Astronomical Body Shape Models Through Stereo Thermoclinometry
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Solution Overview
Problem
Existing shape characterization techniques for astronomical bodies, such as SfS and SPC, struggle with concavities like craters and require high computational resources and human input, making them unsuitable for on-board spacecraft applications.
Innovation Solution
A computationally efficient method called stereo thermoclinometry (STC) uses infrared images and thermophysical models to refine an initial shape model by estimating facet orientations and vertex locations, reducing errors by approximately 80% and enabling autonomous on-board shape estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stereo photoclinometry (SPC) is used to determine accurate shape models, then measurement precision is improved, but device complexity and ease of operation deteriorate due to requiring high-resolution images, computational expense, and human input
Solution Approach 1:
The patent changes the fundamental parameter used for shape determination from optical reflectance (SPC) to thermal radiation (STC). By measuring thermal infrared radiation instead of visible light, the method achieves accurate shape models without requiring high-resolution optical images or iterative photometric modeling, thereby reducing computational complexity while maintaining measurement precision
Solution Approach 2:
The patent replaces the complex optical-mechanical system of SPC (requiring high-resolution cameras and iterative photometric processing) with a thermal radiation-based system. The thermal infrared camera captures thermal emission patterns that directly encode surface orientation information, eliminating the need for complex computational photography algorithms and human intervention
2Measurement precision
If stereo photoclinometry (SPC) is used to determine accurate shape models, then measurement precision is improved, but ease of operation worsens due to requiring human input for convergence
Solution Approach 1:
The STC method is inherently self-calibrating and does not require human input for convergence. The thermal radiation measurements directly provide surface orientation information through the thermophysical model, allowing the algorithm to automatically converge to an accurate shape model without human intervention, thereby improving ease of operation while maintaining measurement precision
Solution Approach 2:
The patent implements an iterative feedback mechanism where the shape model is continuously refined by comparing predicted thermal radiation patterns with actual measurements. This automated feedback loop allows the system to self-correct and converge to an accurate shape model without human input, resolving the contradiction between measurement precision and ease of operation
3Ease of operation
If Shape-from-Silhouette (SfS) algorithm is used for shape characterization, then ease of operation is improved, but measurement precision worsens because concavities like craters are not observable
Solution Approach 1:
The patent changes the measurement parameter from optical silhouette (SfS) to thermal radiation emission. Thermal radiation patterns encode surface orientation and topography information that allows detection of concavities like craters, which are invisible in silhouette-based methods. This parameter change maintains computational efficiency while dramatically improving measurement precision for concavity detection
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
STC provides accurate and efficient shape models for astronomical bodies, overcoming atmospheric limitations and ensuring precise navigation and scientific analysis without human intervention.
Implementation Method 1
The algorithm first identifies the surface orientations for a shape model from a set of measured surface temperatures (e.g., from IR images) and predicted sub-surface temperatures (e.g., from a Thermo-Physical Model)
Implementation Method 2
The thermal model of the astronomical body may be based at least in part on the shape model, temperatures associated with the surface segments of the shape model, thermal properties of the astronomical body, and a location of the sun relative to the astronomical body
Data Source
AI summary
A method for estimating a shape of an astronomical body includes receiving a number of thermal images of the astronomical body, receiving an initial shape model of the astronomical body, the shape model having a number of surface segments defined by a number of parameter values; updating the shape model based at least in part on a thermal model of the astronomical body and the thermal images. The updating includes determining a surface orientation on at least some of the surface segments based at least in part on the thermal model of the astronomical body and the thermal images and updating the of parameter values according to the surface orientations to yield an updated shape model.