

The projected area of the detector's field of view in celestial coordinates is

S ₀ =S ₁₂₃ +S ₁₃₄ =f(Z ₁ ,Z ₂ ,Z ₃ )+f(Z ₁ ,Z ₃ ,Z ₄ )

The sum of the areas of the four spherical triangles formed by the star point and the four points of the rectangular field of view is

S _Star =S _12Star +S _23Star +S _34Star +S _14Star

=f(Z ₁ ,Z ₂ ,Z _Star )+f(Z ₂ ,Z ₃ ,Z _Star )+f(Z ₃ ,Z ₄ ,Z _Star )+f(Z ₁ ,Z ₄ ,Z _Star )

then there are

If S _Star >S ₀ , the star point is not in the field of view of the camera detector;

If S _Star =S ₀ , the star point is within the field of view of the camera detector.

Further, continue to select more dense new observation points in the vicinity of the preferred observation points obtained in step 4, and put the selected new observation points and the preferred observation points obtained in step 3 together to form a new observation point set, and repeat steps 3 and 3. Step 4: Obtain the optimal observation point set, and convert the right ascension and declination of the optimal observation point (α _j , δ _j ), j=1,...,m, and the satellite J2000 inertial system to the attitude transformation matrix C _ib under the system (j), j=1,...,m as output, where m is the number of optimal observation points.

The beneficial effects of the present invention compared with the prior art are:

(1) the present invention is aimed at remote sensing satellites and astronomical observation satellites to carry out multi-field starry sky imaging scenes, and provides a target attitude planning method, so that all imaging optical devices in the observation process are not disturbed by sunlight and air light, And the number of stars entering the camera's field of view is as large as possible to ensure the validity of the observation and improve the quality of the observation;

(2) The present invention provides an optical equipment observable sky area analysis model, which can assist remote sensing satellite and astronomical observation satellite mission analysis and optical observation equipment pointing layout design, and provide technical means of quantitative analysis for satellite scheme design;

(3) The present invention also provides a specific algorithm for calculating the number of stars in the field of view of the detector for the optical load for imaging the starry sky, which makes the method more feasible.

Description of drawings

Fig. 1 is the system composition schematic diagram of the embodiment;

Fig. 2 is the implementation flow chart of the method of the present invention;

Figure 3 is a schematic diagram of the relationship between the optional field of view and the optional sky area projection of the optical equipment;

Figure 4 is a schematic diagram of the influence of different seasons on the optional sky area;

FIG. 5 is a schematic diagram of a method for calculating the area of a spherical triangle.

Detailed ways

The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

As shown in FIG. 2 , a method for planning a target attitude of a multi-field starry sky observation satellite proposed by the present invention includes the following steps:

Step 1: Obtain the season or month of starry sky observation by the satellite, the satellite orbit height, and the stray light suppression angle of the imaging optical equipment;

The stray light suppression angle specifically refers to: the optical device is affected by external stray light, resulting in a decrease in the imaging effect or even failure, and the optical device is constrained by the stray light suppression angle when imaging. When the stray light light is outside the stray light suppression angle, the optical The equipment works normally, on the contrary, the imaging effect of the optical equipment is degraded or cannot work normally; the stray light includes sunlight and atmospheric light.

According to the mission planning of the satellite, select the month or specific date for starry sky imaging, and choose to perform multi-field starry sky imaging in the shadow area, obtain satellite orbit data through satellite-to-ground measurement and control, and extrapolate to obtain the satellite orbit altitude on the starry sky observation day. When the orbit is a circular orbit, the satellite orbit height directly uses the nominal orbit height.

