System and method for spatiotemporal analyte measurement over site using optical network

Abstract

Systems and methods are provided for measuring analytes (e.g., greenhouse gases, such as nitrous oxide) in the air above a site or other area. The optical web may be projected over the site using lasers respectively provided from each of two or more towers disposed around an edge of the site for estimating flux emissions and spatio-temporal parameters thereof. Each laser may be configured to provide light of a respective predetermined wavelength to one or more reflectors disposed around an edge of the site, thereby providing path integration measurements, and then light is returned from the reflectors to a detector co-aligned with each respective laser. By making many such measurements, a set of linear equations may be generated, which may then be used to solve emissions in any one of the grid cells of the venue.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 523,690, filed June 28, 2023, and U.S. Provisional Application Serial No. 63 / 631,904, filed April 9, 2024, the disclosure of each of the aforementioned U.S. Provisional Applications, including all figures, tables, and drawings, which are incorporated herein by reference in their entirety.

[0003] Government support

[0004] This invention was completed with government support from the Department of Energy, grant number DE-AR0001385. The government holds certain rights to this invention. Background Technology

[0005] Agriculture generates numerous greenhouse gases and air pollutants that can negatively impact the environment. Therefore, governments often impose limits on the potential emissions of specific farms or sites before reporting requirements take effect, mitigation measures are implemented, or environmental sustainability claims are made. If the actual generation of specific emissions is minimized or reduced, goods with a lower environmental impact can be sold on the carbon credit market, generating revenue for the owners of the restricted farms or sites. Such practices can also profit from marketing through environmental sustainability claims on their products. Therefore, accurate measurement of greenhouse gas and air pollutant emissions in agricultural practices is crucial. Summary of the Invention

[0006] Embodiments of the present invention provide novel and advantageous systems and methods for measuring analytes (e.g., greenhouse gases such as nitrous oxide (N2O)) in the air above a field or other area (e.g., a field in an agricultural setting). An optical web can be projected onto a field or other area using light sources (e.g., lasers) disposed or mounted on towers or platforms that monitor the field or other area, along with meteorological data for wind speed. With two or more towers disposed around the edge (e.g., immediately outside) of the field or other area, estimates of flux emissions and their spatiotemporal parameters can be obtained. Each light source can be configured to provide light of a respective predetermined wavelength (e.g., mid-infrared (mid-IR) wavelength) to one or more reflectors (e.g., retro-reflectors) disposed around the edge (e.g., immediately outside) of the field or other area, thereby providing path-integrated measurements, with the light then returning from the reflectors to a detector co-aligned with each respective light source. Based on the density and / or arrangement of the reflectors, a "grid cell" is derived from the overlapping beams (e.g., laser beams) on the field (or other area). By taking many such measurements, a set of linear equations can be generated, which can then be used to solve for emissions in any one grid cell of the field (or other area). This information can be combined with meteorological data in an atmospheric inversion model for final emission (or analyte concentration) estimates.

