CN106586041A - Simulation method of Mars object for deep space exploration - Google Patents
Simulation method of Mars object for deep space exploration Download PDFInfo
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Abstract
The invention relates to a simulation method of a Mars object for deep space exploration, which belongs to the field of deep space exploration application. In order to solve the problems in the prior art of lacking of a method for simulating the location, size, contour, imaging orientation and imaging gray level of Mars and existing technical gaps in engineering practices, the simulation method of the Mars object for deep space exploration is proposed. The simulation method includes transforming a center coordinate of Mars from a heliocentric ecliptic coordinate system to a display plane coordinate system and a projector coordinate system, calculating an imaging size of Mars according to an imaging field of view of a Mars explorer and the relative distance between Mars and the Mars explorer, simulating illuminated areas of Mars which are illuminated by the sun and unilluminated areas which are not illuminated by the sun, calculating an imaging orientation of the contour of Mars according to the relation of relative positions among the sun, Mars and the Mars explorer, and mapping a magnitude of Mars to the gray level of a computer to display on an interface. The simulation method of the Mars object for deep space exploration is applicable to the simulation software of deep space exploration.
Description
Technical Field
The invention relates to a mars target simulation method for deep space exploration, and belongs to the field of deep space exploration application.
Background
The cost of the Mars detector is extremely expensive, a large amount of manpower and material resources are consumed, the precision of the Mars detector is improved, and the reduction of the faults of the Mars detector is inevitably required. However, it is not practical for the attitude sensor of the mars detector to shoot the actual starry sky in real time, the manufacturing cost is high, and the real-time performance and the dynamic performance are difficult to achieve, so that the requirement is provided for the mars target simulation.
In space target simulation, the mainstream technology adopted is a dynamic star simulator. The working principle of the dynamic star simulator is as follows: according to the attitude angle and the orbit position of the star body output by the received simulation computer, the direction corresponding to the optical axis of the instantaneous star sensor is determined through coordinate transformation, and a star map in the field of view corresponding to the star sensor is extracted from a star library and is sent to a star map generator. Because the input signal of the star sensor is a navigation star at infinity, the simulator must be output in a parallel light mode through an optical system and received by the star sensor.
However, in the aspect of the mars target simulation research, the fixed star image points are mars backgrounds, and the mars body target simulation is also an important component in the research. The mars cannot be regarded as points when the mars are at a close distance, the coordinate simulation method of the mars is different from the fixed star simulation method at infinity, and meanwhile, the target simulation of the mars needs to include the simulation of the size of the mars. Because the spark is not a light source, the brightness of the spark mainly depends on reflected sunlight, and the brightness, the outline, the imaging direction and the imaging gray level of the spark need to be simulated, the spark target simulation is a process from far to near and from large to small. The position, size, contour, imaging orientation and imaging gray scale of the mars need to be simulated.
The existing star simulation technology mainly focuses on the aspect of star image point simulation, and no engineering practice example appears on the simulation of a mars body.
Disclosure of Invention
The invention aims to solve the problems that the prior art lacks a method capable of simulating the position, size, outline, imaging direction and imaging gray level of a Mars and the technical blank exists in engineering practice, and provides a Mars target simulation method for deep space exploration.
A mars target simulation method for deep space exploration comprises a mars coordinate simulation step, a mars imaging size simulation step, a mars imaging outline simulation step, a mars imaging azimuth simulation step and a mars imaging gray scale simulation step: wherein
The Mars coordinate simulation step is used for transforming the Mars center coordinate from the sunset ecliptic coordinate system to a display plane coordinate system and a projector coordinate system;
the Mars imaging size simulation step is used for calculating the imaging size of the Mars according to the imaging view field of the Mars detector and the relative distance relationship between the Mars and the Mars detector;
the Mars imaging contour simulation step is used for simulating an area where the Mars are illuminated by the sun and an area where the Mars are not illuminated;
the Mars imaging orientation simulation step is used for calculating the imaging orientation of the Mars outline according to the relative position relation of the sun, the Mars and the detector;
and the Mars imaging gray scale simulation step is used for mapping the stars and the like of the Mars to the gray scale of the computer so as to display the gray scale on the interface.
