Fabry-perot interferometer based satellite detection of atmospheric trace gases
Systems, methods, and devices relating to optical imaging systems for gathering data on atmospheric trace gas emissions from a satellite. An optical system used in the satellite has a Fabry-Perot interferometer coupled to a suitable telescope. The interferometer is a wide angle Fabry-Perot interferometer which creates a fringing pattern in concentric circles with each fringe being a different wavelength on the imaging system. A filter is used with the optical system and allows multiple adjacent modes in a selected spectral range to pass through the interferometer to the imaging system. Each pixel in the imaging system collects light at multiple wavelengths within the selected spectral range. The optical system gathers multiple images of the target area allowing light from the target area to be collected at multiple different wavelengths. Different absorption data for different atmospheric trace gases can be gathered in a single satellite pass over the target area.
1. A system for detecting atmospheric trace gas emissions from a specific target location by way of an observation platform, the system comprising:
an image gathering device located at said platform, said platform being for overflying said specific target location, said image gathering device being for gathering multiple images of said specific target location as said platform overflies said specific target location;
a Fabry-Perot interferometer having a range of angles, said interferometer being located at said platform and being configured such that light gathered from said specific target location passes through said interferometer before being received by said image gathering device; and
a filter for filtering light from said specific target location prior to being received by said interferometer, said filter being for allowing multiple modes in a selected spectral range to pass through said filter to said image gathering device;
wherein said Fabry-Perot interferometer comprises at least two mirrors, each of said at least two mirrors having the following characteristics:
a surface roughness of less than 1 nm rms;
a surface curvature of less than 2 nm; and
a surface tilt of less than 2 nm.
2. A system according to claim 1 wherein said multiple modes allowed by said filter to pass through are modes adjacent to one another.
3. A system according to claim 1 further including data processing modules on-board said platform, said data processing modules being for image processing said multiple images, said multiple images being processed prior to being transmitted to a ground station.
4. A system according to claim 3 wherein said data processing modules process said multiple images to thereby transmit a reduced resolution image from said multiple images to a ground station and to thereby receive target data from said ground station in response, said target data being indicative of said specific target location to be imaged by said image gathering device.
5. A system according to claim 4 wherein said target data is used by said data processing modules to determine which parts of which images of said multiple images are to be transmitted to said ground station.
6. A system according to claim 3 wherein at least two of said multiple images are processed by said data processing modules to thereby align said images with one another prior to compressing said multiple images.
7. A system according to claim 3 wherein said multiple images are processed by data processing modules to produce concentration maps.
8. A system according to claim 1 wherein said Fabry-Perot interferometer is produced using at least one of:
a fluid jet polishing technique for obtaining a suitable match between two surfaces of mirrors used in said interferometer;
pre-compensating for expected curvatures due to coatings on said mirrors;
adjusting a tilt between said mirrors by using a plurality of flexures which apply pressure in relative amounts to reduce said tilt.
9. A system according to claim 1 wherein said Fabry-Perot interferometer uses a plane-parallel cavity.
10. A system according to claim 1 further comprising data processing modules on-board said platform, said data processing modules being for determining a spectral response of a plurality of pixels on said image gathering device to said light gathered from said specific target location based on a traversal angle for said interferometer.
11. A system according to claim 10 wherein said system determines said vertical column densities of atmospheric trace gases by recursively adjusting parameters of a predetermined model and recursively comparing said spectral response from said image gathering device with results from said model to determine said vertical column densities of said atmospheric trace gases at said specific target location, said vertical column densities being values which account for relevant atmospheric spectroscopy and a full instrument response from devices on said platform.