[0007] In an implementation, a system for measuring at least one analyte in air above a field (e.g., an agricultural field) can include: at least two towers disposed at or near a perimeter of the field, wherein each of the at least two towers includes at least one mid-infrared (mid-IR) light source (e.g., a laser) disposed thereon and configured to provide a predetermined wavelength of light for a particular analyte, wherein the predetermined wavelength is in a range from 2 micrometers (pm) to 30 pm; a plurality of reflectors disposed around the perimeter of the field and configured to reflect light from each mid-IR light source of each tower; and an analyzer unit in operable communication with the at least one mid-IR light source of each of the at least two towers. Each of the at least two towers can also include a detector (e.g., a mercury cadmium telluride (MCT) detector and / or an image sensor) disposed thereon and configured to receive a signal of light reflected from the plurality of reflectors. The system can also include a weather station in operable communication with the analyzer unit, and the weather station can be configured to obtain weather data for air above the field, air adjacent to the field, or both. The weather data can include, for example, wind speed, wind direction, barometric pressure, air temperature, humidity, or a combination thereof. The weather station can be disposed within or near the field. Each of the at least one analyte can be, for example, a greenhouse gas (e.g., N2O, ammonia (NH3), methane (CH4), carbon dioxide (CO2), ozone (O3), or a combination thereof). The system can be configured to measure the at least one analyte with an accuracy that is able to resolve about one thousandth of an ambient level (i.e., a background level) of each respective gas in the atmosphere that is far from a nearby source. This is on the order of parts per billion (ppb) or less, such as, for example, 100 ppb for CO2, 0.1 ppb for N2O, 0.1 ppb for NH3, and 0.1 ppb for O3. The system can be configured to measure the at least one analyte with a sensitivity / accuracy of 100 ppb or less, 10 ppb or less, 1 ppb or less, 0.1 ppb or less, 1 ppb, about 1 ppb, 0.1 ppb, or about 0.1 ppb. The plurality of reflectors can be disposed at regular intervals around the perimeter of the field and / or can be disposed close enough to each other around the perimeter of the field to generate a concentration map of the at least one analyte with a predetermined granularity by the analyzer unit. The analyzer unit can include software stored thereon that is configured to receive a signal of light reflected from the plurality of reflectors and convert the signal into data indicative of a concentration of the at least one analyte in the air. The analyzer unit can convert the signal by wavelength modulated spectroscopy, direct absorption spectroscopy, or both. The data indicative of the concentration of the at least one analyte in the air can include at least one of: spatial information of the concentration of the at least one analyte in the air; vertical distribution information of the concentration of the at least one analyte in the air; and a flux of the concentration of the at least one analyte in the air.The system can also include a display in operable communication with the analyzer unit, and the analyzer unit can be configured to display data indicative of a concentration of at least one analyte in the air on the display. Each of the plurality of reflectors can be, for example, a retroreflector configured to reflect mid-IR light. The retroreflector can include a substrate and a coating disposed on the substrate. The substrate layer can include a thermoplastic material (e.g., a polymer such as polymethyl methacrylate (PMMA)). The coating can include a metal (e.g., aluminum (Al), gold (Au), silver (Ag), or a combination thereof). The coating can have a thickness of, for example, 10,000 Angstroms or less (e.g., 5,000 Angstroms or less, such as 2,500 Angstroms or about 2,500 Angstroms). The retroreflector can also include: an adhesive layer disposed between the substrate and the coating; and / or a protective layer disposed on the coating. The adhesive layer can include a transition metal (e.g., titanium (Ti), chromium (Cr), or a combination thereof). The adhesive layer can have a thickness of, for example, 10,000 Angstroms or less (e.g., 5,000 Angstroms or less, such as 500 Angstroms or about 500 Angstroms). The protective layer can include an insulating material (e.g., silicon oxide). The retroreflector can have a total thickness of 50 millimeters (mm) or less (e.g., 25 mm or less, 10 mm or less, 4 mm or less, about 4 mm or 4 mm). The at least two towers can include two towers disposed on opposite sides of the site opposite one another. The analyzer unit can include a field programmable gate array (FPGA), such as a custom FPGA. Each of the at least two towers can also include a visible light source (e.g., a visible light laser) disposed thereon and configured to provide light of a visible wavelength to facilitate initial alignment during setup. Each of the at least two towers can also include a gimbal (e.g., a joystick-controlled gimbal) to steer mid-IR light (e.g., a laser beam) to each reflector on the site. The at least mid-IR light source can be, for example, a quantum cascade laser (QCL), an interband cascade laser (ICL), an antimony chalcogenide laser, a lead-salt laser, a light-emitting diode (LED), one or more frequency combs, or light from difference frequency generation. At least two of the towers present can also contain a reflector (i.e., each tower present can contain a reflector).

[0008] In another embodiment, a method for measuring at least one analyte in air above an agricultural field can comprise: i) providing a system as disclosed herein (such as a system having any combination of features from the previous paragraph); ii) sending mid-IR light from at least one mid-IR light source in a first tower of the at least two towers to a first reflector of the plurality of reflectors, and receiving reflected light from the first reflector; iii) moving the at least one mid-IR light source of the first tower, and sending mid-IR light from the at least one mid-IR light source of the first tower to a further reflector of the plurality of reflectors, and receiving reflected light from the further reflector; iv) repeating step iii) for each other reflector of the plurality of reflectors; v) optionally repeating steps ii) to iv) for each other tower of the at least two towers that is present; and vi) converting the signal of the reflected light into data indicative of the concentration of the at least one analyte in the air using the analyzer unit. When each of the first tower and a second tower that is symmetrically opposite to the first tower is directly illuminated by the other, the overlapping path length of the light (e.g., laser beams) enables internal calibration of the at least one mid-IR light source of each tower at exactly the same optical path length. The method can further comprise displaying the data indicative of the concentration of the at least one analyte in the air on a display in operable communication with the analyzer unit. Although this paragraph and the previous paragraph disclose at least two towers, a platform can be used instead of any tower or all towers. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 An image showing a top view of an agricultural field with towers and reflectors according to an embodiment of the present invention. The (red) lines crossing the field represent the path of the laser beams traveling from the towers to the reflectors and back.

