CN115144891A - X-ray focusing type imaging telescope and millisecond pulsar weak signal observation method - Google Patents

Abstract

The invention discloses an X-ray focusing type imaging telescope and a millisecond pulsar weak signal observation method, which solve the problems of various non-pulse noise suppression and limited pulse arrival time measurement precision in the prior art. The high-angular resolution focusing X-ray optical system comprises a light shield, a focusing lens unit and an anti-pollution shielding cylinder which are sequentially connected, and the focusing lens unit is connected with the focal plane detector through the anti-pollution shielding cylinder. The focusing lens unit comprises a lens fixing device, a focusing lens, a lens barrel and an electronic deflector which are sequentially connected. The focusing lens is adhered in the lens fixing device of the scroll, and the lens fixing device is connected with the focusing lens cone.

Description

X-ray focusing type imaging telescope and millisecond pulsar weak signal observation method

The technical field is as follows:

the invention belongs to the technical field of X-ray detection, and relates to an X-ray focusing type imaging telescope and a millisecond pulsar weak signal observation method.

Background art:

the remote millisecond pulsar can construct a constellation similar to a navigation satellite to form a space-time reference service information system with a wider service range. The pulsar signal is free from human interference, high in safety and extremely good in natural navigation beacon of the deep space aircraft. The purpose of X-ray millisecond pulsar timing observation is as follows: 1) The independent and autonomous space-time reference service is provided, and the safe and autonomous global navigation service is realized. It should be noted that, although the accuracy of the current pulsar navigation timing in the near-earth space is not comparable to the accuracy of ground-based navigation or satellite navigation, the usability of the technique in the near-earth space is undoubted; 2) A redundant means of autonomous navigation is provided for a high-value satellite, autonomous navigation capability and on-orbit autonomous operation capability in a large-range long voyage are improved, and the capacity of control space in China is improved; 3) The autonomous navigation capability of the aircraft far away from the action distance of the ground measurement and control station can be enhanced, support is provided for future deep space detection such as solar system marginal detection in China, and the autonomous navigation method is the only autonomous navigation means for the current super-long distance space. With the urgent need for autonomous navigation and the rapid development of related technologies, pulsar navigation becomes a reality after all, thereby opening a brand-new deep space autonomous navigation era.

The X-ray telescope is used as a core device of a pulsar navigation system and is used for acquiring a basic observation quantity pulse TOA (Time of Arrival). The pulse TOA is obtained by folding an X-ray photon sequence according to the rotation parameters of a pulsar to obtain an observed pulse profile, and then comparing the observed pulse profile with a standard profile template. The accuracy of the pulse TOA is closely related to the accuracy of the time measurement of X-ray photons and the signal-to-noise ratio of signals, and the accuracy of pulsar navigation is also directly influenced.

The X-ray telescope mainly comprises a focusing optical system and a detector, wherein the focusing optical system is used for collecting X-ray photons, and the detector is used for performing photoelectric conversion and signal reading. The X-ray optical system has two types, namely a focusing type and an alignment type, because the X-ray radiation signal of the millisecond pulsar is weak and the space disperses the universe background noise, the focusing type optical system is more favorable for background suppression and improves the signal-to-noise ratio, and the alignment type optical system is usually used for strong source observation. According to the difference of grazing incidence reflection structures, focusing telescopes mainly have structures such as KB (Kirkpatrick-Baez), wolter (laser-based) and micropore optical arrays, and X-ray detectors are developed rapidly and are various in types, including gas detectors, microchannel plate type detectors, scintillator detectors and semiconductor detectors. Since Giacconi et al pioneered spatial X-ray astronomical observations in the six and seventies of the 20 th century, scientists developed many different types of X-ray telescopes that transmitted many spatial observation satellites, including HEAO-2 (1978), ROSAT (1990), XMM-Newton (1999), chandra (1999) NuSTAR (2012), and ASTRO-H (2016)

