CN105224731B - The radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor - Google Patents

Abstract

The invention relates to a radiation simulation method for a geostationary satellite ultraviolet imaging sensor, which is based on the preliminary analysis of the existence and characteristics of the "Earth's Ultraviolet Edge Bright Ring", setting the waveband range to 330-360nm, for the "Earth's Ultraviolet Edge Bright Ring""BrightRing" to perform radiance simulation and batch generate UV simulation images at any point in time. The main steps include: the acquisition of the ultraviolet radiation brightness value of the feature point; the projection transformation of the feature point on the imaging plane; the generation of complete simulation data. The radiation simulation method of the geostationary satellite ultraviolet imaging sensor of the present invention can batch and quickly generate simulation data of "bright rings at the edge of the earth's ultraviolet light" in different observation modes within a specified time range (time point or time period), so as to ensure sensitive The smooth implementation of device development.

Description

Radiation Simulation Method for Geostationary Satellite Ultraviolet Imaging Sensor

technical field

The invention relates to remote sensing imaging simulation, in particular to a radiation simulation method for an ultraviolet imaging sensor of a geostationary satellite.

Background technique

The spacecraft autonomous navigation system can determine the position and speed of the spacecraft in real time on-orbit with little or no support from the ground system, realize autonomous operation, and greatly improve the survivability and safety performance of the satellite system. As a more reasonable and optimal choice for autonomous navigation of spacecraft, ultraviolet imaging sensors have received keen attention at home and abroad. The development of the ultraviolet imaging sensor needs to analyze and summarize the ultraviolet characteristics of the earth, that is, the distribution law of the "bright ring of the earth's ultraviolet edge", so as to provide data input for the hardware design of the camera and the system development of application processing.

The foreign ultraviolet sensor first originated from the ultraviolet three-axis attitude sensor (Earth Reference Determination System (ERADS)) developed by Honeywell in 1992. The flight test was completed in 1994, but the details of the test have not been seen. reports. Domestic ultraviolet imaging sensors have been successfully applied to the navigation and positioning of lunar exploration satellites. However, the earth itself has an outer atmosphere and complex surface features. The ultraviolet imaging sensors for lunar mapping and navigation cannot be directly applied to earth mapping and navigation. Relevant personnel have also conducted active research on ultraviolet imaging sensors for earth mapping and navigation and achieved some results. Literature search shows that domestic research on ultraviolet sensors has appeared since 2001: in 2001, Zhang Aihong et al. improved and designed the optical system of a sun-synchronous low-orbit ultraviolet star sensor on the basis of referring to the US patent; in 2004, Wei Chunling et al. The application of UV sensor-based navigation in Earth's medium and low orbits, large elliptical orbits and geosynchronous orbits has been verified by mathematical simulation; in 2007, Geng Jianzhong and others verified the effectiveness of adaptive particle filtering in the application of satellite ultraviolet navigation; in 2013 In 2014, Sun Jun and others proposed a method of autonomous navigation for satellites using the Earth's ultraviolet band and the star's visible light band, which reduced the position and velocity errors; in 2014, Xu Da et al. The simulation method is used for ground calibration and accuracy test of the ultraviolet navigation sensor. It can be seen from the above that the research and development of ultraviolet sensors in my country is still in the development period of gradual exploration. However, none of the above studies and methods can form a simulated image of the "bright ring at the edge of the earth's ultraviolet edge" of a geostationary satellite, which cannot be used for the hardware design and application of ultraviolet sensors. Processing provides data support.

Contents of the invention

The technical problem to be solved by the invention is to overcome the shortcomings of the prior art and propose a radiation simulation method for the ultraviolet imaging sensor of the geostationary satellite.

In order to solve the above technical problems, the radiation simulation simulation method of the geostationary satellite ultraviolet imaging sensor provided by the invention comprises the following steps:

Step 1. Acquisition of the ultraviolet radiance value of feature points——Using the geosynchronous satellite as a platform, select four positions relative to the sub-satellite point, such as the limb point, sub-satellite point, The middle point between the limb point and the sub-satellite point is used as the surface feature point, and the point of each limb point vertically upward to 95km at an interval of 5km is used as the elevation feature point, and the surface feature point and elevation feature at the specified time are extracted The UV radiance value of the point;