[0010] Figure 2 An image showing a tower disposed at an edge portion of an agricultural field according to an embodiment of the present invention. The (red) lines crossing the field represent the path of the laser beams traveling from the tower to the reflectors and back. The inset shows an image of an example reflector that can be used with embodiments of the present invention.

[0011] Figure 3 An example of a spatial map of analyte concentration that can be obtained using systems and methods of embodiments of the present invention is shown. Figure 3 The scale on the right-hand side shows a scale for nitrous oxide (N2O) flux.

[0012] Figure 4 An image of an example reflector that can be used with embodiments of the present invention is shown. The scale bar is 10 millimeters (mm).

[0013] Figure 5 A schematic diagram of an optical arrangement that can be in a tower according to an embodiment of the present invention is shown.

[0014] Figure 6 An image showing different types of reflectors that can be used with the system of embodiments of the application. Figure 6 A graph showing the normalized signal strength (in arbitrary units) of different types of reflectors when used with the system of embodiments of the application.

[0015] Figure 7 An image showing different types of reflectors that can be used with the system of embodiments of the application.

[0016] Figure 8 A graph showing the variation of N20 concentration (in parts per billion (ppb)) over time (top graph in hours and bottom two graphs in seconds).

[0017] Figure 9 An image showing the set-up of a reflector and tower according to embodiments of the application.

[0018] Figure 10 An overhead view (top) of a site for testing a system according to embodiments of the application and an image of an optical arrangement according to embodiments of the application that can be in a tower (bottom).

[0019] Figure 11 A graph showing the variation of N20 concentration (in ppb) over time (left and top two graphs in time of day and right bottom two graphs in seconds).

[0020] Figure 12 A graph showing the time versus space relationship showing atmospheric mixing.

[0021] Figure 13 A calculation of analyte concentration in air is shown.

[0022] Figure 14 An example of spectroscopy is shown. DETAILED DESCRIPTION

[0023] Embodiments of the invention provide novel and advantageous systems and methods for measuring an analyte (e.g., a greenhouse gas such as nitrous oxide (N2O)) in the air above a field or other area (e.g., a field in an agricultural setting). An optical net can be projected over the field or other area using light sources (e.g., lasers) mounted or disposed on towers or platforms that monitor wind speed meteorological data of the field or other area. With two or more towers disposed around the edge (e.g., immediately outside) of the field or other area, estimates of flux emissions and their spatiotemporal parameters can be obtained. Each light source can be configured to provide light of a respective predetermined wavelength (e.g., mid-infrared (mid-IR) wavelength) to one or more reflectors (e.g., retro-reflectors) disposed around the edge (e.g., immediately outside) of the field or other area, thereby providing path-integrated measurements, with the light then returning from the reflectors to a detector co-aligned with each respective light source. Based on the density and / or arrangement of the reflectors, a "grid cell" is derived from the overlapping beams (e.g., laser beams) on the field (or other area). By taking many such measurements, a set of linear equations can be generated, which can then be used to solve for emissions in any one grid cell of the field (or other area). This information can be combined with meteorological data in an atmospheric inversion model for final emission (or analyte concentration) estimates, and this can be done on a grid cell basis. Each light source can be, for example, a quantum cascade laser (QCL), an interband cascade laser (ICL), an antimony chalcogenide laser, a lead-salt laser, a light-emitting diode (LED), one or more frequency combs, or light from difference frequency generation. At least two of the towers present can also contain reflectors (i.e., each tower present can contain a reflector). In many embodiments, each light source is a laser.

[0024] Prior art sensing techniques are limited in either spatial resolution or temporal resolution. For example, drone or vehicle-based measurements can produce spatially resolved measurements, but in practice cannot operate continuously. Eddy covariance and soil flux chambers can be set up to run for months or longer, providing temporal resolution, but cannot resolve the entire field or other area spatially. Eddy covariance flux measurements also cannot be made in light winds or high atmospheric stability conditions, and eddy covariance flux measurements can only measure flux in the upwind direction. Eddy covariance flux cannot resolve spatial heterogeneity within its upwind "footprint." Flux chambers also disturb the soil in which they are embedded, and analysis requires significant off-site labor and consumables for off-site analysis. Embodiments of the invention provide both spatial and temporal resolution, and are limited spatially only by the density of reflectors around the field or other area. The systems and methods of embodiments provide a "gold standard" for measuring emissions of an analyte of interest (e.g., a gas), particularly a greenhouse gas such as N2O.

