A high-precision time offset autonomous calculation method based on satellite speed and gravity acceleration

Abstract

The application discloses a high-precision time offset autonomous calculation method and system based on satellite speed v and gravity acceleration g. By establishing a closed correlation between the gravity field strength and the orbital speed, the traditional multi-parameter relativistic time correction model is simplified to a closed-form calculation depending on only two in-orbit measurable physical quantities, without the need for input of orbital radius, universal gravitational constant, earth mass, external ephemeris, etc. The application has outstanding originality, simple calculation, strong autonomy and reliable precision, can realize a daily cumulative time error of less than 1 ns, is suitable for low-orbit satellites, navigation satellites, constellation systems and various high-reliability time service scenarios, has a wide application range and high industrial value, and can significantly improve the autonomous time service capability of a spacecraft and the stability of a time system.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation and satellite time and frequency synchronization technology. Specifically, it relates to a method for autonomously calculating high-precision time offset using only the satellite's on-orbit velocity v and local gravitational acceleration g. It is particularly suitable for improving on-board autonomous time correction, timing stability, and data reliability of low-orbit satellites, GPS / BeiDou and other navigation satellites and constellation systems. Background Technology

[0002] Current satellite time offset calculations are mainly based on the joint correction of gravitational redshift and special relativistic clock dilation. Traditional models rely on a large number of external parameters such as orbital radius r, gravitational constant G, central body mass M, Earth's oblateness J2, and ground-injected ephemeris. The existing technology has the following shortcomings: The on-board computing model is complex, the parameters are highly coupled, the amount of computation is large, and the requirements for on-board hardware resources are high. Over-reliance on ground-based telemetry and control links and ephemeris data means that a high-precision time reference cannot be maintained autonomously under the condition of link failure. The introduction of multiple parameters into the error propagation chain is not conducive to long-term, stable, autonomous, and real-time on-board time synchronization. Based on the above problems, this invention proposes an autonomous time offset calculation method that relies solely on measurable physical quantities of the satellite itself, is simple to calculate, and has reliable accuracy. Summary of the Invention

