A Pulsar Autonomous Navigation Pulse Phase Estimation System and Method

Abstract

The present invention belongs to the technical field of pulsar autonomous navigation for space vehicles, and provides a pulsar autonomous navigation pulse phase estimation system and method. Taking a satellite system with a distributed layout as a carrier, it includes a high-precision time synchronization timing system, a pulsar detection payload unit, a starlight vector sensitive payload unit, a Earth sensitive payload unit, and an inter-satellite link payload unit. The present invention also proposes a new fusion method for pulse observation profiles and starlight angular distances. This method is a deep fusion method for pulsars and starlight angular distances, which can effectively utilize various types of satellites with inter-satellite links, carry payloads with the functions required by the present invention, and achieve pulse phase estimation. By introducing multiple starlight angular distance measurement values at the same moment, the present invention can achieve bin filtering of profile amplitudes and realize high-precision pulse phase fusion estimation.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulsar autonomous navigation for space vehicles, and particularly relates to a pulsar autonomous navigation pulse phase estimation system and method. Background Art

[0002] The pulsar autonomous navigation technology is a new means for satellites to achieve autonomous navigation. In the process of a satellite using pulsars to achieve autonomous navigation, estimating the phase of a pulse at a reference point is a key technology related to navigation accuracy. Currently, pulsar navigation mainly focuses on research for independent satellites, and navigation and pulse phase estimation are also based on pulsar detectors and their data processing software and hardware systems carried on independent satellites. The main methods for estimating pulse phase include: least squares method, minimum variance method, maximum correlation method, maximum likelihood method, frequency domain correlation method, and related improved methods, etc.

[0003] In recent years, in order to improve the accuracy of pulsar autonomous navigation, technical personnel at home and abroad have carried out a large number of combined navigation researches, integrating pulsar navigation with other navigation methods to obtain higher navigation accuracy. For example, a pulsar and starlight angular distance combined navigation method is adopted, where the pulse phase observation quantity and the starlight angular distance observation quantity are fused and calculated to obtain the satellite position. The characteristic of this method is that the satellite needs to obtain the pulse phase and the starlight angular distance separately, and then perform a fusion calculation. That is to say, the extraction of the pulse phase has nothing to do with the starlight angular distance, and the two are independent. The starlight angular distance does not contribute to improving the accuracy of pulse phase estimation. Its main role is that the starlight angular distance and the pulse phase together constitute a position observation equation, which is fused with the satellite kinematic state equation to improve the positioning accuracy. This method is essentially a loose-coupled combined navigation for navigation and positioning at the level of fusion positioning.

[0004] Distributed pulsar navigation based on inter-satellite links has also been a research hotspot in recent years. The inter-satellite link provides means for communication, ranging, and clock synchronization of distributed satellite systems. Distributed pulsar autonomous navigation uses different satellites to observe different pulsars respectively to obtain pulse phase observation quantities, and based on the inter-satellite link measurement data, the different pulsar phase observation quantities are uniformly processed in the data processing unit to achieve navigation and positioning. Currently, there is no effective method for realizing distributed pulsar navigation based on inter-satellite links. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention proposes a pulsar autonomous navigation pulse phase estimation system, and its specific technical solution is as follows:

[0006] A pulsar autonomous navigation pulse phase estimation system, which takes a satellite system with a distributed layout as a carrier, the satellite system is interconnected by inter-satellite links, and includes a number of satellites arranged distributively. Each satellite carries the following units:

[0007] A high-precision time synchronization timing system, which is used to provide a unified time reference and high-precision timing for the entire system;

[0008] A pulsar detection payload unit, which is used to detect pulsars and obtain the photon arrival time series information of pulsars reaching the satellite; the photon sequence is folded in profile according to the pulsar period to generate an observed pulse profile;

[0009] A starlight vector sensitive payload unit, which is used to observe the star vector;

[0010] An earth sensitive payload unit, which is used to extract the geocentric vector;

[0011] An inter-satellite link payload unit, which is used to realize communication and ranging between satellites. Based on its measurement information, data fusion of satellite pulsar measurement and starlight angular distance is realized, and the starlight angular distance is constructed by the starlight vector and the geocentric vector.

[0012] In a preferred solution, the pulsar detection payload unit is carried on satellites distributed in a distributed manner, or carried on at least one satellite that realizes pulse phase estimation.

