Real-time precise orbit determination method for low-orbit satellites when onboard GNSS observations are discontinuous

Abstract

The present invention discloses a method for real-time precise orbit determination of a low-orbit satellite when onboard GNSS observation is discontinuous, the method comprising: obtaining GNSS observation data and real-time products required for orbit determination of a low-orbit satellite; solving a first unknown parameter using a simplified dynamic orbit determination observation model that introduces random acceleration according to the obtained data, thereby obtaining a first orbit determination result; solving a second unknown parameter using a simplified dynamic orbit determination observation model that does not introduce random acceleration according to the obtained data, thereby obtaining a second orbit determination result; splicing the first and second orbit determination results according to the GNSS observation discontinuity start time and the GNSS observation discontinuity end time, and performing real-time orbit prediction of the low-orbit satellite according to the spliced ​​orbit determination results. The present invention can realize real-time high-precision orbit determination when a GNSS satellite receiver successfully unloads data in real time, but fails to unload lagging data, resulting in a GNSS observation discontinuity of several hours.

Description

Technical Field

[0001] The present invention belongs to the field of satellites, and in particular relates to a real-time precise orbit determination method for a low-orbit satellite when onboard GNSS (Global Navigation Satellite System, GNSS) observation is discontinuous. Background Art

[0002] In recent years, low Earth Orbit (LEO) satellites have a series of advantages over GNSS satellites located in medium and high orbits, namely GEO (Geostationary Earth Orbit), such as better satellite geometry, stronger anti-interference ability, lower cost, and multipath effect whitening, due to their low flight altitude and high speed. They have gradually attracted attention and favor in the field of satellite positioning, navigation and timing, and have become the focus of the development of the next generation of satellite navigation systems. Real-time high-precision low-orbit satellite orbit and clock error products are an important prerequisite for realizing low-orbit enhanced services.

[0003] The global satellite navigation system includes a variety of orbit determination technologies, mainly L-band pseudorange phase observation, satellite laser ranging (SLR) and C-band self-transmitting and self-receiving ranging. Among them, the L-band pseudorange phase observation technology is mainly based on monitoring receivers. Its advantages are low cost of monitoring receivers, easy to implement and promote. According to the different characteristics of satellite orbit and clock error relative to the ground monitoring network, the orbit and clock error parameters can be separated to perform precise orbit determination. Different from GNSS using ground monitoring station network to solve satellite orbit, such as Figure 1 As shown in the figure, it is difficult for low-orbit satellites to continuously obtain ground observation data due to their low orbital altitude and small earth projection area. Therefore, low-orbit satellites receive GNSS observation data by carrying onboard GNSS receivers, and use various channels to obtain high-precision GNSS orbit and clock error products, so that low-orbit satellites, as users of GNSS signals, can obtain precise LEO orbits and clock errors. Therefore, the quality of observation data is a direct factor affecting the real-time orbit determination accuracy of low-orbit satellites.

[0004] In real-time state, due to the limitation of multi-satellite unloading channels and the short overpass period of low-orbit satellites relative to ground stations, which is only 10 to 20 minutes, GNSS satellite receivers are often unable to simultaneously realize real-time unloading and batch observation delayed unloading. Here, batch observation delayed unloading refers to the unloading of several hours of observation data stored in the satellite receiver during the interval between two overpasses. When the real-time unloading is successful and the delayed unloading is limited, one or two rounds of batch observations will be missing. There will often be several hours of observation interruption 10 to 20 minutes before the end of the observation arc, which seriously affects the accuracy of real-time orbit determination. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for real-time precise orbit determination of a low-orbit satellite when onboard GNSS observation is discontinuous.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] A method for real-time precise orbit determination of a low-orbit satellite when onboard GNSS observation is discontinuous, comprising:

[0008] Acquire relevant data required for orbit determination of a low-orbit satellite; the relevant data includes GNSS observation data and real-time products; and there are observation gaps in the observation arc of the GNSS observation data;

[0009] According to the relevant data, a first unknown parameter is solved by using a simplified dynamic orbit determination observation model that introduces random acceleration to obtain a first solution result; a first orbit determination result is inferred according to the first solution result; wherein the first unknown parameter includes: six Kepler elements at the initial epoch of the low-orbit satellite, constant terms and random accelerations of the solar pressure in the radial, tangential and normal directions, the low-orbit satellite clock error, and the code and phase ionospheric-free combined floating-point ambiguity of the GNSS satellite;

[0010] According to the relevant data, a second unknown parameter is solved by using a simplified dynamic orbit determination observation model without introducing random acceleration to obtain a second solution result; a second orbit determination result is inferred according to the second solution result; wherein the second unknown parameters include: six Kepler elements at the initial epoch of the low-orbit satellite, nine solar pressure parameters, a low-orbit satellite clock error, and a code and phase ionospheric-free combined floating-point ambiguity of the GNSS satellite; the nine solar pressure parameters include a constant term, a sine term, and a cosine term of the solar pressure in three directions: radial, tangential, and normal;

[0011] splicing the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time to obtain a third orbit determination result;

[0012] A real-time orbit prediction of the low-orbit satellite is performed based on the third orbit determination result.