The invention has the beneficial effects that: the simulation system can comprehensively simulate the light and shade, the outline, the imaging direction and the imaging gray scale of the Mars, and can be effectively applied to a ground target simulation test system of a Mars detector.
Drawings
FIG. 1 is a flow chart of a Mars target simulation method for deep space exploration in accordance with the present invention;
FIG. 2 is a schematic diagram of an SKY2000 simplified star chart according to the present invention;
FIG. 3 is a schematic diagram showing a relationship between a centroid ecliptic coordinate system and a posture sensor coordinate system;
FIG. 4 is a schematic diagram of any star coordinate;
FIG. 5 is a schematic diagram showing the relationship between the attitude sensor coordinate system and the CMOS planar coordinate system;
FIG. 6 is a schematic view of a camera field of view;
FIG. 7 is a schematic diagram of Mars imaging size simulation;
FIG. 8 is a schematic view of a plane formed by the sun, the Mars, and the detectors;
FIG. 9 is a geometrical model diagram of a Mars profile celestial body;
FIG. 10 is a two-dimensional projection of a Mars profile;
fig. 11 is a schematic diagram of different imaging orientations of a spark.
Detailed Description
The first embodiment is as follows: as shown in fig. 1, the method for simulating a spark target for deep space exploration according to the present embodiment includes a spark coordinate simulation step SA, a spark imaging size simulation step SB, a spark imaging contour simulation step SC, a spark imaging orientation simulation step SD, and a spark imaging gray scale simulation step SE: wherein,
a mars coordinate simulation step SA is used to transform the mars central coordinates from the centrosolar ecliptic coordinate system to the display plane coordinate system.
And a Mars imaging size simulation step SB is used for calculating the imaging size of the Mars according to the imaging view field of the Mars detector and the relative distance relationship between the Mars and the Mars detector.
A mars imaging contour simulation step SC is used to simulate the area where the mars are illuminated by the sun and the area that is not illuminated.
And the Mars imaging orientation simulation step SD is used for calculating the imaging orientation of the Mars outline according to the relative position relation of the sun, the Mars and the detector.
A mars imaging gray scale simulation step SE is used to map the mars and so on of mars to the gray scale of the computer for display on the interface.
It should be noted that although the execution sequence is written in fig. 1, there is no clear sequence between the steps, and the execution after exchanging the sequence can also achieve the object of the present invention.
Since the Mars can not be regarded as points and light sources, the invention simulates the coordinates, the size, the outline, the imaging direction and the imaging gray scale. The invention firstly carries out coordinate simulation of the mars, assumes the mars to exist in a central point form on the basis of determining the visual axis direction of the mars detector, and transforms the central coordinate of the mars under J2000 from a sunset ecliptic coordinate system to a display plane coordinate system and a projector coordinate system for display through translation transformation, rotation transformation and coordinate normalization processing. After the visual axis direction and the imaging center coordinate of the Mars detector are determined, the simulation of the Mars imaging size is completed through the imaging visual field of the Mars detector and the relative distance relationship between the Mars and the Mars detector. The sun, Mars, and detectors were then modeled geometrically for celestial bodies, simulating the areas where Mars were illuminated by the sun and in the dark. And then, the simulation of the imaging direction of the Mars outline is finished through the relative position relation of the sun, the Mars and the detector. And finally, establishing a celestial body reflection model of sunlight irradiating on the mars by using a diffuse reflection theory, obtaining brightness information of the mars, and mapping the mars and the like to the gray scale of a computer according to the same linear mapping for displaying.