Step 2: According to the projection relationship between the optional field of view of the optical device and the observable sky area, the optional sky area of each optical device is given; specifically:

After obtaining the satellite orbit height H and the stray light suppression angle B of the imaging optical device, the angle A between the XOY plane of the orbital coordinate system and the edge of the earth and atmosphere is

The available cone C of the field of view of the optical device is

where p is the thickness of the atmosphere and _Re is the radius of the earth;

The observation sky area is analyzed in the celestial coordinate system, and the projection of the available conical field of view of the optical device's field of view on the celestial sphere is recorded as the optional sky area of the optical device. When the optical axis of the optical device points in the direction of R _Z When it is any direction within the conical range of the generatrix, it will not be disturbed by the air and air, α ₀ is the right ascension center point of the optional sky area of the optical equipment, and α ₀ is related to the specific season/month of the observation; The optional observation center points of the sky area for the vernal equinox, summer solstice, autumn equinox, and winter solstice are:

Spring Equinox α ₀ = 180°

Summer Solstice α ₀ = 270°

Autumnal Equinox α ₀ =0°

Winter Solstice α ₀ =90°

The optional sky area set is

S={α,δ:cos ² (α-α ₀ )cos ² δ+sin ² δ≤sin ² C}

If B>A, then C<90°, δ _e ∈(-C,C), the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

If B<A, then C>90°, δ _e ∈ [-90°, 90°], the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

Step 3: Select a set of observation points according to the distribution of stars in the optional sky area, obtain the pointing of each optical device under the observation point in the celestial coordinate system, determine whether it is in its available sky area, and delete the unavailable observation point;

Select a set of observation points, specifically:

When selecting observation points, each observation point contains two celestial sphere coordinate points, one coordinate point is the satellite + Z-axis pointing point, and the coordinates are marked as (α ₁ ,δ ₁ ), and the other coordinate point is located in the XOZ plane of the satellite system. , the pointing point of the vector with a certain positive angle between the +X axis and the +Z axis, and the coordinates are marked as (α ₂ ,δ ₂ );

When selecting the observation point set, follow the principles from wide to narrow and from sparse to dense. When selecting the observation point set for the first time, the optical equipment with the largest coverage is selected, and the density is sparse; after one calculation, the observation point is selected for the second time. When collecting, the observation point is selected near the first available observation point, and the density is more encrypted than the last time, and so on;

According to the conversion relationship between the celestial coordinate system and the inertial coordinate system, the attitude transformation matrix C _ib from the inertial coordinate system of the satellite J2000 to the satellite system is calculated by the following formula:

in,

X^T＝Y^T×Z^T

X ^T =Y ^T ×Z ^T

According to the installation orientation of each optical device on the satellite, calculate the orientation of each optical device in the celestial coordinate system; set the installation array of the optical device in the satellite system as C _bCam , then the attitude matrix of the optical device in the J2000 inertial system is :

为光学设备光轴在惯性系下的矢量表示，z₁、z₂、z₃为矢量的三个分量；in,

is the vector representation of the optical axis of the optical device in the inertial frame, and z ₁ , z ₂ , and z ₃ are the three components of the vector;

在天球坐标系下的坐标(α,δ)为The optical axis of the optical device

The coordinates (α, δ) in the celestial coordinate system are

Next, determine whether the coordinates (α, δ) of the optical device in the celestial coordinate system are in the available sky area obtained in step 2:

This observation point is available when all optics are in their respective optional sky zones;

When the optical axis of one or two optical devices is not in the optional sky area and cannot meet the mission requirements, the observation point is unavailable;

Delete unavailable observations to obtain available observations.

Step 4: Count the number of stars in the camera's field of view under the available observation points, and optimize the available observation points;

Specifically:

First, according to the camera installation matrix, the field of view shape and the definition of the coordinate system, the camera field of view edge pointing vector array under the satellite system is established as

Among them, n is the number of edge points of the field of view, [z _1i z _2i z _3i ] ^T is the direction of the i-th edge vector in the satellite system, i=1,...,n;

The coordinate array Cam _ball of the edge vector of the camera's field of view under the celestial sphere system is obtained by the method described in step 3;

According to the field of view of the camera detector, determine whether a certain star point is within the field of view of the detector of the optical device, calculate the number of star points in the field of view of the camera, and select the observation point with the largest number of star points as the preferred observation point.

specific:

When judging whether a star point is within the detector's field of view of the optical device, if the detector's field of view is a circular detector's field of view, proceed as follows:

Calculate the angle between the star point coordinates (α _Star , δ _Star ) and the camera optical axis coordinates (α _Cam , δ _Cam )

Ang=arccos(Z _Star · Z _Cam )

Among them, the coordinates of the star point are derived from the known star catalog information;

The semi-vertebral angle of the camera's circular field of view is D _r , then there are

If Ang≥D _r , the star point is not in the field of view of the camera detector;

If Ang<D _r , the star point is in the field of view of the camera detector.