[0025] Embodiments of this invention can be used for tomographic imaging of analyte flux (e.g., gases) in any space. The system can be built and / or optimized for measurements over farmland, but any site, body of water, or large indoor / outdoor space (such as an animal farm or industrial facility) can also be used as the target for measurement. This system and method can be used to measure greenhouse gases, such as N2O, which is particularly relevant to carbon credit markets and regulatory compliance. In some embodiments, the reflector can be attached to a drone, a small radio-controlled (RC) car or boat, a buoy, a tower, or other structure, and imaging can be performed in different environmental groups and dynamically, with the laser tower tracking the moving platform.

[0026] In a preferred embodiment, the system includes mid-IR retroreflectors arranged along the perimeter of the site and a rotating tower-based optical system comprising a mid-IR light source (e.g., a laser) and a detector (e.g., a mercury cadmium telluride (MCT) detector and / or an image sensor). The system may also include one or more mirrors and / or custom field-programmable gate array (FPGA) electronics. The system may also include one or more visible light lasers to aid in alignment. The gimbal position of each retroreflector can be stored by an analyzer unit (or computer) for repeated probing of each reflector. The gimbal can move the output beam from the respective tower to different retroreflectors. The laser can be aimed at any retroreflector for a predetermined amount of time (e.g., within a range from 1 minute to 10 minutes, or any subrange contained therein, such as from 2 minutes to 7 minutes) before continuing to move to aim at the next reflector. The path integral measurements from each reflector, and in some cases from multiple towers, can then be deconvolved into a global analyte concentration map using tomographic imaging methods.

[0027] In many implementations, a weather station (e.g., an acoustic anemometer or similar weather sensor) can be mounted on at least one tower (which may be the same as or different from a tower with a laser) to record wind and / or other meteorological parameters. By combining wind measurements with concentration maps using an inverse dispersion method, emission maps based on space and time can be created.

[0028] Figure 1 An image showing a top view of a site with two towers and multiple reflectors according to an embodiment of the present invention is provided. Figure 2 An image of a tower located at the edge of a site, according to an embodiment of the present invention, is shown. Figure 1 and Figure 2 In the diagram, the line crossing the site represents the path of the laser beam from the tower to the reflector and back. (See reference...) Figure 1 and Figure 2The towers can send light (e.g., mid-IR light) to reflectors, which are then reflected back to the respective towers to be detected by detectors (e.g., MCT detectors and / or image sensors). The reflectors can be positioned around the outside of the site (e.g., around the perimeter) so that, in use, an optical web or network of detection laser beams is generated. Figure 5 A schematic of an optical arrangement that can be used in a tower in one example is shown. The system can use an open-path sensing device or sensor (i.e., optical arrangement). An open-path sensing device or sensor means that air is passively brought into the sampling volume by wind or movement of the sensing device or sensor (e.g., via a mobile platform), and the sampling volume is directly exposed to ambient conditions.

[0029] In some embodiments, the system can include an analyzer unit in operable communication with each tower. The analyzer unit can be, for example, a computer having software stored thereon that is configured to receive the signal (or reflected light from the reflectors) and convert it to data indicative of the concentration of the analyte in the air. The signal of optical absorption can be converted via, for example, wavelength modulated spectroscopy or direct absorption spectroscopy, although embodiments are not limited thereto (see also examples of spectroscopy at Figure 14 ). The data indicative of the concentration of the analyte in the air can include spatial information (e.g., concentration in a space within the site) and / or vertical information (e.g., concentration of the space and concentration of the height off the ground taken with appropriately spaced reflectors). The data indicative of the concentration of the analyte can also include flux of the concentration of the analyte. The analyzer unit can include custom FPGA electronics. The analyzer unit can be in operable communication with a display on which the data indicative of the concentration of the analyte in the air can be displayed. The display can be located on the tower with the analyzer unit or can be remote from such a tower, in which case the data can be transmitted to the display wirelessly or via a line (e.g., buried line). When the towers send light to reflectors around the site, a full picture of the concentration of the analyte in the entire site can be obtained, as shown at Figure 3 .