[0003] Purpose of the invention To overcome the shortcomings of existing satellite time correction methods, such as reliance on external parameters, computational complexity, and weak autonomy, this paper proposes a method that can perform high-precision time offset calculations using only the on-orbit measured velocity v and gravitational field strength g. This simplifies on-board computation, achieves autonomous timekeeping with a daily cumulative time error better than 1 ns, and improves the on-orbit time synchronization stability and navigation data availability of the satellite. Technical solution 1. Core Principles Under the conditions of a weak gravitational field and a low-speed approximation, the relationship between gravitational field strength and orbital velocity is derived: g = v 4 / (GM) By substituting this formula into the relativistic time correction system and introducing the Earth's oblateness J2 correction, and by algebraically simplifying and eliminating parameters that cannot be directly measured in orbit, such as orbital radius r, gravitational constant G, and celestial mass M, a closed-form formula for calculating the daily time offset of a satellite, determined solely by v and g, is finally established. 2. Calculation Formula Daily time offset of the satellite relative to the ground observation station: ΔT = [-1 / 2・(v² / c²) + K・(g³J2R²) / (v 4 c²) × 86400 In the formula: ΔT: Daily time offset; v: Instantaneous tangential velocity of the satellite in orbit; g: The intensity of the gravitational field at the location of the satellite; c: Speed ​​of light in a vacuum; K: Geometric coefficient related to track inclination; J2: Earth's second-order zone harmonic coefficient; R: Earth's equatorial radius. 3. Implementation Steps The satellite's on-orbit velocity v is acquired in real time by the onboard velocity measurement module; The local gravitational field strength g is acquired in real time by the spaceborne gravity measurement module; The onboard computing unit substitutes v and g into the formula to calculate the daily time offset; Based on the calculation results, frequency or phase closed-loop corrections are performed on the spaceborne atomic clock; Achieve autonomous, high-precision time synchronization and timing output under conditions without ground injection. Technological advancement This invention represents a fundamental innovation in the field of satellite time and frequency synchronization. It establishes for the first time a closed correlation model based on the satellite's on-orbit velocity and gravitational acceleration, simplifying the traditional multi-parameter coupled relativistic time correction method into a closed calculation that relies solely on two physical quantities. This breaks through the technical limitations of existing satellite time correction methods that require reliance on orbital radius, gravitational constant, Earth's mass, external ephemeris, and ground-based telemetry and control input. This method can achieve a daily cumulative time error of better than 1ns under near-circular orbit, weak gravitational field, and low-speed flight conditions, which is equivalent to the accuracy of traditional precision orbit correction models. At the same time, it significantly reduces the amount of computation, consumes less hardware resources, and has strong autonomous operation capabilities. It has outstanding technical originality and non-obviousness, and its overall technical level has reached the advanced level in the industry. Innovation Autonomous calculation of dual parameters: Only v and g are needed to complete the joint time correction of relativism and Earth's oblateness, without the need for external parameters such as orbital radius, GM, ephemeris, etc. The computational workload is greatly simplified: there is no orbital recursion and no high-order expansion in the gravity field, making it suitable for on-board embedded real-time computing. Autonomous timekeeping even when the link is broken: It does not rely on ground telemetry and control or inter-satellite links, which significantly improves the system's resilience and reliability; Accuracy is stable and reliable: Under near-circular, weak field, and low-speed mainstream satellite orbits, the accuracy is equivalent to that of traditional precision models, with a daily cumulative time error better than 1 ns. Attached Figure Description Figure 1 is a structural block diagram of the satellite autonomous timing system of the present invention; Explanation of markings in the diagram: 1— Velocity measurement module; 2— Gravitational acceleration measurement module; 3— Onboard calculation and control unit; 4— Onboard atomic clock; 5— Time correction and timing output. Beneficial effects Extremely simplified calculation: Only velocity v and gravitational acceleration g are needed; few parameters, fast calculation, and extremely low hardware burden on the satellite; High degree of autonomy: Free from dependence on ground-based telemetry and control and ephemeris injection, it can maintain high-precision timekeeping even when the link is interrupted; Reliable accuracy: The daily cumulative time error is better than 1 ns, which is equivalent to the accuracy of traditional precision track correction models; Wide applicability: It can be used for low-Earth orbit satellites, GPS / BeiDou and other navigation satellites and constellations, with low engineering difficulty; High stability: Reduces the propagation of multi-parameter errors and improves the long-term operational reliability of the satellite time system. Detailed Implementation Velocity measurement module: It adopts a spaceborne GNSS carrier phase differential or satellite laser ranging module to obtain the satellite's on-orbit velocity v, with a measurement accuracy better than 0.01 mm / s; Gravity measurement module: Employs a high-precision accelerometer or cold atom interferometer to obtain the local gravitational field strength g, with a measurement accuracy better than 1 μGal; Calculation unit: Substitutes the real-time measured v and g into the formula of this invention to complete the calculation of the daily time offset; Time correction: The calculation results are output to the onboard atomic clock for frequency or phase adjustment to achieve autonomous time synchronization. Under near-circular orbit conditions of 200 km–2000 km, this method can stably achieve a daily cumulative time error better than 1 ns, meeting the high-precision time and frequency requirements of navigation, communication, and scientific exploration satellites. Scope of application and breadth of use This method has a wide range of applications and strong engineering feasibility. It can be widely used in various spacecraft platforms such as low-Earth orbit communication constellations, navigation satellites, remote sensing satellites, manned spacecraft, and space stations. It is especially suitable for autonomous onboard time correction in global navigation satellite systems such as GPS, BeiDou, and Galileo. It can also be extended to fields with rigid requirements for high-precision time synchronization and autonomous and controllable time service, such as 5G / 6G communication, power grid, financial transactions, data centers, and critical national defense infrastructure. It can effectively improve the stability and reliability of the system's time base in denial-of-service environments and disconnection scenarios, and has broad market application prospects and industrial promotion value.

Claims

1. A method for autonomously calculating high-precision time offset of satellites, characterized in that, Using only the instantaneous velocity v measured by the satellite in orbit and the local gravitational acceleration g, the daily time offset ΔT is calculated using the following formula: ΔT = [-1 / 2・(v² / c²) + K・(g³J2R²) / (v 4 c²) ] × 86400 And based on this offset, on-board autonomous time correction is completed; Where c is the speed of light, K is the orbital inclination correlation coefficient, J2 is the Earth's second-order zonal harmonic coefficient, and R is the Earth's radius.

2. The method according to claim 1, characterized in that, It is suitable for near-circular orbits, weak gravitational fields, and on-orbit operation environments far below the speed of light, without requiring orbital radius, gravitational constant, celestial mass, or external ephemeris parameters.

3. The method according to claim 1, characterized in that, Autonomous time correction is achieved through onboard measurements of v and g, with a daily cumulative time error better than 1 ns.

4. The method according to claim 1, characterized in that, Applicable to low-Earth orbit satellites, GPS / BeiDou and other navigation satellites and constellation systems, it can achieve high-precision time offset calculation with a daily cumulative time error of better than 1ns by measuring the velocity v and gravitational acceleration g in orbit, thereby improving the satellite's autonomous timing capability and the reliability of time data.

5. A satellite autonomous timing system, characterized in that, It includes a velocity measurement module, a gravity measurement module, and an on-board computing unit, wherein the unit executes the method described in any one of claims 1-4 to achieve high-precision time synchronization under conditions without ground injection.

Images