Star Tracker Out-of-Field Rejection Filter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional star trackers require bulky sun shades for out-of-field rejection, which increase weight, bulk, and mechanical energy storage, leading to undesirable jitter and limited operational windows due to stray light from sources like the Sun, Earth, or Moon.
Innovation Solution
The implementation of an out-of-field rejection filter (OFRF) that converts randomly polarized light to p-polarized light and uses an angular selectivity layer to reject out-of-field p-polarized light, allowing for a sunshadeless or minimally sized star tracker design, combined with adaptive optical elements for aberration correction and calibration capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional star trackers use sun shades to block stray light, then out-of-field rejection is improved, but device volume and mass increase
Solution Approach 1:
The patent changes the optical parameters of incoming light by converting random polarization to linear polarization, then using angular selectivity based on polarization state to reject out-of-field light. This replaces the geometric parameter-based sun shade approach with a polarization-based optical parameter approach, enabling compact filter integration without bulky mechanical shades.
Solution Approach 2:
The patent replaces the mechanical sun shade structure with an optical out-of-field rejection filter that uses polarization conversion and angular selectivity. This substitutes a mechanical blocking system with an optical filtering system, achieving the same stray light rejection function in a much more compact form factor.
2Object-affected harmful factors
If conventional star trackers use sun shades to block stray light, then out-of-field rejection is improved, but device mass increases
Solution Approach 1:
The patent changes the optical parameters of incoming light by converting random polarization to linear polarization, then using angular selectivity based on polarization state to reject out-of-field light. This replaces the geometric parameter-based sun shade approach with a polarization-based optical parameter approach, enabling compact filter integration without bulky mechanical shades.
Solution Approach 2:
The patent replaces the mechanical sun shade structure with an optical out-of-field rejection filter that uses polarization conversion and angular selectivity. This substitutes a mechanical blocking system with an optical filtering system, achieving the same stray light rejection function in a much more compact form factor.
3Object-affected harmful factors
If conventional star trackers use sun shades, then stray light blocking is improved, but mechanical energy storage increases causing jitter
Solution Approach 1:
The patent replaces the mechanical sun shade structure with an optical out-of-field rejection filter that uses polarization conversion and angular selectivity. This substitutes a mechanical blocking system with an optical filtering system, achieving the same stray light rejection function in a much more compact form factor.
Solution Approach 2:
The patent changes the optical parameters of incoming light by converting random polarization to linear polarization, then using angular selectivity based on polarization state to reject out-of-field light. This replaces the geometric parameter-based sun shade approach with a polarization-based optical parameter approach, enabling compact filter integration without bulky mechanical shades.
4Object-affected harmful factors
If sun shades are used for out-of-field rejection, then stray light from Sun/Earth/Moon is blocked, but operational window is limited
Solution Approach 1:
The patent changes the optical parameters of incoming light by converting random polarization to linear polarization, then using angular selectivity based on polarization state to reject out-of-field light. This replaces the geometric parameter-based sun shade approach with a polarization-based optical parameter approach, enabling compact filter integration without bulky mechanical shades.
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 solution enables star trackers with reduced volume and mass, improved manufacturability, and a wider operational window, reducing jitter and maintaining high-resolution imaging capabilities while allowing multiple trackers to be packaged compactly for enhanced attitude determination.
Implementation Method 1
a converter to convert randomly polarized light to p-polarized light
Implementation Method 2
an angular selectivity layer to select in-field p-polarized light and reject out-of-field p-polarized light
Implementation Method 3
An interior side of the angular selectivity layer can be reflective to s-polarized light
Data Source
AI summary
A small, ultra-light-weight star tracker for space applications uses an out-of-field rejection filter to reduce the physical size and mass of the star tracker by effectively eliminating the need for a sun shade. The out-of-field rejection filter combines a converter for converting randomly polarized light to p-polarized light with an angular selectivity filter that can reject out-of-field p-polarized light. The underside of the angular selectivity filter can be used to reflect a calibrated light source into the optical path.