Ground-Based Orbit Determination via Doppler Shift and Time of Flight
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Solution Overview
Problem
Current satellite orbit determination methods require expensive and high-mass on-board systems, which increase the cost of deploying satellites for applications like altimeters and imaging systems.
Innovation Solution
A ground-based ranging and Doppler-based technique is used to determine satellite orbits, shifting the orbit determination function from the satellite to known ground locations, utilizing pseudonoise and KGL signals to calculate range and Doppler shift, thereby reducing the need for costly on-board components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive and high-mass on-board systems are used for orbit determination, then measurement precision is improved, but weight and cost increase
Solution Approach 1:
The orbit determination function is extracted from the satellite and relocated to ground-based stations. The satellite only needs to transmit signals and receive ground commands, while the computationally intensive orbit determination calculations are performed on the ground using received signal data, thereby eliminating the need for heavy on-board orbit determination equipment.
Solution Approach 2:
A ground-based station acts as an intermediary between the satellite and the orbit determination process. The ground station receives signals from the satellite, processes the data to determine orbital parameters, and then provides feedback to the satellite, thereby mediating the complex calculations that would otherwise require heavy on-board processing capability.
2Measurement precision
If expensive and high-mass on-board systems are used for orbit determination, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The expensive orbit determination system is extracted from the satellite and implemented as ground-based infrastructure. This allows the satellite to be manufactured with simpler, cheaper components while the sophisticated orbit determination capability is provided by ground equipment that can be shared across multiple satellites.
Solution Approach 2:
Instead of equipping each satellite with its own expensive orbit determination system, the ground-based station serves as a shared resource that provides orbit determination services to multiple satellites, effectively copying the functionality across different satellite missions without duplicating the expensive hardware.
3Device complexity
If ground-based ranging and Doppler techniques are used, then device complexity is reduced, but measurement precision may be affected
Solution Approach 1:
The orbit determination problem is shifted from the spatial dimension (on-board processing) to the temporal dimension (ground-based processing over time). By collecting signal data over multiple orbital passes and processing it ground-based, the system achieves precise orbit determination through temporal integration rather than through complex on-board spatial processing.
Solution Approach 2:
Complex mechanical and electronic on-board orbit determination systems are replaced with signal processing techniques based on ranging and Doppler measurements. The physical complexity of on-board sensors and processors is substituted with mathematical processing of transmitted and received signals at the ground station.
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 allows for accurate and precise orbit determination at a lower cost, reducing the mass and power requirements of satellites while maintaining high precision, and is suitable for low Earth orbit satellites.
Implementation Method 1
A ground-based ranging and Doppler-based technique is used to determine satellite orbits
Implementation Method 2
utilizing pseudonoise and KGL signals to calculate range and Doppler shift
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A known ground location (KGL) satellite transceiver can include a position and elevation acquisition module configured to determine a time of flight (TOF) of a pseudonoise (PN) signal and a Doppler shift in a KGL signal for use in determining an orbit of a satellite. The PN signal can include a transmitted PN signal and a transponded PN signal. The KGL signal can include a transmitted KGL signal and a transponded KGL signal. The transmitted PN signal and the transmitted KGL signal can be transmitted sequentially on a first frequency carrier from the KGL satellite transceiver to the satellite. The transponded PN signal and the transponded KGL signal can be retransmitted back sequentially on a second frequency carrier from the satellite to the KGL satellite transceiver. The first frequency carrier and the second frequency carrier use a same frequency carrier or a different frequency carrier from each other.