The second step, the projection transformation of the feature points in the imaging plane - converting the three-dimensional spherical coordinates of the feature points to the plane coordinates of the two-dimensional image formed by the sensor, the specific steps are as follows:

a1) First, take the sub-satellite point as the center, and obtain the spherical coordinates of each feature point according to the geometric relationship between the sensor and the earth; secondly, take the direction of the earth center-sub-satellite point as the X axis, and the horizontal axis direction of the projection plane as the Y axis , the direction of the vertical axis of the projection plane is the Z axis, and the transformation is carried out according to the coordinate transformation relationship between the spherical coordinates and the space Cartesian coordinate system, and the spherical coordinates of the feature points are converted into the space Cartesian coordinates, and then the projection coordinates of the feature points on the projection plane are obtained;

a2), convert the projected coordinates of each feature point into polar coordinates;

a3), define the distance of 95km above the earth's surface as M standard units, and define the distance from the earth's surface to the center of the earth as N standard units, and establish a simulated disk with M+N standard units as the radius. The polar coordinates of each feature point obtained in step a2) are converted into polar coordinates of the simulated disk;

The third step is to obtain the complete simulation data, the steps are as follows:

b1), Forward coordinate conversion: Transform the simulated disc into a simulated rectangle whose length is the circumference of the simulated disc and whose width is the radius of the simulated disc. The length of the simulated rectangle is the Y axis, and the width is the X axis. The polar coordinates under the simulated disk are transformed into Cartesian coordinates under the simulated rectangle;

b2), radiance interpolation: use the linear interpolation method to interpolate adjacent feature points to obtain the ultraviolet radiance value of the interpolation point;

b3) Reverse coordinate conversion: reversely transform the simulation rectangle into a simulation disk, the length of the simulation rectangle is the circumference of the simulation disk, the width of the simulation rectangle is the radius of the simulation disk, and each feature point and interpolation point is in the simulation Cartesian coordinates under the rectangle are transformed into polar coordinates under the simulated disk;

In the fourth step, the finally obtained polar coordinate values of all feature points and interpolation points under the simulation disk and their respective radiance are the radiation simulation data of the UV imaging sensor of the geostationary satellite at a specified time.

In order to solve the above technical problems, the present invention also has the following further features:

1. In the first step, the ultraviolet radiance value of all feature points is obtained through the atmospheric radiation transfer simulation software MODTRAN. The parameters input for the acquisition of the ultraviolet radiance value include the atmospheric simulation conditions and the orbit type of the simulated satellite. The atmospheric simulation conditions are each Standard atmospheric and climate models for feature points; the simulated satellite is a geostationary satellite with a distance of 36,000 km from the earth's surface, and the sub-satellite point is at the equator, 102º east longitude.

2. In step a1), the spherical coordinates of the i-th feature point are (lon _i , lat _i , R _i ), where lon _i is the longitude of the i-th feature point, and lat _i is the latitude of the i-th feature point , R _i is the sum of the cut height h _i of the i-th feature point and the radius r of the earth in this area.

3. In step a3), M=95, N=100.

4. In step b1), the method of transforming the simulated disc into a simulated rectangle is as follows: Cut the simulated disc along any radius direction as the x-axis, rotate the right side of the cut radius clockwise, and move the center of the circle along the y-axis The positive stretch is the length of the circumference of the simulated disc, forming a simulated rectangle whose length is the circumference of the simulated disc and whose width is the radius of the simulated disc.

5. In step b2), the interpolation step of the X axis is 1/8 standard unit, and the interpolation step of the Y axis is 1/2 standard unit.

6. In step b3), the method of transforming the simulated rectangle into a simulated disc is as follows: Scale the long side formed by stretching the center of the simulated rectangle to a point, and the point on the other long side whose y value is not 0 moves counterclockwise The orientation rotation meets the point with a y value of 0, regenerating the simulated disk.

The radiation simulation method of the geostationary satellite ultraviolet imaging sensor of the present invention can batch and quickly generate the simulation data of "bright ring at the edge of the earth's ultraviolet light" under different observation modes within the specified time range (time point or time period), so as to ensure the sensitive The smooth implementation of device development.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Fig. 1 is a flow chart of the radiation simulation method of the geostationary satellite ultraviolet imaging sensor of the present invention.

Fig. 2 is a schematic diagram of feature points of the method of the present invention.

Fig. 3 is a schematic diagram of projection transformation of feature points on an imaging plane in the method of the present invention.

Fig. 4 is a schematic diagram of positive and negative coordinate transformation of feature points in the method of the present invention.

Fig. 5 is a schematic diagram of the simulated data of the "bright ring at the edge of the Earth's ultraviolet" at 10:00 am on June 15, 2013 obtained through the simulation of the present invention.

Detailed ways

The present invention will be described in detail below according to the accompanying drawings, so as to make the technical route and operation steps of the present invention clearer.