[0013] A pulsar autonomous navigation pulse phase estimation method, which includes the following steps:

[0014] A1: Represent each satellite by S1, S2, Si... SN. The pulsar detection payload unit, the starlight vector sensitive payload unit, and the earth sensitive payload unit have an observed vector of the star s i , i = 1, 2,..., an observed vector of the geocenter e j , j = 1, 2..., and the starlight angular distance synthesized by each satellite through observing the star and the earth is θ i , i = 1, 2,...;

[0015] A2: At a certain moment t0: Using the photon arrival time series received by the pulsar detector, fold the photon arrival time series into the first pulse period in the form of a histogram according to the pulsar period Ps to obtain an observed profile p(t);

[0016] A3: Perform high-precision pulse phase estimation.

[0017] Furthermore, the specific process of step A2 includes:

[0018] B1: Taking t0 as the starting point, taking the remainder of the photon sequence of the pulsar photons whose arrival time is greater than one Ps with respect to Ps, and inserting the remainder correspondingly into the time period from t0 to t0 + Ps, so as to obtain photon points distributed in the time period from t0 to t0 + Ps;

[0019] B2: Draw a bar chart with the bin as the width, and the vertical axis represents the number of photons falling within that bin.

[0020] B3: The amplitude sequence of the bar chart is the observed value p(k) of the profile on the bin, and its continuous form is p(t).

[0021] B4: Consider the bin as the filtering step size k, and the profile value p(k) corresponding to each bin is used as the pulse profile observed value on that bin.

[0022] B5: Use the starlight vector sensitive payload and the earth sensitive payload to detect the synthesized starlight angular distance θ i , i = 1, 2,..., the directions of starlight measurement should be as diverse as possible, and the number of starlight angular distances should be as large as possible; for each bin, randomly match the starlight angular distance observed value with the pulse profile observed value on that bin to form a two-dimensional observation combination (p(k), θ k ).

[0023] B6: Combine the standard profile information, construct a Kalman filter, perform filtering calculations, and obtain the pulse phase value at this moment after convergence. Specifically:

[0024] The pulsar standard profile s p (t) and the phase function can be obtained through long-term observations on the ground and in orbit, which are the basis of pulsar navigation; when the satellite performs on-orbit pulsar autonomous navigation, by using the on-board detector to detect the arrival time information of pulsar photons, it is transformed to the SSB at a large scale and folded into a profile, and then compared with the standard profile to obtain the phase information. The observed profile can be modeled as:

[0025] p(t) = as p (t - τ p ) + b + v p (7)

[0026] Among them, a represents the amplitude coefficient of the folded profile, which can be converted to 1 by normalizing the folded profile. b represents the overall upward shift of the observed profile due to the influence of noise in profile folding and is regarded as a constant. τ p is the pulse delay and can be converted to the pulse phase Φ (which is the parameter to be estimated), and v p is the detector and background equivalent Gaussian white noise.

[0027] The satellite obtains the starlight observation vector by observing the stars through the starlight vector sensitive payload, and obtains the geocentric vector by sensing the horizon through the earth sensitive payload and calculating. The starlight angular distance observation quantity of the star and the geocenter can be constructed; from the geometric relationship, the star-geocenter starlight angular distance θ is a function of the position, and the observation equation can be established as:

[0028]

[0029] where, θ i is the star - geocentric starlight angular distance of the \(i\) - th satellite in the distributed satellite system; \(s\ i is the unit starlight vector of a known star \(i\) being observed, \(r\ sat is the satellite position vector in the solar - system barycentric coordinate system (SSB system), the symbol represents the large - scale space - time transformation, represents the estimation of \(r\ sat in the SSB system, represents the position estimation error, \(\varPhi=[\varPhi_1\varPhi_2\varPhi_3] T is the phase to be estimated in the directions of the three pulsar vectors, \(P s =[P s1 P s2 P s3 T is the periods of the three pulsars, \(n = [n_1 n_2n_3] T is the unit vectors of the three pulsars, is the inter - satellite phase difference between the satellite corresponding to the \(i\) - th starlight angular distance and the satellite for realizing the fusion phase estimation, \(c\) is the speed of light, \(L is is the projection of the inter - satellite distance between this satellite and satellite \(S1\) in the direction of the observed pulsar, \(f s is the pulse frequency emitted by the pulsar, \(v θ is the measurement noise;

[0030] For a satellite observing pulsars in three directions, let represent the three pulsar standard profiles, \(J=[J 1 J 2 J 3 T represent the function obtained by differentiating the three standard profiles, \(b = [b 1 b 2 b 3 T is the upward shift of the three observation profiles, then the state equation can be established as

