Spacecraft Angular Positioning via Antenna Triplet Path Difference
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Solution Overview
Problem
Existing methods for determining the relative angular position between distant spacecraft, such as those in formation flight, require dual-frequency measurement chains which are complex, resource-intensive, and prone to measurement errors due to inter-channel biases and carrier phase ambiguities.
Innovation Solution
A method using a triplet of antennas on one spacecraft to sequentially transmit and receive radiofrequency signals, measuring path differences between the main and secondary antennas, and processing these measurements to deduce the relative angular position without the need for dual-frequency chains, employing a TDMA frame for signal transmission and reception, and reducing phase ambiguity through controlled rotations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual-frequency measurement chains are used to determine relative position between spacecraft, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the dual-frequency measurement chain from the system, replacing it with a single-frequency approach using a triplet of antennas. This removes the complex calibration requirements and inter-channel bias issues while maintaining angular measurement precision through geometric configuration of the antenna triplet.
Solution Approach 2:
The patent changes the fundamental measurement parameter from dual-frequency signal processing to single-frequency path difference measurement. By using the geometric arrangement of three antennas and measuring path differences to a fourth antenna, the system achieves angular positioning without requiring dual-frequency operations, thereby simplifying the measurement system.
2Adaptability or versatility
If multiple receiving chains operate simultaneously on each satellite, then measurement capability is improved, but inter-channel bias errors increase
Solution Approach 1:
The patent merges the receiving functions into a single receiving chain that serves all antennas. Instead of having separate receiving chains for each antenna (which causes inter-channel bias), the system uses one receiving chain to receive signals from multiple antennas sequentially or simultaneously, eliminating the source of measurement errors while maintaining the capability to measure angular positions.
Solution Approach 2:
The single receiving chain is designed to be universal, serving multiple antennas and multiple measurement functions. This multi-functional approach replaces the need for dedicated receiving chains for each antenna, reducing system complexity and eliminating inter-channel bias errors while maintaining measurement versatility.
3Measurement precision
If dynamic calibration chain with internal measurement loop is introduced, then measurement errors are reduced, but system size increases
Solution Approach 1:
The system uses self-service calibration where the same antenna triplet that performs measurements also performs its own calibration. By using the geometric configuration and signal processing algorithms, the system calibrates itself without requiring external calibration equipment or additional hardware, thereby maintaining measurement accuracy without increasing system volume.
4Measurement precision
If prior alignment and rotation maneuvers are performed, then carrier phase ambiguity is resolved, but energy consumption increases
Solution Approach 1:
The system performs preliminary alignment and rotation maneuvers to establish the initial geometric configuration of the antenna triplet relative to the target spacecraft. This preliminary action resolves carrier phase ambiguity by establishing known geometric relationships, allowing subsequent measurements to be performed without additional energy-intensive maneuvers.
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 simplifies the system, improves angular measurement precision, and reduces measurement errors, enabling accurate relative angular positioning between spacecraft without the complexity and resource requirements of dual-frequency systems.
Implementation Method 1
to sequentially emit at least three radio frequency signals from a triplet of antennas mounted on one face of a first spacecraft called the host spacecraft
Implementation Method 2
to measure on board each companion spacecraft, path differences between the signal from the main antenna and the signals from each of the two secondary antennas
Data Source
Figure 1~2
Figure 3~5a
Figure 5b~5c
AI summary
The system comprises: - on board a first craft (10), called the host craft, a triplet of antennas consisting of a transmitting and receiving antenna (11) and two transmitting antennas (12, 13), a transmitting chain (16) which can be successively coupled to each antenna (11, 12, 13) of the triplet of antennas by a radio frequency switch (19), a receiving chain (17) which can be coupled to the transmitting and receiving antenna (11), and a processing device (14) intended to determine a relative angular position between, on the one hand, the host craft (10) and, on the other hand, several spacecraft (20), called companion craft, from measurements of path differences made and transmitted by the companion craft (20), - on board the companion craft (20), a transmitting and receiving antenna (21),a transmission chain (23) and a reception chain (24) coupled to the transmission and reception antenna (21) and a measuring device (22) intended to measure path differences between three signals from the three antennas (11, 12, 13) of the host craft's antenna triplet.