The contents of each step are specifically described below:
a Mars coordinate simulation step: the main purpose is to determine the coordinates of the Mars in the display plane coordinate system and the projector coordinate system. Firstly, the central coordinate visual axis direction of the Mars detector is determined, and the attitude quaternion describing the Mars detector is converted into the right ascension and the declination of the visual axis. Then, converting the coordinates of the Mars under the sun-centered ecliptic coordinate system SKY2000 star chart and the coordinates of the Mars detector to the coordinates under the attitude sensor coordinate system, and specifically realizing the steps of translating the coordinates of the Mars to a coordinate system which takes the Mars detector as the center and three axes of which are parallel to the sun-centered ecliptic coordinate system, and setting the Mars to be a unit sphere which takes the Mars detector as the center through coordinate normalization processing. And finally, determining the central coordinates of the Mars in a display plane coordinate system and a projector coordinate system through rotation transformation processing similar to the fixed star coordinate determination.
Mars imaging size simulation: the Mars size simulation determines the imaging range of the Mars on the CMOS image plane coordinate system. The imaging size of the Mars is determined through the imaging view field of the Mars detector and the relative distance relationship between the Mars and the Mars detector, and then the imaging pixel number is determined through the size of the analog pixel size of the CMOS camera area array.
Mars imaging contour simulation: the mars contour simulation simulates the area of the mars illuminated by the sun and the area in darkness on the CMOS planar coordinate system. The invention establishes a celestial body geometric model on the basis of taking a plane formed by the sun, the Mars and the Mars detector as a reference plane, and obtains a two-dimensional imaging contour of the Mars contour on a CMOS plane when an included angle between a Mars-to-detector vector and a Mars-to-sun vector is 0-180 degrees. And obtaining the contour determination method when the included angle between the vector from the Mars to the detector and the vector from the Mars to the sun is not 0-180 degrees by judging the quantity product of the vectors.
Simulating Mars imaging orientation: the orientation of the spark imaging determines the orientation of the illuminated area of the spark. The vector r from the sun to the Mars0The imaging orientation of the Mars on the CMOS area array is determined. HeadVector r is first0Converting the coordinate system of the ecliptic of the sun center into the coordinate system of the attitude sensor to obtain a vector r0′，r0' r in CMOS plane coordinate system0From the image plane and r0"the vertical relationship yields the imaging orientation of the Mars.
Simulating the imaging gray level of Mars: because the Mars body simulation focuses more on the Mars profile, the Mars imaging method adopts an ideal Lambert reflection theory and assumes that the Mars imaging gray scale does not change along with the observation angle.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the method further comprises a preprocessing step executed before the steps, wherein the preprocessing step specifically comprises the following steps:
parameters in each data item in the SKY2000 star list are deleted, only parameter information of right ascension, declination, stars and the like of stars of each data item under J2000 is reserved, and all the data items are arranged according to the descending of the right ascension.
FIG. 2 is a schematic diagram of a SKY2000 simplified star chart.
As shown in fig. 2, the star table is a file for recording information such as star number, position, star, etc. of stars in astronomy. The invention uses SKY2000 star catalogue, and deletes the star catalogue, only keeps the stars and the like in the range which can be identified by human eyes, and comprises three parameter information of right ascension, declination, stars and the like of stars under J2000, the range of stars and the like is 0-6, and 5062 stars are in total. The star table can delete useless information such as star numbers, self-movement, spectrums and the like under the condition of ensuring high enough precision, can accelerate the search efficiency, and simultaneously adopts the TXT format for storage, thereby providing convenience for the search of software. The first column of the star table is the right ascension of the fixed star, the second column is the declination of the fixed star, the third column is the star of the fixed star, and the like, all data are arranged from large to small according to the right ascension, and the right ascension takes values within the range of 0-2 pi to cover the whole celestial sphere.
Other steps and parameters are the same as those in the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that:
the Mars coordinate simulation step comprises:
step A1: and determining the central coordinate visual axis direction of the Mars detector.
Step A2: and converting the attitude quaternion for describing the Mars detector into the right ascension and the declination of the visual axis.