[0031]

[0032] As described above, using the pulsar observation profile \(p\) and the starlight angular distance \(\theta\), through geometric relationships, the observation equation can be constructed as:

[0033]

[0034] Let \(X φ =[s p ,\varPhi,b] T , \(Y φ =[p,\theta] T ​​​, the above equation can be arranged as follows:

[0035]

[0036] Y φ = g φ (X φ ) + V φ (12)

[0037] where U φ = [J O 3×1 O ×3 1 T , g φ (·) is a non - linear observation equation, W φ = [w p O 3×1 O 3×1 T and are state noise and observation noise respectively, equivalent to Gaussian white noise;

[0038] According to the above state equation and observation equation, the pulse phase Φ is estimated using the Kalman filter.

[0039] Furthermore, the specific process of step A3 includes:

[0040] C1: Taking the on - satellite high - precision clock timing and synchronization system as the time reference, making each satellite in the distributed system maintain good time synchronization and timing accuracy; Starting the task with a satellite responsible for task scheduling, setting the task start point as t0, carrying out the observation and accumulation of pulsar radiation signals, and synchronously carrying out the observation of starlight vector and geocentric vector, as well as the observation of inter - satellite distance and the direction vector of satellite S1 on each satellite;

[0041] C2: Satellite S1 takes the moment of t0 as the reference, synthesizes the photon arrival time series information detected by the pulsar into a profile with a certain number of bins, and obtains N1 profile amplitude observables p(k), k = 1...N1

[0042] C3: At the moment of t0, each satellite synthesizes the starlight angular distance information using the observed starlight vector and geocentric vector, and packs it together with the inter - satellite distance data at this moment and sends it to satellite S1;

[0043] C4: Satellite S1 uses the received starlight angular distance information and the pulsar observation profile, for each bin of the corresponding profile, constructs the observation combination (p(k), θ k ), and constructs the observation equation as shown in equation (4) and the state equation as shown in equation (3), regards the bin as the filtering step k, and uses the Kalman filter for calculation to obtain a high - precision pulse phase estimation value.

[0044] ​The beneficial effects achieved by the present invention are as follows:

[0045] Combining the characteristics of pulsar and starlight angular distance combined navigation methods and distributed pulsar navigation methods based on inter-satellite link measurements, the present invention proposes a new pulsar autonomous navigation pulse phase estimation system and method. The system adopts a distributed satellite system architecture based on inter-satellite links. Each satellite conducts starlight angular distance observations by carrying starlight vector sensitive payloads and Earth sensitive payloads. The satellite realizes the pulse detection function by carrying pulsar detection payloads. When the satellite calculates the pulse phase using the observed pulsar pulse information, it simultaneously uses the starlight angular distance information observed by each satellite at the same moment. Both of them constitute the observables at this moment. Using the pulsar standard timing model and profile model at this moment, information fusion is carried out with the abscissa interval bin of the synthesized columnar pulse profile as the step size, so as to obtain the pulse phase information at this moment. Obviously, the method proposed in this project fuses pulsar detection data and starlight angular distance information in the phase estimation stage, making full use of the starlight angular distance data provided by each satellite, which is a deeper-level combined navigation method and is of great significance for further improving the accuracy of pulsar navigation. Specifically as follows:

[0046] First, the new fusion method of the pulse observation profile and starlight angular distance proposed by the present invention and its payload system composition realize the filtering of the profile amplitude by bin and thus realize phase estimation by introducing multiple starlight angular distance measurement values at the same moment.

[0047] Second, the present invention proposes a new pulsar autonomous navigation pulse phase estimation system and method with a distributed architecture, which can realize high-precision pulse phase fusion estimation.

[0048] Third, the present invention proposes a brand-new pulse profile / starlight angular distance information fusion method, which is a deep fusion method of pulsars and starlight angular distances and can realize high-precision pulse phase fusion estimation.

[0049] Fourth, the present invention can effectively utilize various types of satellites with inter-satellite links, carry payloads with the functions required by the present invention, and realize pulse phase estimation. Description of the Drawings

[0050] Figure 1 It is a schematic diagram of a satellite system with a distributed layout;

[0051] Among them, S1-SN represent satellites S1-N in the distributed satellite system. Each satellite carries pulsar detection payloads, starlight vector sensitive payloads, Earth sensitive payloads, inter-satellite link payloads, and high-precision time synchronization timing systems. The black double-headed arrows represent inter-satellite links, and the dotted lines represent the observations of stars or the Earth by satellites using sensors.

