A large-aperture radio telescope system for the far side of the moon

Abstract

This invention discloses a large-aperture radio telescope system for the far side of the moon, comprising: an antenna interferometer array, an electro-optic conversion link, a lunar digital center, a relay transmitting antenna, a lunar relay satellite, and a ground data processing center. The antenna interferometer array acquires scene radiation signals using the principle of integrated aperture interferometry and transmits these signals to the electro-optic conversion link. The electro-optic conversion link receives the scene radiation signals, performs electro-optic modulation to convert them into optical signals, and transmits them to the lunar digital center. The lunar digital center demodulates the signals and transmits the modulated signals to the lunar relay satellite via the relay transmitting antenna. After up-conversion and forwarding, the signals are sent back to the ground data processing center for large-scale data processing and inversion imaging. This invention lays an important foundation for the engineering realization of a lunar-based large-aperture radio telescope.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, and in particular relates to a large-aperture radio telescope system for use on the far side of the moon. Background Technology

[0002] Building an array of very long-wave radio telescopes on the far side of the moon to conduct radio astronomy observations in the Sub-30MHz band will enable high-resolution detection of very low-frequency radio signals from ionized hydrogen, solar bursts, planets, quasars, and other objects. This could potentially lead to groundbreaking discoveries in cosmology and the study of exoplanets.

[0003] There is currently no plan to build a radio telescope on the far side of the moon, which would not meet the requirements for detecting very low frequency signals such as those from the Dark Ages, background radiation, and exoplanets. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a large-aperture radio telescope system for the far side of the moon, laying an important foundation for the engineering realization of a lunar-based large-aperture radio telescope.

[0005] The objective of this invention is achieved through the following technical solution: a large-aperture radio telescope system for the far side of the moon, comprising: an antenna interferometric array, an electro-optical conversion link, a lunar digital center, a relay transmitting antenna, a lunar relay satellite, and a ground data processing center; wherein, the antenna interferometric array acquires scene radiation signals through the principle of integrated aperture interferometry and transmits the scene radiation signals to the electro-optical conversion link; the electro-optical conversion link receives the scene radiation signals, processes them to obtain optical signals, and transmits the optical signals to the lunar digital center through optical fibers; the lunar digital center demodulates the optical signals to obtain modulated signals, transmits the modulated signals to the lunar relay satellite through the relay transmitting antenna, performs up-conversion and forwarding, and then sends them back to the ground data processing center for big data processing and inversion imaging.

[0006] In the large-aperture radio telescope system applied to the far side of the moon, the antenna interferometric array includes a central compact array and a surrounding sparse array; wherein, the central compact array includes multiple array elements; wherein, the multiple array elements are arranged periodically in equilateral triangles to form a regular hexagonal compact array; the surrounding sparse array diffuses outward along the radial direction of the central compact array.

[0007] In the large-aperture radio telescope system applied to the far side of the moon, the distance between two adjacent elements in the central compact array is 20m-25m.

[0008] In the large-aperture radio telescope system applied to the far side of the moon described above, the center distance of the nth element in each arm of the surrounding sparse array from the center distance of the first element is proportional to n.2.2 .

[0009] In the large-aperture radio telescope system applied to the far side of the moon, each array element is an antenna subarray. Each antenna subarray includes a dipole element, a base plate, and a claw-shaped support. One end of the claw-shaped support is connected to the base plate, and the other end of the claw-shaped support is connected to the dipole element. When the antenna subarray is folded up, it can form a square "box" structure. When unfolded, the four claw-shaped supports rotate simultaneously and unfold in a "petal" shape.

[0010] In the large-aperture radio telescope system applied to the far side of the moon, the number of dipole units is 16, and the 16 dipole units form a 4×4 equally spaced rectangular dipole array structure.

[0011] In the aforementioned large-aperture radio telescope system applied to the far side of the moon, the dipole unit includes four radiators, a dual-polarized feed network, and a central support rod. All four radiators are connected to the central support rod. The dual-polarized feed network is located at the top of the central support rod. Each radiator includes a feed arm, a radiating arm, a telescopic arm, and a short-circuit arm. One end of the feed arm is connected to the central support rod, the other end of the feed arm is connected to one end of the radiating arm, the other end of the radiating arm is connected to one end of the telescopic arm, the other end of the telescopic arm is connected to one end of the short-circuit arm, and the other end of the short-circuit arm is connected to the central support rod.

[0012] In the large-aperture radio telescope system applied to the far side of the moon described above, the output response of the antenna interferometer array is obtained by the following formula:

[0013]

[0014] Among them, R c This is the output response of the antenna interferometer array. For source brightness, Here, v is the direction vector, and v is the observation frequency. Let be the baseline function, c be the speed of light, and dΩ be the solid angle integral.