As shown in Figure 1, it is a flow chart of a radiation simulation method for a geostationary satellite ultraviolet imaging sensor in an embodiment of the present invention, including the following steps:

Step 1. Acquisition of the ultraviolet radiance value of the feature point—as shown in Figure 2, using the geosynchronous satellite as a platform, select four positions relative to the sub-satellite point, up, down, left, and right, and the limb where the straight line with an inclination angle of ±45º intersects the earth point, the sub-satellite point, the middle point between the limb point and the sub-satellite point as the surface feature point (there are 17 surface feature points in total), and the points of the geocentric direction of each limb point vertically upward to 95km at intervals of 5km are used as the elevation feature Points (there are 152 elevation feature points in total), the number of all feature points is 169, extract all surface feature points and elevation feature points at the specified time (in this example, 10 am on June 15, 2013, Beijing time) 330- The luminance value of ultraviolet radiation in the 360nm band;

In this step, the ultraviolet radiance values of all feature points are obtained through the atmospheric radiative transfer simulation software MODTRAN. The parameters input for the acquisition of ultraviolet radiance values include the atmospheric simulation conditions and the orbit type of the simulated satellite. The atmospheric simulation conditions are the Standard atmospheric and climate model; the simulated satellite is a geostationary satellite, the distance from the earth's surface is 36000 km, and the position of the sub-satellite point of the satellite is: equator 0.00, east longitude 102.00.

The second step, the projection conversion of feature points in the imaging plane-the three-dimensional spherical coordinates of the feature points are converted to the plane coordinates of the two-dimensional image formed by the sensor (the schematic diagram of projection conversion is shown in Figure 3), and the specific steps are as follows:

a1) First, take the sub-satellite point as the center, and obtain the spherical coordinates of each feature point according to the geometric relationship between the sensor and the earth; secondly, take the direction of the earth center-sub-satellite point as the X axis, and the horizontal axis direction of the projection plane as the Y axis , the direction of the vertical axis of the projection plane is the Z axis, and the transformation is carried out according to the coordinate transformation relationship between the spherical coordinates and the space Cartesian coordinate system, and the spherical coordinates of the feature points are converted into the space Cartesian coordinates, and then the projection coordinates of the feature points on the projection plane are obtained; In this step, the spherical coordinates of the i-th feature point are (loni, lati, Ri), where loni is the longitude of the i-th feature point, lati is the latitude of the i-th feature point, and Ri is the i-th feature point The sum of the tangent height hi and the earth radius r in this area;

a2), convert the projected coordinates of each feature point into polar coordinates;

a3), define the distance of 95 km above the earth's surface as 95 standard units, and define the distance from the earth's surface to the center of the earth as 100 standard units, and establish a simulation disk with a radius of 195 standard units, and step a2 The polar coordinates of each feature point obtained in ) are transformed into the polar coordinates of the simulated disk.

The third step is to obtain the complete simulation data, the steps are as follows:

b1), Forward coordinate transformation: As shown in Figure 4, transform the simulated disc into a simulated rectangle whose length is the circumference of the simulated disc and whose width is the radius of the simulated disc. The length of the simulated rectangle is the Y axis and the width is On the X-axis, the polar coordinates of each feature point under the simulation disk are transformed into Cartesian coordinates under the simulation rectangle; the method of transforming the simulation disk into a simulation rectangle is as follows: cut the simulation disk along any radial direction as the x-axis, The right side of the cutting radius is rotated clockwise, and the center of the circle is stretched along the positive direction of the y-axis to the length of the circumference of the simulated disc, forming a simulated rectangle whose length is the circumference of the simulated disc and whose width is the radius of the simulated disc;

b2) Interpolation of radiance: use linear interpolation to interpolate adjacent feature points to obtain the radiance value of the interpolated point; it should be noted during the interpolation process that if the density of the interpolation result is equal to the density of the simulated rectangle, then After the inverse coordinate conversion is completed, the simulation data of "Earth's Ultraviolet Edge Bright Ring" will have bad point data (the radiance is 0, black dots in the illustration), so during the interpolation process, the X-axis interpolation of the simulation rectangle needs to be encrypted To 8 times or more can imitate the appearance of bad point data. In this embodiment, the interpolation step of the X axis is 1/8 standard unit, and the interpolation step of the Y axis is 1/2 standard unit;

b3) Reverse coordinate conversion: reversely transform the simulation rectangle into a simulation disk, the length of the simulation rectangle is the circumference of the simulation disk, the width of the simulation rectangle is the radius of the simulation disk, and each feature point and interpolation point is in the simulation The Cartesian coordinates under the rectangle are transformed into the polar coordinates under the simulated disk; the method of transforming the simulated rectangle into a simulated disk is as follows: scale the long side formed by stretching the center of the circle in the simulated rectangle to a point, and the y value in the other long side Points that are not 0 rotate counterclockwise to meet points with a y value of 0 to regenerate the simulation disk.

In the fourth step, the finally obtained polar coordinate values of all feature points and interpolation points under the simulation disk and their respective radiance are the radiation simulation data of the UV imaging sensor of the geostationary satellite at a specified time. Figure 5 is a schematic diagram of the bright ring of the Earth's ultraviolet edge generated based on the simulation data.