[0013] Optionally, the simplified dynamic orbit determination observation model introducing random acceleration is:

[0014] ,

[0015] ;

[0016] in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, It is a subset of the constant terms of the solar pressure in the radial, tangential and normal directions; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, Represents the random acceleration of the solar pressure in the radial, tangential and normal directions; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase for the code and phase ionization-free code layer combination.

[0017] Optionally, the simplified dynamic orbit determination observation model without introducing random acceleration is:

[0018] ,

[0019] ;

[0020] in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, represents the nine solar pressure parameters; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase values ​​in the ionosphere-free combination.

[0021] Optionally, the splicing of the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time is implemented by the following formula:

[0022] ;

[0023] in, represents the first orbit determination result, represents the second orbit determination result, Indicates the start time of GNSS observation interruption. Indicates the end time of GNSS observation interruption. Indicates the GNSS observation start time, Indicates the end time of GNSS observation. represents the third orbit determination result.

[0024] Optionally, performing real-time orbit prediction of a low-orbit satellite according to the third orbit determination result includes:

[0025] According to the third orbit determination result, a batch least squares fitting is performed on the six Kepler elements and nine solar pressure parameters corresponding to the low-orbit satellite orbit using a linearized equation to obtain the six Kepler elements and nine solar pressure parameters within the fitting interval;

[0026] The linearized equation is:

[0027] ;

[0028] in, Indicates epochs, represents the six Kepler numbers at the initial moment of the fitting interval, represents the nine solar pressure parameters within the fitting interval, Indicates the initial state of the low-orbit satellite orbit The partial guide, Indicates the initial state of the low-orbit satellite orbit The partial guide, represents the orbit of the third orbit determination result within the fitting interval, represents the expectation operation;

[0029] According to the six Kepler numbers at the initial moment of the fitting interval and the nine solar light pressure parameters in the fitting interval, the precise orbit of the low-orbit satellite in the prediction interval is obtained by using the numerical integration method.

[0030] Optionally, the real-time product includes a GNSS real-time orbit clock error product;

[0031] The method also includes: performing cycle slip detection and gross error elimination on the GNSS observation data, and eliminating outliers on the GNSS real-time orbit clock error product.

[0032] The present invention also provides a low-orbit satellite real-time precise orbit determination device when onboard GNSS observation is discontinuous, comprising:

[0033] An acquisition module is used to acquire relevant data required for orbit determination of a low-orbit satellite; the relevant data includes GNSS observation data and real-time products; and there are observation discontinuities in the observation arc of the GNSS observation data;

[0034] A first solution module is used to solve the first unknown parameter according to the relevant data by using a simplified dynamic orbit determination observation model that introduces random acceleration to obtain a first solution result; and to infer the first orbit determination result according to the first solution result; wherein the first unknown parameter includes: six Kepler elements at the initial epoch of the low-orbit satellite, constant terms and random accelerations of the solar pressure in the radial, tangential and normal directions, the low-orbit satellite clock error, and the code and phase ionospheric-free combined floating-point ambiguity of the GNSS satellite;

[0035] A second solution module is used to solve the second unknown parameters according to the relevant data by using a simplified dynamic orbit determination observation model without introducing random acceleration to obtain a second solution result; and to infer the second orbit determination result according to the second solution result; wherein the second unknown parameters include: six Kepler elements at the initial epoch of the low-orbit satellite, nine solar pressure parameters, a low-orbit satellite clock error, and a code and phase ionospheric-free combined floating-point ambiguity of the GNSS satellite; the nine solar pressure parameters include a constant term, a sine term, and a cosine term of the solar pressure in three directions: radial, tangential, and normal;

[0036] A splicing module, configured to splice the first orbit determination result and the second orbit determination result according to a GNSS observation interruption start time and a GNSS observation interruption end time to obtain a third orbit determination result;

[0037] A prediction module is used to perform real-time orbit prediction of the low-orbit satellite according to the third orbit determination result.

[0038] Optionally, the simplified dynamic orbit determination observation model introducing random acceleration is:

[0039] ,

[0040] ;

[0041] in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, It is a subset of the constant terms of the solar pressure in the radial, tangential and normal directions; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, Represents the random acceleration of the solar pressure in the radial, tangential and normal directions; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase for the code and phase ionization-free code layer combination.