[0015] In the large-aperture radio telescope system applied to the far side of the moon described above, when the antenna interferometer array is a two-dimensional antenna array, the far-field radiation pattern of the antenna interferometer array is as follows:

[0016] F(u,v)=f e (u,v)AF(u,v);

[0017] in, θ and f represents the elevation and azimuth angles of the antenna interferometer array in three-dimensional space, respectively. e(u,v) represents the active radiation pattern of the array element, AF(u,v) is the array factor, and u and v are both spatial frequency functions.

[0018] In the large-aperture radio telescope system applied to the far side of the moon described above, the array factor AF(u,v) is:

[0019]

[0020] Among them, A mn Let M be the excitation amplitude of the (m, n)th element in the two-dimensional matrix, where m and n are counting units, M is the number of rows in the matrix, and N is the number of columns in the matrix. k is the wave vector, λ is the free space wavelength, and d is the array spacing.

[0021] In the aforementioned large-aperture radio telescope system applied to the far side of the moon, the electro-optic conversion link includes a low-noise amplifier processor, an analog-to-digital converter (AD) processor, and an electro-optic modulator. The low-noise amplifier processor amplifies the scene radiation signal to obtain an analog signal, which is then transmitted to the AD processor. The AD processor processes the analog signal to obtain a digital signal, which is then transmitted to the electro-optic modulator. The electro-optic modulator processes the digital signal to obtain an optical signal.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) This invention relates to the construction of systems such as antenna interferometer array, lunar surface data interaction, and relay satellite data backhaul, which can achieve detection sensitivity better than 1mJy and spatial angular resolution performance characteristics at the arcsecond level, filling the technological gap in this field;

[0024] (2) The large-aperture antenna interference array layout design of the present invention adopts a new configuration layout design of hexagonal dense array + double Y-shaped sparse array. Under the condition of introducing a relatively small number of antenna array elements, on the one hand, it effectively increases the short baseline density and central area sensitivity of the antenna interference array, and on the other hand, it effectively increases the spatial sampling range and angular resolution.

[0025] (3) The low-profile deployable antenna subarray structure of the present invention can realize the integrated folding and unfolding of 16 dipole units, with a structure folding ratio close to 4:1, providing a new solution for the design of spaceborne deployable antennas and improving the efficiency of rocket launch.

[0026] (4) The ultra-wideband dual-polarized dipole unit design of the present invention has the characteristics of wide bandwidth, miniaturization and easy convergence. By adopting a specific short-circuit loading method, the lateral envelope size of the antenna is effectively reduced by nearly 50%, which has important reference significance for the miniaturization design of low frequency antennas. Attached Figure Description

[0027] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0028] Figure 1 This is a block diagram of a large-aperture radio telescope system applied to the far side of the moon, provided in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the antenna interference array layout design provided in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the antenna subarray provided in an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of a dipole unit provided in an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the unfolded structure of the ultra-wideband dual-polarized antenna unit provided in an embodiment of the present invention;

[0033] Figure 6 This is the radiation pattern of the ultra-wideband low-frequency antenna element provided in the embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the 4×4 antenna subarray structure provided in an embodiment of the present invention;

[0035] Figure 8 This is the UV coverage map of the central compact array of the antenna array provided in the embodiment of the present invention;

[0036] Figure 9 This is a sparse array UV coverage map around the antenna array provided in an embodiment of the present invention. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Building a radio telescope on the far side of the moon offers several advantages. First, it avoids the influence of Earth's ionosphere, allowing observation of cosmic radiation with frequencies below 30MHz that are inaccessible from Earth due to ionospheric reflection, thus capturing ancient cosmic signals. Second, the moon effectively blocks low-frequency radio signal interference from Earth's surface, providing an extremely "clean" space observation environment and significantly improving the sensitivity of astronomical observations. The lunar surface also facilitates the arrangement of ultra-large aperture radio telescope antenna arrays and offers better technological continuity; the backend data processing system can be entirely based on ground-based radio observation systems.

[0039] However, constructing a large-aperture radio telescope antenna array on the far side of the moon requires several considerations. First, the envelope size of the very low frequency (VLF) antenna elements must be excessively large, necessitating miniaturization and deployability to match the envelope size limitations of the satellite platform. Second, the sensitivity and resolution requirements for scientific target detection must be considered, requiring the antenna array to have sufficient effective receiving area and baseline length to ensure the sampling density and beam gain requirements of synthetic aperture interferometry. Finally, the construction of high-speed, wide-bandwidth data transmission links between the lunar surface and the Earth requires consideration to ensure that observational data can be transmitted back to Earth in a timely and effective manner for processing. This represents a completely new operating mode compared to ground-based observatories.