In addition to the above-mentioned embodiments, the present invention can also have other implementations. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (7)

1. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor, comprises the following steps：

The acquisition of the first step, characteristic point ultraviolet radioactive brightness value --- using Geo-synchronous fixed statellite as platform, choose relative to Substar up and down four positions and ± 45o inclination angle straight lines intersect with the earth face edge point, substar, face under edge point and star Intermediate point between point is respectively faced edge point the earth's core direction and is made vertically upward with the point of 5km increments to 95km as topographical features point For elevation features point, the ultraviolet radioactive brightness value of the topographical features point and elevation features point of specified time is extracted；

The projection transform of second step, characteristic point in imaging plane --- the three-dimensional sphere coordinate of the characteristic point is changed to quick Sensor into two dimensional image plane coordinates, comprise the following steps that：

a1）, first centered on substar, according to the geometrical relationship of sensor and the earth, try to achieve the spherical coordinate of each characteristic point； Secondly, using the earth's core-substar direction as X-axis, projection plane horizontal axis is Y-axis, and projection plane vertical axis is Z axis, Changed, obtained the spherical coordinate transformation of characteristic point according to the coordinate transformation relation of spherical coordinate and rectangular coordinate system in space For rectangular space coordinate, and then obtain the projection coordinate of characteristic point on a projection plane；

a2）, the projection coordinate of each characteristic point switched into polar coordinate representation；

a3）, by the distance definition of earth surface above atmosphere 95km be M standard unit, and earth surface is to the earth's core The distance definition of 6371km is N number of standard unit, establishes the emulation disk using M+N standard unit as radius, by step a2）In The polar coordinates of each characteristic point obtained are converted to the polar coordinates of the emulation disk；

The acquisition of 3rd step, complete emulation data, step are as follows：

b1）, forward reference conversion：Emulation disk is transformed to emulate disk Zhou Changwei long, to emulate disc radius to be wide Rectangle is emulated, emulates a length of Y-axis of rectangle, width is X-axis, and polar coordinate transform of each characteristic point in the case where emulating disk is emulation rectangle Under rectangular co-ordinate；

b2）, radiance interpolation：Row interpolation is clicked through to adjacent feature using the method for linear interpolation, obtains the ultraviolet of interpolation point Radiance value；

b3）, backward reference conversion：It is emulation disk by the reciprocal transformation of emulation rectangle, emulates the week of a length of emulation disk of rectangle Long, the width for emulating rectangle is the radius of emulation disk, and the rectangular coordinates transformation of each characteristic point and interpolation point in the case where emulating rectangle is Emulate the polar coordinates under disk；

The polar value and respective radiance of 4th step, all characteristic points finally obtained and interpolation point in the case where emulating disk Data are emulated for the radiomimesis of the geostationary satellite ultraviolet imagery sensor under specified time.

2. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor according to claim 1, its feature It is：In the first step, ultraviolet radioactive brightness value is carried out to all characteristic points by atmospheric radiative transfer simulation softward MODTRAN Obtain, the parameter input that ultraviolet radioactive brightness value obtains includes the classification of track of atmospheric simulation condition and analog satellite, air mould Plan condition is the normal atmosphere and climatic model of each characteristic point；Analog satellite is Geo-synchronous fixed statellite, with earth surface Distance is 36000 km, and the position of sub-satellite point is：Equator, east longitude 102o.

3. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor according to claim 1, its feature It is：Step a1）In, the spherical coordinate of ith feature point is（lon_i, lat_i, R_i）, wherein, lon_iFor ith feature point Longitude, lat_iFor the latitude of ith feature point, R_iHeight is cut for ith feature pointh _i With the ith feature point location earth RadiusrThe sum of.

4. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor according to claim 1, its feature It is：Step a3）In, M=95, N=100.

5. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor according to claim 1, its feature It is：Step b1）In, the method that emulation disk is transformed to emulation rectangle is as follows：Emulation disk is cut along any radial direction Open as x-axis, cut and rotated clockwise on the right side of radius, the center of circle is stretched as to the length of emulation disk girth along y-axis forward direction, Formed to emulate disk Zhou Changwei long, to emulate disc radius as wide emulation rectangle.

6. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor according to claim 1, its feature It is：Step b2）In, the interpolation step-length of X-axis is 1/8 standard unit, and the interpolation step-length of Y-axis is 1/2 standard unit.

7. the radiomimesis emulation mode of geostationary satellite ultraviolet imagery sensor according to claim 1, its feature It is：Step b3）In, it is as follows for the method for emulation disk that rectangular transform will be emulated：Formed being stretched in emulation rectangle by the center of circle Long side be scaled a bit, in another long side y values for 0 point rotate in the counterclockwise direction with y values be 0 point congregation, again Generation emulation disk.