[0042] Optionally, the simplified dynamic orbit determination observation model without introducing random acceleration is:

[0043] ,

[0044] ;

[0045] in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, represents the nine solar pressure parameters; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase values ​​in the ionosphere-free combination.

[0046] Optionally, the splicing module splices the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time, which is implemented by the following formula:

[0047] ;

[0048] in, represents the first orbit determination result, represents the second orbit determination result, Indicates the start time of GNSS observation interruption. Indicates the end time of GNSS observation interruption. Indicates the GNSS observation start time, Indicates the end time of GNSS observation. represents the third orbit determination result.

[0049] The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous provided by the present invention aims at the problem that when the GNSS satellite receiver successfully unloads data in real time but fails to unload the lagging data, several hours of GNSS observation interruption will occur, resulting in the inability to achieve real-time high-precision orbit determination. The advantages of simplified dynamics orbit determination with the introduction of random acceleration and simplified dynamics orbit determination without the introduction of random acceleration are combined. According to the start time of the GNSS observation interruption and the end time of the GNSS observation interruption, the simplified dynamics orbit determination result with the introduction of random acceleration and the dynamics orbit determination result without the introduction of random acceleration are spliced ​​into a near-real-time precise orbit determination result of the low-orbit satellite, i.e., the third orbit determination result. Then, the real-time orbit prediction of the low-orbit satellite is performed according to the third orbit determination result, thereby achieving real-time high-precision orbit determination in a manner of first orbit determination, then splicing, and then prediction.

[0050] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is an application scenario diagram of a method for real-time precise orbit determination of a low-orbit satellite when onboard GNSS observation is discontinuous provided by an embodiment of the present invention;

[0052] Figure 2 It is a flow chart of a method for real-time precise orbit determination of a low-orbit satellite when onboard GNSS observation is discontinuous provided by an embodiment of the present invention;

[0053] Figure 3 It is a structural schematic diagram of a low-orbit satellite real-time precise orbit determination device provided by an embodiment of the present invention when onboard GNSS observation is discontinuous. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0055] To achieve orbit determination of low-orbit satellites in real time, we can choose to abandon the 10 to 20 minutes of observations in the tail arc, perform simplified dynamic orbit determination by processing the more complete arc before, and use the orbit determination results for long-term prediction to catch up with the corresponding real-time window. In this case, we need to make a choice between the following two situations:

[0056] (1) The observations of the last 10 to 20 minutes of the arc segment are discarded, and the orbit determination is performed using the more complete arc segment. However, due to the serious lag between the observation and real-time, a long forecast is required to correspond to the real-time window.

[0057] (2) Keep the observations of the last 10 to 20 minutes of the processing arc segment, and perform orbit determination when there is a gap of several hours in the observation arc segment. In this case, the overall orbit determination accuracy is impaired, but the lag from real time is short, and a short forecast corresponding to the real-time window can be performed.

[0058] However, the simplified dynamic orbit determination that introduces Kepler's six numbers, random acceleration and constant solar pressure parameters requires good continuity of GNSS observation data to achieve precise orbit determination. If there is a long observation gap, whether the tail observation value is discarded for long-term forecast to catch up with the real-time window, or the arc tail observation data is used for short-term forecast, the forecast accuracy is poor.

[0059] Therefore, in order to achieve real-time high-precision orbit determination when the GNSS satellite receiver successfully downloads data in real time, but fails to download delayed data, resulting in a GNSS observation interruption of several hours, an embodiment of the present invention provides a method for real-time precise orbit determination of a low-orbit satellite when onboard GNSS observation is discontinuous, such as Figure 2 As shown, the method comprises the following steps:

[0060] S10. Acquire relevant data required for orbit determination of low-orbit satellites; the relevant data include GNSS observation data and real-time products; and there are observation gaps in the observation arc of the GNSS observation data.

[0061] Specifically, low-orbit satellites receive GNSS observation data through onboard GNSS receivers, and obtain high-precision real-time products through various channels, including GNSS real-time orbit clock products. In practice, real-time products can be obtained through the NTRIP protocol. Here, the NTRIP protocol is the network transmission protocol for RTCM (Radio Technology Committee of Marine) data, and is an application layer protocol for GNSS data transmission using the Internet network.

[0062] In addition, after obtaining the relevant data required for orbit determination of low-orbit satellites, cycle slip detection and gross error elimination can be performed on the GNSS observation data, and outliers can be eliminated from the GNSS real-time orbit clock error products.

