Piezoelectric Star Tracker for CubeSat Jitter Compensation
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Solution Overview
Problem
Conventional satellite systems for attitude estimation and science image stabilization suffer from high-frequency jitter due to satellite subsystems, limiting the pointing accuracy and image quality, especially in small-mass satellites like nanosatellites which are prone to perturbations.
Innovation Solution
An optical system for Earth-orbiting satellites that combines star camera, star tracking, and science data collection using image sensors on a piezoelectric translation stage, with a two-stage control system for coordinated attitude control and high-precision image stabilization, where coarse attitude control is achieved using reaction wheels and fine control is achieved using a piezoelectric actuator to translate image sensors with precision within several microns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional star camera and star tracker systems are used for attitude estimation and image stabilization, then the satellite can perform basic attitude control, but the high-frequency jitter from satellite subsystems limits the pointing accuracy and image quality
Solution Approach 1:
The patent combines the star camera and star tracker into a single integrated optical system with a shared optics assembly and focal plane. Multiple image sensors are arranged on the focal plane to simultaneously perform star detection for attitude estimation and guide star tracking for jitter compensation, eliminating the need for separate components and reducing system complexity while improving measurement precision
Solution Approach 2:
The patent introduces a piezoelectric translation stage that dynamically adjusts the position of image sensors in real-time to compensate for high-frequency jitter. The system continuously measures guide star positions and actuates the piezoelectric stage to maintain precise pointing, transforming the static sensor platform into a dynamically adjustable system that actively counteracts disturbances
2Adaptability or versatility
If separate components are used for star camera, star tracker, and science optical payloads, then each function can be independently optimized, but the size, mass and complexity of the satellite increases
Solution Approach 1:
The patent designs a universal optical system where a single optics assembly serves multiple functions: the same optical path is used by multiple image sensors for both star detection (attitude estimation) and guide star tracking (jitter compensation). This multi-functional approach allows the satellite to perform science observations, attitude determination, and image stabilization using one integrated system rather than separate dedicated components
Solution Approach 2:
The patent merges the star camera and star tracker functions into a single integrated system with shared optics and focal plane, reducing the number of separate components. Multiple image sensors are combined on one focal plane, and the same optical assembly serves all sensors, thereby reducing overall system complexity while maintaining all required functional capabilities
3Measurement precision
If conventional single-stage attitude control is used, then the system structure is simple, but the pointing accuracy cannot achieve arcsecond-level precision due to high-frequency jitter
Solution Approach 1:
The patent segments the attitude control into two distinct stages: coarse attitude control using reaction wheels for overall orientation, and fine pointing control using the piezoelectric translation stage for arcsecond-level precision. This segmentation allows each control loop to operate at its optimal level, with the fine control stage specifically addressing high-frequency jitter without being constrained by the slower coarse control system
Solution Approach 2:
The piezoelectric translation stage acts as an intermediary between the coarse attitude control system and the image sensors. It receives commands from the fine pointing control loop based on guide star position measurements and physically adjusts sensor positions to compensate for jitter, serving as a mediator that translates control signals into precise mechanical adjustments without requiring complete redesign of the overall control architecture
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 configuration enhances pointing accuracy by one to two orders of magnitude over conventional methods, achieving precise stabilization of star images and improving photometric precision, enabling detection of exoplanets and other extraterrestrial objects with high sensitivity.
Implementation Method 1
a piezoelectric actuator coupled to the image sensors and configured to translate the image sensors in at least two axes each orthogonal to the reference axis
Implementation Method 2
optics configured to focus incident light onto the image sensors
Data Source
AI summary
An optical system for use in an Earth-orbiting satellite includes a plurality of image sensors disposed on a focal plane having a reference axis orthogonal thereto, optics configured to focus incident light onto the image sensors, a piezoelectric actuator coupled to the image sensors and configured to translate the image sensors in at least two axes each orthogonal to the reference axis, and at least one controller operably coupled to the plurality of image sensors and the piezoelectric actuator. The image sensors are configured to generate at least one image frame from light detected by the plurality of image sensors, the image frame including a target star and at least one guide star. The controller is configured to stabilize the position of the target star by adjusting the position of the piezoelectric actuator based on the changes in the position of the guide star.