Step A3: and converting the Mars coordinate and the Mars detector coordinate under the sun center ecliptic coordinate system and the star table into the coordinate under the attitude sensor coordinate system.
Step A4: the coordinates of the spark's center in the display plane coordinate system and the projector coordinate system are determined.
Specifically, the method for determining the visual axis in step a1 and the method for determining the expression of right ascension and declination of the visual axis in step a2 are as follows:
the invention assumes that the attitude sensor is fixedly connected with the detector body, namely, the coordinate system of the detector body is considered to be coincident with the coordinate system of the attitude sensor. The attitude of the detector is given in a quaternion form, namely the position relation of the attitude sensor coordinate system relative to the daylight-center ecliptic coordinate system. In the invention, the visual axis direction of the attitude sensor is taken as an OZ axis, and the visual axis direction is determined, namely the right ascension and the declination of the visual axis are determined, as shown in figure 3:
O-UVW is a sunset ecliptic coordinate system, the OU axis points to the spring minute point, O-XYZ is a posture sensor coordinate system, the OZ axis points to the detector visual axis, ON is an intersection line of an O-XY plane and an O-UV plane, and OM is perpendicular to ON in the O-XY plane. The included angle between the OZ axis and the OW axis is theta, and the included angle between the OX axis and the intersection line ON is
Provided with detectorsThe attitude quaternion is q ═ q1, q2, q3, q4]TAnd the first three represent the direction of an Euler axis, the fourth represents an Euler corner, and the constraint conditions are met:
q1 2+q2 2+q3 2+q4 2＝1 (1-1)
the direction cosine matrix is:
the attitude matrix represented by the attitude quaternion is:
the formula for conversion between quaternion to euler angle in 3-1-3 rotation mode:
θ＝arccos(Azz) (1-5)
wherein A isijIs an element in the formula directional cosine matrix.
Let the right ascension and declination of the visual axis be (α)0,0) The declination and the right ascension of the visual axis can be calculated as follows:
wherein, the value of the red channel is within 0-2 pi, and the judgment of A is neededzx、AzyTo determine the quadrant. The declination takes a value within-pi/2. Thus, the visual axis direction is determined, and the visual axis direction is combined with the visual field to judge whether the fixed star is in the effective visual field range.
The specific process of the step A3 is as follows:
the ecliptic coordinate system belongs to the celestial coordinate system. In the SKY2000 star chart, all star positions are expressed in the form of right ascension and declination in a celestial coordinate system, and the celestial coordinate system needs to be transformed to a posture sensor coordinate system. Because the fixed star is far from the detector and the centroid, the distance between the detector and the sun can be ignored, the ecliptic coordinate system of the centroid and the coordinate system of the attitude sensor can be regarded as the same origin, and therefore the conversion of the fixed star to the coordinate system of the attitude sensor can only consider rotation conversion and does not consider translation conversion. Let the attitude matrix be a.
According to the coordinate rotation transformation theory, the following results are obtained:
u, V, W is the coordinate of the star image point under the celestial coordinate system, X, Y, Z is the coordinate of the star image point under the attitude sensor coordinate system.
Let the matrix rotate by an angle theta about the x-axis be Rx(theta), and the corresponding matrix of the rotation angle theta around the y-axis and the z-axis is Ry(θ)、Rz(theta). Wherein:
in addition, the attitude matrix is related to the rotation order of the coordinate system, and the numbers 1, 2, and 3 represent the x-axis, y-axis, and z-axis of the coordinate system, respectively. There are 12 euler rotation sequences, which can be expressed as follows:
the invention adopts a mode that the Euler angle rotation sequence is 3-1-3, and the angles of each rotation are sequentially marked as psi,And theta. Then rotation A is recorded asThe following relationships apply:
the attitude matrix of the euler angle formula is obtained as follows:
the position of the fixed star in the celestial coordinate system is represented by the right ascension and the declination, the three-dimensional coordinates from the right ascension and the declination to the celestial coordinate system are shown in fig. 4, and the formula is expressed as follows:
in the formula: u, V, W is a three-dimensional coordinate system in a celestial coordinate system.
