Star Tracker Using Polarization Sensors for Space Navigation
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Solution Overview
Problem
Conventional star trackers are bulky, power-hungry, and limited in their ability to determine location and orientation in space due to reliance on imaging optics and polarized light, which is not readily available from stars.
Innovation Solution
A star tracker system utilizing polarization-sensitive sensors that detect unpolarized electromagnetic radiation from stars by comparing signals from sensors oriented along different axes, allowing for the calculation of the angle of incidence without the need for imaging optics or polarized light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional imaging optics and pixelated sensors are used in a star tracker, then the star tracker can accurately measure angles to stars, but the device becomes bulky, heavy, and power-hungry
Solution Approach 1:
The patent extracts and removes the heavy imaging optics (lens and digital camera) from the star tracker system, retaining only the essential light-detecting function through simplified photocells or photodetectors. This extraction eliminates the bulk and weight while preserving the core capability of measuring star positions for navigation.
Solution Approach 2:
The patent replaces the mechanical/optical imaging system with an electromagnetic field-based detection system using polarized light sensors. Instead of using heavy lenses and pixelated cameras to form images, the system uses polarization-sensitive detectors to directly measure star light properties, substituting a lighter electromagnetic detection approach for the traditional mechanical-optical system.
2Measurement precision
If conventional imaging optics and digital cameras are used in a star tracker, then the star tracker can accurately measure angles to stars, but the device consumes significant electrical power
Solution Approach 1:
The patent extracts and removes the power-hungry digital camera subsystem from the star tracker, keeping only the essential light-detecting function. By eliminating the complex image sensor array and associated electronics, the system dramatically reduces electrical power consumption while maintaining the ability to detect star positions through simpler photodetector elements.
Solution Approach 2:
The patent replaces the high-power digital camera imaging system with a low-power polarization-based detection system. Instead of using energy-intensive pixelated sensors that require complex readout electronics, the system employs polarization-sensitive photodetectors that consume minimal power to directly measure the polarization state of star light for navigation calculations.
3Adaptability or versatility
If polarization-based navigation is used with unpolarized starlight, then the star tracker can operate in space, but conventional polarization sensors require strongly polarized light which stars do not provide
Solution Approach 1:
The patent changes the detection parameter from measuring the degree of polarization (which requires strongly polarized light) to measuring the angle of polarization directly. By detecting the orientation angle of the electric field oscillations in star light, the system can reliably navigate using unpolarized or weakly polarized starlight without requiring the strong polarization that conventional sensors need.
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
Enables a smaller, lighter, and more power-efficient star tracker capable of determining location and orientation in space using unpolarized starlight, overcoming the limitations of conventional systems.
Implementation Method 1
A star tracker system utilizing polarization-sensitive sensors that detect unpolarized electromagnetic radiation from stars by comparing signals from sensors oriented along different axes
Data Source
AI summary
A star tracker determines a location or orientation of an object, such as a space vehicle, by observing unpolarized light from one or more stars or other relatively bright navigational marks, without imaging optics, pixelated imaging sensors or associated pixel readout electronics. An angle of incidence of the light is determined by comparing signals from two or more differently polarized optical sensors. The star tracker may be fabricated on a thin substrate. Some embodiments have vertical profiles of essentially just their optical sensors. Some embodiments include micro-baffles to limit field of view of the optical sensors.