However, most of the existing X-ray telescopes are developed for astronomy research and are not established for pulsar deep space navigation, but the requirements of the latter on the performance of detection equipment are higher than those of common astronomy research. High-precision deep space navigation requires an X-ray telescope to record each X-ray photon rapidly and finely so as to obtain an observation signal with high signal-to-noise ratio. However, the radiation flux of the X-ray millisecond pulsar for deep space navigation is weak and is generally less than 1X 10 ^-3 cts/s/cm ² And the pulse signals are often submerged in various noises such as the radiation of the satellite cloud, the background of the spatial dispersion and the like. The X-ray telescope with the highest on-orbit capability is XTI (X-ray Timing Instrument) of NICER (Neutron star interference coordination Explorer), the number of pulse photons of two navigation pulsar PSR J1824-2452A and PSR J1939+2134 at 1-5.5keV is measured to be 0.055cts/s and 0.021cts/s, while the intensity of received background noise is 0.90cts/s and 0.49cts/s, which is more than 10 times of the pulse signal, and the data analysis shows that the background noise mainly originates from pulsar clouds and spatial dispersion background. Therefore, how to suppress various non-impulse noises is the key point for improving the measurement accuracy of the impulse TOA, and the latter directly influences the accuracy of the pulsar deep space navigation.

The invention content is as follows:

the invention aims to provide an X-ray focusing type imaging telescope and a millisecond pulsar weak signal observation method, which solve the problems of incomplete suppression of various non-pulse noises and unobvious improvement of pulse TOA measurement precision in the prior art.

In order to achieve the purpose, the invention adopts the technical scheme that:

an X-ray focusing type imaging telescope, characterized in that: the high-angular resolution focusing X-ray optical system comprises a light shield, a focusing lens unit and an anti-pollution shielding cylinder which are sequentially connected, wherein the focusing lens unit is connected with the focal plane detector through the anti-pollution shielding cylinder; the focusing lens unit comprises a lens fixing device, a focusing lens, a lens barrel and an electronic deflector which are sequentially connected; the focusing lens is adhered in the lens fixing device of the scroll, and the focusing lens cone is connected with the lens fixing device.

The X-ray focusing imaging telescope is designed to have a short focal length, and the focal length is 1000-1200 mm.

The focal plane detector is a domestic high-speed CCD, the CCD is composed of a plurality of pixel type CCDs, the side length of each pixel type CCD is not more than 100 micrometers, and the exposure time is not more than 10 microseconds.

The focusing lens is made of monocrystalline silicon materials and is made by a monocrystalline silicon slicing method.

The X-ray focusing imaging telescope adopts an X-ray telescope array.

A method for observing weak signals of a millisecond pulsar by adopting an X-ray focusing type imaging telescope is characterized by comprising the following steps of: the method comprises the following steps:

(1) Collection of X-ray photons: when X-ray photons enter the surface of a smooth high-Z-value material acting on a telescope focusing optical system lens at a grazing incidence angle smaller than 3 degrees, a grazing incidence type reflection phenomenon is generated, and the X-ray photons are collected on a focal plane and collected by a high-speed CCD (charge coupled device);

(2) Reading of X-ray photons: reading time energy information of X-ray photons by adopting a high-speed CCD (charge coupled device), wherein the high-speed CCD consists of a preamplifier, an analog circuit, a digital circuit and a power line, the preamplifier converts charges generated by the X-ray photons into current signals, and the charge quantity is in direct proportion to the energy of incident photons; converting the current pulse signal into a trigger signal through a comparator, marking the arrival time of the trigger by using a satellite-borne rubidium clock, and recording the trigger position of the X-ray photon by using a CCD (charge coupled device);

(3) Extracting pulsar signals: when the X-ray telescope observes the millisecond pulsar, the noise from pulsar cloud, high-energy charged particles, electromagnetic radiation and the like is received at the same time, the noise intensity brought by the pulsar cloud is far beyond a pulse signal, most of the noise brought by the pulsar cloud is filtered through image processing based on the acquired pulsar and pulsar cloud pictures, the range of the pulsar cloud is further determined by utilizing a star point boundary tracking detection and extraction algorithm by combining with pulsar prior information, and the pulsar cloud radiation is abandoned, so that most of the noise is filtered. A large amount of noise still exists in the detected pulsar image, and different time domain and frequency domain methods are adopted for processing aiming at different noise characteristics, so that the noise level is further reduced.

