CN102243311B - Pulsar selection method used for X-ray pulsar navigation - Google Patents

Abstract

A pulsar selection method used for X-ray pulsar navigation is disclosed, which comprises the steps of: (1) removing pulsars capable of flickering; (2) eliminating the unusable pulsars by predicting the usability of pulsars according to a flight mission orbit of a spacecraft; (3) calculating the TOA (Time Of Arrival) estimated accuracy of the usable X-ray pulsars in a pulsar catalog database; (4) in combination with the flight mission orbit and season of the spacecraft, calculating the influence of a pulsar catalog position error of the usable pulsars in the pulsar catalog database on pulsar signal measurement precision; (5) calculating the comprehensive influence of the TOA estimated accuracy and the pulsar catalog position error on pulsar signal measurement; and (6) calculating the optimal navigation X-ray pulsar combination according to a navigation location error matrix of the X-ray pulsars to cause the navigation location error matrix to be the smallest, wherein the X-ray pulsars of the optimal combination can be used for navigation. The method disclosed by the invention is easy to popularize and use, and has the advantages of simple principle, strong operability, the capacity of increasing navigation stability and reliability, etc.

Description

The satellite selection method that a kind of X ray pulsar navigation uses

Technical field

The present invention is mainly concerned with the air navigation aid field, refers in particular to a kind of satellite selection method for the X ray pulsar navigation, and the high accuracy X-ray pulsar navigation that is applicable to different aerial missions uses.

Background technology

The X ray pulsar navigation is a kind of perspective navigate mode, its navigation ultimate principle be in solar system barycenter inertial system relatively the pulse of forecast arrive pulse that true origin time and spacecraft measure arrives initial point through extrapolation time, the difference of the two has reflected actual position and has estimated the deviation of position on the pulsar direction, utilize the measurement result of a plurality of different pulsars, adopt the Navigation algorithm just can realize simultaneously the navigation calculating of spacecraft in conjunction with the spacecraft dynamics equation.

X ray pulsar navigation principle and GPS navigation are similar.For improving navigation accuracy, GPS needs to consider the GDOP problem in navigation, namely select suitable nautical star.For the X ray pulsar navigation, different pulsars has different waveform signal features and star catalogue positional accuracy measurement, and pulsar signal waveform character paired pulses time of arrival (TOA) estimated accuracy has a direct impact.The star catalogue site error is relevant in the position of solar system geocentric coordinate system with spacecraft on the impact of navigation accuracy.Therefore pulsar navigation is different from again GPS navigation, need to consider the various influence factors such as TOA estimated accuracy and star catalogue azimuthal error, there is no at present to be applicable to the satellite selection method that the high accuracy X-ray pulsar navigation uses.

Summary of the invention

The technical problem to be solved in the present invention is: for the technical matters that prior art exists, the invention provides the satellite selection method that a kind of principle X ray pulsar navigation simple, workable, that easily promote and use, can improve navigation stability and reliability uses.

For solving the problems of the technologies described above, the present invention by the following technical solutions:

The satellite selection method that a kind of X ray pulsar navigation uses is characterized in that step is:

(1) based on the astronomical sight data, removes the pulsar that flickering can occur;

(2) according to the availability of the aerial mission orbit prediction pulsar of spacecraft, remove out of use pulsar;

(3) calculate the TOA estimated accuracy of available X ray pulsar in the catalogue data storehouse by following formula:

${\mathrm{\σ}}_{\mathrm{TOA}}=\frac{\sqrt{\frac{1}{4}{T}_{50}^2+T_b^2}}{\sqrt{A\·\mathrm{\Δt}}}\·\frac{\sqrt{{\mathrm{\λ}}_n+{\mathrm{\λ}}_p}}{{\mathrm{\λ}}_p}$

Wherein, T ₅₀It is the half flux density duration of X ray pulse signal; T _bIt is the detector temporal resolution; λ _pAnd λ _nBe respectively the average discharge density of pulse signal and ground unrest, A is detector aperture, and Δ t is the observation duration;