The specific process of the step A4 is as follows:
after the star image point realizes the coordinate transformation from the celestial coordinate system to the attitude sensor, the attitude sensor coordinate system needs to be transformed to the image plane coordinate system. The image plane coordinate system is a CMOS imaging area array.
A two-dimensional plane coordinate system, i.e., an image plane coordinate system, is established on the focal plane of the attitude sensor, so that the X-axis of the image plane coordinate system is consistent with the X-axis direction of the attitude sensor coordinate system, and the Y-axis of the image plane coordinate system is consistent with the Y-axis direction of the attitude sensor coordinate system, as shown in fig. 5.
Let the coordinates of any star projected onto the image plane coordinate system be (x, y), and x and y represent the number of pixels on the CMOS camera area array. Let the actual sizes of the CMOS camera pixels be tmpPixelsizeX and tmpPixelsizeY, respectively, where tmpPixelsizeX represents the pixel size in the X direction of the area array, and tmpPixelsizeY represents the pixel size in the Y direction of the area array. Then the following relationship is used:
Nxnumber of pixels in X direction of camera CMOS imaging area array, NyThe number of pixels in the Y direction of a camera CMOS imaging area array is shown, and f is the focal length of the camera. The field of view of the camera is known as the FOVx×FOVyThen, from fig. 6, it can be derived:
wherein X, Y and Z are coordinates in the attitude sensor coordinate system.
Other steps and parameters are the same as those in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is:
in step A2, the right ascension α of visual axis0Declination of weft0Is shown in formulas (1-7) and (1-8), wherein Azx＝2(q1q3+q2q4)，Azy＝2(q2q3-q1q4)，Azz＝-q1 2-q2 2+q3 2+q4 2，q1,q2,q3,q4Are respectively attitude quaternions q ═ q1,q2,q3,q4]TThe corresponding component of (a).
Other steps and parameters are the same as those in one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is:
the Mars imaging size simulation step comprises the following steps:
step B1: and determining the imaging size of the Mars through the imaging view field of the Mars detector and the relative distance relationship between the Mars and the Mars detector.
Step B2: the number of the imaging pixels is determined by the size of the analog pixel size of the CMOS camera area array.
The specific process is as follows:
firstly, carrying out Mars target simulation:
stars cannot be viewed as points compared to mars, so mars target simulations must include mars size simulations. Because the spark is not a light source, the brightness of the spark mainly depends on reflecting sunlight, and the position, size, outline, imaging direction and brightness of the spark need to be simulated, the spark target simulation is a process from far to near and from small to large.
And then transforming the coordinates of the Mars center:
in order to simulate the size, contour, etc. of the spark, the imaging position of the spark is obtained first. First, assuming that the spark exists in the form of a point, the transformation of the spark center is involved, including translation transformation, rotation transformation and coordinate normalization.
Errors due to coordinate translation may not be considered because the stars are abnormally far away. The invention determines the position relation among the sun, the mars and the detector according to the mars coordinate and the mars detector coordinate under the ecliptic coordinate system of the solar heat under J2000, wherein the coordinate unit is kilometer, which results in large numerical value. Suppose that the coordinates of Mars under the O-UVW coordinate system are (u)m,vm,wm) The coordinate of the detector under the coordinate system of the ecliptic is (u)s,vs,ws). Let the translated Mars coordinate be (u'm,v’m,w’m) At this time, the coordinate system is translated to the Mars detector as the center, and the three axes are parallel to the sunset eclipse-centered ecliptic coordinate system.