[0063] S20. According to the above-mentioned relevant data, a first unknown parameter is solved by using a simplified dynamic orbit determination observation model that introduces random acceleration to obtain a first solution result; and a first orbit determination result is inferred according to the first solution result.

[0064] The simplified dynamic orbit determination observation model with random acceleration is:

[0065] (1),

[0066] (2);

[0067] In formula (1) and formula (2), Indicates epochs, Indicates GNSS satellite The received code and phase combination is ionospheric-free (IF) for The partial derivative is:

[0068] ;

[0069] in, is the six Kepler numbers at the initial epoch of the low-orbit satellite. The initial epoch is expressed as ; Indicated in The rough processing orbit of the low-orbit satellite at the epoch, Indicated in GNSS satellites per epoch track. Indicated in epoch, GNSS satellite The received code and phase ionospheric-free combination is In addition, Indicated in The partial derivative of the GNSS observation data with respect to the orbital position of the low-orbit satellite at the epoch; Indicated in At epoch, the orbital position of the low-orbit satellite is about These terms are based on the numerical integration expansion of the variational equation.

[0070] In formula (1) and formula (2), Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial derivative is:

[0071] ;

[0072] in, It is a subset of the constant terms of the solar pressure in the radial, tangential and normal directions; Indicated in epoch, GNSS satellite The received code and phase ionospheric-free combination is In addition, Indicated in At epoch, the orbital position of the low-orbit satellite is about The partial derivative of , which is also based on the numerical integration expansion of the variational equation.

[0073] The solar pressure parameters are nine parameters of the CODE (Center for Orbit Determination in Europe, CODE) orbit model (Empirical CODE Orbit Model, ECOM), referred to as the nine solar pressure parameters, expressed as:

[0074] ;

[0075] in, They represent the constant terms of the solar pressure in the radial (R), tangential (S) and normal (W) directions respectively. They represent the sine terms of the solar pressure in the radial, tangential and normal directions respectively. The cosine terms of the solar pressure in the radial, tangential and normal directions are represented in turn. Represents the transpose of a vector.

[0076] The nine solar pressure parameters are combined into the solar pressure acceleration in the radial, tangential and normal directions, which are expressed as follows:

[0077] ,

[0078] ,

[0079] ;

[0080] in, is the mean anomaly angle. In order to avoid over-parameterization, in the embodiment of the present invention, The subset of constant terms representing the solar pressure in the radial, tangential and normal directions is represented by Represents the random acceleration of the solar pressure in the radial, tangential and normal directions.

[0081] In formula (1) and formula (2), Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial derivative is:

[0082] ;

[0083] in, Represents the random acceleration of the solar pressure in the radial, tangential and normal directions; Indicated in epoch, GNSS satellite The received code and phase ionospheric-free combination is In addition, Indicated in At epoch, the orbital position of the low-orbit satellite is about The partial derivative of , which is also based on the numerical integration expansion of the variational equation.

[0084] In formula (1) and formula (2), represents the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, is the code and phase ionospheric-free combined pseudorange hardware delay of the low-orbit satellite; From the expression, we can see that the code and phase ionospheric-free combined floating point ambiguity includes not only the absorbed phase hardware delay, but also the pseudorange hardware delay, which is to offset the pseudorange hardware delay absorbed in the clock error of the onboard GNSS receiver. represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase for the code and phase ionization-free code layer combination.

[0085] The first unknown parameters mentioned above include: the six Kepler numbers at the initial epoch of the low-orbit satellite , the constant term of the solar pressure in the radial, tangential and normal directions and random acceleration , low-orbit satellite clock error , and the ionospheric-free combined floating point ambiguities of the code and phase of the GNSS satellite , so the first unknown parameter can be expressed as .

[0086] It can be understood that the simplified dynamic orbit determination is a process of precise orbit determination based on a series of gravitational perturbations and non-gravitational perturbations, among which tidal perturbations, solid earth perturbations and N-body perturbations in gravitational perturbations all have relatively mature models, but non-gravitational perturbations such as solar light pressure perturbations and atmospheric drag cannot perfectly establish effective models, so the physical parameters that cannot perfectly establish effective models can be used as physical parameters to be estimated, and random acceleration is introduced to make up for the shortcomings of the dynamic model, and the batch least squares method is used together with the six Kepler roots to solve. In addition, when performing batch least squares solution, GNSS observation data and a series of mature models can also be used to calculate the difference between the observed value and the model value (Observed-Minus-Computed term, OC term), and the code and phase ionosphere-free combination (IF combination) is used to eliminate the influence of the first-order ionospheric delay. The specific solution process belongs to the prior art, and the embodiment of the present invention is not repeated.