(4) in conjunction with aerial mission track and season of spacecraft, calculate the impact of the star catalogue site error pulse signals measuring accuracy of available pulsar in the catalogue data storehouse; Star catalogue site error pulse signals measuring accuracy affect Normal Distribution, its mean square deviation is:

$\left\{\begin{array}{c}{\mathrm{\σ}}_{\mathrm{PE}}=\sqrt{A^2+B^2}\\ A=[-(X_B+x)\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}+(Y_B+y)\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}]{\mathrm{\σ}}_a\\ B=[(X_B+x)\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}+(Y_B+y)\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}-(Z_B+z)\cos \widetilde{\mathrm{\δ}}]{\mathrm{\σ}}_{\mathrm{\δ}}\end{array}\right.$

Wherein, it is zero normal distribution that right ascension and declination error are obeyed average, and their mean square deviation is respectively σ _α, σ _δX _B, Y _BAnd Z _BBe the location components of center gravitation celestial body in solar system geocentric coordinate system of spacecraft, obtain by accurate astronomical ephemeris computation; X, y and z are respectively spacecrafts with respect to the position of the center gravitation celestial body component on three change in coordinate axis direction in solar system geocentric coordinate system;

X ray pulsar right ascension,

It is X ray pulsar declination;

(5) combined influence of calculating TOA estimated accuracy and star catalogue site error paired pulses star signal measurement, the measurement mean square deviation of X ray pulsar navigation signal is:

${\mathrm{\σ}}_M=\sqrt{C^2{\·\mathrm{\σ}}_{\mathrm{TOA}}^2+{\mathrm{\σ}}_{\mathrm{PE}}^2}$

Wherein C is the light velocity;

(6) calculate the combination of optimum navigation X ray pulsar, X ray pulsar number for choice for use, navigation positioning error matrix in the calculating catalogue data storehouse under all permutation and combination of available X ray pulsar, the X ray pulsar combination that minimum positioning error matrix is corresponding is optimum X ray pulsar combination, uses as the navigation pulsar.

As a further improvement on the present invention:

The navigation positioning error matrix is in the described step (6):

Wherein, H is the observing matrix of X ray pulsar navigation system; σ _{M, i}The measurement mean square deviation of i pulsar in the expression catalogue data storehouse, σ _{M, j}The measurement mean square deviation of j pulsar in the expression catalogue data storehouse, σ _{M, k}The measurement mean square deviation of k pulsar in the expression catalogue data storehouse.

Compared with prior art, the invention has the advantages that: the satellite selection method that X ray pulsar navigation of the present invention uses, principle is simple, workable, easily promote and use, by considering the aspect factors such as star catalogue site error, spacecraft position, the degree of stability of signal period, signal characteristic, TOA estimated accuracy and detector performance to X ray pulsar navigation Accuracy, guaranteed the bearing accuracy of X ray pulsar navigation under each season, the reliability and stability of pulsar navigation have greatly been improved, for its popularization provides condition.

Description of drawings

Fig. 1 is the schematic flow sheet of the concrete Application Example of the present invention;

Fig. 2 be in the concrete application implementation of the present invention celestial body to the availability impact synoptic diagram of X ray pulsar.

Embodiment

Below with reference to the drawings and specific embodiments the present invention is described in further detail.

In concrete application example, the spacecraft that adopts is a kind of lunar orbiter.

As shown in Figure 1, the concrete steps of satellite selection method of the present invention are as follows:

1, based on the astronomical sight data, removes the pulsar that glitches occurs.

The X ray pulsar is the neutron star of high speed rotation, and its rotation period is very stable, and long-time stability are extremely stable galaxy beacons with now the same good as the cesium-beam atomic clock of time standard.But some pulsars self rotary speed has irregular variation, be called " flickering " (glitches), if flickering is larger, then being unsuitable for navigation uses, therefore at first need to based on the stability of astronomical sight data forecast pulsar signal, remove the X ray pulsar that glitches may occur in the spacecraft run duration Guide star database.