According to the coordinate translation transformation theory, the following results are obtained:
u′m＝um-us(2-1)
v′m＝vm-vs(2-2)
w′m＝wm-ws(2-3)
in a ecliptic coordinate system, the coordinates of the mars and the detector are given by a real distance, the numerical value is huge, great trouble is caused in the calculation process, and the translated coordinates need to be normalized. After normalization, the Mars can be considered to be on a unit sphere centered on the Mars probe. Let coordinate after Mars normalization be (u)m1,vm1,wm1) Let the original coordinates of Mars subjected to translation transformation be (u'm,v'm,w'm) Then the following equation is satisfied:
the rotary transformation of the mars center relates to the transformation from a sunset ecliptic coordinate system to a posture sensor coordinate system, the transformation from the posture sensor coordinate system to an image plane coordinate system, and finally the transformation from the image plane coordinate system to a display plane coordinate system and a projector plane coordinate system, and the basic process is consistent with the transformation of fixed stars.
Mars imaging size simulation process:
compared with the simulation of a star image point, the ratio of the diameter to the distance of the spark is large and cannot be ignored, so that the imaging size of the spark on a CMOS area array also needs to be simulated. Within the distance of the detector approaching the Mars stage, the Mars detector visual axis points to the Mars center, and then the Mars detector is positioned at the central position of the visual field, and the relationship is shown in figure 7.
The invention considers the spark to be a perfect sphere. As shown in fig. 7, where FOV is the field of view, for a spark with radius R, the following relationship is given:
wherein R is the Mars radius, l is the distance from the detector to the Mars, R is the radius of Mars imaging on the CMOS camera area array, and at the moment, R is represented by the size and needs to be converted into a pixel for representation.
Other steps and parameters are the same as in one of the first to fourth embodiments.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is:
in step B2, the number of pixels imaged is determined by the following formula:
given that the pixel size in the X direction of the CMOS camera area array is tmpPixelsizeX, and the pixel size in the Y direction of the camera area array is tmpPixelsizeY, there is a conversion formula as follows:
wherein n isxAs an image occupied in the X directionNumber of elements, nyIs the number of pixels occupied in the Y direction.
Other steps and parameters are the same as those in one of the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to fifth embodiments is:
the Mars imaging contour simulation step comprises the following steps:
step C1: and calculating a two-dimensional imaging contour of the Mars contour on the CMOS plane when an included angle between a Mars-to-detector vector and a Mars-to-sun vector is 0-180 degrees by taking a plane formed by the sun, the Mars and the Mars detector as a reference plane.
The specific process is as follows:
the mars contour simulation simulates the area where the mars are illuminated by the sun and the area in darkness on the CMOS image plane coordinate system. A spark is not a light source and its brightness mainly comes from reflected sunlight, for a spark, it can be considered that the sunlight hits the spark in parallel, one half of the spark is illuminated by the sun at each moment, while the other half is in a dark state. In addition, due to the fact that the detectors observe different mars at different positions, light and shade conditions can also occur when the mars are imaged on the camera area array, namely the mars have different outlines, and therefore celestial body geometric modeling is conducted on the sun, the mars and the detectors, and the celestial body geometric modeling is conducted as shown in fig. 8.
Plane O formed by sun, spark and spark detectorsOmOpIs a reference plane. Since the sparks are spherical, they are all spherical when observed from different angles, OsOmOpThe plane may be different from the plane of revolution of the spark and the equatorial plane of the spark. Based on this, a geometric model of the celestial body as shown in fig. 9 can be established.
As shown in FIG. 9, the sun, Mars, and detector plane OsOmOpIs a reference plane. In this figure OmXmYmThe plane is centered on the spark and is connected with the OsOmOpPlane with coincident reference planes, OmLocated in the center of the spark, YmThe axis pointing to the sun, parallel and opposite to the sun's rays, XmAxis and YmThe axis is vertical and points to the spark light and dark junction, ZmAxis and XmAxis, YmThe axis constitutes the right hand rule, where the circle AFCE is the light and dark boundary circle. Mars detector is also located at OmXmYmThis plane, let OmG is the Mars to Detector vector, OmD is a Mars-to-sun vector. O ismG and OmAnd D, forming an included angle theta. FK perpendicular to YmThe shaft, so there are:
OmK＝R·sinα (2-12)
wherein R is the Mars radius, α is ∠ KFOm。
Then for any point M on the semi-circular AFC:
O'mK＝R'·sinα (2-13)
wherein O'mIs the center of the plane circle where M is located, K 'is the foot, and R' is the radius of the plane circle where M is located. A two-dimensional projection of the spark profile can be obtained as shown in figure 10.
