CN103837150A - Method for performing rapid celestial fix through CCD (charge coupled device) zenith telescope on ground - Google Patents

Abstract

The invention discloses a method for performing rapid celestial fix through a CCD (charge coupled device) zenith telescope on the ground. According to the method, the CCD zenith telescope is used for imaging a fixed star in a sky region near to the zenith of an observation point twice (the barrel of the telescope rotates by 180 degrees around a rotating shaft during the two times of imaging); precise astronomical longitudes and latitudes of the observation point can be rapidly obtained by processing the two shot fixed star images, the corresponding precise time and inclinometer data. Compared with the conventional generally used satellite positioning method, the method disclosed by the invention has the advantages of full autonomy, high reliability, high invisibility, working safety, no electromagnetic interference and the like. Compared with other celestial fix methods, the method disclosed by the invention has the advantage of high precision. Furthermore, star selection is not needed in the method, so that the observation process is simplified, and the observation efficiency is greatly improved; the shortcomings that the conventional astronomical telescope is complicated in observation and low in efficiency, needs an observation foundation pier and cannot perform mobile observation are overcome. The method has extremely good development and application prospects.

Description

The method of the quick astronomical fixation in a kind of CCD zenith telescope ground

Technical field

The present invention relates to uranometry field, be specifically related to the method for the quick astronomical fixation in a kind of ground.

Background technology

Along with the development of space technology, satnav is widely used in every field, is even used as unique positioning means.But the feature of global position system is the navigation message with characteristic frequency broadcast specific format by signal specific, navigation signal is extremely faint, very easily under attack and interference.Therefore depend on satnav unduly and have very large danger.

Compared with satnav, the radiation of celestial body is only accepted in astronomical fixation passively, has reliability high, good concealment, and work safety, is not subject to the advantages such as electromagnetic interference (EMI), is a kind of completely autonomous locator meams that does not rely on other means.Astronomical fixation security and vital role is under special circumstances that satnav positioning system is incomparable, thereby is that various countries continue one of navigator fix means that adopt always.On the warship of the United States, Russia, English, Fa Deng military power and submarine, using astronomical fixation always.

Astronomical fixation is by astronomical sight, determines the spatial direction of observation station pedal line, i.e. astronomical longitude and latitude.The ultimate principle of utilizing CCD zenith telescope to carry out the quick astronomical fixation in ground is that the fixed star in day district is determined near given moment observation station zenith.Observation station position, time and star place three connect each other.In time and star place, known in the situation that, topocentric position is well-determined.Traditional astronomical positioning method adopts visual sextant as scope, determine the longitude and latitude of observation station by observing a certain moment sun or other celestial body and sea horizon or horizontal angle, but precision is low, automaticity is low, cannot meet current location needs.

Along with the development of technology, engender star tracker (star sensor) and the radio sextant taking radio source as observed object of robotization.The precision of star tracker is still lower, cannot meet the needs of hi-Fix.Radio sextant needs the antenna for radio astronomy bulky, cost is high, and available radio source quantity is few, radio signal is faint, thereby be difficult to realize continuous location, positioning precision is low, location guarantee is discontinuous, directly affects the application and development of radio astronomy location technology.

Summary of the invention

The object of the present invention is to provide a kind of CCD of utilization zenith telescope to carry out the method for the quick astronomical fixation in ground.

The CCD of utilization zenith telescope provided by the invention carries out the method for the quick astronomical fixation in ground, compared with the satellite positioning method of current general practicality, has full independence, is not subject to electromagnetic interference (EMI), and reliability is high, good concealment, the advantages such as work safety.Because the method is passive reception fixed star starlight only, fixed star is to exist in the moment, and cannot be disturbed or destroy, the global position system such as GPS, the Big Dipper needs to rely on the radio signal of artificial satellite transmitting, and satellite is easy under attack, and the radio signal of its transmitting is very easily interfered.