For example, there are a large amount of X ray observations of pulsar data in astronomical observatory and regularly publish result, can by in official website of the astronomical observatory enquiry navigation X ray pulsar database or the X ray pulsar of glitches may occur in a short time, removing these pulsars need not.

2, usability analyses.

Although the X ray pulsar is very remote apart from the solar system, when spacecraft enters in the shadow region of certain celestial body, namely anyly can stop all that through the celestial body between spacecraft and the X ray pulsar spacecraft detection device is to the observability of X ray pulsar.In addition, because X ray pulsar ray flow is lower, and the relative X ray pulsar of X-radiation of other celestial bodies such as fixed star and Jupiter is very high, so X-ray detector should be avoided pointing to these celestial bodies in order to avoid detector is saturated.So, will be according to the availability of the aerial mission orbit prediction pulsar of spacecraft, namely consider the impact that the celestial bodies such as celestial body blocks, the sun/Jupiter cause the aspects such as detector is saturated, according to the availability of the aerial mission orbit prediction pulsar of spacecraft, remove out of use pulsar.

As shown in Figure 2, in the time of in lunar orbiter enters moon shadow region, a month club stops that X-ray detector receives the X ray pulsar signal.Angle [alpha] is spacecraft with respect to the angle between the direction n of the position vector r of the moon and X ray pulsar among the figure, and a month radius of a ball is R, works as α ₁＜α＜α ₂The time, spacecraft is arranged in the shade of the moon, and this moment, this pulsar was unavailable, and spacecraft is positioned at when blocking the celestial body shaded side and will satisfies:

$\mathrm{\π}-\arccos \left(\frac{\sqrt{{\left|r\right|}^2-R^2}}{\left|r\right|}\right)\≤\arccos (n\·r)\≤\mathrm{\π}+\arccos \left(\frac{\sqrt{{\left|r\right|}^2-R^2}}{\left|r\right|}\right)---\left(1\right)$

In addition, because X ray pulsar ray flow is lower, and the sun is very high with the relative X ray pulsar of X-radiation of other celestial bodies such as Jupiter, will be saturated when X-ray detector points to these celestial bodies, can't effectively measure the X ray pulsar signal, therefore also to analyze other celestial body to the availability of X ray pulsar according to formula (1), guarantee that X-ray detector can successfully measure pulsar signal.

3, calculate the TOA estimated accuracy of available X ray pulsar in the catalogue data storehouse.

Detector measurement to the photon arrival event be to obey Poisson distribution, equal the character of variance according to the Poisson distribution average, can calculate with following model the estimated accuracy of TOA:

${\mathrm{\σ}}_1=\frac{{\mathrm{HWHM}}^{*}}{S/\sqrt{S+B}}---\left(2\right)$

${\mathrm{HWHM}}^{*}=\sqrt{{\mathrm{HWHM}}^2+T_b^2}---\left(3\right)$

Wherein, HWHM is pulse signal half flux density duration T ₅₀Half; S is the photon number from pulsar that detects during the observation; B is the photon number of the ground unrest that detects; T _bIt is the detector temporal resolution.

S=Aλ _pΔt （4）

B＝Aλ _nΔt （5）

Wherein, λ _pAnd λ _nBe respectively the average discharge density of pulse signal and ground unrest, A is detector aperture, and Δ t is the observation duration.

With (3) to (5) formula substitutions (2) formula, then have the TOA estimated accuracy of X ray pulsar to be:

${\mathrm{\σ}}_1=\frac{\sqrt{\frac{1}{4}{T}_{50}^2+T_b^2}}{\sqrt{A\·\mathrm{\Δt}}}\·\frac{\sqrt{{\mathrm{\λ}}_n+{\mathrm{\λ}}_p}}{{\mathrm{\λ}}_p}---\left(6\right)$

Wherein, T ₅₀It is the half flux density duration of X ray pulse signal; T _bIt is the detector temporal resolution; λ _pAnd λ _nBe respectively the average discharge density of pulse signal and ground unrest, A is detector aperture, and Δ t is the observation duration.

