CN106404002A - In-orbit calibration method for high precision imaging moment - Google Patents

Abstract

The invention provides an in-orbit calibration method for high precision imaging moment. The method comprises the following steps: step 1, acquiring the imaging moment sent from the ground on satellite; step 2, based on the acquired imaging moment, using the forecast satellite information from GPS receiver to acquire the satellite position and speed of the moment; step 3, based on the position and speed coordinated with the position of the imaging target point, calculating the calibrating the time deviation; step 4, calculating to obtain the calibrated imaging moment; step 5, judging whether the time deviation calibration meets the precision requirement. If not met, selecting the time acquired in step 4 to be the imaging moment, repeating the procedure from step 2 to step 5; if the requirement is met, the calibration calculation of imaging moment is completed, using the calibrated imaging moment to start the imaging device. The method has the advantages of low calculation burden and easy management for the satellite-borne computer. The method can be used for the determination of the high precision imaging moment during the normal working period of satellites, and provides a high precision time benchmark for the imaging.

Description

A kind of in-orbit bearing calibration of high accuracy imaging moment

Technical field

The invention belongs to satellite high-precision technical field of imaging is and in particular to a kind of in-orbit correction side of high accuracy imaging moment Method.

Background technology

The imaging precision of satellite requires more and more higher now, and the factor of every impact imaging precision is required for carrying out accordingly Optimize and make error minimize.The factor that one of which affects imaging precision is exactly the accurate determination of imaging moment.

According to the floor planning of satellite task, will upload the geographical longitude and latitude of many everyday interior imageable target points with corresponding Imaging start moment t_k.Due to ground rail recursion error, imageable target point corresponding imaging optimal boot time there may be Certain error, needs on star, the start moment to be corrected, to expect to obtain optimal observation effect.Current shortage can By optimizing the method that correction measure is calculated high accuracy imaging moment, the precision of existing method in terms of software design from the star Not high or algorithm is complicated, is unfavorable for the realization of spaceborne computer.

Content of the invention

In order to in-orbit high precision computation obtains the optimal imaging moment, to expect to obtain optimal observation effect, present invention profit With the data of the in-orbit kinetic characteristic of satellite and GPS, based on the algorithm setting, provide a kind of high accuracy imaging moment in-orbit correction Method.

In order to achieve the above object, technical program of the present invention lies in providing a kind of high accuracy imaging moment in-orbit correction side Method, comprises the steps：

Step 1, obtains by the imaging moment point of note on ground on star；

Step 2, according to the imaging moment point obtaining, using the satellite information of GPS forecast, obtains this moment satellite Position and speed；

Step 3, according to the imageable target point position of note on position and speed combined ground, calculates correction time deviation；

Step 4, is calculated revised imaging moment；

Step 5, judges whether correction time deviation meets required precision, if being unsatisfactory for, using the time of step 4 as one-tenth As moment point, repeat step 2～step 5；If meeting, imaging moment correction calculating terminates, with the start of revised imaging moment Imaging.

The in-orbit bearing calibration of high accuracy imaging moment of the present invention, is carried out using GPS parameter on star due to taking It is corrected into the computational methods as time deviation, solve ground long-range mission planning and there is the corresponding imaging of imageable target point most preferably Available machine time there may be the problem of certain error, solves on star if independently calculating possible needs very macrooperation amount for a long time Problem, the method calculates simply, is suitable for independently realizing on star, the precision of correction can reach ms level, achieves using correction The start moment is applied to the start imaging of high accuracy satellite and points to benchmark beneficial effect.

Brief description

Fig. 1 is the schematic flow sheet of the in-orbit bearing calibration of high accuracy imaging moment of the present invention.

Specific embodiment

Hereinafter first introduce the relative theory of the specific embodiment of the invention：

Doppler centroid f_DIt is defined as

In formula：λ_SARFor load operation wavelength；Velocity for satellite relative target point；R is satellite relative target point Position vector；R is the distance of satellite relative target point.

Wherein,

R=R_s-R_t(2)

In formula：R_sFor satellite relative to the earth's core position vector；R_tFor impact point relative to the earth's core vector.