When judging whether a star point is in the detector field of view of the optical device, if the detector field of view is a circular detector field of view, it can also be judged whether a star point is in a rectangular field of view by using the directionality of the cross product. inside the way:

The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), construct vectors p ₁₂ (α ₂ -α ₁ ,δ ₂ -δ ₁ ), p ₂₃ (α ₃ -α ₂ ,δ ₃ -δ ₂ ), p ₃₄ (α ₄ -α ₃ ,δ ₄ -δ ₃ ), p ₄₁ (α ₁ -α ₄ ,δ ₁ -δ ₄ ), p _Star1 (α ₁ -α _Star ,δ ₁ -δ _Star ), p _Star2 (α ₂ -α _Star ,δ ₂ -δ _Star ) , p _Star3 (α ₃ -α _Star , δ ₃ -δ _Star ), p _Star4 (α ₄ -α _Star ,δ ₄ -δ _Star );

If (p ₁₂ ×p _Star1 )*(p ₃₄ ×p _Star3 )≥0 and (p ₂₃ ×p _Star2 )*(p ₄₁ ×p _Star4 )≥0, then the star point is within the field of view of the camera detector; otherwise , the star point is not in the field of view of the camera detector.

When judging whether a star point is within the detector's field of view of the optical device, if the detector's field of view is a rectangular detector's field of view, proceed as follows:

Calculate the area of the rectangular field of view. The star point and the four points of the rectangular field of view form four spherical triangles. The sum of the areas of the four spherical triangles is compared with the rectangular area. If they are equal, the star point is in the field of view. outside the field of view;

The calculation method of the area of a spherical triangle is as follows: the area of a spherical triangle P _A P _B P _C with a radius of 1 is

S=P _A +P _B +P _C -π

和

分别为点P_B和点P_C到直线OP_A的垂线，则球面角P_A为矢量

和

的夹角，则Among them, P _A , P _B , P _C are spherical angles, and the spherical angle is measured by the angle formed by the two planes, that is, the spherical angle P _A is the angle between the plane P _A OP _B and the plane P _A OP _C ,

and

are the perpendiculars from point P _B and point P _C to the straight line OP _A , respectively, then the spherical angle P _A is a vector

and

the included angle, then

分别为点O到点P_A、点P_B、点P_C的矢量；则Among them, then

are the vectors from point O to point _{P A} , point P _B , and point PC respectively; then

计算其构成的球面三角形面积的函数为

则有Note through the vector inside the sphere

The function to calculate the area of the spherical triangle formed by it is

then there are

The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), the corresponding vector coordinates in the inertial frame are Z _star , Z ₁ , Z ₂ , Z ₃ , Z ₄ , then

The projected area of the detector's field of view in celestial coordinates is

S ₀ =S ₁₂₃ +S ₁₃₄ =f(Z ₁ ,Z ₂ ,Z ₃ )+f(Z ₁ ,Z ₃ ,Z ₄ )

The sum of the areas of the four spherical triangles formed by the star point and the four points of the rectangular field of view is

S _Star =S _12Star +S _23Star +S _34Star +S _14Star

=f(Z ₁ ,Z ₂ ,Z _Star )+f(Z ₂ ,Z ₃ ,Z _Star )+f(Z ₃ ,Z ₄ ,Z _Star )+f(Z ₁ ,Z ₄ ,Z _Star )

then there are

If S _Star >S ₀ , the star point is not in the field of view of the camera detector;

If S _Star =S ₀ , the star point is within the field of view of the camera detector.

Step 5: Repeat steps 3 and 4 until a satisfactory set of observation points is found, and output the right ascension, declination and satellite attitude transformation matrix of the optimal observation point.

