Push-broom Fourier Transform Spectrometer Wide Swath Design
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Solution Overview
Problem
Conventional Fourier Transform Spectroscopy (FTS) systems face challenges in achieving wide swath widths due to the need for fast focal plane array (FPA) frame rates, which results in a short stare time and negatively impacts the signal-to-noise ratio (SNR), increasing instrument complexity and limiting their use for wide area satellite-based hyperspectral imaging.
Innovation Solution
A push-broom scanning Fourier Transform Spectrometer that effectively stares at nadir, varying the optical path difference by sweeping a mirror to generate an interferogram, allowing each in-track row of the FPA to provide a different point along the interferogram, enabling efficient data collection over a wide area with slight overlap to prevent data gaps during reversals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If fast FPA frame rates are used to collect interferogram data, then the swath width can be increased, but the stare time becomes short which negatively impacts the signal-to-noise ratio
Solution Approach 1:
The patent transitions from static step-staring to dynamic push-broom scanning where the FPA moves across the field of view. This dynamic approach allows the system to maintain wide swath width while extending the effective stare time during the push-broom scan, thereby improving the signal-to-noise ratio without sacrificing area coverage.
Solution Approach 2:
The patent introduces a temporal dimension to the data collection process by scanning through the field of view over time. This transforms the single-shot simultaneous capture into a multi-frame sequential capture, effectively increasing the stare time while maintaining wide swath width through the push-broom scanning mechanism.
2Area of stationary object
If fast FPA frame rates are used to achieve wide swath width, then the instrument complexity increases
Solution Approach 1:
The patent segments the FPA into multiple rows that can be processed independently during the push-broom scan. This segmentation allows the system to handle wide swath width data more efficiently by processing rows in sequence rather than requiring simultaneous processing of all pixels, thereby reducing the effective instrument complexity.
Solution Approach 2:
The push-broom scanning mechanism enables continuous data collection across the entire field of view without interruption. This continuous action eliminates the need for rapid sequential frame rates, simplifying the instrument requirements while maintaining wide swath width capability through sustained scanning motion.
3Measurement precision
If conventional step-stare FTS is used, then the data quality can be maintained, but the system cannot achieve wide swath widths
Solution Approach 1:
The patent merges the push-broom scanning capability with Fourier transform spectroscopy to create a hybrid system that achieves both wide swath width and high data quality. The combination of scanning motion with interferogram acquisition allows the system to cover wide areas while maintaining the spectral resolution and signal-to-noise ratio characteristic of FTS systems.
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 approach allows for high-quality hyperspectral data collection over a wide area with improved signal-to-noise ratio and reduced instrument complexity, enabling efficient satellite-based imaging systems to operate effectively.
Implementation Method 1
varying the optical path difference by sweeping a mirror to generate an interferogram
Implementation Method 2
each in-track row of the FPA provides a different point along the interferogram
Data Source
AI summary
Methods and systems to record amplitudes of an interference pattern of a source light at successive rows of a focal plane array as an interferometer traverses the source light, while varying an optical path difference of the interferometer. A fixed frame rate of the focal plane array may be selected such that each in-track row of the focal plane array provides a different point along the interferogram, for the same ground location.