(4) Pulse profile and energy spectrum: and collecting and processing the collected X-ray photon arrival time series and energy information, and folding and reconstructing a pulsar pulse profile and an observation energy spectrum according to the pulsar ephemeris to provide observation information for pulsar deep space navigation.

Compared with the prior art, the invention has the following advantages and effects:

the millisecond pulsar is positioned at the core of the cloud of the historical trace of the supernew star, has the radius of about ten kilometers and is at least 1 optical year away from the earth, radiates signals with obvious periodic profile characteristics and can form a small imaging area on a telescope focal plane detector. By means of a Focusing Imaging Telescope (FIT) with high resolution, X-ray photons in a pulsar target area can be extracted from an image area, and the influence of pulsar clouds without periodic characteristics and other space backgrounds can be greatly reduced, so that detection sensitivity is improved. Meanwhile, for noise signals left in a pulsar image area, aiming at the characteristics of different noises, the influence of the noises is further reduced by utilizing a method of combining a time domain and a frequency domain, and finally, high-precision pulse TOA is provided for pulsar deep space navigation application.

Description of the drawings:

FIG. 1 is a schematic diagram of a single X-ray telescope;

FIG. 2 is an array diagram of an X-ray telescope for deep space reference detection according to the present invention;

FIG. 3 is a schematic diagram of the operation of the X-ray focusing imaging telescope;

FIG. 4 is an observation signal-to-noise ratio diagram of three X-ray telescopes under different pulse radiation flow rates;

FIG. 5 is a pulsar observation signal-to-noise ratio graph of three X-ray telescopes under different non-pulse radiation flow rates;

fig. 6 is a diagram of various signal simulations in the observation of the novel telescope on the millisecond pulsar.

In FIG. 1, 1-a light shield, 2-a focusing lens unit, 3-a lens fixture, 4-a focusing lens and lens barrel, 5-an electronic deflector, 6-a contamination-proof shielding barrel, and 7-a focal plane detector.

The specific implementation mode is as follows:

in order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The Focusing Imaging Telescope (FIT) is composed of:

the FIT is composed of a high-angular resolution focusing type X-ray optical system, a high-speed focal plane detector and the like, wherein the focusing type X-ray optical system comprises a lens hood, a focusing lens unit, an anti-pollution shield and other components, and the focusing lens unit comprises a lens fixing device, a focusing lens, a lens barrel and an electronic deflector. The focusing lens and the focal plane detector are connected through an anti-pollution shielding cylinder. Referring to fig. 1, the high-angular-resolution focusing type X-ray optical system comprises a high-angular-resolution focusing type X-ray optical system and a high-speed focal plane detector, wherein the high-angular-resolution focusing type X-ray optical system comprises a shading cover 1, a focusing mirror unit 2 and an anti-pollution shielding cylinder 6 which are sequentially connected, and the focusing mirror unit 2 is connected with the focal plane detector 7 through the anti-pollution shielding cylinder 6. The focusing lens unit 2 comprises a lens fixing device 3, a focusing lens and lens barrel 4 and an electronic deflector 5 which are connected in sequence. The focusing lens is adhered in the lens fixing device 3 of the scroll, and the focusing lens cone is connected with the lens fixing device 3.

The light shield 1 is used for restricting an observation field and shielding most of stray X-ray light.

The focusing lens is adhered in the fixing device of the scroll to ensure that the lens is not deformed by stress, and the focusing lens cone is connected with the lens fixing device 3 and used for protecting the lens. The focusing lens is primarily used to reflect X-ray photons within grazing incidence to the focal plane detector.