[0030] Each laser can be configured to provide light in the mid-IR range (i.e., 2 microns (pm) to 30 pm) and a specific wavelength for a particular analyte. That is, each tower can include at least one laser, which can include a first laser configured to provide light at a first mid-IR wavelength targeted to obtain a concentration of a first analyte, a second laser configured to provide light at a second mid-IR wavelength targeted to obtain a concentration of a second analyte, a third laser configured to provide light at a third mid-IR wavelength targeted to obtain a concentration of a third analyte, and / or a fourth laser configured to provide light at a fourth mid-IR wavelength targeted to obtain a concentration of a fourth analyte, etc. Where there is more than one laser, only one laser is operated at a time to obtain a concentration of a single analyte at a time.

[0031] The reflectors can be positioned around the site in any reasonable manner. For example, the reflectors can be positioned at regular intervals around the site. The reflectors can also be arranged in an irregular manner. In preferred embodiments, the reflectors are arranged at regular intervals around the site and close enough to one another to generate an analyte concentration map having a desired granularity. Figure 6 and Figure 7 Images showing examples of reflectors that can be used are shown.

[0032] Each reflector can be any suitable reflector that reflects mid-IR laser light. In some embodiments, a new type of reflector that is both inexpensive and effective can be used. Each reflector can be a retroreflector configured for mid-IR light and is of a type that is used in the prior art only for visible light. The retroreflector can include a substrate (e.g., a thermoplastic material such as a polymer (e.g., polymethyl methacrylate (PMMA)), an optional adhesive layer disposed on the substrate, a coating disposed on the substrate and any optional adhesive layer, and an optional protective layer disposed on the coating. The coating can be, for example, a metal such as aluminum (Al), gold (Au), silver (Ag), or a combination thereof. The coating can have a thickness of, for example, 10,000 angstroms or less (e.g., 5,000 angstroms or less, such as 2,500 angstroms or about 2,500 angstroms). The optional adhesive layer can include, for example, a transition metal (e.g., titanium (Ti), chromium (Cr), or a combination thereof). The optional adhesive layer can have a thickness of, for example, 10,000 angstroms or less (e.g., 5,000 angstroms or less, such as 500 angstroms or about 500 angstroms). The optional protective layer can include, for example, an insulating material (e.g., silicon oxide). The retroreflector can have a total thickness of, for example, 50 millimeters (mm) or less (e.g., 25 mm or less, 10 mm or less, 4 mm or less, about 4 mm or 4 mm). Figure 4 An image showing such a retroreflector is shown. While reflectors of the related art can cost thousands of United States Dollars (USD), a retroreflector of the type discussed in detail herein can be effective while costing only tens of dollars or less by orders of magnitude.

[0033] Embodiments of the present invention effectively project an optical mesh to estimate flux emissions and their spatiotemporal parameters. Light can be sent from each tower to a reflector, providing a path-integrated measurement, and then the light is returned from the retroreflector to a detector that is co-aligned with the laser on the corresponding tower.

[0034] Systems and methods of embodiments of the present invention can measure peaks of analyte concentration above background concentration (see also, for example, U.S. Patent No. 9, 1 1 1, 1 10, which is incorporated by reference herein in its entirety). Figure 13). In this way, any horizontal flux that can exist from an adjacent agricultural field (e.g., from wind blowing) can already be accounted for in the background, and the peak (and trough) values of analyte concentration compared to the background can be considered to identify hot spots (or "cold" spots, e.g., deposition) of the analyte in the field being monitored.

[0035] The analyte can be a greenhouse gas or an air pollutant, such as nitrous oxide (N20), ammonia (NH3), methane (CH4), or carbon dioxide (C02). In some embodiments, the concentration of more than one analyte in the air can be detected, and each analyte can be a greenhouse gas or an air pollutant (such as those listed in the preceding sentence). Figure 12 Atmospheric mixing diagrams are shown for many different gases.

[0036] Systems and methods of embodiments of the invention can detect analyte concentrations in the air with a sensitivity of 500 parts per billion (ppb) or less, such as 100 ppb or less, 50 ppb or less, 10 ppb or less, 1 ppb or less, 0.1 ppb or less, about 1 ppb, 1 ppb, about 0.1 ppb, or 0.1 ppb.

[0037] In many embodiments, it is important that the distance between each tower and each reflector is known. If the distance "drifts" by 1 meter in a distance of 400 meters, this can equate to an error of 400th of a part, or by analogy, a retrieved concentration of 335 ppb is about 1 ppb. Thus, the distance between each reflector and each tower can be determined by direct measurement (e.g., tape measure, laser range finder, etc.) or optically derived (time delay of a pulse from a light source and receipt of that pulse, which can be converted to distance based on the speed of light; another option is to look at the phase shift of the outgoing light relative to the returning received light, which can give a time (and thus a distance)). The distance between each tower and each reflector should be known to within 1 part in 1000 (i.e., an error of no more than 0.1% of the actual distance). The distance can be determined / known by having a solid tower and / or reflector mount.