Compared with other astronomical positioning method, have the advantages that precision is high.Other astronomical fixation mainly contains: star sensor, sextant, transit etc.But precision is lower, the precision of the star sensor that precision is the highest is in the world about 1 " (corresponding ground positioning error is about 30 meters); the precision of sextant is about 6 " 12 " (corresponding ground positioning error is about 180-360 rice), and the accuracy of observation of transit is about 0.5 " (corresponding positioning error is about 15 meters).This invention adopts zenith observing pattern, only, near district's imaging in observation station zenith (intersection point of the certain pedal line direction in ground and sky background) day, has reduced to greatest extent the impact of atmospheric refraction, has improved accuracy of observation.Adopt 180 ° of twice imaging observations of rotating shaft simultaneously, eliminated instrument error of collimation, CCD zero point drift.Adopt the inclination of high precision inclinator detecting instrument to carry out inclination correction simultaneously, eliminated the impact that instrument tilts on observed result.Experiment shows, the positioning precision of the method is about 0.2 " (corresponding positioning error is about 6 meters).

Compared with the observation of traditional astronomical telescope, the method for this invention has volume urine in mobile observation, does not need to observe base pause the advantage that observed efficiency is high.Traditional astronomical telescope is bulky, very heavy, only can observe at point of fixity, and need to be at observation station construction observation foundation pier.The method of this invention instrument volume used is little, lightweight, is easy to mobile observation, does not need to observe foundation pier simultaneously.When simultaneously traditional astronomical telescope observation, need observational program, can only within the time of subscribing, observe, and only observe a star at every turn, observed efficiency is low.The method of this invention can real-time monitored, observes tens to up to a hundred stars at every turn, adopts the overall treatment of many stars, has greatly improved observed efficiency, has improved accuracy of observation.

The method of utilizing CCD zenith telescope to carry out the quick astronomical fixation in ground comprises observation and data reduction.In observation process, concrete steps are as follows:

CCD zenith telescope is positioned in after observation station, and horizontalization system is carried out accurate horizontalization according to high precision tilt meter data to telescope, makes telescopical horizontality in given scope;

Electric-control system reads high precision dipmeter survey data, and transfers to computing machine;

CCD zenith telescope carries out imaging for the first time near day district observation station zenith;

Telescope electric-control system reads pps pulse per second signal and the precise time information that atomic clock or radio time dissemination system provide, the trigger pip of exposing using this pulse per second (PPS) as CCD, CCD is with given exposure time exposure, and precise time is transferred to computing machine by electric-control system simultaneously, and imaging for the first time finishes;

Electric control system controls drive systems lens cone for telescope (comprising CCD camera) is around 180 ° of vertical axis revolvings;

Electric-control system reads high precision dipmeter survey data again, and transfers to computing machine;

CCD zenith telescope carries out imaging for the second time near day district observation station zenith;

Telescope electric-control system reads pps pulse per second signal and the precise time information that atomic clock or radio time dissemination system provide, the trigger pip of exposing using this pulse per second (PPS) as CCD, CCD is with given exposure time exposure, and precise time is transferred to computing machine by electric-control system simultaneously, and imaging for the second time finishes;

The ccd image that data handling system is obtained twice imaging and separately precise time and the tilt meter data of imaging moment record are processed, and obtain the astronomical longitude and latitude of observation station.

Brief description of the drawings

Fig. 1 is the quick astronomical fixation observation in CCD zenith telescope ground flow process;

Fig. 2 is the quick astronomical fixation flow chart of data processing in CCD zenith telescope ground.

Embodiment

As shown in Figure 1, astronomical positioning method provided by the invention comprises the following steps:

Telescope horizontalization.CCD zenith telescope is placed in after observation station, and horizontalization system is carried out accurate horizontalization according to high precision tilt meter data to telescope, makes telescopical horizontality in given scope.