According to the relation of the vector included angles, the value range of the two vector included angles is 0-180 degrees, and the vector from the Mars to the detector may be as the vector O in FIG. 9mH, the vector included angle is not taken within 0-180 degrees, the profiles are different, and therefore judgment is made by vector product.
Other steps and parameters are the same as those in one of the first to sixth embodiments.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that:
the Mars imaging orientation simulation step comprises the following steps:
step D1: vector r from sun to Mars0Converting the coordinate system of the sun center ecliptic into the coordinate system of the attitude sensor to obtain a vector r under the coordinate system of the attitude sensor0′；
Step D2: r under the coordinate system of the attitude sensor0' conversion to vector r in CMOS planar coordinate System0″；
Step D3: from the CMOS image plane and r0"the vertical relationship yields the imaging orientation of the Mars.
The specific process is as follows:
the orientation of the spark imaging determines the orientation of the illuminated area of the spark. The imaging Mars profile on the CMOS area array can present different orientations, as shown in the following figure, in a CMOS image plane coordinate system, the part which is not irradiated by the sun is also in a crescent shape, but can present a plurality of imaging orientations, and three situations are shown in figure 11; it should be noted that there are countless situations in practice, and fig. 11 only shows three exemplary cases.
Let the vector from sun to Mars be r0Vector r0Determines the orientation of Mars imaging when the vector r0In the coordinates of the ecliptic, the vector r is divided into0Converting the coordinate system of the attitude sensor to obtain a vector r0′。
Vector r under attitude sensor coordinate system0', in the image plane coordinate system with XbThe angle formed by the positive direction of the shaft is γ.
Wherein the value range of gamma is 0-2 pi, and the value angle of gamma can be judged by judging the positive and negative values of x and y.
Other steps and parameters are the same as those in one of the first to seventh embodiments.
The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that:
the Mars imaging gray scale simulation step comprises the following steps:
step E1: the Mars et al of Mars is mapped to the gray level of the computer by the following linear gray level formula:
gray＝75+30·(6-m) (2-15)
wherein, gray is gray value of star, and m is star.
Specifically, stars and the like are used for measuring the luminosity of celestial bodies and are used for measuring the brightness of celestial bodies, the gray value refers to the color depth in black and white images, the range is divided into 256 levels, namely 0-255, the gray level is no color, and the RGB color components are all equal. The star and the like are represented by a computer gray value, and by adopting the principle of RGB three component equality, the gray value is equal to any component of RGB, and can be represented as follows:
f(x,y)＝(R(x,y),G(x,y),B(x,y))/3 (2-16)
the 0-6 stars are subjected to gray scale linearization using the formula (2-15), the gray scale value is 75 when the equality is 6m, and the maximum gray scale value is 255, i.e. brightest, when the star equality is 0 m.
Although stars can be regarded as point light sources, representing stars by one pixel point causes the stars to be extremely small on a display device, which is inconvenient for shooting and extracting, so that a plurality of pixel points are designed to represent one star. The identification of later-stage star maps is not influenced by the multiple pixel points, and the centroid of the fixed star needs to be extracted in the edge detection process, so that the accuracy can be guaranteed, and the visibility of the fixed star can be guaranteed.
Other steps and parameters are the same as those in one to eight of the embodiments.
The present invention is capable of other embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and scope of the present invention.