[0087] Therefore, batch least squares method is used to perform batch processing in combination with equation (1) and equation (2), and real-time high-precision GNSS real-time orbit clock error products are introduced in batch processing to estimate the optimal solution of the first unknown parameter, and then numerical integration is performed based on the solved parameters to calculate the near-real-time low-orbit satellite precise orbit product, that is, the first orbit determination result. Among them, orbit determination by numerical integration is an existing mature technology, and the embodiments of the present invention will not be described in detail.

[0088] It is worth mentioning that when the continuity of GNSS observation data is good, the first orbit determination result obtained by introducing a simplified dynamic orbit determination observation model with random acceleration is more accurate.

[0089] S30. According to the above-mentioned relevant data, a second unknown parameter is solved using a simplified dynamic orbit determination observation model without introducing random acceleration to obtain a second solution result; and a second orbit determination result is inferred according to the second solution result.

[0090] The simplified dynamic orbit determination observation model without introducing random acceleration is:

[0091] (3),

[0092] (4);

[0093] In formula (3) and formula (4), Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial derivative is:

[0094] ;

[0095] in, Represents nine solar pressure parameters; Indicates the orbital position of the low-orbit satellite with respect to The partial derivative of , the interpretation of the other parameters in equation (3) and (4) can be found above.

[0096] The second unknown parameters mentioned above include: the six Kepler numbers at the initial epoch of the low-orbit satellite 、Nine solar pressure parameters 、Low-Earth Orbit Satellite Clock Error , and the ionospheric-free combined floating point ambiguities of the code and phase of the GNSS satellite , so the second unknown parameter can be expressed as .

[0097] Therefore, batch least squares method is used to perform batch processing in combination with equation (3) and equation (4), and real-time high-precision GNSS real-time orbit clock error products are introduced in batch processing to estimate the optimal solution of the second unknown parameter; then numerical integration is performed based on the solved parameters to calculate the near-real-time low-orbit satellite precise orbit product, i.e., the second orbit determination result. Among them, orbit prediction by numerical integration belongs to the existing mature technology, and the embodiment of the present invention will not be described in detail.

[0098] It is worth mentioning that the simplified dynamic orbit determination without introducing random acceleration has a lower dependence on the continuity of GNSS observations. Therefore, when there are long interruptions in GNSS observation data, the orbit determination accuracy of the simplified dynamic orbit determination model without introducing random acceleration is better.

[0099] S40, splicing the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time to obtain a third orbit determination result.

[0100] Specifically, according to the start time and the end time of the GNSS observation interruption, the simplified dynamic orbit determination result with the introduction of random acceleration is used in the continuous observation arc segment, and the dynamic orbit determination result without the introduction of random acceleration is used in the non-continuous observation arc segment with observation interruptions, so that the two orbit determination results are spliced ​​into a higher-precision near-real-time precise orbit determination result of the low-orbit satellite, that is, the third orbit determination result.

[0101] Here, the first orbit determination result and the second orbit determination result are spliced ​​according to the start time of the GNSS observation interruption and the end time of the GNSS observation interruption, which is achieved by the following formula:

[0102] ;

[0103] in, Indicates the start time of GNSS observation interruption. Indicates the end time of GNSS observation interruption. Indicates the GNSS observation start time, Indicates the end time of GNSS observation. represents the first orbit determination result, Indicates that the first orbit determination result is taken. to Data during this time period; Indicates that the first orbit determination result is taken. to Data during this period; represents the second orbit determination result, Indicates that the second orbit determination result is taken. to The data during this period, The third orbit determination result is shown in Figure 1. to , so it can also be expressed as .

[0104] S50. Perform real-time orbit prediction of the low-orbit satellite according to the third orbit determination result.

[0105] Specifically, the real-time orbit prediction of low-orbit satellites is carried out according to the third orbit determination results, including:

[0106] (1) Based on the third orbit determination result, the six Kepler elements and nine solar pressure parameters corresponding to the low-orbit satellite orbit are fitted by batch least squares using the linearized equation to obtain the six Kepler elements and nine solar pressure parameters within the fitting range.

[0107] The linearized equation is:

[0108] ;

[0109] in, Indicates epochs, represents the six Kepler numbers at the initial moment of the fitting interval, represents the nine solar pressure parameters within the fitting interval, Indicates the initial state of the low-orbit satellite orbit The partial guide, Indicates the initial state of the low-orbit satellite orbit The partial guide, Indicates the orbit of the third orbit determination result within the fitting interval. The fitting interval is usually the last few hours of the near-real-time precise orbit of the low-orbit satellite. The fitting interval is expressed as express.