To near day district observation station zenith is carried out to imaging for the first time.Electric-control system reads high precision dipmeter survey data, and transfers to computing machine; CCD zenith telescope carries out imaging for the first time near day district observation station zenith; Telescope electric-control system reads pps pulse per second signal and the precise time information that atomic clock or radio time dissemination system provide, the trigger pip of exposing using this pulse per second (PPS) as CCD, CCD is with given exposure time exposure, and precise time is transferred to computing machine by electric-control system simultaneously, and imaging for the first time finishes.

Near day district observation station zenith is carried out to imaging for the second time.Electric control system controls drive systems lens cone for telescope (comprising CCD camera) is around 180 ° of vertical axis revolvings; Electric-control system reads high precision dipmeter survey data again, and transfers to computing machine; CCD zenith telescope carries out imaging for the second time near day district observation station zenith; Telescope electric-control system reads pps pulse per second signal and the precise time information that atomic clock or radio time dissemination system provide, the trigger pip of exposing using this pulse per second (PPS) as CCD, CCD is with given exposure time exposure, and precise time is transferred to computing machine by electric-control system simultaneously, and imaging for the second time finishes.

The ccd image that data handling system is obtained twice imaging and separately precise time and the tilt meter data of imaging moment record are carried out data reduction processing, obtain the astronomical longitude and latitude of observation station.

As shown in Figure 2, data reduction process comprises: star image is extracted and the apparent sidereal time calculating of star image centroid calculation, star apparent place and Greenwich, importance in star map recognition, zenith point position calculation and telescope inclination correction.

Detailed step is as follows:

(1) star image is extracted and star image centroid calculation

In entire image, search for brightness value and be greater than the pixel of a certain threshold value.If with same this threshold value that is greater than of gray-scale value of this pixel pixel around, think that the region of this pixel and surrounding pixel composition thereof is star image region.

By being done to weighted mean, the gray-scale value of each pixel in star image region obtains star image centroid position.

(2) star catalogue astre fictif apparent place and Greenwich sidereal time calculate

The mean place that is fixed star under standard epoch providing in star catalogue, this mean place is converted to apparent place epoch of observation by the impact (mainly comprise fixed star voluntarily, precession of the equinoxes, nutating, aberration, parallax etc.) that will become factor in calculating when many.

Utilize UTC and the UT1 in observation moment in observation moment to calculate Greenwich apparent sidereal time.

(3) reference star ideal coordinates are calculated

(2) in, gained star apparent place is the spherical co-ordinate under celestial coordinate system, and in ccd image, the position of star image is planimetric coordinates.For determining contacting between star catalogue reference star and star image, need set up the ideal coordinates system of reference star, project in zenith position and the tangent plane of celestial sphere with reference to the equatorial coordinate of star, obtain the ideal coordinates of reference star in section.

(4) star pattern matching

Before the function transformation model of setting up between star image ccd image measured coordinate and reference star ideal coordinates, need to carry out importance in star map recognition, determine reference star corresponding with star image in ccd image in star catalogue.There is similar geometric properties according to star image distribution in ccd image to the distribution of reference star in star catalogue and carry out importance in star map recognition.

First utilize quadrilateral star Pattern Recognition Algorithm to match four bright stars.Calculate the initial conversion model between ccd image measured coordinate system and ideal coordinates system.Complete the coupling of all stars according to star image coordinate in the Coordinate Transformation Models of gained, ccd image and reference star ideal coordinates.Utilization completes the ccd image measured coordinate of all stars of coupling and the ideal coordinates of reference star, recalculates Coordinate Transformation Models.For ensureing the precision of Coordinate Transformation Models, the star that deleted residual is larger, recalculates Coordinate Transformation Models.

(5) astronomic coordinates of zenith point is calculated

First, suppose that the picture point of zenith point on ccd image is positioned at ccd image center, its image metric coordinate is (0,0).Utilize formula to calculate respectively ideal coordinates corresponding to ccd image center and equatorial coordinate.