[0052] Figure 2 It is a schematic diagram of the pulse profile folding process;

[0053] Figure 3 It is a schematic diagram of the construction of observables;

[0054] Figure 4 It is the distributed satellite system architecture in Embodiment 1;

[0055] Figure 5 It is a schematic diagram of the payload system of satellite S1; [[ID=I4]]

[0056] Figure 6 It is a schematic diagram of the payload systems of satellites S2 - SN. Detailed implementation manners

[0057] To facilitate the understanding of those skilled in the art of the present invention, the following combines embodiments and accompanying drawings to illustrate the detailed implementation manners of the present invention.

[0058] The present invention provides a pulsar autonomous navigation pulse phase estimation system, which takes a satellite system with a distributed layout as a carrier. The satellite system is interconnected by inter - satellite links and includes a number of satellites arranged distributively. Each satellite carries the following units: a high - precision time - synchronization timing system for providing a unified time reference and high - precision timing for the entire system; a pulsar detection payload unit for detecting pulsars and obtaining the photon arrival time series information of pulsars reaching the satellites. This photon sequence is folded in profile according to the pulsar period to generate an observed pulse profile; a starlight vector sensitive payload unit for observing the star vector; a geocenter sensitive payload unit for extracting the geocenter vector; an inter - satellite link payload unit for realizing communication and ranging between satellites. Based on its measurement information, data fusion of satellite measurements of pulsars and starlight angular distances is achieved, and the starlight angular distance is constructed from the starlight vector and the geocenter vector.

[0059] The pulsar detection payload unit is carried on satellites arranged distributively on each satellite, or carried on at least one satellite for realizing pulse phase estimation.

[0060] The pulsar autonomous navigation pulse phase estimation method of the present invention includes the following steps:

[0061] A1: Represent each satellite by S1, S2, Si... SN. The pulsar detection payload unit, the starlight vector sensitive payload unit, and the geocenter sensitive payload unit have the observed star vector as s i , i = 1, 2,... and the observed geocenter vector as e j , j = 1, 2... The starlight angular distance synthesized by each satellite through observing the star and the earth is θ i , i = 1, 2,...;

[0062] A2: At a certain moment t0: Using the arrival time sequence of pulsar photons received by the pulsar detector, fold the photon arrival time sequence into the first pulse period in the form of a histogram according to the pulsar period Ps to obtain the observation profile p(t);

[0063] A3: Perform high-precision pulse phase estimation.

[0064] The specific process of step A2 includes:

[0065] B1: Taking t0 as the starting point, take the remainder of the pulsar photon sequence with an arrival time greater than one Ps with respect to Ps, and insert this remainder into the time period from t0 to t0 + Ps correspondingly, so as to obtain photon points distributed in the time period from t0 to t0 + Ps;

[0066] B2: Draw a histogram with bin as the width, and the ordinate is the number of photons falling within this bin;

[0067] B3: The amplitude sequence of the histogram is the observed value p(k) of the profile on the bin, and its continuous form is p(t);

[0068] B4: Regard the bin as the filtering step k, and the profile value p(k) corresponding to each bin is used as the observed value of the pulse profile on this bin;

[0069] B5: Use the starlight vector sensitive payload and the earth sensitive payload to detect the synthetic starlight angular distance θ i , i = 1, 2,..., the directions of starlight measurement are as diverse as possible, and the number of starlight angular distances is as large as possible; for each bin, randomly match the observed value of the starlight angular distance with the observed value of the pulse profile on this bin to form a two-dimensional observation combination (p(k), θ k );

[0070] B6: Combine the standard profile information, construct a Kalman filter, perform filtering calculations, and obtain the pulse phase value at this moment after convergence. Specifically:

[0071] The pulsar standard profile s p (t) and the phase function can be obtained through long-term observations on the ground and in orbit, and are the basis of pulsar navigation; when the satellite performs on-orbit pulsar autonomous navigation, by using the on-board detector to detect the arrival time information of pulsar photons, perform large-scale space-time conversion to the SSB and fold it into a profile, and then compare it with the standard profile to obtain phase information. The observation profile can be modeled as:

[0072] p(t) = as p (t - τ p ) + b + v p (13)

[0073] Among them, a represents the amplitude coefficient of the folded profile, which can be normalized to 1 for the folded profile. b reflects the overall upward shift of the observed profile due to the influence of noise in profile folding and is regarded as a constant. τ p is the pulse time delay and can be converted into the pulse phase Φ (which is the parameter to be estimated), v p is the equivalent Gaussian white noise of the detector and the background;