Claims (9)
1. A mars target simulation method for deep space exploration is characterized by comprising a mars coordinate simulation step, a mars imaging size simulation step, a mars imaging contour simulation step, a mars imaging azimuth simulation step and a mars imaging gray scale simulation step: wherein,
the Mars coordinate simulation step is used for converting the Mars center coordinate from the sunset ecliptic coordinate system to the display plane coordinate system;
the Mars imaging size simulation step is used for calculating the imaging size of the Mars according to the imaging view field of the Mars detector and the relative distance relationship between the Mars and the Mars detector;
the Mars imaging contour simulation step is used for simulating an area where the Mars are illuminated by the sun and an area where the Mars are not illuminated;
the Mars imaging orientation simulation step is used for calculating the imaging orientation of the Mars outline according to the relative position relation of the sun, the Mars and the detector;
and the Mars imaging gray scale simulation step is used for mapping the stars and the like of the Mars to the gray scale of the computer so as to display the gray scale on the interface.
2. The method according to claim 1, further comprising a pre-processing step performed before the steps, the pre-processing step being specifically:
parameters in each data item in the SKY2000 star list are deleted, only parameter information of right ascension, declination, stars and the like of stars of each data item under J2000 is reserved, and all the data items are arranged according to the descending of the right ascension.
3. The method of claim 1, wherein the Mars coordinates modeling step comprises:
step A1: determining the central coordinate visual axis direction of the Mars detector;
step A2: converting the attitude quaternion for describing the Mars detector into a right ascension and a declination of a visual axis;
step A3: converting the Mars coordinate and the Mars detector coordinate of the sun center ecliptic coordinate system under the star chart into the coordinate of the attitude sensor coordinate system;
step A4: the coordinates of the spark's center in the display plane coordinate system and the projector coordinate system are determined.
4. The method of claim 1, wherein in step A2, the right ascension of visual axis α0Declination of weft0The expression of (a) is:
wherein A iszx＝2(q1q3+q2q4)，Azy＝2(q2q3-q1q4)，Azz＝-q1 2-q2 2+q3 2+q4 2，
q1,q2,q3,q4Are respectively attitude quaternions q ═ q1,q2,q3,q4]TThe corresponding component of (a).
5. The method of claim 1, wherein the Mars imaging size simulation step comprises:
step B1: determining the imaging size of the Mars through the imaging view field of the Mars detector and the relative distance relationship between the Mars and the Mars detector;
step B2: the number of the imaging pixels is determined by the size of the analog pixel size of the CMOS camera area array.
6. The method according to claim 5, wherein in step B2, the number of image elements to be imaged is determined by the following formula:
wherein n isxIs the number of pixels occupied in the X direction, nyThe number of pixels occupied in the Y direction is shown, tmpPixelsize X is the pixel size in the X direction of the CMOS camera area array, tmpPixelsize Y is the Y direction of the camera area arrayUpward pixel size; and r is the radius of Mars imaging on the CMOS camera area array.
7. The method of claim 1, wherein the Mars imaging profile modeling step comprises:
step C1: and calculating a two-dimensional imaging contour of the Mars contour on the CMOS plane when an included angle between a Mars-to-detector vector and a Mars-to-sun vector is 0-180 degrees by taking a plane formed by the sun, the Mars and the Mars detector as a reference plane.
8. The method of claim 1, wherein the Mars imaging orientation simulation step comprises:
step D1: vector r from sun to Mars0Converting the coordinate system of the sun center ecliptic into the coordinate system of the attitude sensor to obtain a vector r under the coordinate system of the attitude sensor0′；
Step D2: r under the coordinate system of the attitude sensor0' conversion to vector r in CMOS planar coordinate System0″；
Step D3: from the CMOS image plane and r0"the vertical relationship yields the imaging orientation of the Mars.
9. The method of claim 1, wherein the Mars imaging gray scale simulation step comprises:
step E1: the Mars et al of Mars is mapped to the gray level of the computer by the following linear gray level formula:
gray＝75+30·(6-m)
wherein, gray is gray value of star, and m is star.
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