$\left\{\begin{array}{c}X=a_1+b_{1}x+c_{1}y\\ Y=a_2+b_{2}x+c_{2}y\end{array}\right.$

$\left\{\begin{array}{c}\mathrm{\α}={\mathrm{\α}}_0+{\tan }^{-1}\frac{X}{\cos {\mathrm{\δ}}_0-Y\sin {\mathrm{\δ}}_0}\\ \mathrm{\δ}=\frac{{\tan }^{-1}(Y+{\tan \mathrm{\δ}}_0)\cos (\mathrm{\α}-{\mathrm{\α}}_0)}{1-Y{\tan \mathrm{\δ}}_0}\end{array}\right.$

(X, Y) is ideal coordinates; (x, y) is ccd image measured coordinate; (a ₁, b ₁, c ₁, a ₂, b ₂, c ₂) be the Coordinate Transformation Models parameter of importance in star map recognition gained; (α ₀, δ ₀) be the initial equatorial coordinate of zenith point; (α, δ) is for calculating gained zenith point equatorial coordinate.Apparent sidereal time calculate astronomical longitude and latitude corresponding to ccd image center in conjunction with Greenwich, be designated as (Φ ₁, Λ ₁), (Φ ₂, Λ ₂).According to the rotational symmetry of two width ccd images, can obtain the astronomical longitude and latitude of observation station by getting the average of astronomical longitude and latitude corresponding to two width picture centres.

(3) in, replace the true equatorial coordinate of zenith point with the approximate equatorial coordinate of zenith point, for the impact that reduces to bring because of point of contact site error, by the astronomic coordinates inverse of calculated zenith point to equatorial coordinate, recalculate the ideal coordinates of reference star and the ccd image measured coordinate system transformation model between with ideal coordinates being as point of contact, the astronomic coordinates of iterative computation zenith point, until the difference of the astronomical longitude and latitude calculating for double time is less than a certain set-point (0.0001 ").

(6) telescope inclination correction

Telescope is not in strict horizontality in observation process, but has small inclination, telescope optic axis is pointed to and depart from zenith point.The accurate coordinates that therefore, obtain zenith point must carry out inclination correction.The heeling condition of telescope in observation process is by high-precision two-dimensional inclinator Accurate Measurement, and its measuring accuracy is 0.04 " 0.05 ".Inclination correction step is as follows:

According to the tilt meter data computing equipment tilting value in twice observation moment;

$\left\{\begin{array}{c}{n}_1=\frac{n_1^I-n_1^{\mathrm{II}}}{2}\\ n_2=\frac{n_2^I-n_2^{\mathrm{II}}}{2}\end{array}\right.$

it is the inclinator reading in two width ccd image observation moment; (n ₁, n ₂) be instrument tilting value.

Tilting value is projected to meridian and fourth of the twelve Earthly Branches direction at the tenth of the twelve Earthly Branches;

$\left\{\begin{array}{c}\mathrm{\Δ\Φ}=\cos (A+B)n_1-\sin (A+B)n_2\\ \mathrm{\Δ\Λ}=\sin (A+B)n_1+\cos (A+B)n_2/\cos \mathrm{\Φ}\end{array}\right.$

ΔΦ, Δ Λ is meridian direction and fourth of the twelve Earthly Branches direction at tenth of the twelve Earthly Branches inclination correction value; A is the position angle (angle of ccd image measured coordinate axle and thing or North and South direction) of ccd image; B is the angle of inclinator axle and ccd image measured coordinate axle; Φ is the astronomical latitude that does not add inclination correction.

Astronomical longitude and latitude is carried out to inclination correction;

$\left\{\begin{array}{c}{\mathrm{\Φ}}^{\′}=\mathrm{\Φ}+\mathrm{\Δ\Φ}\\ {\mathrm{\Λ}}^{\′}=\mathrm{\Λ}+\mathrm{\Δ\Λ}\end{array}\right.$

(Φ ', Λ ') be the astronomical longitude and latitude after inclination correction; (Φ, Λ) astronomical longitude and latitude for not carrying out inclination correction.