After satellite in orbit carries out two dimension guiding, the Doppler frequency that center of antenna points to imaging point relatively in theory is zero, I.e. optimal imaging point is relative position and the speed Relative vertical of satellite and impact point.Therefore, the purpose of imaging moment correction It is to revise the imaging moment point of floor planning, finally make imaging momentOrthogonal with R, that is,

Due to many days inner orbit recursion errors less, the start moment after predetermined start moment and correction is more or less the same, little In 1s, in the range of this time, velocity vector can be considered as constant value.Under ground is admittedly, in Δ t near the design start moment Satellite position can be expressed as

R_s=R₀+V₀Δt (4)

In formula, R₀And V₀It is respectively and upload satellite position and the velocity vector that the corresponding moment GPS that starts shooting provides.R_tBy upper The position vector that changes into of impact point longitude and latitude passing is representing.The lower target spot speed of the solid system in ground is 0, thenRight for uploading start Answer the satellite velocity vector that moment GPS provides, i.e. V₀.

These variables are substituted into formula (3), obtains

V₀·(R₀+V₀·Δt-R_t)=0 (5)

Then correction time be

Wherein, R₀、V₀There is provided by corresponding to the gps data uploading imaging moment point；R_tBy being turned by target geographic longitude and latitude The ground of chemical conversion be admittedly under position vector representing.

Imaging moment t after correction₁=t₀+Δt.

Due to employing the approximate of speed in above-mentioned correcting mode, once revise and certainly there is certain deviation, to Seek higher time complexity curve precision it is necessary to carry out successive ignition correction.

Find out from above-mentioned computational methods, application the method calculates the operand very little that the moment is revised in high accuracy imaging, spaceborne Computer is easily achieved.

As shown in figure 1, the in-orbit bearing calibration of high accuracy imaging moment of the present invention, comprise the steps：

Step 1, obtains by the imaging moment point t of note on ground on star_k, this moment point t_kDuring for needing the imaging revised Punctum；

Step 2, according to the imaging moment point t obtaining_kWith the satellite information of GPS forecast, obtain this t_kMoment satellite Position and speed R_k、V_k.

Step 3, according to t_kThe position in moment and speed R_k、V_kThe imageable target point position R of note on combined ground_t, calculate school The positive time

Step 4, is calculated imaging moment point t after correction_k=t_k+Δt_k；

Step 5, judges Δ t_kWhether meet required precision.If time precision is unsatisfactory for requiring, step 4 is calculated Time (t_kValue) as the imaging moment point needing correction, return to step 2 again execution step 2～step 5, carry out next Secondary iterated revision calculates；Otherwise imaging moment correction calculating terminate, with the end of step 4 calculated time (t_kValue) conduct Revised high accuracy imaging moment point, start imaging at this moment on star.

In sum, the method for the present invention calculates simple and flexible, can be applicable to satellite normal work period high-precision one-tenth As the moment determines, provide high-precision time reference for imaging.

Although present disclosure has been made to be discussed in detail by above preferred embodiment, but it should be appreciated that above-mentioned Description is not considered as limitation of the present invention.After those skilled in the art have read the above, for the present invention's Multiple modifications and substitutions all will be apparent from.Therefore, protection scope of the present invention should be limited to the appended claims.

Claims (1)

1. a kind of in-orbit bearing calibration of high accuracy imaging moment is it is characterised in that comprise the steps：

Step 1, obtains by the imaging moment point t of note on ground on star_k, as the imaging moment point needing correction；

Step 2, according to the imaging moment point t obtaining_kWith the satellite information of GPS forecast, respectively obtain t_kMoment satellite Position R_kWith speed V_k；

Step 3, the imageable target point position R of note on combined ground_t, calculate correction time：

${\mathrm{\Δt}}_k=\frac{V_k\·(R_t-R_k)}{V_k\·V_k}$

Step 4, calculates t_k=t_k+Δt_kAs revised imaging moment point；

Step 5, judges Δ t_kWhether meet time precision requirement；If meet requiring, imaging moment correction calculating terminates, to tie Step 4 calculated t during bundle_kValue boots up imaging as revised imaging moment point；

If being unsatisfactory for requiring, enter next iteration corrected Calculation：By calculated for step 4 t_kValue is revised as needs Imaging moment point, the step 2 substituting into next iteration corrected Calculation, and execution step 2～step 5 again.