The electron deflector 5 is used for deflecting electrons from the universe, so that the electrons cannot reach the focal plane detector under the action of a magnetic field, and the universe background and irradiation dose are reduced.

The anti-pollution shielding cylinder 6 mainly isolates an X-ray photon reflection light path from a space environment, and particles in the space environment are prevented from entering the X-ray photon reflection light path.

The focal plane detector 7 is a high-speed CCD, and can realize the rapid forming and reading of X-ray photon signals and the acquisition of photon arrival time and energy information.

The optical system structure of FIT is of Wolter-I type or its approximate type having excellent focusing performance. The lens material adopts monocrystalline silicon, and compared with glass, the monocrystalline silicon has high thermal conductivity, low thermal expansion coefficient, larger Young elastic modulus, low density and no internal stress, and the monocrystalline silicon lens has better thermal stability, surface shape precision and higher surface-to-mass ratio due to the characteristics. In order to achieve a larger effective area, by taking The experience of SEXTANT (The Station expander for X-Ray Timing and Navigation) success as a reference, an X-Ray telescope array is also adopted, and aiming at The light weight requirement of deep space pulsar Navigation, a short focal length design is adopted, and The focal length is 1000-1200 mm. As shown in fig. 2.

The working process of the X-ray focusing type imaging telescope comprises the following steps:

referring to fig. 3, the working process of the x-ray focusing type imaging telescope includes the following steps:

(1) Collection of X-ray photons: the pulsar is very far from the earth, and the X-ray photons it radiates to reach the telescope can be considered as collimated light. When X-rays enter the smooth high-Z value material surface of the lens of the focusing optical system of the telescope at a glancing incidence angle of less than 3 degrees, glancing incidence type reflection phenomena can be generated, and the glancing incidence type reflection phenomena are collected on a focal plane and collected by a high-speed CCD.

(2) Reading of X-ray photons: the high-speed CCD is used for reading out the photon information of X-ray and consists of a preamplifier, an analog circuit, a digital circuit and a power line. The preamplifier converts the charge generated by the X-ray photons into a current signal, the amount of charge being proportional to the incident photon energy. The current pulse signal is converted into a trigger signal through a comparator, the arrival time of the trigger is marked by a satellite-borne rubidium clock, and the X-ray photon trigger position is recorded by a CCD.

(3) Extracting pulsar signals: when the X-ray telescope observes the millisecond pulsar, the noise from pulsar clouds, high-energy charged particles, electromagnetic radiation and the like is received at the same time, and the noise intensity brought by the pulsar clouds is far higher than that of a pulse signal, so that the noise source is one of main noise sources for pulsar observation. However, pulsar is much smaller than the area of the satellite cloud, based on the acquired pulsar and the image of the satellite cloud, most of noise caused by the pulsar satellite cloud can be filtered through image processing, then the range of the pulsar is further determined by combining the prior information of the pulsar and utilizing a star point boundary tracking detection extraction algorithm, and the radiation of the pulsar cloud is abandoned, so that most of noise is filtered. A large amount of noise still exists in the detected pulsar image, and different methods are required to be adopted for processing different noises, so that the noise level is further reduced.

(4) Pulse profile and energy spectrum: and collecting the arrival time series and energy information of the collected X-ray photons, and folding and reconstructing a pulsar pulse profile and an observation energy spectrum according to a pulsar ephemeris to provide observation information for pulsar deep space navigation.

In practice, when X-ray photons with an energy in the range of 0.5-5keV reach the focal plane detector CCD, they are received by the pixel CCD at the corresponding location and generate electron-hole pairs. A CCD is a two-dimensional position sensitive semiconductor detector formed by an array of many microcell pixels, each cell being a semiconductor detector based on P-type silicon, the positive electrode being separated from the semiconductor material by a thin layer of silicon dioxide, and applying a positive voltage to the electrode to form a depletion region in the semiconductor and accumulate charge in a thin layer of about 10nm below the electrode. And transferring the charges collected on each small electrode to a reading electrode by adopting a method of periodically changing a driving voltage to generate a current signal. When the current signal is larger than a certain threshold value, an X-ray photon signal is triggered to be generated, the arrival time is marked through a rubidium clock 10MHz signal, and energy information of the X-ray photon is obtained according to the amplitude of the current signal.