According to the method for this invention, utilize the CCD zenith telescope of succeeding in developing, when without foundation pier flow measurement, (about 30s) astronomical fixation precision is about 0.2 fast ".

Claims (9)

1. use CCD zenith telescope to carry out a method for the quick astronomical fixation in ground, comprise the following steps:

By CCD zenith telescope horizontalization;

Electric-control system reads high precision dipmeter survey data, and transfers to computing machine;

CCD zenith telescope carries out imaging for the first time near day district observation station zenith;

Telescope electric-control system reads pps pulse per second signal and the precise time information that atomic clock or radio time dissemination system provide, the trigger pip of exposing using this pulse per second (PPS) as CCD, CCD is with given exposure time exposure, and precise time is transferred to computing machine by electric-control system simultaneously, and imaging for the first time finishes;

Electric control system controls drive systems lens cone for telescope (comprising CCD camera) is around 180 ° of vertical axis revolvings;

Electric-control system reads high precision dipmeter survey data again, and transfers to computing machine;

CCD zenith telescope carries out imaging for the second time near day district observation station zenith;

Telescope electric-control system reads pps pulse per second signal and the precise time information that atomic clock or radio time dissemination system provide, the trigger pip of exposing using this pulse per second (PPS) as CCD, CCD is with given exposure time exposure, and precise time is transferred to computing machine by electric-control system simultaneously, and imaging for the second time finishes;

The ccd image that data handling system is obtained twice imaging and separately precise time and the tilt meter data of imaging moment record are carried out data processing, obtain the astronomical longitude and latitude of observation station.

2. the method that use CCD zenith telescope as claimed in claim 1 carries out the quick astronomical fixation in ground, wherein comprises CCD zenith telescope horizontalization:

CCD zenith telescope is placed in to observation station, and horizontalization system is carried out accurate horizontalization according to high precision tilt meter data to telescope, makes telescopical horizontality in given scope.

3. the method that use as claimed in claim 1 CCD zenith telescope carries out the quick astronomical fixation in ground, wherein data processing comprise that star image is extracted and star image centroid calculation, star apparent place and Greenwich apparent sidereal time calculate, the calculating of reference star ideal coordinates, importance in star map recognition, zenith point position calculation and telescope inclination correction.

4. the method that use CCD zenith telescope as claimed in claim 3 carries out the quick astronomical fixation in ground, wherein star image extraction and star image centroid calculation comprise the following steps:

In entire image, search for brightness value and be greater than the pixel of a certain threshold value;

The gray-scale value of above-mentioned pixel is done to weighted mean and obtain star image centroid position.

5. the method that use CCD zenith telescope as claimed in claim 3 carries out the quick astronomical fixation in ground, wherein star apparent place and Greenwich apparent sidereal time calculate and comprise the following steps:

According to precise time and the catalogue data in observation moment, the fixed star mean place providing in this star catalogue is converted to apparent place epoch of observation;

Calculate Greenwich apparent sidereal time according to the precise time in observation moment.

6. the method that use CCD zenith telescope as claimed in claim 3 carries out the quick astronomical fixation in ground, reference star ideal coordinates calculation procedure is as follows:

Project in zenith position and the tangent plane of celestial sphere with reference to the equatorial coordinate of star, obtain the ideal coordinates of reference star in section.

7. the method that use CCD zenith telescope as claimed in claim 3 carries out the quick astronomical fixation in ground, wherein importance in star map recognition comprises the following steps:

Utilize quadrilateral star Pattern Recognition Algorithm to match four bright stars;

Calculate the initial conversion model between ccd image measured coordinate system and ideal coordinates system;

Complete the coupling of all stars according to star image coordinate in the Coordinate Transformation Models of gained, ccd image and reference star ideal coordinates;

Utilization completes the ccd image measured coordinate of all stars of coupling and the ideal coordinates of reference star, recalculates Coordinate Transformation Models;

For ensureing the precision of Coordinate Transformation Models, the star that deleted residual is larger, recalculates Coordinate Transformation Models.