[0074] The satellite obtains the starlight observation vector by observing stars through the starlight vector sensitive payload, and obtains the geocentric vector by sensing the horizon through the Earth sensitive payload and calculating, and can construct the starlight angular distance observable of the star and the geocenter; from the geometric relationship, it can be known that the star - geocenter starlight angular distance θ is a function of the position, and the observation equation can be established as:

[0075]

[0076] Among them, θ i is the i-th star - geocenter starlight angular distance in the distributed satellite system; s i is the unit starlight vector of a certain known star i being observed, r sat is the satellite position vector in the solar system barycentric coordinate system (SSB system), The symbol represents the large - scale space - time conversion, represents the estimation of r sat in the SSB system, represents the position estimation error, Φ = [Φ1 Φ2 Φ3] T is the phase to be estimated in the directions of three pulsar vectors, P s = [P s1 P s2 P s3 T is the periods of three pulsars, n = [n1 n2 n3] T is the unit vectors of three pulsars, is the inter - satellite phase difference between the satellite corresponding to the i - th starlight angular distance and the satellite realizing the fusion phase estimation, c is the speed of light, L is is the distance projection of the inter - satellite distance between this satellite and satellite S1 in the direction of the observed pulsar, f s is the pulse frequency emitted by the pulsar, v θ is the measurement noise;

[0077] For the satellite observing pulsars in three directions, let represent the standard profiles of three pulsars, J = [J 1 J 2 J 3 T represents the function obtained by taking the derivative of the three standard profiles, b = [b 1 b 2 ​​b 3 T Let the upward displacement of the three observation profiles be, then the state equation can be established as

[0078]

[0079] As mentioned above, using the pulsar observation profile p and the angular distance θ of starlight, through geometric relations, the observation equation can be constructed as:

[0080]

[0081] Let X φ = [s p , Φ, b] T , Y φ = [p, θ] T , then the above equation can be arranged as:

[0082]

[0083] Y φ = g φ (X φ ) + V φ (18)

[0084] where, U φ = [J O 3×1 O ×3 1 T , g φ (·) is a non - linear observation equation, W φ = [w p O 3×1 O 3×1 T and are the state noise and the observation noise respectively, equivalent to Gaussian white noise;

[0085] According to the above state equation and observation equation, the Kalman filter is used to estimate the pulse phase Φ.

[0086] The specific process of step A3 includes:

[0087] C1: Taking the on - satellite high - precision clock timing and synchronization system as the time reference, making each satellite in the distributed system maintain good time synchronization and timing accuracy; Starting the task with a satellite responsible for task scheduling, setting the task starting point as t0, carrying out the observation and accumulation of the pulsar radiation signal, and synchronously carrying out the observation of the starlight vector and the geocentric vector, as well as the observation of the inter - satellite distance and the direction vector of satellite S1 on each satellite;

[0088] ​C2: Taking the time t0 as a reference, satellite S1 synthesizes the photon arrival time series information detected by the pulsar into profiles with a certain number of bins, and obtains N1 profile amplitude observables p(k), where k = 1...N1

[0089] C3: At time t0, each satellite synthesizes the starlight angular distance information using the observed starlight vector and the geocentric vector, and packs and transmits it together with the inter-satellite distance data at this moment to satellite S1;

[0090] C4: Satellite S1 uses the received starlight angular distance information and the pulsar observation profile, and for each bin of the corresponding profile, constructs an observation combination (p(k), θ k ), and constructs the observation equation as shown in Equation (4) and the state equation as shown in Equation (3). Regarding the bin as the filtering step k, use the Kalman filter for calculation to obtain a high-precision pulse phase estimation value.

[0091] Embodiment 1:

[0092] The following combines specific cases to illustrate the pulsar autonomous navigation pulse phase estimation system and method of the present invention, which are specifically executed according to the following steps:

[0093] 1. Establishment of a distributed satellite system

[0094] (1) Arbitrarily select low, medium, and high-orbit satellites in the Earth's space. The satellites are equipped with pulsar detection payloads, starlight vector sensitive payloads, Earth sensitive payloads, inter-satellite link payloads, and time synchronization timing payloads. Construct a distributed satellite system as Figure 4 shown.

[0095] (2) In the distributed satellite system, at least one satellite serves as a carrier for realizing high-precision pulse phase calculation, such as satellite S1 in the figure. The extraction of the starlight angular distance is realized by the observation of multiple satellites through the starlight vector sensitive payload and the Earth sensitive payload, as shown by satellite S1 - satellite SN.