Example:

In this embodiment, the satellite is configured with one imaging camera, one star camera, and two star sensors. It should be noted that in practical applications, the number of cameras and the number of star sensors can be arbitrarily configured. FIG. 1 shows a schematic diagram of the system composition of the present embodiment, and FIG. 2 shows a flow chart for implementing the method of the present invention. The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

In step 1, according to the mission planning of the satellite, select the month or specific date for starry sky imaging, and choose to perform multi-field starry sky imaging in the shadow area, obtain satellite orbit data through satellite-ground measurement and control, and extrapolate to obtain the satellite orbit of the starry sky observation day. Altitude, in order to simplify the calculation, when the satellite has a circular orbit, the satellite orbit altitude can be directly replaced by the nominal orbit altitude.

In step 2, after obtaining the satellite orbit height H and the stray light suppression angle B of the imaging optical device, the angle A between the XOY plane of the orbital coordinate system and the edge of the earth and atmosphere is:

The available cone C of the field of view of an optical device is

where p is the thickness of the atmosphere and _Re is the radius of the Earth.

The observation sky area is analyzed in the celestial coordinate system, and the projection of the available conical field of view of the optical device's field of view on the celestial sphere is recorded as the optional sky area of the optical device. Figures 3 and 4 show the options for an optical device. The projection relationship between the conical field of view and the optional sky area, when the optical axis of the optical device points to any direction within the conic range with R _Z as the generatrix, it will not be disturbed by the air light, α ₀ is the optical The right ascension center point of the optional sky area of the device, α ₀ is related to the specific season/month of the observation. In particular, the optional observation center points of the sky area when observing at the vernal equinox, summer solstice, autumn equinox, and winter solstice are:

Spring Equinox α ₀ = 180°

Summer Solstice α ₀ = 270°

Autumnal Equinox α ₀ =0°

Winter Solstice α ₀ =90°

The optional sky area set is

S={α,δ:cos ² (α-α ₀ )cos ² δ+sin ² δ≤sin ² C}

If B>A, then C<90°, δ _e ∈(-C,C), the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

If B<A, then C>90°, δ _e ∈ [-90°, 90°], the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

Similarly, the optional sky areas where the imaging camera, the star camera and the two star sensors can be obtained are S _CAM , S _SC , S _STSA , and S _STSB , respectively. The available sky areas of optical devices with different stray light suppression angles are different, including overlapping areas and non-overlapping areas.

In step 3, when selecting observation points, each observation point contains two celestial sphere coordinate points, one point is the satellite + Z axis pointing point, the coordinates are marked as (α ₁ ,δ ₁ ), and the other point is located in the satellite system XOZ. The point of the plane, the vector that has a certain positive angle with the +X axis and the +Z axis, and the coordinates are marked as (α ₂ ,δ ₂ ).

The selection of observation point sets should follow the principles from wide to narrow and from sparse to dense. When selecting the observation point set for the first time, it should cover the largest optical equipment optional sky area, and the density is sparse; after one calculation, the second observation The point should be selected in the vicinity of the first available observation point, the density can be properly encrypted compared with the last time, and so on.

According to the conversion relationship between the celestial coordinate system and the inertial system, the attitude transformation matrix C _ib from the inertial system of the satellite J2000 to this system can be calculated by the following formula

in,

X^T＝Y^T×Z^T

X ^T =Y ^T ×Z ^T

Then, according to the installation orientation of each optical device on the satellite, the orientation of each optical device in the celestial coordinate system is calculated. The installation array of an optical device in the satellite system is C _bCam , then the attitude matrix of the optical device in the J2000 inertial system is

在天球坐标系下的坐标(α,δ)为The optical axis of the optical device

The coordinates (α, δ) in the celestial coordinate system are

Next, determine whether the optical axis pointing coordinates (α, δ) of an optical device are in the available sky area obtained in step 2

inside:

当所有的光学设备均在各自的可选天区中时，则该观测点可用；

This observation point is available when all optics are in their respective optional sky zones;

当有一台或两台光学设备光轴指向不在可选天区中，无法满足任务需求时，该观测点不可用；

When the optical axis of one or two optical devices is not in the optional sky area and cannot meet the mission requirements, the observation point is unavailable;

Delete unavailable observations to obtain available observations.