8. the method that use CCD zenith telescope as claimed in claim 3 carries out the quick astronomical fixation in ground, wherein zenith point position calculation comprises the following steps:

Suppose that the picture point of zenith point on ccd image is positioned at ccd image center, its image metric coordinate is (0,0);

Utilize following formula to calculate respectively ideal coordinates corresponding to ccd image center and equatorial coordinate;

$\left\{\begin{array}{c}X=a_1+b_{1}x+c_{1}y\\ Y=a_2+b_{2}x+c_{2}y\end{array}\right.$

$\left\{\begin{array}{c}\mathrm{\α}={\mathrm{\α}}_0+{\tan }^{-1}\frac{X}{\cos {\mathrm{\δ}}_0-Y\sin {\mathrm{\δ}}_0}\\ \mathrm{\δ}=\frac{{\tan }^{-1}(Y+{\tan \mathrm{\δ}}_0)\cos (\mathrm{\α}-{\mathrm{\α}}_0)}{1-Y{\tan \mathrm{\δ}}_0}\end{array}\right.$

Wherein (X, Y) is ideal coordinates; (x, y) is ccd image measured coordinate; (a ₁, b ₁, c ₁, a ₂, b ₂, c ₂) be the Coordinate Transformation Models parameter of importance in star map recognition gained; (α ₀, δ ₀) be the initial equatorial coordinate of zenith point; (α, δ) is for calculating gained zenith point equatorial coordinate;

Apparent sidereal time calculate astronomical longitude and latitude corresponding to ccd image center in conjunction with Greenwich;

According to the rotational symmetry of two width ccd images, obtain the astronomical longitude and latitude of observation station by getting the average of astronomical longitude and latitude corresponding to two width picture centres.

9. the method that use CCD zenith telescope as claimed in claim 3 carries out the quick astronomical fixation in ground, wherein telescope inclination correction comprises:

According to the tilt meter data computing equipment tilting value in twice observation moment;

$\left\{\begin{array}{c}{n}_1=\frac{n_1^I-n_1^{\mathrm{II}}}{2}\\ n_2=\frac{n_2^I-n_2^{\mathrm{II}}}{2}\end{array}\right.$

it is the inclinator reading in two width ccd image observation moment; (n ₁, n ₂) be instrument tilting value.

Tilting value is projected to meridian and fourth of the twelve Earthly Branches direction at the tenth of the twelve Earthly Branches;

$\left\{\begin{array}{c}\mathrm{\Δ\Φ}=\cos (A+B)n_1-\sin (A+B)n_2\\ \mathrm{\Δ\Λ}=\sin (A+B)n_1+\cos (A+B)n_2/\cos \mathrm{\Φ}\end{array}\right.$

Wherein ΔΦ, Δ Λ is meridian direction and fourth of the twelve Earthly Branches direction at tenth of the twelve Earthly Branches inclination correction value; A is the position angle of ccd image; B is the angle of inclinator axle and ccd image measured coordinate axle; For not adding the astronomical latitude of inclination correction;

Astronomical longitude and latitude is carried out to inclination correction;

$\left\{\begin{array}{c}{\mathrm{\Φ}}^{\′}=\mathrm{\Φ}+\mathrm{\Δ\Φ}\\ {\mathrm{\Λ}}^{\′}=\mathrm{\Λ}+\mathrm{\Δ\Λ}\end{array}\right.$

Wherein (Φ ', Λ ') be the astronomical longitude and latitude after inclination correction; (Φ, Λ) astronomical longitude and latitude for not carrying out inclination correction.

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