[0096] (3) Satellite S1 is interconnected with other satellites through an inter-satellite link, and can realize functions such as inter-satellite ranging, communication, and time synchronization.

[0097] (4) Using the inter-satellite synchronous timing system, each satellite maintains time synchronization. A certain satellite conducts the observation task planning for the entire system to realize the extraction of the pulsar observables, starlight angular distance observables, and the starlight vector of satellite S1 relative to each satellite corresponding to a certain moment t0.

[0098] (5) Satellite S1 uses the obtained pulsar observables and starlight angular distance observables, and according to the proposed method, constructs an information fusion filtering system, and uses the Kalman filter to realize pulse phase estimation.

[0099] 2. Satellite Payload Design

[0100] For satellite S1 that realizes pulse phase estimation, a satellite payload system is designed. The scheme is as Figure 5 shown, where the solid lines represent the payloads that must be equipped, and the dashed lines represent the payloads that can be equipped. Through this payload configuration, satellite S1 mainly completes the observation of pulsar signals based on the synchronized timing of the distributed satellite system clock and can synthesize the pulsar observation profile. Its starlight angular distance is mainly obtained from each distributed satellite through the inter-satellite link, and part of the starlight angular distance observation can also be carried out by carrying starlight vector sensitive payloads and earth sensitive payloads. The pulse phase estimation unit in it uses the method proposed in this invention to establish an information fusion system and uses the Kalman filter to achieve pulse phase estimation.

[0101] For satellites S2 - SN, a payload system is designed. The scheme is as Figure 6 shown, where the solid lines represent the payloads that must be equipped, and the dashed lines represent the payloads that can be equipped. Based on the synchronized timing of the distributed satellite system clock, satellites S1 - N mainly realize the measurement of the stellar vector and the geocentric vector at time t0 and synthesize the starlight angular distance.

[0102] In order to finally represent the starlight angular distance using the pulse phase, the functions that still need to be completed are: at this time t0, measure the inter-satellite distance L using the inter-satellite link, observe satellite S1 using the starlight vector sensitive payload to obtain the direction vector Rs1 of satellite S1, and calculate the projection L of L in the pulsar direction using L and Rs1 is , and this function can be realized on satellite S1.

[0103] The following is an explanation of the detectors carried on the distributed satellites:

[0104] (1) Pulsar Detector

[0105] It consists of a photon probe, a signal amplification and acquisition unit, a photon sequence encoding unit, etc., and can realize the detection and acquisition of pulsar photons, forming a photon time series and sending it to the pulse profile folding unit. The pulsar detector can be installed on a turntable, and the turntable rotation ensures the tracking of the detected pulsar.

[0106] (2) Earth Sensitive Payload

[0107] The planet sensitive payload consists of an optical probe, a signal amplification and acquisition circuit, a geocenter extraction module, a geocentric vector calculation module, etc. It is used to realize the acquisition of the geocentric vector and jointly construct the starlight angular distance observation quantity with the stellar vector.

[0108] (3) Starlight Vector Sensitive Payload

[0109] The starlight vector sensitive payload consists of an optical probe, a signal amplification and acquisition circuit, a star map database, a star map matching module, a starlight vector extraction module, etc. The starlight vector sensitive payload conducts observations with a large field of view. By installing multiple starlight vector sensitive probes, it can observe stars in multiple directions and obtain more starlight observation vectors. One starlight vector sensitive payload is set up to observe satellite S1, thereby obtaining the direction vector of satellite S1.

[0110] (4) Inter-satellite link

[0111] The inter-satellite link uses traditional and mature payloads to achieve communication and precise ranging between satellites. As satellite S1, the satellite receives the starlight angular distance observation information sent by other satellites through the inter-satellite link; as satellite 2 - satellite SN, the satellite transmits the starlight angular distance information to satellite S1 through the inter-satellite link. The inter-satellite distance can be measured by satellite S1, or can be measured and pre-processed by satellite 2 - satellite SN and then sent to satellite S1 together with the starlight angular distance after being packaged.

[0112] (5) Pulse phase estimation unit

[0113] This unit uses an embedded system as the carrier, takes the pulsar observation profile and the starlight angular distance measurement information of each satellite as inputs, distributes the starlight angular distance information into the pulsar profile bins, constructs a filter based on the pulse observation profile and the starlight angular distance information, completes information fusion, and realizes pulse phase calculation.

