Satellite Clock Stability Evaluation via Frequency Offset
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Solution Overview
Problem
Current methods for evaluating satellite clock stability using delay time differences result in substantial orbiting and signal processing errors, especially when the satellite's position is not precisely known, leading to imprecise estimates of clock stability.
Innovation Solution
A system that uses a receiver clock with higher precision than the satellite clock to determine the frequency offset, frequency drift, and Allan deviation of the transmission signal, allowing for precise evaluation of satellite clock stability by analyzing the frequency and phase of the received signal, while correcting for relativistic, ionospheric, and tropospheric errors using precalculated models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If delay time differences are used to evaluate satellite clock stability, then the evaluation can be performed, but substantial orbiting errors and signal processing errors are included in the measurement
Solution Approach 1:
The patent replaces the mechanical/time-domain approach (delay time differences) with a frequency-domain approach (frequency offset and frequency drift measurement). By measuring frequency parameters instead of time delays, the system eliminates the need for precise orbit knowledge and avoids the errors associated with delay time calculations, thereby improving both measurement precision and reliability.
2Ease of manufacture
If delay time differences are used for evaluation, then the method is simple, but the satellite position must be precisely defined which increases system complexity
Solution Approach 1:
The patent substitutes the complex position determination system with a frequency measurement system. Instead of requiring precise knowledge of satellite position and complex delay time calculations, the system measures frequency offset and frequency drift from the received signal, which can be done with standard radio frequency equipment without needing precise orbit data.
3Duration of action of moving object
If the satellite moves substantially in its orbit during measurement, then orbiting errors increase, but the evaluation signal arrives time-delayed when position is not precisely known
Solution Approach 1:
The patent measures frequency parameters (frequency offset and frequency drift) which are invariant to the satellite's position and motion state. This allows the system to maintain measurement precision throughout the entire measurement duration even as the satellite moves significantly in its orbit, eliminating the time-delay and position-error problems associated with delay time difference methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more accurate determination of satellite clock stability by avoiding errors associated with delay time differences and improving precision through error correction, especially when the satellite's trajectory is uncertain, and ensures reliable information over a sufficient time period.
Implementation Method 1
determining a received signal frequency and/or a received signal phase from the received signal by using the receiver clock
Implementation Method 2
determining a frequency offset, a frequency drift and/or an Allan deviation of the transmission frequency from the received signal frequency
Implementation Method 3
correct errors that occur in the received signal frequency or the received signal phase because of relativistic effects
Implementation Method 4
compensate for an ionospheric error in the signal transmission path between the satellite and the system, by using a precalculated ionosphere compensation model
Implementation Method 5
compensate a tropospheric error in the signal transmission path between the satellite and the system by using a precalculated tropospheric compensation model
Data Source
AI summary
In a system for characterizing a satellite clock in a satellite, the satellite has a transmitting device that emits a transmission signal at a transmission frequency indicative of a state of the satellite clock, and a receiver clock which has a higher precision than the satellite clock. A receiving device is configured to receive the transmission signal and to determine a received signal therefrom, as well as a received signal frequency and/or phase, using the receiver clock. Finally, an evaluation device is configured to determine a frequency offset, drift, and/or an Allan deviation of the transmission frequency from the received signal frequency and/or the received signal phase. The evaluation device determines the stability of the satellite clock, or the validity of its time indication, from the determined frequency offset, frequency drift, and/or the Allan deviation, to thereby characterize the satellite clock.