In step 4, for the available observation points obtained in step 3, the number of stars in the field of view of the camera is calculated. First, according to the camera installation matrix, the field of view shape and the definition of the coordinate system, the camera field of view edge pointing vector array under the satellite system is established as

Among them, n is the number of edge points in the field of view, [z _1i z _2i z _3i ] ^T is the direction of the i-th edge vector in the satellite system, i=1,...,n.

The coordinate array Cam _ball of the edge vector of the camera's field of view in the celestial sphere system can be obtained by the method described in the third step.

According to the field of view of the camera detector, determine whether a certain star point is within the field of view of the detector of the optical device, calculate the number of star points in the field of view of the camera, and select the observation point with the largest number of star points as the preferred observation point.

The present invention provides a specific method for judging whether a certain star point is within the field of view of the detector of the optical device, and the common methods for judging the field of view of a circular detector and a rectangular detector of a camera are as follows.

·Circular field of view judgment method 1: Calculate the angle between the star point coordinates (α _Star , δ _Star ) and the camera optical axis coordinates (α _Cam , δ _Cam )

Ang=arccos(Z _Star · Z _Cam )

Among them, the coordinates of the star point are derived from the known star catalog information.

The semi-vertebral angle of the camera's circular field of view is D _r , then there are

若Ang≥D_r，则该星点不在相机探测器视场内；

If Ang≥D _r , the star point is not in the field of view of the camera detector;

若Ang<D_r，则该星点在相机探测器视场内。

If Ang<D _r , the star point is in the field of view of the camera detector.

Judgment method 1 of the rectangular field of view: Calculate the area of the rectangular field of view. The star point and the four points of the rectangular field of view can form four spherical triangles. The sum of the areas of the four spherical triangles is compared with the rectangular area. In the field of view, the larger the star point is outside the field of view.

First, the calculation method of spherical triangle area is given. As shown in Figure 5, the area of spherical triangle P _A P _B P _C with radius 1 is

S=P _A +P _B +P _C -π

和

分别为点P_B和点P_C到直线OP_A的垂线，则球面角P_A为矢量

和

的夹角，则Among them, P _A , P _B , P _C are spherical angles, and the spherical angle is measured by the angle formed by the two planes, that is, the spherical angle P _A is the angle between the plane P _A OP _B and the plane P _A OP _C ,

and

are the perpendiculars from point P _B and point P _C to the straight line OP _A , respectively, then the spherical angle P _A is a vector

and

the included angle, then

分别为点O到点P_A、点P_B、点P_C的矢量。则Among them, then

are the vectors from point O to point _{P A} , point P _B , and point PC respectively. but

计算其构成的球面三角形面积的函数为

则有Note through the vector inside the sphere

The function to calculate the area of the spherical triangle formed by it is

then there are

The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), the corresponding vector coordinates in the inertial frame are Z _star , Z ₁ , Z ₂ , Z ₃ , Z ₄ , then

The projected area of the detector's field of view in celestial coordinates is

S ₀ =S ₁₂₃ +S ₁₃₄ =f(Z ₁ ,Z ₂ ,Z ₃ )+f(Z ₁ ,Z ₃ ,Z ₄ )

The sum of the areas of the four spherical triangles formed by the star point and the four points of the rectangular field of view is

S _Star =S _12Star +S _23Star +S _34Star +S _14Star

=f(Z ₁ ,Z ₂ ,Z _Star )+f(Z ₂ ,Z ₃ ,Z _Star )+f(Z ₃ ,Z ₄ ,Z _Star )+f(Z ₁ ,Z ₄ ,Z _Star )

then there are

若S_Star>S₀，则该星点不在相机探测器视场内；

If S _Star >S ₀ , the star point is not in the field of view of the camera detector;

若S_Star＝S₀，则该星点在相机探测器视场内。

If S _Star =S ₀ , the star point is within the field of view of the camera detector.