[0040] Figure 1 This is a block diagram of a large-aperture radio telescope system for the far side of the moon, provided in an embodiment of the present invention. Figure 1 As shown, the large-aperture radio telescope system applied to the far side of the moon includes: an antenna interferometer array, an electro-optical conversion link, a lunar digital center, a relay transmitting antenna, a lunar relay satellite, and a ground data processing center.

[0041] in,

[0042] The antenna interferometer array acquires scene radiation signals using the principle of integrated aperture interferometry and transmits the scene radiation signals to the electro-optic conversion link. The electro-optic conversion link receives the scene radiation signals, processes them to obtain optical signals, and transmits the optical signals to the lunar digital center via optical fiber. The lunar digital center demodulates the optical signals to obtain modulated signals, transmits the modulated signals to the lunar relay satellite via a relay transmitting antenna, performs up-conversion and forwarding, and then sends them back to the ground data processing center for big data processing and inversion imaging.

[0043] The electro-optic conversion link includes a low-noise amplifier processor, an analog-to-digital (AD) processor, and an electro-optic modulator. The low-noise amplifier processor amplifies the scene radiation signal to obtain an analog signal, which is then transmitted to the AD processor. The AD processor processes the analog signal to obtain a digital signal, which is then transmitted to the electro-optic modulator. The electro-optic modulator processes the digital signal to obtain an optical signal.

[0044] like Figure 2 As shown, the antenna interferometric array includes a central compact array and a surrounding sparse array; wherein, the central compact array includes multiple array elements; wherein, the multiple array elements are arranged periodically according to equilateral triangles to form a regular hexagonal compact array; the surrounding sparse array diffuses outward along the radial direction of the central compact array.

[0045] Specifically, the antenna interferometric array adopts a layout design of a central compact array and a surrounding sparse array, with each interferometric element being an antenna subarray. The central compact array has approximately 331 elements, each arranged periodically in an equilateral triangle pattern, forming a regular hexagonal compact array distributed within an area of ​​approximately 500m in diameter. The spacing between adjacent elements is approximately 20m-25m (preferably 20m). The surrounding sparse array has approximately 120 elements, arranged in a "double Y-shape" outward diffusion pattern. Each arm has 20 elements, and the distance from the nth element of an arm to the center of the first element is proportional to n. α (α≈2.2). The maximum baseline length is approximately 30 km, and the minimum baseline length is approximately 20 m.

[0046] like Figure 3 As shown, an array element is an antenna subarray; each antenna subarray includes a dipole element, a base plate, and a claw-shaped support; one end of the claw-shaped support is connected to the base plate, and the other end of the claw-shaped support is connected to the dipole element; when the antenna subarray is folded up, it can form a square "box" structure, and when unfolded, the four claw-shaped support bases rotate simultaneously and unfold in a "petal" shape.

[0047] like Figure 7 As shown, the antenna subarray consists of 16 antenna elements arranged in a 4×4 rectangular array with equal spacing. The spacing between each dipole element is approximately 2m, and the rear end is synthesized using a simulated beamforming network. It mainly consists of a base plate, claw-shaped supports, dipoles, and various hinges, providing both collapsible and deployable functionality. When collapsed, it forms a square "box" structure with dimensions of approximately 2m×2m×0.1m. When deployed, the movement of the hinges causes the four claw-shaped supports to rotate simultaneously, unfolding in a "petal-like" pattern, with dimensions of approximately 7.5m×7.5m×0.75m. The antenna subarray deployment process involves three steps:

[0048] The first step involves unlocking the claw-shaped support from the base plate. Through the rotational movement of two hinge supports 1 and two hinge supports 2, all four claw-shaped support seats simultaneously rotate outwards, unfolding in a "petal-like" pattern until they reach a flat plane, at which point the hinge supports lock. The power source for unfolding the hinge supports can be a motor or a spring mechanism.

[0049] The second step is to unlock the antenna unit, which then disengages from the claw-shaped support slot. The 16 retracted antenna units unfold under the power of the root spring hinge and lock when they are perpendicular to the claw-shaped support.

[0050] The third step is to unlock the antenna unit, which unfolds into place under the power of the spring hinge, ultimately forming the designed antenna subarray structure.

[0051] The telescope antenna array of this invention employs the principle of synthetic aperture interferometry, with a central compact array having a sufficiently high density of short baselines. The UV distribution pattern is shown below. Figure 8 As shown. A sparse matrix around the perimeter can achieve the longest baseline length, as shown in the UV distribution map. Figure 9 As shown.