[0038] In some embodiments, a beam splitter and / or expander can be included on at least one tower. If the beam is wider, alignment becomes easier. However, if the beam is too wide, less light is reflected back to the sensor, which results in more noise and less accurate measurements of analyte concentration.

[0039] In some embodiments, the system can include a reference cell (e.g., disposed in or on at least one tower) for line locking and calibration, where a portion (e.g., 5% or about 5%) of the output beam is directed by a beamsplitter to a reference cell containing a gas of interest (e.g., N2O). The light that passes through the reference cell can then be focused onto a mid-IR detector. The reference cell can include a reference detector and can be used for absolute concentration referencing and also for line locking the light source (e.g., laser) to the absorption line of interest. Such line locking can be important for high precision, high stability measurements and in situations where rain and optical devices are likely to be covered with droplets, possibly with little or no light returning from the reflector.

[0040] In some embodiments, some or all reflectors and / or at least one tower can include a shield (e.g., a short shield) to help minimize the impact of precipitation on the measurements. The shield can be, for example, a small umbrella over the outgoing / returning beam and reflector. This can increase the robustness of the system.

[0041] In some embodiments, the reflectors can be positioned vertically with respect to the tower itself to obtain vertical distribution information of the analyte (e.g., within the canopy of the crop in the field, and possibly even above the canopy if the reflector is on a pole that extends above it). This data can be important for accurate flux measurements, as the concentration distribution helps to determine the flux in conjunction with the wind speed (which is easier to predict with height).

[0042] The methods and processes described herein can be embodied as code and / or data. The software code and data described herein can be stored on one or more machine-readable media (e.g., computer-readable media), which can include any device or medium that can store code and / or data for use by a computer system. When a computer system and / or processor reads and executes the code and / or data stored on the computer-readable medium, the computer system and / or processor performs the methods and processes embodied as data structures and code stored within the computer-readable storage medium.

[0043] Those skilled in the art will appreciate that computer readable media includes removable and non-removable, volatile and non-volatile structures / devices that can be used to store information such as computer readable instructions, data structures, program modules, and other data used by a computing system / environment. Computer readable media includes, but is not limited to, volatile memory such as random access memory (RAM, DRAM, SRAM), and non-volatile memory, e.g., flash memory, various read-only memories (ROM, PROM, EPROM, EEPROM), magnetic and ferromagnetic / ferroelectric memories (MRAM, FeRAM), and magnetic and optical storage devices (hard disk drives, magnetic tape, CDs, DVDs); network devices; or other media now known or later developed that can store computer readable information / data. Computer readable media should not be interpreted or read to include any propagating signals. The computer readable media of embodiments of the present invention can be, for example, a compact disc (CD), a digital video disc (DVD), a flash memory device, a volatile memory, or a hard disk drive (HDD) such as an external HDD or a HDD of a computing device, although embodiments are not limited thereto. The computing device can be, for example, a laptop computer, a desktop computer, a server, a cellular phone, or a tablet computer, although embodiments are not limited thereto.

[0044] When ranges are used herein, combinations and subcombinations of ranges, e.g., any sub-range within the disclosed ranges, and specific embodiments therein are intended to be explicitly included. When the term“about” is used in conjunction with a value, it is understood that the value can be within 95% of the value to 105% of the value, i.e., the value can be + / - 5% of the stated value. For example,“about 1 kg” means 0.95 kg to 1.05 kg.

[0045] The embodiments of the present application, and many of its advantages, can be better understood by reference to the following examples, given by way of illustration. The following examples illustrate some methods, applications, embodiments, and variations of the present application. Of course, they are not to be considered as limiting the present application. Numerous changes and modifications can be made to the embodiments of the present application.

[0046] Example 1

[0047] A tower system was developed to perform laser scanning over a field of cheap reflectors, essentially projecting a grid of light over the field. The system’s image as Figure 1As shown. Laser scanning tomographic reconstruction, combined with meteorological data and an atmospheric inversion model, enables continuous (30 minutes) and high-resolution (<1 acre) N2O emission mapping. The QCL, aligned with a visible diode laser and an MCT detector, is aligned with the first reflector. The system then rotates to the other reflectors, spending several minutes on each reflector to complete a full site scan. The entire system uses two towers for symmetrical and complete site scanning while maintaining self-calibration as the towers align with each other. Custom FPGA electronics control the laser, detectors, and all signal and data processing, offering low power consumption suitable for site deployment. The integrated path length of N2O was measured over a 400-meter round trip, as shown in the figure. Figure 3 As shown.