·Rectangular field of view judgment method 2: Use the directionality of the cross product to judge whether a star point is in the rectangular field of view. The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), construct vectors p ₁₂ (α ₂ -α ₁ ,δ ₂ -δ ₁ ), p ₂₃ (α ₃ -α ₂ ,δ ₃ -δ ₂ ), p ₃₄ (α ₄ -α ₃ ,δ ₄ -δ ₃ ), p ₄₁ (α ₁ -α ₄ ,δ ₁ -δ ₄ ), p _Star1 (α ₁ -α _Star ,δ ₁ -δ _Star ), p _Star2 (α ₂ -α _Star ,δ ₂ -δ _Star ) , p _Star3 (α ₃ -α _Star , δ ₃ -δ _Star ), p _Star4 (α ₄ -α _Star ,δ ₄ -δ _Star ).

then there are

若(p₁₂×p_Star1)*(p₃₄×p_Star3)≥0且(p₂₃×p_Star2)*(p₄₁×p_Star4)≥0，则该星点在相机探测器视场内；

If (p ₁₂ ×p _Star1 )*(p ₃₄ ×p _Star3 )≥0 and (p ₂₃ ×p _Star2 )*(p ₄₁ ×p _Star4 )≥0, then the star point is within the field of view of the camera detector;

反之，则该星点不在相机探测器视场内。

Otherwise, the star point is not in the field of view of the camera detector.

It should be noted that since the spherical surface has a radian, there will be a certain error in the judgment of the star point located at the edge of the field of view using this method.

In step 5, repeat steps 3 and 4 until a satisfactory set of observation points is found, and output the right ascension, declination and satellite attitude transformation matrix of the optimal observation point.

Continue to select more dense new observation points near the preferred observation points obtained in step 4, and put the selected new observation points and the preferred observation points obtained in step 3 together to form a new observation point set, repeat steps 3 and 4, Obtain the optimal observation point set, and convert the right ascension and declination (α _j , δ _j ), j=1,...,m, satellite J2000 inertial system of the optimal observation point to the attitude transformation matrix C _ib (j) under this system ,j=1,...,m as the output, where m is the number of optimal observation points.

Steps 3, 4, and 5 can be repeated many times according to the task requirements and the tolerance to the amount of computation to achieve the desired optimization results.

The contents not described in detail in the specification of the present invention belong to the known technology in the art.

Claims (10)

1. a multi-field-of-view starry sky observation satellite target attitude planning method is characterized in that the steps are as follows: Step 1: Obtain the season or month of starry sky observation by the satellite, the satellite orbit height, and the stray light suppression angle of the imaging optical equipment; Step 2: According to the projection relationship between the optional field of view of the optical equipment and the observable sky area, the optional sky area of each optical device is given; Step 3: Select a set of observation points according to the distribution of stars in the optional sky area, obtain the pointing of each optical device under the observation point in the celestial coordinate system, determine whether it is in its available sky area, and delete the unavailable observation point; Step 4: Count the number of stars in the camera's field of view under the available observation points, and optimize the available observation points; Step 5: Repeat steps 3 and 4 until a satisfactory set of observation points is found, and output the right ascension, declination and satellite attitude transformation matrix of the optimal observation point. 2. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 1, it is characterized in that: described stray light suppression angle specifically refers to: the optical equipment is affected by external stray light and causes the imaging effect to decline or even to fail , The optical device is constrained by the stray light suppression angle when imaging. When the stray light is outside the stray light suppression angle, the optical device works normally. On the contrary, the imaging effect of the optical device is reduced or cannot work normally; the stray light includes sunlight and earth atmosphere. Light. 3. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 1, is characterized in that: according to the mission planning of satellite, select the month or specific date of starry sky imaging, and select to carry out multi-field of view in shadow area For starry sky imaging, satellite orbit data is obtained through satellite-ground measurement and control, and the satellite orbit height on the starry sky observation day is extrapolated. When the satellite is in a circular orbit, the satellite orbit height directly uses the nominal orbit height. 4. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 1, is characterized in that: described step 2 provides each optical device according to the projection relationship of the optional field of view and the observable sky area of the optical equipment. The optional sky area of the device, specifically: After obtaining the satellite orbit height H and the stray light suppression angle B of the imaging optical device, the angle A between the XOY plane of the orbital coordinate system and the edge of the earth and atmosphere is