[0052] like Figure 4 As shown, the dipole unit includes four radiators, a dual-polarized feed network, and a central support rod; wherein, all four radiators are connected to the central support rod; the dual-polarized feed network is disposed at the top of the central support rod; each radiator includes a feed arm, a radiating arm, a telescopic arm, and a short-circuit arm; wherein, one end of the feed arm is connected to the central support rod, the other end of the feed arm is connected to one end of the radiating arm, the other end of the radiating arm is connected to one end of the telescopic arm, the other end of the telescopic arm is connected to one end of the short-circuit arm, and the other end of the short-circuit arm is connected to the central support rod.

[0053] The ultra-wideband dual-polarized antenna element, also known as the dipole element, adopts a conical double-layer four-arm dipole design, including a feed arm, a radiating arm, a telescopic arm, a short-circuit arm, a dual-polarized feed network, and a central support rod. The feed arm, radiating arm, telescopic arm, and short-circuit arm together form the radiator of the antenna. Compared to traditional 1 / 2 wavelength dipole antennas, this design significantly shortens the length of the four arms by bending them downwards, resulting in a total projected aperture of approximately 1.5m. The central support rod consists of a centrally hollowed-out metal rod and dielectric supports between them, primarily providing support for the antenna and the dual-polarized feed network. The dual-polarized feed network uses an active loading method and can operate at frequencies ranging from 1MHz to 100MHz.

[0054] like Figure 5 and Figure 6 As shown, the dipole unit structure consists of four sets of identical linkages evenly distributed circumferentially. Each linkage comprises one linear joint and five revolute joints, enabling the array to fold and unfold. The joints connected to the central rod utilize leaf spring hinges, and any one of the revolute joints is driven by a spring hinge. No power source is required at the remaining nodes to achieve array deployment. The antenna has a single arm length of 0.75m, bilinear polarization, and an operating bandwidth covering 1MHz to 100MHz. The antenna beam is omnidirectional, with a peak gain of approximately 0dB at 50MHz.

[0055] Data exchange between the interferometer elements on the lunar surface is achieved through fiber optic transmission, ensuring a data transmission rate of 1Gbps. Earth-Moon data exchange is achieved through wireless radio frequency links (Ka band) between the lunar data center transmitting antenna and the lunar relay satellite, and between the lunar relay satellite and the ground data processing center, ensuring a data transmission rate of over 100Mbps and a transmission bandwidth of 2GHz.

[0056] The antenna array of this invention adopts the principle of integrated aperture interferometry. It uses the pairwise correlation of a small aperture antenna array to realize the spatial frequency domain measurement of the observation scene (called spatial frequency sampling). The radiation signal of the scene is replaced by a pair of small antennas to receive and fit the measurement data. The visibility function obtained by measurement is sampled and inverted for imaging. This can effectively solve the problem of large aperture of real aperture antenna and improve the resolution.

[0057] For a target source, the output response of the interferometer array can be obtained by integrating over the solid angle of the sky. Ignoring the frequency factor, this response can be expressed as:

[0058]

[0059] Among them, R c This is the output response of the antenna interferometer array. For source brightness, Here, v is the direction vector, and v is the observation frequency. Let be the baseline function, c be the speed of light, and dΩ be the solid angle integral.

[0060] here, Let β be the source brightness, β be a function of the baseline, and σ be the direction vector. The cosine and sinine terms in the above equation are called the fringe pattern. Therefore, the effect of correlation interference can be viewed as multiplying the source brightness distribution with the fringe pattern and integrating over the sky. The direction of the fringes depends on the baseline vector, while the fringe spacing is related to the length of the baseline (angular scale λ / b) and the observation wavelength. For a two-dimensional antenna array, the far-field pattern of a rectangular array can be written as the product of the element active pattern and the array factor, as shown below:

[0061] F(u,v)=f e (u,v)AF(u,v)

[0062] in, θ and f represents the elevation and azimuth angles of the antenna interferometer array in three-dimensional space, respectively. e (u,v) represents the active radiation pattern of the array element, AF(u,v) is the array factor, and u and v are both spatial frequency functions.

[0063] The array factor AF(u,v) of the planar array can be written as:

[0064]

[0065] Among them, A mn Let M be the excitation amplitude of the (m, n)th element in the two-dimensional matrix, where m and n are counting units, M is the number of rows in the matrix, and N is the number of columns in the matrix. k is the wave vector, λ is the free space wavelength, and d is the array spacing.