[0110] (2) Based on the six Kepler numbers at the initial moment of the fitting interval and the nine solar pressure parameters within the fitting interval, the precise orbit of the low-orbit satellite in the prediction interval is obtained by numerical integration method.

[0111] Specifically, by combining the six Kepler numbers at the initial moment of the fitting interval, the nine solar pressure parameters in the fitting interval, and the existing high-precision orbital perturbation model, the orbit can be extrapolated through numerical integration using existing mature technologies to obtain the prediction interval. The precise orbit of low-orbit satellites can be determined in real time with high precision, including the prediction interval The precise orbit of the low-orbit satellite is expressed as .

[0112] The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous provided in an embodiment of the present invention aims at the problem that when the GNSS satellite receiver successfully unloads data in real time but fails to unload the lagging data, several hours of GNSS observation interruption will occur, resulting in the inability to achieve real-time high-precision orbit determination. The advantages of the simplified dynamics orbit determination with the introduction of random acceleration and the simplified dynamics orbit determination without the introduction of random acceleration are combined. According to the start time of the GNSS observation interruption and the end time of the GNSS observation interruption, the simplified dynamics orbit determination result with the introduction of random acceleration and the dynamics orbit determination result without the introduction of random acceleration are spliced ​​into a higher-precision near-real-time precise orbit determination result of the low-orbit satellite, that is, the third orbit determination result. Then, the real-time orbit prediction of the low-orbit satellite is performed according to the third orbit determination result, thereby achieving real-time high-precision orbit determination in the manner of first orbit determination, then splicing, and then prediction.

[0113] The method provided in the embodiment of the present invention can be applied to electronic devices. Specifically, the electronic devices can be: desktop computers, portable computers, intelligent mobile terminals, servers, etc.

[0114] Corresponding to the above-mentioned method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous, the present invention also provides a real-time precise orbit determination device for low-orbit satellites when onboard GNSS observation is discontinuous, such as Figure 3 As shown, the device comprises:

[0115] Acquisition module 201, used to acquire relevant data required for orbit determination of low-orbit satellites; the relevant data includes GNSS observation data and real-time products; wherein the observation arc of GNSS observation data has observation discontinuities;

[0116] The first solution module 202 is used to solve the first unknown parameter according to the above-mentioned relevant data by using the simplified dynamic orbit determination observation model introducing random acceleration to obtain a first solution result; and infer the first orbit determination result according to the first solution result; wherein the first unknown parameter includes: the six Kepler elements at the initial epoch of the low-orbit satellite, the constant term and random acceleration of the solar pressure in the radial, tangential and normal directions, the low-orbit satellite clock error, and the code and phase ionospheric-free combined floating point ambiguity of the GNSS satellite;

[0117] The second solution module 203 is used to solve the second unknown parameters according to the above-mentioned relevant data using a simplified dynamic orbit determination observation model without introducing random acceleration to obtain a second solution result; and infer the second orbit determination result according to the second solution result; wherein the second unknown parameters include: six Kepler elements at the initial epoch of the low-orbit satellite, nine solar pressure parameters, low-orbit satellite clock error, and ionospheric-free combined floating-point ambiguity of the code and phase of the GNSS satellite; the nine solar pressure parameters include constant terms, sine terms and cosine terms of solar pressure in the radial, tangential and normal directions;

[0118] A splicing module 204, configured to splice the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time to obtain a third orbit determination result;

[0119] The prediction module 205 is used to perform real-time orbit prediction of the low-orbit satellite according to the third orbit determination result.

[0120] In one embodiment, a simplified dynamic orbit determination observation model with random acceleration is:

[0121] ,

[0122] ;

[0123] in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, It is a subset of the constant terms of the solar pressure in the radial, tangential and normal directions; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, Represents the random acceleration of the solar pressure in the radial, tangential and normal directions; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase for the code and phase ionization-free code layer combination.

[0124] In one embodiment, a simplified dynamic orbit determination observation model without introducing random acceleration is:

[0125] ,

[0126] ;

[0127] in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, Represents nine solar pressure parameters; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase values ​​in the ionosphere-free combination.

[0128] In one embodiment, the splicing module 204 splices the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time, by the following formula:

[0129] ;

[0130] in, represents the first orbit determination result, represents the second orbit determination result, Indicates the start time of GNSS observation interruption. Indicates the end time of GNSS observation interruption. Indicates the GNSS observation start time, Indicates the end time of GNSS observation. Indicates the third orbit determination result.

[0131] In one embodiment, the forecast module 205 is specifically configured to:

[0132] According to the third orbit determination result, the six Kepler numbers and nine solar pressure parameters corresponding to the low-orbit satellite orbit are fitted by batch least squares using the linearized equation to obtain the six Kepler numbers and nine solar pressure parameters within the fitting interval.