The available cone C of the field of view of the optical device is

where p is the thickness of the atmosphere and _Re is the radius of the earth; The observation sky area is analyzed in the celestial coordinate system, and the projection of the available conical field of view of the optical device's field of view on the celestial sphere is recorded as the optional sky area of the optical device. When the optical axis of the optical device points in the direction of R _Z When it is any direction within the conical range of the generatrix, it will not be disturbed by the air and air. α ₀ is the right ascension center point of the optional sky area of the optical device, and α ₀ is related to the specific season/month of the observation; The optional sky area observation center points for the vernal equinox, summer solstice, autumn equinox, and winter solstice are respectively the vernal equinox α ₀ =180° Summer Solstice α ₀ = 270° Autumnal Equinox α ₀ =0° Winter Solstice α ₀ =90° The optional sky area set is S={α,δ:cos ² (α-α ₀ )cos ² δ+sin ² δ≤sin ² C} If B>A, then C<90°, δ _e ∈(-C,C), the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

If B<A, then C>90°, δ _e ∈ [-90°, 90°], the coordinates (α _e ,δ _e ) describing the edge of the optional sky area are obtained by the following formula

5. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 4, is characterized in that: in described step 3, select observation point set, be specifically: When selecting observation points, each observation point contains two celestial sphere coordinate points, one coordinate point is the satellite + Z-axis pointing point, and the coordinates are marked as (α ₁ , δ ₁ ), and the other coordinate point is located in the XOZ plane of the satellite body system. , the pointing point of the vector with a certain positive angle between the +X axis and the +Z axis, and the coordinates are marked as (α ₂ ,δ ₂ ); When selecting the observation point set, follow the principles from wide to narrow and from sparse to dense. When selecting the observation point set for the first time, the optical equipment with the largest coverage is selected, and the density is sparse; after one calculation, the observation point is selected for the second time. When collecting, the observation point is selected near the first available observation point, and the density is more encrypted than the last time, and so on; According to the conversion relationship between the celestial coordinate system and the inertial coordinate system, the attitude transformation matrix C _ib from the inertial coordinate system of the satellite J2000 to the satellite system is calculated by the following formula:

in,

X ^T =Y ^T ×Z ^T According to the installation orientation of each optical device on the satellite, the orientation of each optical device in the celestial coordinate system is calculated; if the installation array of the optical device in the satellite system is C _bCam , the attitude matrix of the optical device in the J2000 inertial system is :

in,

is the vector representation of the optical axis of the optical device in the inertial frame, and z ₁ , z ₂ , and z ₃ are the three components of the vector; The optical axis of the optical device

The coordinates (α, δ) in the celestial coordinate system are

Next, determine whether the coordinates (α, δ) of the optical device in the celestial coordinate system are in the available sky area obtained in step 2: This observation point is available when all optics are in their respective optional sky zones; When the optical axis of one or two optical devices is not in the optional sky area and cannot meet the mission requirements, the observation point is unavailable; Delete unavailable observations to obtain available observations. 6. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 5, is characterized in that: described step 4 counts the number of stars in the camera's field of view under the available observation points, and optimizes the available observation points, Specifically: First, according to the camera installation matrix, the field of view shape and the definition of the coordinate system, the camera field of view edge pointing vector array under the satellite system is established as

Among them, n is the number of edge points of the field of view, [z _1i z _2i z _3i ] ^T is the direction of the i-th edge vector in the satellite system, i=1,...,n; The coordinate array Cam _ball of the edge vector of the camera's field of view under the celestial sphere system is obtained by the method described in step 3;

According to the field of view of the camera detector, determine whether a star point is within the field of view of the detector of the optical device, calculate the number of star points in the camera field of view, and select the observation point with the largest number of star points as the preferred observation point. 7. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 6 is characterized in that: when judging whether a certain star point is in the detector field of view of optical equipment, if the detector field of view is a circle shape detector field of view by: Calculate the angle between the star point coordinates (α _Star , δ _Star ) and the camera optical axis coordinates (α _Cam , δ _Cam ) Ang=arccos(Z _Star · Z _Cam ) Among them, the coordinates of the star point are derived from the known star catalog information;