[0066] The above formula describes the fundamental transformation relationship in synthetic aperture imaging. That is, the source's brightness and visibility functions form a Fourier transform pair. This means that if we measure the visibility, we can deduce the brightness distribution of the emitted source. In subsequent data processing, we can define an antenna sampling function and convolve it to obtain the original brightness of the image.

[0067] This embodiment addresses the detection requirements of very low frequency signals from the cosmic dark ages, background radiation, and exoplanets. It involves array layout design and data exchange link system design, achieving detection sensitivity better than 1 mJy and spatial angular resolution at the arcsecond level. Furthermore, it innovatively proposes a 16-element deployable subarray structure design, fully meeting the limitations of the launch vehicle envelope size, laying a crucial foundation for the engineering realization of a lunar-based large-aperture radio telescope.

[0068] This invention relates to the construction of systems such as antenna interferometer arrays, lunar surface data interaction, and relay satellite data backhaul, achieving detection sensitivity better than 1 mJy and spatial angular resolution performance at the arcsecond level, filling a technological gap in this field. The large-aperture antenna interferometer array layout design of this invention adopts a novel configuration of a hexagonal compact array + a double Y-shaped sparse array. While introducing a relatively small number of antenna elements, it effectively increases the short baseline density and central area sensitivity of the antenna interferometer array, and also effectively increases the spatial sampling range and angular resolution. The low-profile deployable antenna subarray structure of this invention can achieve integrated folding and unfolding of 16 dipole elements, with a structural folding ratio close to 4:1, providing a new solution for the design of spaceborne deployable antennas and improving rocket launch efficiency. The ultra-wideband dual-polarized dipole element design of this invention features wide bandwidth, miniaturization, and easy folding. Using a specific short-circuit loading method, it effectively reduces the antenna's lateral envelope size by nearly 50%, providing important reference for the miniaturization design of low-frequency antennas.

[0069] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A large-aperture radio telescope system applied to the back of the moon, characterized by The application relates to a lunar satellite remote sensing system. The system comprises an antenna interference array, an electro-optical conversion link, a lunar surface digital center, a relay transmitting antenna, a lunar relay satellite and a ground data processing center. The antenna interference array collects scene radiation signals through a synthetic aperture interferometry principle and transmits the scene radiation signals to the electro-optical conversion link. The electro-optical conversion link receives the scene radiation signals, processes the scene radiation signals to obtain optical signals, and transmits the optical signals to the lunar surface digital center through an optical fiber. The lunar surface digital center demodulates the optical signals to obtain modulated signals, transmits the modulated signals to the lunar relay satellite through the relay transmitting antenna, up-converts and forwards the modulated signals to the ground data processing center for big data processing and inversion imaging. The antenna interference array comprises a central dense array and a surrounding sparse array. The central dense array comprises a plurality of array elements. The surrounding sparse array diffuses outward along the radial direction of the central dense array. The distance between two adjacent array elements in the central dense array is 20-25 m. The center distance of the nth array element of each arm of the peripheral sparse array is proportional to n 2.2 ; Each array element is an antenna subarray. When the antenna subarray is folded, a square "box" structure is formed. When the antenna subarray is unfolded, the four claw-shaped support seats are simultaneously rotated and unfolded in a "petal" shape. The number of dipole units is 16, and the 16 dipole units form a 4x4 equidistant rectangular dipole array structure. Each dipole unit comprises four radiators, a dual-polarization feed network and a central support rod. The four radiators are connected with the central support rod. The dual-polarization feed network is arranged at the top end of the central support rod.

2. The large-aperture radio telescope system for lunar-based application according to claim 1, characterized in that: Each radiator comprises a feed arm, a radiation arm, an extension arm and a short-circuit arm. where R c is the output response of the antenna interferometric array, is the source luminosity, is the direction vector, v is the observation frequency, is the baseline function, c is the speed of light, dΩ is the solid angle integral.

3. The large-aperture radio telescope system for lunar-based application according to claim 1, characterized in that: The output response of the antenna interference array is obtained through the following formula. F(u,v) = f e (u,v) AF(u,v); wherein θ and respectively represent the elevation and azimuth angles of the antenna interferometric array in three-dimensional space, f e (u, v) represents the array element active pattern, AF(u, v) is the array factor, and u and v are both spatial frequency functions.

4. The large-aperture radio telescope system for lunar-based application according to claim 3, characterized in that: When the antenna interference array is a two-dimensional antenna array, the far-field pattern of the antenna interference array is The array factor AF(u,v) is wherein A mn is the excitation amplitude of the (m, n)th element of the two-dimensional matrix, m and n are both in count units, M is the number of rows of the matrix, and N is the number of columns of the matrix, k is the wave vector, λ is the free-space wavelength, and d is the array pitch.

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