Gas leak emission quantification with a gas cloud imager
An instrument and method for analyzing a gas leak. The instrument can obtain a time series of spectra from a scene. The instrument can compare spectra from different times to determine a property of a gas cloud within the scene. The instrument can estimate the column density of the gas cloud at one or more locations within the scene. The instrument can estimate the total quantity of gas in the cloud. The instrument can estimate the amount of gas which has left the field of view of the instrument. The instrument can also estimate the amount of gas in the cloud which has dropped below the sensitivity limit of the instrument.
1. An infrared (IR) imaging system for quantifying one or more parameters of a gas cloud, the imaging system comprising:
an optical system including an optical focal plane array (FPA) unit, the optical system having components defining at least two optical channels thereof, said at least two optical channels being spatially and spectrally different from one another, each of the at least two optical channels positioned to transfer IR radiation incident on the optical system towards the optical FPA unit; and
a data-processing unit comprising one or more processors, said data-processing unit configured to acquire spectral optical data from the IR radiation received at the optical FPA unit,
wherein said data-processing unit is configured to determine absorption spectra data at one or more given pixels of a given frame by comparing spectral data for said one or more pixels of said frame with spectral data from one or more prior frames.
2. A system according to claim 1 , wherein said data-processing unit is configured to consider signal to noise as a criteria for determining whether to include data for a particular prior frame in said comparison.
3. A system according to claim 2 , wherein said data-processing unit is configured to assess signal to noise based on a standard deviation, variance, or a value based on the standard deviation or variance of the spectral data of a plurality of prior frames at said pixel.
4. A system according to claim 1 , wherein said data-processing unit is configured to determine absorption spectra data at one or more given pixels of a given frame by comparing spectral data with a statistical value based on data from prior frames.
5. A system according to claim 4 , wherein said statistical value comprises a running average.
6. A system according to claim 4 , wherein said data-processing unit is configured to consider noise as a criteria for determining whether to incorporate data for a particular prior frame into the computation of said statistical value.
7. A system according to claim 6 , wherein said data-processing unit is configured to assess noise based on variation in spectral data of said prior frames at said pixel.
8. A system according to claim 1 , wherein said data-processing unit is configured to determine absorption spectra data at one or more given pixels of a given frame by determining the mathematical difference of said spectral data compared to a running average computed from prior frames.
9. A system according to claim 8 , wherein said determining the mathematical difference comprises subtracting radiance spectral data for a pixel for a current frame and a running average of the radiance spectrum for that pixel for prior frames.
10. A system according to claim 1 , wherein said spectral data comprises luminance or radiance data.
11. A system according to claim 1 , wherein said data-processing unit is configured to compare said spectral data without knowing whether a leak has occurred.
12. A system according to claim 1 , wherein the optical system comprises a plurality of IR spectral filters for the different channels.
13. A system according to claim 1 , wherein the optical system comprises a plurality of imaging lenses for the different channels.
14. A system according to claim 1 , further comprising a display.
15. A system according to claim 1 , wherein said data-processing unit is located at least in part remotely from said optical system.
16. A system according to claim 15 , wherein said data-processing unit is located at least 10-3000 feet from said optical system.
17. A system according to claim 1 , wherein said data processing unit is in operable cooperation with a tangible, non-transitory computer-readable storage medium that contains a computer-readable program code that, when loaded onto the data processing unit, enables the data processing unit to determine absorption spectra data at one or more given pixels of a given frame by comparing spectral data for said pixel of said frame with spectral data from prior frames.
18. The system according to claim 1 , wherein the data processing unit is configured to estimate emission rate data for a gas leak using said spectral data.
19. The system according to claim 1 , wherein the data processing unit is configured to determine an estimate of gas column density at a selected location within the field of view of the optical system.
20. The system according to claim 19 , wherein the data processing unit is configured to determine the estimate of the gas column density at the selected location within the field of view by averaging over one or more spectral bands a plurality of values from a time series of data that correspond to the selected location.
21. The system according to claim 19 , wherein the data processing unit is configured to determine the estimate of the gas column density at the selected location within the field of view by fitting a cross-section spectrum of the gas to a plurality of values from a time series of data that correspond to the selected location.
22. The system according to claim 1 , wherein the data processing unit is configured to determine an estimate of the total quantity of gas in the gas cloud at a selected location using said spectral data.
23. The system according to claim 22 , wherein the data processing unit is configured to determine the estimate of the total quantity of gas at the selected location using knowledge of one or more specifications of the FPA unit, one or more specification of the optical system, distance of the optical system to the gas cloud, or combinations thereof.
24. The system according to claim 22 , wherein the data processing unit is configured to determine an estimate the total quantity of gas in the gas cloud at a plurality of locations within the field of view of the optical system and sum said estimates to determine an estimate of the total quantity of gas within the field of view.
25. The system according to claim 1 , wherein the sampling rate of the acquired spectral optical data is at least 15 Hz.