The semi-vertebral angle of the camera's circular field of view is D _r , then there are If Ang≥D _r , the star point is not in the field of view of the camera detector; If Ang<D _r , the star point is in the field of view of the camera detector. 8. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 6 is characterized in that: when judging whether a certain star point is in the detector field of view of optical equipment, if the detector field of view is a circle The field of view of the shaped detector can also be judged by using the directionality of the cross product to determine whether a star point is within the rectangular field of view: The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), construct vectors p ₁₂ (α ₂ -α ₁ ,δ ₂ -δ ₁ ), p ₂₃ (α ₃ -α ₂ ,δ ₃ -δ ₂ ), p ₃₄ (α ₄ -α ₃ ,δ ₄ -δ ₃ ), p ₄₁ (α ₁ -α ₄ ,δ ₁ -δ ₄ ), p _Star1 (α ₁ -α _Star ,δ ₁ -δ _Star ), p _Star2 (α ₂ -α _Star ,δ ₂ -δ _Star ) , p _Star3 (α ₃ -α _Star ,δ ₃ -δ _Star ), p _Star4 (α ₄ -α _Star ,δ ₄ -δ _Star ); If (p ₁₂ ×p _Star1 )*(p ₃₄ ×p _Star3 )≥0 and (p ₂₃ ×p _Star2 )*(p ₄₁ ×p _Star4 )≥0, then the star point is within the field of view of the camera detector; otherwise , the star point is not in the field of view of the camera detector. 9. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 6 is characterized in that: when judging whether a certain star point is in the detector field of view of the optical device, if the detector field of view is a rectangle The detector field of view is performed as follows: Calculate the area of the rectangular field of view. The star point and the four points of the rectangular field of view form four spherical triangles. The sum of the areas of the four spherical triangles is compared with the rectangular area. If they are equal, the star point is in the field of view. outside the field of view; The calculation method of the area of a spherical triangle is as follows: the area of a spherical triangle P _A P _B P _C with a radius of 1 is S=P _A +P _B +P _C -π Among them, P _A , P _B , P _C are spherical angles, and the spherical angle is measured by the angle formed by the two planes, that is, the spherical angle P _A is the angle between the plane P _A OP _B and the plane P _A OP _C ,

and

are the perpendiculars from point P _B and point P _C to the straight line OP _A , respectively, then the spherical angle P _A is a vector

and

the included angle, then

Among them, then

are the vectors from point O to point _{P A} , point P _B , and point PC respectively; then

Note through the vector inside the sphere

The function to calculate the area of the spherical triangle formed by it is

then there are

The coordinates of the star point are (α _Star ,δ _Star ) and the coordinates of the four points of the camera detector are (α ₁ ,δ ₁ ), (α ₂ ,δ ₂ ), (α ₃ ,δ ₃ ), (α ₄ ,δ ₄ ), the corresponding vector coordinates in the inertial frame are Z _star , Z ₁ , Z ₂ , Z ₃ , Z ₄ , then The projected area of the detector's field of view in celestial coordinates is S ₀ =S ₁₂₃ +S ₁₃₄ =f(Z ₁ ,Z ₂ ,Z ₃ )+f(Z ₁ ,Z ₃ ,Z ₄ ) The sum of the areas of the four spherical triangles formed by the star point and the four points of the rectangular field of view is S _Star =S _12Star +S _23Star +S _34Star +S _14Star =f(Z ₁ ,Z ₂ ,Z _Star )+f(Z ₂ ,Z ₃ ,Z _Star )+f(Z ₃ ,Z ₄ ,Z _Star )+f(Z ₁ ,Z ₄ ,Z _Star ) then there are If S _Star >S ₀ , the star point is not in the field of view of the camera detector; If S _Star =S ₀ , the star point is within the field of view of the camera detector. 10. a kind of multi-field of view starry sky observation satellite target attitude planning method according to claim 6, is characterized in that: continue to select more intensive new observation points in the vicinity of the preferred observation point obtained in step 4, the selected new observation point Put together the optimal observation points obtained in step 3 to form a new observation point set, repeat steps 3 and 4 to obtain the optimal observation point set, and set the right ascension and declination (α _j , δ _j ) of the optimal observation point ,j=1,...,m, the attitude transformation matrix C _ib (j),j=1,...,m of the satellite J2000 inertial system to the system as the output, where m is the number of optimal observation points.

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