[0048] Example 2

[0049] use Figure 9 The equipment and site shown in the image were used to test the tower system of Example 1 using a pyramidal prism array retroreflector. The results are as follows: Figure 8 As shown, this demonstrates that the system is suitable for long-path measurements (400 meters between the tower and the reflector).

[0050] Example 3

[0051] exist Figure 10 On the field shown, a 4×4 array of plastic retroreflectors (approximately 10 meters apart) was used. Figure 10 The open-path optical sensor shown in the bottom image (and) Figure 5 The system was tested (illustratively shown in the diagram). Compared to Example 2, the reflector in this example was positioned closer to the sensor (e.g., for the sensor made by...). Figure 10 The "reflector" arrow highlights the reflector, with a round-trip distance of 98 meters. The results are shown in... Figure 11 The system was tested and demonstrated to function with high precision as expected.

[0052] It should be understood that the examples and implementations described herein are for illustrative purposes only, and those skilled in the art will make various modifications or changes based on them, and such modifications or changes will be included within the spirit and scope of this application.

[0053] All patents, patent applications, provisional applications and publications mentioned or cited herein, including all figures and tables, are incorporated herein in their entirety by reference, provided that they are not inconsistent with the express teachings of this specification.

Claims

1. A system for measuring at least one analyte in the air above a site, the system comprising: A first tower and a second tower, each located at or near the periphery of the site, wherein each of the first tower and the second tower includes at least one mid-infrared (mid-IR) light source, the at least one mid-infrared (mid-IR) light source being disposed on each of the first tower and the second tower and configured to provide light of a predetermined wavelength for a specific analyte, wherein the predetermined wavelength is in the range of 2 micrometers (μm) to 30 μm; A plurality of reflectors are arranged around the perimeter of the site and configured to reflect light from the medium IR light source of each of the first and second towers; and An analyzer unit that is operatively in communication with at least one IR light source in each of the at least one tower.

2. The system according to claim 1, wherein, Each of the first tower and the second tower further includes a first detector disposed on each of the first tower and the second tower and configured to receive signals of light reflected from the plurality of reflectors.

3. The system according to any one of claims 1 to 2, further comprising a weather station operatively communicatively with the analyzer unit, wherein, The weather station is configured to obtain meteorological data on the air above the site, the air adjacent to the site, or both.

4. The system according to claim 3, wherein, The meteorological data includes wind speed, wind direction, air pressure, temperature, humidity, or combinations thereof.

5. The system according to any one of claims 3 to 4, wherein, The weather station is located within or near the site.

6. The system according to any one of claims 1 to 5, wherein, Each of the at least one analyte is a greenhouse gas or an air pollutant.

7. The system according to claim 6, wherein, The at least one analyte includes nitrous oxide (N2O), ammonia (NH3), methane (CH4), carbon dioxide (CO2), or a combination thereof.

8. The system according to any one of claims 1 to 7, wherein, The system is configured to measure at least one analyte with a sensitivity of 100 parts per billion (ppb) or less.

9. The system according to claim 8, wherein, The system is configured to measure the at least one analyte with a sensitivity of 10 ppb or less.

10. The system according to any one of claims 8 to 9, wherein, The system is configured to measure the at least one analyte with a sensitivity of 1 ppb or less.

11. The system according to any one of claims 1 to 10, wherein, The plurality of reflectors are arranged at regular intervals around the perimeter of the site.

12. The system according to any one of claims 1 to 11, wherein, The plurality of reflectors are arranged sufficiently close to each other around the perimeter of the site so that the analyzer unit can generate a concentration map of the at least one analyte at a predetermined granularity.

13. The system according to claim 12, wherein, The analyzer unit includes software stored thereon, the software being configured to receive signals of light reflected from the plurality of reflectors and convert the light signals into data indicating the concentration of the at least one analyte in the air.

14. The system according to claim 13, wherein, The analyzer unit converts the signal using wavelength modulation spectroscopy, direct absorption spectroscopy, or both.

15. The system according to any one of claims 13 to 14, wherein, The data indicating the concentration of the at least one analyte in the air includes at least one of the following: spatial information of the concentration of the at least one analyte in the air; vertical distribution information of the concentration of the at least one analyte in the air; And the flux of the concentration of the at least one analyte in the air.

16. The system according to any one of claims 13 to 15, further comprising a display operatively communicatively with the analyzer unit, wherein, The analyzer unit is configured to display data on the display indicating the concentration of the at least one analyte in the air.