4, based on aerial mission track and season of spacecraft, calculate the impact of the star catalogue site error pulse signals measuring accuracy of available pulsar in the catalogue data storehouse.

The right ascension of pulsar is α, and declination is δ, and then the unit vector of pulsar direction is in inertial system:

$n=\left[\begin{array}{c}\cos \mathrm{\δ}\cos \mathrm{\α}\\ \cos \mathrm{\δ}\sin \mathrm{\α}\\ \sin \mathrm{\δ}\end{array}\right]---\left(7\right)$

The position of X ray pulsar is in the star catalogue

Its error is (Δ α, Δ δ), has

$\left\{\begin{array}{c}\mathrm{\α}=\widetilde{\mathrm{\α}}+\mathrm{\Δ\α}\\ \mathrm{\β}=\widetilde{\mathrm{\β}}+\mathrm{\Δ\β}\end{array}\right.---\left(8\right)$

With (8) formula substitution (7) formula, can get

$n=\left[\begin{array}{c}\cos (\widetilde{\mathrm{\δ}}+\mathrm{\Δ\δ})\cos (\widetilde{\mathrm{\α}}+\mathrm{\Δ\α})\\ \cos (\widetilde{\mathrm{\δ}}+\mathrm{\Δ\δ})\sin (\widetilde{\mathrm{\α}}+\mathrm{\Δ\α})\\ \sin (\widetilde{\mathrm{\δ}}+\mathrm{\Δ\δ})\end{array}\right]---\left(9\right)$

Following formula is carried out Taylor expansion, be taken to the single order item, have

$n=\left[\begin{array}{c}\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}-\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α}-\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\δ}+\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α\Δ\δ}\\ \cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}+\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α}\\ -\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\δ}-\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α\Δ\δ}\\ \sin \widetilde{\mathrm{\δ}}+\cos \widetilde{\mathrm{\δ}}\·\mathrm{\Δ\δ}\end{array}\right]---\left(10\right)$

Ignore the second order event, can get

$n=\left[\begin{array}{c}\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\\ \cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\\ \sin \widetilde{\mathrm{\δ}}\end{array}\right]+\left[\begin{array}{c}-\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α}-\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\δ}\\ \cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α}-\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\δ}\\ \cos \widetilde{\mathrm{\δ}}\·\mathrm{\Δ\δ}\end{array}\right]---\left(11\right)$

Note

$\mathrm{\Δn}=\left[\begin{array}{c}-\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α}-\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\δ}\\ \cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}\·\mathrm{\Δ\α}-\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}\·\mathrm{\Δ\δ}\\ \cos \widetilde{\mathrm{\δ}}\·\mathrm{\Δ\δ}\end{array}\right]---\left(12\right)$

Then (11) formula can be converted into

$n=\tilde{n}+\mathrm{\Δn}---\left(13\right)$

Arrive the impulse phase φ of satellite _kThe time that propagates into the SSB initial point is

${\tilde{t}}_{\mathrm{SSB}}=t_{\mathrm{sc}}+\frac{\tilde{n}\·(R_B+r)}{c}---\left(14\right)$

In the formula, t _ScBe the pulse arrival time of measuring on the satellite; C is the light velocity; R _B=[X _BY _BZ _B] ^TCentered by the gravitation celestial body with respect to the position vector of SSB coordinate system; R=[x y z] ^TThat spacecraft is with respect to the position vector of center gravitation celestial body.