For the high-resolution imaging X-ray telescope designed by the invention, pulsar, starcloud background and spatial dispersion background noise scenes can generate signals in different ranges in a focal plane detector CCD, the pulsar radiated pulse signals can be concentrated in a very small area, the starcloud background radiation can be distributed in a certain range, the spatial dispersion background radiation can be uniformly distributed in the whole focal plane detector, and the distribution of different signals is shown in figure 6. If pulsar pulse signals, a star cloud background and space dispersion background noise can be correctly separated, the observation precision of the millisecond pulsar can be greatly improved, and because the current X-ray detector belongs to a design stage and has no actual observation data, the simulation data is generated in a simulation mode in fig. 6.

Performance evaluation of the novel X-ray telescope of the invention

The observation accuracy of a millisecond pulsar is defined as:

σ _T ＝FWHM/SNR (1)

where FWHM is the full width at half maximum of the pulse and SNR is the signal-to-noise ratio of the pulse. The X-ray telescope observation pulsar is interfered by various noise sources, and the SNR of the pulsar is expressed as follows:

in the formula, C _p Counting pulsed photons for millisecond pulsar radiation; c _up Non-pulsed photon counting, which is a matter of millisecond pulsar radiation, contains a cloud of radiation, which is small for millisecond pulsars; c _b Counting for spatially dispersed particle noise, C _d And counting the background noise of the telescope X-ray detector.

The following variables are defined:

A _S 、η ₁ respectively the geometric area and equivalent reflection efficiency of the telescope optical system; as the telescope reflection efficiency changes along with the energy, the equivalent reflection efficiency is obtained according to the radiation energy spectrum of the millisecond pulsar and the comprehensive consideration of the telescope performance within the range of 0.5-5keV of the main observation frequency band of the millisecond pulsar. For collimated X-ray telescopes, eta ₁ ＝1.

A _J 、η ₂ The receiving area and the quantum conversion efficiency of the telescope detector are respectively; since the X-ray detector has high quantization efficiency at 0.5-5keV, generally more than 95%, η is made for simplifying calculation ₂ ＝1.

F _X ，F _B The pulse photon flux and the non-pulse photon flux of the X-ray pulsar radiation;

B _b is the spatial dispersion background; for pulsar in galaxy, there is also additional background radiation, which is not considered here for the moment.

B _d Is the noise floor of the X-ray detector.

D. Theta is the focal length and angular resolution of the telescope, respectively.

f _PSF The Point Spread Function (PSF) part in the detection area of the pulsar of the telescope can be considered as the PSF is uniformly distributed in the field of view of the telescope due to the extreme remote range of the pulsar.

Ω _ef The solid angle is probed for an equivalent pulsar within the Field of View (FOV) of the telescope in units of steradians (Sr).

Within the Δ t observation time, we can obtain:

because the flux of the pulsar photon is extremely weak, the photon flux at all positions in the whole telescope area is summed, so that the two-dimensional distribution in the formula can be simplified into one dimension and substituted into the formula (2). In addition, due to the lack of a telescope point spread function, the following calculations assume that the pulsar signals are uniformly distributed under the view of the telescope. The following can be obtained:

for FIT, since the X-ray detector has position information, then A _J ＝[Dθ/(50μm)] ² ·(50μm) ² Therein []Is rounded up. At this time, a proportionality coefficient, K =2'× 3'/(θ × θ), needs to be introduced into the non-impulsive part signal of the pulsar, and since the influence of the background noise of the partial star cloud is removed, equation (4) becomes:

