Spacecraft Antenna Pointing Accuracy via PSM Couplers
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Solution Overview
Problem
Spacecraft antenna pointing errors exceed the desired accuracy of 0.03° due to thruster-induced transients and other disturbances, which existing RF autotracking techniques fail to adequately address.
Innovation Solution
A spacecraft system comprising a payload subsystem with a tracking receiver, input multiplexer, antenna pointing mechanism (APM) controller, and pseudo-monopulse (PSM) couplers, where each antenna reflector is mechanically coupled with an APM and illuminated by a tracking feed element, receiving uplink beacon signals to adjust pointing errors through a closed-loop system, with PSM couplers disposed proximate to tracking feed elements and thermally coupled waveguides to minimize temperature differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RF autotracking techniques are used, then basic antenna pointing control is achieved, but pointing accuracy exceeds the desired 0.03° requirement due to thruster-induced transients and disturbances
Solution Approach 1:
The system implements a closed-loop feedback mechanism using a tracking receiver that continuously monitors the spacecraft's pointing accuracy by receiving uplink beacon signals from ground stations. The receiver generates error signals that are fed back to the antenna pointing mechanism (APM) to correct deviations from the desired pointing direction, thereby maintaining accuracy within 0.03° even during thruster operations.
Solution Approach 2:
Pseudo-monopulse (PSM) couplers are introduced as intermediary components that extract phase error information from the tracking receiver's signal paths. These couplers provide intermediate measurement data about pointing errors, which are then used by the control system to generate corrective commands without requiring direct mechanical intervention during transient events.
Solution Approach 3:
The system dynamically adjusts operational parameters including APM step size (reducing to less than 1.5 mdeg during transients), waveguide temperature management (thermally coupling waveguides to reduce temperature differences), and signal processing gains to maintain pointing accuracy under varying operational conditions and transient disturbances.
2Use of energy by moving object
If large unfurlable reflectors are used to meet communications demands, then desired RF beam narrowness is achieved, but antenna pointing errors increase beyond 0.03°
Solution Approach 1:
The closed-loop feedback system continuously monitors the actual pointing direction of large unfurlable reflectors and generates real-time correction commands to compensate for their inherent pointing errors, enabling these large apertures to achieve both narrow RF beams and high pointing accuracy within 0.03°.
Solution Approach 2:
The antenna pointing mechanism (APM) employs dynamic control with variable step sizes (capable of less than 1.5 mdeg) and adaptive response to transient conditions, allowing the system to precisely control the position of large unfurlable reflectors and maintain accurate pointing despite their size and flexibility.
3Measurement precision
If PSM couplers are disposed proximate to tracking feed elements with short waveguide runs, then phase error uncertainty is reduced, but device complexity increases
Solution Approach 1:
Pseudo-monopulse (PSM) couplers are introduced as intermediary components that extract phase error information from the tracking receiver's signal paths. These couplers provide intermediate measurement data about pointing errors, which are then used by the control system to generate corrective commands without requiring direct mechanical intervention during transient events.
4Object-affected harmful factors
If electric thrusters are used instead of chemical thrusters, then transient disturbances are reduced, but propulsive maneuver capability is limited
Solution Approach 1:
The system dynamically adjusts operational parameters including APM step size (reducing to less than 1.5 mdeg during transients), waveguide temperature management (thermally coupling waveguides to reduce temperature differences), and signal processing gains to maintain pointing accuracy under varying operational conditions and transient disturbances.
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
The system achieves a significant reduction in antenna pointing errors, with a 6 mdeg improvement in accuracy, by minimizing phase error uncertainty and temperature variations, and using electric thrusters to reduce transient disturbances during payload operation.
Implementation Method 1
each respective tracking feed element being configured to receive an uplink beacon signal from the ground by way of one of the antenna reflectors
Implementation Method 2
each separate signal path may include a respective waveguide, the respective waveguides being thermally coupled together to reduce temperature differences between respective waveguides
Data Source
AI summary
A spacecraft payload subsystem includes a tracking receiver, an input multiplexer, an antenna pointing mechanism (APM) controller and a plurality of antenna reflectors. Each antenna reflector is mechanically coupled with a respective APM, and illuminated by a respective tracking feed element. Each respective tracking feed element is configured to receive an uplink beacon signal from the ground by way of one of the antenna reflectors and is coupled, by way of a respective pseudo-monopulse (PSM) coupler and the input multiplexer, to the tracking receiver. The tracking receiver is configured to receive multiplexed signals from the PSM couplers by way of the input multiplexer and output corresponding pointing error information to the APM controller. The APM controller is configured to send commands to one or more of the APMs. Each APM is configured to point a respective antenna reflector in response to the commands.