[0114] (6) Time synchronization timing system

[0115] It consists of an on-board clock, an inter-satellite link, an embedded system, and clock synchronization algorithm software. It ensures the accuracy and synchronization of the timing of each satellite.

[0116] 3 Data processing flow implementation plan

[0117] ① At time t0, start the pulse phase estimation task, with the duration until tN. During this time period, the pulsar detector continuously detects the arrival time sequence ph of the photons radiated by the pulsar;

[0118] ② At time t0, the starlight vector sensitive payload detects the starlight vector s i of the star and the vector Rs1 of satellite S1, the earth sensitive payload detects the geocentric vector Re, and the inter-satellite link detects the inter-satellite distance L;

[0119] ③ Taking time t0 as the reference starting point, set a certain number of bins N1. Fold the arrival time sequence ph of the pulsar photons according to the pulsar signal period Ps to synthesize the observation profile p(t), and this profile is the observation pulse profile corresponding to time t0. As Figure 2 shown;

[0120] ④At time t0, each satellite synthesizes the measured starlight vector and the geocentric vector to obtain the starlight angular distance θ i (where i represents the serial number of the obtained starlight angular distance), and calculates the projection L of the inter-satellite distance in the pulsar direction by using the inter-satellite link and the starlight vector of satellite S1 is ;

[0121] ⑤Pack the starlight angular distances of each satellite and their corresponding projections L of the inter-satellite distances is and send them to satellite S1 through the inter-satellite link.

[0122] ⑥Satellite S1 receives and collates the pulsar profile, the starlight angular distance data of each satellite, and the projection L of the inter-satellite distance at time t0 is data. In the pulse phase estimation unit, the following operations are carried out:

[0123] I: The starlight angular distance and the observed profile are used to form an observable quantity, and each bin corresponds to a set of observable quantities (p(k), θ k ), where k is the serial number of the kth bin, that is, the kth filtering step. The form of the constructed observable equation is:

[0124]

[0125] The specific parameters are the same as those in formula (4).

[0126] II: Using the standard profile, a state equation is constructed, which has the form of formula (3):

[0127]

[0128] III: Perform Kalman filtering calculation to obtain the estimated value of the pulse phase Φ

[0129] ⑦Output the pulse phase estimate Φ, and the current pulse phase estimation task ends.

[0130] The above embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention. In particular, for the pulse phase estimation method proposed by the present invention, in addition to being applied to the distributed satellite system mentioned in the present invention, it can also be applied to the pulse star phase estimation of a single satellite. At this time, it is required that the single satellite platform can obtain a sufficient number and quality of starlight vectors so as to synthesize sufficient starlight angular distances. The situation where a single satellite uses the method in the present invention to achieve pulse phase extraction can be considered as a special case of distributed pulse phase extraction.