By (13) Shi Kede With its substitution (14) formula, have

${\tilde{t}}_{\mathrm{SSB}}=t_{\mathrm{sc}}+\frac{n\·(R_B+r)}{c}-\frac{\mathrm{\Δn}\·(R_B+r)}{c}---\left(15\right)$

In order to carry out the precise time conversion, (15) formula need to be considered the impact of various factors, then arrives the pulse signal φ of satellite _kThe time that propagates into the SSB initial point is

${\tilde{t}}_{\mathrm{SSB}}=t_{\mathrm{sc}}+\frac{n\·(R_B+r)}{c}-\frac{\mathrm{\Δn}\·(R_B+r)}{c}+\mathrm{\δ}{t}_a+\mathrm{\δ}{t}_v+\mathrm{\δ}{t}_D+\mathrm{\δ}{t}_G---\left(16\right)$

Wherein, δ t _aIt is the annual parallax impact; δ t _vIt is the kinetic Doppler shift impact of pulsar; δ t _DIt is the dispersion time delay; δ t _GIt is the crooked and gravitation time delay of light path.

Because the impact of Δ n in rear four is a small amount of, its impact can be ignored, and then can obtain the pulsar site error by (16) formula on the impact of measuring equation to be

$\mathrm{\δt}=\frac{\mathrm{\Δn}\·r_{\mathrm{sc}}}{c}=[-(X_B+x)\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}+(Y_B+y)\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}]\mathrm{\Δ\α}...---\left(17\right)$

$-[(X_B+x)\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}+(Y_B+y)\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}-(Z_B+z)\cos \widetilde{\mathrm{\δ}}]\·\mathrm{\Δ\δ}$

Because right ascension and declination error are separate and obey average is zero normal distribution, their mean square deviation is (σ _α, σ _δ), then the star catalogue site error on the measurement mean square deviation of X ray pulsar navigation observation equation impact is:

$\left\{\begin{array}{c}{\mathrm{\σ}}_2=\sqrt{A^2+B^2}\\ A=[-(X_B+x)\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}+(Y_B+y)\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}]{\mathrm{\σ}}_{\mathrm{\α}}\\ B=[(X_B+x)\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}+(Y_B+y)\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}-(Z_B+z)\cos \widetilde{\mathrm{\δ}}]{\mathrm{\σ}}_{\mathrm{\δ}}\end{array}\right.---\left(18\right)$

Wherein, (σ _α, σ _δ) be the mean square deviation of X ray pulsar right ascension and declination measuring error; X _B, Y _BAnd Z _BBe the location components of center gravitation celestial body in solar system geocentric coordinate system of spacecraft, obtain by accurate astronomical ephemeris computation; X, y and z are respectively that spacecraft is with respect to the location components of central body.

5, calculate the combined influence of TOA estimated accuracy and star catalogue site error paired pulses star signal measurement.

Although the site error of X ray pulsar is fixed in a short time, can only provide the statistical information of position and variance by long-term observation.Because TOA estimated accuracy and star catalogue site error are separate on the impact of measuring equation, then the mean square deviation of TOA estimated accuracy and star catalogue site error paired pulses star signal measurement combined influence is

$\mathrm{\σ}=\sqrt{C^2\·{\mathrm{\σ}}_1^2+{\mathrm{\σ}}_2^2}---\left(19\right)$

Wherein C is the light velocity.

6, calculate the combination of optimum navigation X ray pulsar.

Requirement observation X ray pulsar number n according to aerial mission calculates the navigation positioning error matrix P under all permutation and combination of residue X ray pulsar in the catalogue data storehouse, and concrete model is:

Wherein, H is the observing matrix of X ray pulsar navigation system; The lower footnote of σ represents the X ray pulsar sequence number in the catalogue data storehouse, and σ is the measurement mean square deviation of X ray pulsar navigation signal herein.The X ray pulsar combination that minimum positioning error matrix is corresponding is optimum X ray pulsar combination, uses as the navigation pulsar.X ray pulsar number for choice for use, navigation positioning error matrix in the calculating catalogue data storehouse under all permutation and combination of available X ray pulsar, the X ray pulsar combination that minimum positioning error matrix is corresponding is optimum X ray pulsar combination, can be used as the navigation pulsar and uses.