17. The system according to any one of claims 1 to 16, wherein, Each of the plurality of reflectors is a retroreflector configured to reflect IR light in the atmosphere.

18. The system according to claim 17, wherein, The retroreflector includes a substrate and a coating disposed on the substrate.

19. The system according to claim 18, wherein, The retroreflector further includes at least one of the following: an adhesive layer disposed between the substrate and the coating; and a protective layer disposed on the coating.

20. The system according to claim 19, wherein, The adhesive layer comprises a transition metal.

21. The system according to any one of claims 19 to 20, wherein, The adhesive layer has a thickness of 10,000 angstroms or less.

22. The system according to any one of claims 19 to 21, wherein, The protective layer includes an insulating material.

23. The system according to any one of claims 18 to 22, wherein, The substrate layer comprises a thermoplastic material.

24. The system according to any one of claims 18 to 23, wherein, The coating comprises metal.

25. The system according to claim 24, wherein, The coating comprises aluminum (Al), gold (Au), silver (Ag), or a combination thereof.

26. The system according to any one of claims 18 to 25, wherein, The coating has a thickness of 10,000 angstroms or less.

27. The system according to any one of claims 17 to 26, wherein, The retroreflector has a total thickness of 50 mm or less.

28. The system according to claim 27, wherein, The retroreflector has a total thickness of 10 mm or less.

29. The system according to any one of claims 1 to 28, wherein, The first tower and the second tower are symmetrically arranged on opposite sides of the site.

30. The system according to any one of claims 1 to 29, wherein, The analyzer unit includes a field-programmable gate array (FPGA).

31. The system according to any one of claims 1 to 30, wherein, Each of the first tower and the second tower also includes a visible light source disposed on each of the first tower and the second tower and configured to provide light of visible wavelengths.

32. The system according to any one of claims 1 to 31, wherein, Each of the first and second towers also includes a universal joint.

33. The system according to claim 32, wherein, The universal joint is a joystick-controlled universal joint.

34. The system according to any one of claims 1 to 33, wherein, The at least one of the IR light sources is a laser.

35. The system according to any one of claims 1 to 34, wherein, At least one of the first tower and the second tower further includes a reference detector disposed thereon, and the reference detector is configured for line locking and calibration.

36. A method for measuring at least one analyte in the air above a site, the method comprising: i) Provide a system according to any one of claims 1 to 35; ii) Sending medium IR light from at least one medium IR light source from the first tower to the first reflector of the plurality of reflectors, and receiving reflected light from the first reflector; iii) Move at least one intermediate IR light source of the first tower and send intermediate IR light from the at least one intermediate IR light source of the first tower to another reflector among the plurality of reflectors, and receive reflected light from the other reflector; iv) Repeat step iii) for each of the other reflectors in the plurality of reflectors. v) Repeat steps ii) to iv) for the second tower, and vi) Using the analyzer unit, the signal of the reflected light is converted into data indicating the concentration of the at least one analyte in the air.

37. The method of claim 36, wherein, When overlapping beams occur between the first tower and the second tower, the first detector of the first tower and the second detector of the second tower are internally calibrated with each other.

38. The method according to any one of claims 36 to 37, further comprising displaying data indicating the concentration of the at least one analyte in the air on a display operatively in communication with the analyzer unit.

39. A retroreflector, comprising: substrate; A coating disposed on the substrate; An adhesive layer disposed between the substrate and the coating; as well as A protective layer is disposed on the coating. The retroreflector has a total thickness of 50 millimeters (mm) or less.

40. The retroreflector according to claim 39, wherein, The adhesive layer comprises a transition metal.

41. The retroreflector according to any one of claims 39 to 40, wherein, The adhesive layer has a thickness of 10,000 angstroms or less.

42. The retroreflector according to any one of claims 39 to 41, wherein, The protective layer includes an insulating material.

43. The retroreflector according to any one of claims 39 to 42, wherein, The substrate layer comprises a thermoplastic material.

44. The retroreflector according to any one of claims 39 to 43, wherein, The coating comprises metal.

45. The retroreflector according to claim 44, wherein, The coating comprises aluminum (Al), gold (Au), silver (Ag), or a combination thereof.

46. ​​The retroreflector according to any one of claims 39 to 45, wherein, The coating has a thickness of 10,000 angstroms or less.

47. The retroreflector according to any one of claims 39 to 46, wherein, The retroreflector has a total thickness of 10 mm or less.

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