Satellite Scanning Imaging Using Dual-Axis Line-of-Sight Control
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Solution Overview
Problem
Existing scanning imaging systems for capturing Earth's surface temperatures face challenges in achieving spatial and spectral coregistration, limited radiation collection, and inaccurate calibration due to atmospheric absorption and emission variations, which hinder precise temperature determination.
Innovation Solution
A novel scanning imaging system with a scanning device that varies the line of sight using a closed-loop movement, incorporating rectilinear photodetectors and spectral filters to allow spatial and spectral coregistration, and includes internal and external calibration methods for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotating plane mirror scanning device is used to achieve two different line-of-sight inclination values, then atmospheric absorption and emission effects can be numerically removed, but spatial coregistration and spectral coregistration cannot be achieved due to curved trajectories
Solution Approach 1:
The patent applies dynamics by transitioning from a simple rotating plane mirror to a scanning device with variable inclination that can dynamically adjust its orientation. The scanning device includes a first scanning element that rotates about a first axis and a second scanning element that tilts about a second axis, enabling dynamic control of the line of sight trajectory to achieve both atmospheric correction and spatial coregistration
Solution Approach 2:
The patent introduces another dimension by adding a second scanning element that tilts about a second axis perpendicular to the first scanning element's rotation axis. This dual-axis scanning mechanism transforms the single-axis curved trajectory into a two-dimensional scanning pattern, enabling the image trajectory to be rectilinear and achieving both spatial and spectral coregistration simultaneously
2Measurement precision
If the scanning device rotates continuously in a constant direction, then atmospheric effects can be corrected, but the scanning speed is limited and radiation collection is insufficient
Solution Approach 1:
The scanning device dynamically adjusts its scanning speed and trajectory through the coordinated rotation of the first scanning element and tilting of the second scanning element. This enables optimization of the scanning pattern to maximize radiation collection from the same scene location while maintaining the capability to correct atmospheric effects
Solution Approach 2:
The patent ensures continuity of useful action by maintaining continuous scanning operation with the ability to revisit the same scene location multiple times. The dual-axis scanning mechanism allows the line of sight to return to previously scanned areas, enabling repeated radiation measurement for improved signal accumulation without interrupting the continuous scanning process
3Measurement precision
If image capture is performed at multiple times during satellite orbit passage, then two different line-of-sight inclination values can be obtained, but the same scene location cannot be captured successively by multiple photodetectors
Solution Approach 1:
The patent resolves this contradiction by introducing a second scanning dimension. The first scanning element provides the primary scanning motion, while the second scanning element adds a tilting dimension that enables the line of sight to return to the same scene location. This dual-dimensional scanning allows multiple photodetectors to capture the same location successively while maintaining spatial coregistration
Solution Approach 2:
The scanning device dynamically controls the trajectory of the line of sight through coordinated rotation and tilting movements. This dynamic control enables the system to position the line of sight at different inclination values at different times while still capturing the same scene location, thereby achieving both atmospheric correction and spatial coregistration
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
The system enables precise temperature determination by enhancing spatial and spectral coregistration, increasing radiation collection, and improving calibration accuracy, thereby improving the precision of temperature measurements.
Implementation Method 1
a scanning device, which is adapted to vary the line of sight of the imaging system according to a closed-loop movement
Implementation Method 2
imaging instruments have been carried on board satellites placed in orbit around the Earth, these instruments being sensitive to the thermal radiation emitted by the Earth's surface
Implementation Method 3
the atmosphere that is present above each portion of the Earth's surface causes a partial absorption of thermal radiation between the Earth's surface and the satellite, as well as an additional emission of thermal radiation
Data Source
Figure 1~2
Figure 3
Figure 4a
AI summary
The invention relates to a scanning imaging system (1) intended to be carried on board a satellite in orbit around a planet, to capture images of portions of the planet's surface at two different inclination values of a line of sight (L) of said imaging system. A scanning device (4) varies the line of sight such that the image of each portion of the planet's surface moves in a direction that is constant. The imaging system thus allows spatial coregistration, and each image sensor (3) that is used in the imaging system can be of the TDI type. In addition, a rotational speed of the scanning device can be reduced when the image sensor comprises a plurality of juxtaposed, parallel columns.