[0133] The linearized equation is:

[0134] ;

[0135] in, Indicates epochs, represents the six Kepler numbers at the initial moment of the fitting interval, represents the nine solar pressure parameters within the fitting interval, Indicates the initial state of the low-orbit satellite orbit The partial guide, Indicates the initial state of the low-orbit satellite orbit The partial guide, represents the orbit of the third orbit determination result within the fitting interval, represents the expectation operation;

[0136] According to the six Kepler numbers at the initial moment of the fitting interval and the nine solar pressure parameters in the fitting interval, the precise orbit of the low-orbit satellite in the prediction interval is obtained by numerical integration method.

[0137] In one embodiment, the real-time product includes a GNSS real-time orbit and clock product;

[0138] The above-mentioned device also includes: a preprocessing module; the preprocessing module is used to detect cycle slips and eliminate gross errors in GNSS observation data, and eliminate outliers in GNSS real-time orbit clock error products.

[0139] It should be noted that, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0140] It should be noted that the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention.

[0141] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0142] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art can understand and implement other changes to the disclosed embodiments by viewing the drawings and the disclosed content. In the description of the present invention, the term "comprising" does not exclude other components or steps, "one" or "an" does not exclude multiple situations, and "multiple" means two or more, unless otherwise clearly and specifically limited. In addition, certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0143] It should be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, devices (equipment), or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects, which are collectively referred to as "modules" or "systems" herein. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The computer program is stored / distributed in a suitable medium, provided together with other hardware or as part of the hardware, or may take other distribution forms, such as through the Internet or other wired or wireless telecommunications systems.

[0144] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observations are discontinuous, characterized in that: include: Obtain relevant data required for orbit determination of low-orbit satellites; The relevant data include GNSS observation data and real-time products; There are observation discontinuities in the observation arc of the GNSS observation data; According to the relevant data, a first unknown parameter is solved by using a simplified dynamic orbit determination observation model that introduces random acceleration to obtain a first solution result; The first orbit determination result is calculated according to the first solution result; wherein the first unknown parameters include: the six Kepler elements at the initial epoch of the low-orbit satellite, the constant term and random acceleration of the solar pressure in the radial, tangential and normal directions, the low-orbit satellite clock error, and the ionospheric-free combined floating-point ambiguity of the code and phase of the GNSS satellite; According to the relevant data, a second unknown parameter is solved by using a simplified dynamic orbit determination observation model without introducing random acceleration to obtain a second solution result; a second orbit determination result is inferred according to the second solution result; wherein the second unknown parameters include: six Kepler elements at the initial epoch of the low-orbit satellite, nine solar pressure parameters, a low-orbit satellite clock error, and a code and phase ionospheric-free combined floating-point ambiguity of the GNSS satellite; the nine solar pressure parameters include a constant term, a sine term, and a cosine term of the solar pressure in three directions: radial, tangential, and normal; splicing the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time to obtain a third orbit determination result; A real-time orbit prediction of the low-orbit satellite is performed based on the third orbit determination result.

2. The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous according to claim 1, characterized in that: The simplified dynamic orbit determination observation model introducing random acceleration is: ， ； in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, It is a subset of the constant terms of the solar pressure in the radial, tangential and normal directions; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, Represents the random acceleration of the solar pressure in the radial, tangential and normal directions; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase for the code and phase iono-free code layer combination.

3. The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous according to claim 1, characterized in that: The simplified dynamic orbit determination observation model without introducing random acceleration is: ， ； in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, represents the nine solar pressure parameters; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase values ​​in the ionosphere-free combination.

4. The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous according to claim 1, characterized in that: The splicing of the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time is achieved by the following formula: ； in, represents the first orbit determination result, represents the second orbit determination result, Indicates the start time of GNSS observation interruption. Indicates the end time of GNSS observation interruption. Indicates the GNSS observation start time, Indicates the end time of GNSS observation. represents the third orbit determination result.

5. The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous according to claim 1, characterized in that: Performing real-time orbit prediction of a low-orbit satellite according to the third orbit determination result includes: According to the third orbit determination result, a batch least squares fitting is performed on the six Kepler elements and nine solar pressure parameters corresponding to the low-orbit satellite orbit using a linearized equation to obtain the six Kepler elements and nine solar pressure parameters within the fitting interval; The linearized equation is: ； in, Indicates epochs, represents the six Kepler numbers at the initial moment of the fitting interval, represents the nine solar pressure parameters within the fitting interval, Indicates the initial state of the low-orbit satellite orbit The partial guide, Indicates the initial state of the low-orbit satellite orbit The partial guide, represents the orbit of the third orbit determination result within the fitting interval, represents the expectation operation; According to the six Kepler numbers at the initial moment of the fitting interval and the nine solar light pressure parameters in the fitting interval, the precise orbit of the low-orbit satellite in the prediction interval is obtained by using the numerical integration method.