The above only is preferred implementation of the present invention, and protection scope of the present invention also not only is confined to above-described embodiment, and all technical schemes that belongs under the thinking of the present invention all belong to protection scope of the present invention.Should propose, for those skilled in the art, in the improvements and modifications that do not break away under the principle of the invention prerequisite, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (2)

1. the satellite selection method that uses of an X ray pulsar navigation is characterized in that step is:

(1) based on the astronomical sight data, removes the pulsar that flickering can occur the spacecraft run duration;

(2) according to the availability of the aerial mission orbit prediction pulsar of spacecraft, remove out of use pulsar;

(3) calculate the TOA estimated accuracy of available X ray pulsar in the catalogue data storehouse by following formula:

${\mathrm{\σ}}_{\mathrm{TOA}}=\frac{\sqrt{\frac{1}{4}{T}_{50}^2+T_b^2}}{\sqrt{A\·\mathrm{\Δt}}}\·\frac{\sqrt{{\mathrm{\λ}}_n+{\mathrm{\λ}}_p}}{{\mathrm{\λ}}_p}$

Wherein, T ₅₀It is the half flux density duration of X ray pulse signal; T _bIt is the detector temporal resolution; λ _pAnd λ _nBe respectively the average discharge density of pulse signal and ground unrest, A is detector aperture, and Δ t is the observation duration;

(4) in conjunction with aerial mission track and season of spacecraft, calculate the impact of the star catalogue site error pulse signals measuring accuracy of available pulsar in the catalogue data storehouse; Star catalogue site error pulse signals measuring accuracy affect Normal Distribution, its mean square deviation is:

$\left\{\begin{array}{c}{\mathrm{\σ}}_{\mathrm{PE}}=\sqrt{A^2+B^2}\\ A=[-(X_B+x)\cos \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}+(Y_B+y)\cos \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}]{\mathrm{\σ}}_a\\ B=[(X_B+x)\sin \widetilde{\mathrm{\δ}}\cos \widetilde{\mathrm{\α}}+(Y_B+y)\sin \widetilde{\mathrm{\δ}}\sin \widetilde{\mathrm{\α}}-(Z_B+z)\cos \widetilde{\mathrm{\δ}}]{\mathrm{\σ}}_{\mathrm{\δ}}\end{array}\right.$

Wherein, it is zero normal distribution that right ascension and declination error are obeyed average, and their mean square deviation is respectively σ _α, σ _δX _B, Y _BAnd Z _BBe the location components of center gravitation celestial body in solar system geocentric coordinate system of spacecraft, obtain by accurate astronomical ephemeris computation; X, y and z are respectively spacecrafts with respect to the position of the center gravitation celestial body component on three change in coordinate axis direction in solar system geocentric coordinate system;

X ray pulsar right ascension,

It is X ray pulsar declination;

(5) combined influence of calculating TOA estimated accuracy and star catalogue site error paired pulses star signal measurement, the measurement mean square deviation of X ray pulsar navigation signal is:

${\mathrm{\σ}}_M=\sqrt{C^2{\·\mathrm{\σ}}_{\mathrm{TOA}}^2+{\mathrm{\σ}}_{\mathrm{PE}}^2}$

Wherein C is the light velocity;

(6) calculate the combination of optimum navigation X ray pulsar, X ray pulsar number for choice for use, navigation positioning error matrix in the calculating catalogue data storehouse under all permutation and combination of available X ray pulsar, the X ray pulsar combination that minimum positioning error matrix is corresponding is optimum X ray pulsar combination, uses as the navigation pulsar.

2. the satellite selection method that uses of X ray pulsar navigation according to claim 1, it is characterized in that: the navigation positioning error matrix is in the described step (6):

Wherein, H is the observing matrix of X ray pulsar navigation system; σ _{M, i}The measurement mean square deviation of i pulsar in the expression catalogue data storehouse, σ _{M, j}The measurement mean square deviation of j pulsar in the expression catalogue data storehouse, σ _{M, k}The measurement mean square deviation of k pulsar in the expression catalogue data storehouse.

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