Inertial Sensing Augmentation for Spacecraft Navigation
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Solution Overview
Problem
Low-thrust spacecraft navigation faces challenges due to accumulating errors in inertial sensing, especially during prolonged acceleration periods, as existing inertial sensors are not accurate enough to compensate for uncertainties in non-ballistic forces, leading to significant trajectory deviations and increased communication demands with Earth-based tracking systems.
Innovation Solution
The use of a high-accuracy accelerometer with an inaccuracy of less than 1 micro-g, capable of rotating and taking measurements in multiple positions, to calculate instrument bias and corrected acceleration, enabling continuous and accurate trajectory estimation for low-thrust spacecraft, thereby reducing reliance on external reference navigation systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low-thrust propulsion systems are used for prolonged acceleration, then fuel efficiency and mass are improved, but navigation accuracy deteriorates due to accumulating inertial sensing errors
Solution Approach 1:
The patent changes the accuracy parameter of the accelerometer from conventional levels to ultra-high precision (inaccuracy less than 1 micro-g). This parameter change enables the accelerometer to maintain navigation accuracy over prolonged thrusting periods, resolving the contradiction between fuel efficiency gains from low-thrust propulsion and navigation accuracy degradation from accumulating errors.
2Device complexity
If conventional accelerometers are used for inertial navigation, then device complexity is reduced, but navigation accuracy deteriorates during prolonged thrusting
Solution Approach 1:
The patent applies parameter changes by specifying ultra-high precision accelerometers with inaccuracy less than 1 micro-g. This single parameter change in sensor precision allows the system to maintain both simplicity (single sensor type) and high accuracy during prolonged low-thrust operations, resolving the contradiction between device complexity and navigation precision.
3Measurement precision
If external reference navigation systems are used frequently to correct trajectory, then navigation accuracy is improved, but communication frequency with Earth increases operational costs
Solution Approach 1:
The patent applies preliminary action by equipping the spacecraft with ultra-high precision accelerometers before launch that can maintain accurate trajectory estimation independently for extended periods. This preliminary capability reduces the need for frequent correction updates from Earth, allowing spacecraft to operate autonomously and reducing communication frequency, thereby resolving the contradiction between trajectory accuracy and communication cost.
Data Source
AI summary
The use of an accelerometer for inertial navigation of a low thrust spacecraft undergoing acceleration wherein the inaccuracy of the accelerometer is less than the uncertainty in the accuracy of a modeled non-gravitational component of the acceleration that the spacecraft is undergoing is disclosed. A method of navigating a spacecraft having a low thrust propulsion system is also disclosed. The method comprises engaging the low thrust propulsion system, measuring the acceleration of the spacecraft using an accelerometer with an inaccuracy less than the uncertainty in the acceleration imparted by the low thrust propulsion system and acquiring a trajectory estimate using the measured acceleration. The trajectory estimate may be updated using an external reference navigation sensor.