the instrument background counting rate of the NICER telescope is 0.05cts/s, the spatial dispersion background is 0.15cts/s, and the FOV is 5'. NICER consists of 56X-ray telescopes, each telescope having a diameter of 10.5cm and a geometric area of 4849.048cm ² The total area of the sensitive device SDD is 14cm ² Then, the background flow of the SDD detector is calculated to be 0.00357cts/s/cm ² The space dispersion background flow is 0.00445cts/s/cm ² And/sr. As the CCD also belongs to a silicon-based X-ray detector, the detector background and the space dispersion background of the rear FIT observation pulsar are consistent with NICER, namely B _b ＝0.00445cts/s/cm ² /sr，B _d ＝0.00357cts/s/cm ² . Assuming a single FIT diameter of 10.5cm and a geometric effective area of 86.59cm ² It is noted that the XTI of NICER employs a single grazing incidence non-imaging viewing mode, whereas FIT employs a double reflectance imaging viewing mode. For comparative analysis, both the XTI and collimated X-ray of NICER of equal area were consideredThe field angle of the telescope (Collimating X-ray telescope CXT) is 1 degree.

Firstly, the influence of different pulse radiation flow rates on the observation performance of three X-ray telescopes is analyzed. Suppose F _B ＝0.001cts/s/cm ² The single reflection efficiency of the lens was 80%, the observation time was 10000s, the angular resolution of FIT was 30 ″, F _X At 10 ^-6 -10cts/s/cm ² See fig. 4 for the results of the calculations.

As can be seen from FIG. 4, following F _B And the signal-to-noise ratio of observation of the three X-ray telescopes is increased. When F is _B At weaker levels, the SNR for FIT observed pulsar is best, while F _B When stronger, the SNR of CXT observation pulsar is better. For focusing type X-ray telescopes, in F _B ＝0.001cts/s/cm ² In case of F _X ＝0.002cts/s/cm ² When FIT is comparable to the SNR of the XTI observed pulsar, when F _X FIT performance is better than XTI when flow is weak, whereas F _X At high flow rates, XTI performance is superior to FIT.

And secondly, the influence of non-pulse radiation of different pulsar on the observation performance of the three X-ray telescopes is analyzed. Suppose F _X ＝0.001cts/cm ² S, other conditions being as before, F _B At 10 ^-6 -10cts/cm ² The calculated results are shown in FIG. 5.

As can be seen in FIG. 5, when F _B Smaller time (1)<10 ^-4 cts/s/cm ² ) The pulsar observation performance of the three X-ray detectors is basically kept stable, the pulsar observation signal-to-noise ratio of XTI is about 26, FIT is about 24, and CXT is about 10. With F _B Increasing, a decrease in SNR occurs for all three X-ray telescopes, where XTI faces strong flux F _B When the signal is in use, XTI performance tends to CXT, and FIT has strong non-pulse signal inhibition capability. At F _X ＝0.001cts/s/cm ² In case of F _B ＝2×10 ^-4 cts/s/cm ² FIT is comparable to the pulsar observed performance of XTI. When F is present _B XTI performance is better than FIT when flow is weak, and F _B At high flow rates, FIT performs better than XTI.

Further, three types of X-ray telescopes for 5 guides were analyzedThe observation performance of the aeropulsar is shown in the table 1, and the basic parameters of the pulsar are shown in the table 1, wherein the geometric effective area of the three X-ray telescopes is 86.59cm ² The results are shown in Table 1.