6. The method for real-time precise orbit determination of low-orbit satellites when onboard GNSS observation is discontinuous according to claim 1, characterized in that: The real-time products include GNSS real-time orbit and clock products; The method also includes: performing cycle slip detection and gross error elimination on the GNSS observation data, and eliminating outliers on the GNSS real-time orbit clock error product.

7. A real-time precise orbit determination device for low-orbit satellites when onboard GNSS observation is discontinuous, characterized in that: include: An acquisition module is used to obtain relevant data required for orbit determination of low-orbit satellites; The relevant data include GNSS observation data and real-time products; There are observation discontinuities in the observation arc of the GNSS observation data; A first solving module is used to solve the first unknown parameter according to the relevant data by using a simplified dynamic orbit determination observation model that introduces random acceleration to obtain a first solving result; The first orbit determination result is calculated according to the first solution result; wherein the first unknown parameters include: the six Kepler elements at the initial epoch of the low-orbit satellite, the constant term and random acceleration of the solar pressure in the radial, tangential and normal directions, the low-orbit satellite clock error, and the ionospheric-free combined floating-point ambiguity of the code and phase of the GNSS satellite; A second solution module is used to solve the second unknown parameters according to the relevant data by using a simplified dynamic orbit determination observation model without introducing random acceleration to obtain a second solution result; and to infer the second orbit determination result according to the second solution result; wherein the second unknown parameters include: six Kepler elements at the initial epoch of the low-orbit satellite, nine solar pressure parameters, a low-orbit satellite clock error, and a code and phase ionospheric-free combined floating-point ambiguity of the GNSS satellite; the nine solar pressure parameters include a constant term, a sine term, and a cosine term of the solar pressure in three directions: radial, tangential, and normal; A splicing module, configured to splice the first orbit determination result and the second orbit determination result according to a GNSS observation interruption start time and a GNSS observation interruption end time to obtain a third orbit determination result; A prediction module is used to perform real-time orbit prediction of the low-orbit satellite according to the third orbit determination result.

8. The low-orbit satellite real-time precise orbit determination device when onboard GNSS observation is discontinuous according to claim 7, characterized in that: The simplified dynamic orbit determination observation model introducing random acceleration is: ， ； in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The code and phase ionospheric-free combination is The partial guide, It is a subset of the constant terms of the solar pressure in the radial, tangential and normal directions; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, Represents the random acceleration of the solar pressure in the radial, tangential and normal directions; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase for the code and phase iono-free code layer combination.

9. The low-orbit satellite real-time precise orbit determination device when onboard GNSS observation is discontinuous according to claim 7, characterized in that: The simplified dynamic orbit determination observation model without introducing random acceleration is: ， ； in, Indicates epochs, Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, is the six Kepler numbers at the initial epoch of the low-orbit satellite; Indicates GNSS satellite The received code and phase ionospheric-free combination is The partial guide, represents the nine solar pressure parameters; is the speed of light, represents the low-orbit satellite clock error; It is a dual-frequency ionospheric-free combination wavelength. and are the frequencies of the first and second frequency bands respectively; It is a GNSS satellite The code and phase ionospheric-free combined floating point ambiguity of , yes The corresponding wavelength, yes The corresponding wavelength, yes The fuzziness, yes The fuzziness, It is the hardware delay of the code and phase of the low-orbit satellite without ionospheric combination phase. It is a GNSS satellite The code and phase of the ionospheric-free combined phase hardware delay, It is the hardware delay of the code and phase ionospheric-free combined pseudorange of the low-orbit satellite; represents the expectation operation, Indicates GNSS satellite The difference between the observed and modeled values ​​of the code for the ionospheric-free combination of code and phase; Indicates GNSS satellite The difference between the observed and modeled phase values ​​in the ionosphere-free combination.

10. The low-orbit satellite real-time precise orbit determination device when onboard GNSS observation is discontinuous according to claim 7, characterized in that: The splicing module splices the first orbit determination result and the second orbit determination result according to the GNSS observation interruption start time and the GNSS observation interruption end time, and is implemented by the following formula: ； in, represents the first orbit determination result, represents the second orbit determination result, Indicates the start time of GNSS observation interruption. Indicates the end time of GNSS observation interruption. Indicates the GNSS observation start time, Indicates the end time of GNSS observation. represents the third orbit determination result.

Images