Claims

1. A method for estimating pulse phase of a pulsar autonomous navigation, characterized by: The steps include: A1: S1, S2, Si...SN represent the satellites. The star observation vectors of the pulsar detection payload unit, the starlight vector sensitive payload unit, and the earth sensitive payload unit are: , the observation vector to the center of the Earth is The starlight angular distance synthesized by each satellite through observation of stars and the Earth is ; A2: At some point :Use the arrival time sequence of pulsar photons received by the pulsar detector to calculate the time series according to the pulsar period The photon arrival time series is folded into the first pulse period in the form of a histogram to obtain the observation profile ; A3: Perform high-precision pulse phase estimation; The specific process of step A2 includes: B1: As the starting point, the arrival time is greater than one Pulsar photon arrival time series Take the remainder and insert it into arrive , thus obtaining the distribution in arrive Photon point of time period; B2: Draw a bar chart with bin width as the width, and the vertical axis is the number of photons falling into the bin; B3: The amplitude sequence of the histogram is the observed value of the contour on the bin , its continuous form is ; B4: Treat bin as filter step size , the contour value corresponding to each bin As the pulse profile observation value on this bin; B5: Detecting the synthetic starlight angular distance using a starlight vector-sensitive payload and an earth-sensitive payload For each bin, the starlight angular distance observation value is randomly matched with the pulse profile observation value on the bin to form a two-dimensional observation combination ; B6: Combine the standard profile information to construct a Kalman filter and perform filtering calculations. After convergence, the pulse phase value at that moment is obtained, specifically: Pulsar Standard Profile The sum and phase functions can be obtained through long-term observations on the ground and in orbit, and are the basis of pulsar navigation. When a satellite performs autonomous pulsar navigation on orbit, it uses onboard detectors to detect the arrival time of pulsar photons, converts the large-scale space-time to the solar system's center of mass coordinate system, and folds it into a profile. The phase information is then compared with the standard profile to obtain the observed phase information. The observed profile can be modeled as: ( ) in, The amplitude coefficient representing the folding profile can be converted to 1 by normalizing the folding profile. It is reflected in the overall upward shift of the observed contour due to the noise effect in the contour folding, which is regarded as a constant. The pulse delay can be converted into pulse phase , is the equivalent Gaussian white noise of the detector and background; The satellite observes stars through the starlight vector sensitive payload to obtain the starlight observation vector, and uses the earth sensitive payload to sense the horizon and calculate the geocentric vector, so as to construct the starlight angular distance observation quantity between the star and the center of the earth. According to the geometric relationship, the starlight angular distance between the star and the center of the earth is As a function of position, the observation equation can be established as: ( ) in, For a known star being observed The unit starlight vector, is the satellite position vector in the solar system barycentric coordinate system, The symbol represents a large-scale space-time transformation, Represents the coordinate system of the solar system's center of mass valuation, represents the position estimation error, is the pulse phase in the vector direction of the three pulsars, are the three pulsar periods, are the unit vectors of the three pulsars, For the The inter-satellite phase difference between the satellite corresponding to the starlight angular distance and the satellite that realizes the fusion phase estimation, is the speed of light, is the projection of the inter-satellite distance between this satellite and satellite S1 in the direction of the observed pulsar, where S1 is the main satellite for navigation calculations. is the pulse frequency emitted by the pulsar, To measure noise; For a satellite that observes pulsars in three directions, let represents three standard pulsar profiles, represents the function obtained by differentiating the three standard contours, is the upward shift of the three observation contours, then the state equation can be established as ( ) As mentioned above, using pulsar observation profiles and the angular distance of the starlight , through geometric relations, the observation equation can be constructed as: ( ) make , , then the above equation can be rearranged as: ( ) ( ) in, , is the nonlinear observation equation, and are state noise and observation noise respectively, which are equivalent to Gaussian white noise; According to the above state equation and observation equation, the pulse phase is analyzed using Kalman filter. Make an estimate.

2. The method for estimating pulse phase of a pulsar autonomous navigation according to claim 1, wherein: The specific process of step A3 includes: C1: Using the high-precision clock timing and synchronization system on board as the time reference, the satellites in the distributed system maintain good time synchronization and timing accuracy; starting the mission with a satellite responsible for mission scheduling, with the mission starting point set as , carry out observation accumulation of pulsar radiation signals, and simultaneously carry out starlight vector and geocentric vector observations on each satellite, as well as inter-satellite distance and satellite S1 direction vector observations; C2: Satellite S1 The time series information of the photon arrival time of the pulsar detection is synthesized into a certain number of bins to obtain N1 profile amplitude observations. ; C3: At this moment, each satellite uses its observed starlight vector and geocentric vector to synthesize the starlight angular distance information, and packages it together with the inter-satellite distance data at that moment and sends it to satellite S1; C4: Satellite S1 uses the received starlight angular distance information and pulsar observation profile to construct an observation combination corresponding to each bin of the profile , and construct the observation equation (4) and the state equation (3), taking bin as the filter step size , the Kalman filter is used to calculate and obtain a high-precision pulse phase estimate.

3. A pulsar autonomous navigation pulse phase estimation system for implementing the pulsar autonomous navigation pulse phase estimation method according to any one of claims 1 to 2, characterized in that: It is based on a distributed satellite system, which is interconnected by inter-satellite links and includes several distributed satellites, each of which carries the following units: High-precision time synchronization timing system, used to provide a unified time base and high-precision timing for the entire system; Pulsar detection payload unit, used to detect pulsars and obtain the arrival time series information of photons from pulsars to the satellite; The photon arrival time series is profile-folded with the pulsar period to generate the observed pulse profile; Starlight vector sensitive payload unit, used for observing star vectors; Earth-sensitive load unit, used to extract the geocentric vector; Intersatellite link payload unit, used to achieve communication and ranging between satellites; Based on its measurement information, the data fusion of satellite pulsar measurement and starlight angular distance is realized, and the starlight angular distance is constructed by the starlight vector and the geocentric vector.

4. The system according to claim 3, wherein: The pulsar detection payload unit is carried on each satellite in a distributed arrangement, or on at least one satellite that realizes pulse phase estimation.

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