TABLE 1 SNR for three X-ray telescopes observing 5 pulsar

As can be seen from Table 1, for Crab pulsar (PSR J0534+ 2200), the pulsar and the astron cloud radiation flux were strong, the XTI performance was comparable to the CXT performance, and the FIT observation performance was better than the XTI and the CXT. For other millisecond pulsar of radiation flow, the CXT observation performance is poorer, and the focusing observation effect is better than that of collimation observation; it is worth noting that the signal-to-noise ratio of the pulse signal obtained by FIT observation is improved to different degrees compared with XTI under the condition of the same telescope area, particularly PSR J1937+2134, and FIT is improved by more than two times compared with XTI. Actually, the millisecond pulse star radiation flux for establishing deep space navigation is generally weak, so that the X-ray telescope relied on suppresses various non-pulse noises by means of imaging observation, so as to improve the pulse SNR and further improve the pulse TOA measurement precision.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the specification and the drawings of the present invention should be included in the scope of the present invention.

Claims (6)

1. An X-ray focusing type imaging telescope, characterized in that: the high-angular resolution focusing X-ray optical system comprises a lens hood (1), a focusing lens unit (2) and an anti-pollution shielding cylinder (6) which are sequentially connected, wherein the focusing lens unit (2) is connected with the focal plane detector (7) through the anti-pollution shielding cylinder; the focusing lens unit (2) comprises a lens fixing device (3), a focusing lens and a lens cone (4) and an electronic deflector (5) which are connected in sequence; the focusing lens is adhered in the lens fixing device (3) of the scroll, and the focusing lens barrel is connected with the lens fixing device (3).

2. The X-ray focusing imaging telescope of claim 1, wherein: the X-ray focusing imaging telescope is designed to have a short focal length, and the focal length is 1000-1200 mm.

3. The X-ray focusing imaging telescope of claim 1, wherein: the focal plane detector (7) is a domestic high-speed CCD, the CCD is composed of a plurality of pixel type CCDs, the side length of each pixel type CCD is not more than 100 micrometers, and the exposure time is not more than 10 microseconds.

4. The X-ray focusing imaging telescope according to claim 1, wherein: the focusing lens is made of monocrystalline silicon materials and is made by a monocrystalline silicon slicing method.

5. The X-ray focusing imaging telescope of claim 1, wherein: the X-ray focusing imaging telescope adopts an X-ray telescope array.

6. A method for observing weak signals of a millisecond pulsar by using the X-ray focusing type imaging telescope as claimed in claim 1, wherein: the method comprises the following steps:

(1) Collection of X-ray photons: when X-ray photons enter the surface of a smooth high-Z-value material acting on a telescope focusing optical system lens at a grazing incidence angle smaller than 3 degrees, a grazing incidence type reflection phenomenon is generated, and the X-ray photons are collected on a focal plane and collected by a high-speed CCD (charge coupled device);

(2) Reading of X-ray photons: reading time energy information of X-ray photons by adopting a high-speed CCD (charge coupled device), wherein the high-speed CCD consists of a preamplifier, an analog circuit, a digital circuit and a power line, the preamplifier converts charges generated by the X-ray photons into current signals, and the charge quantity is in direct proportion to the energy of incident photons; converting the current pulse signal into a trigger signal through a comparator, marking the arrival time of the trigger by using a satellite-borne rubidium clock, and recording the trigger position of the X-ray photon by using a CCD (charge coupled device);

(3) Extracting pulsar signals: when the X-ray telescope observes a millisecond pulsar, noise from pulsar clouds, high-energy charged particles, electromagnetic radiation and the like is received at the same time, the noise intensity brought by the pulsar clouds is far beyond a pulse signal, most of the noise brought by the pulsar clouds is filtered through image processing based on the acquired pulsar and pulsar cloud pictures, the range of the pulsar clouds is further determined by utilizing a star point boundary tracking detection extraction algorithm by combining pulsar prior information, and the pulsar cloud radiation is abandoned, so that most of the noise is filtered. A large amount of noise still exists in the detected pulsar image, and different time domain and frequency domain methods are adopted for processing aiming at different noise characteristics, so that the noise level is further reduced.

(4) Pulse profile and energy spectrum: and collecting and processing the collected X-ray photon arrival time series and energy information, and folding and reconstructing a pulsar pulse profile and an observation energy spectrum according to the pulsar ephemeris to provide observation information for pulsar deep space navigation.

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