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In situ CO2 concentrations versus altitude measured by the DOE Cessna aircraft with an infrared gas analyser. Left-hand profile is from a noon flight and the right-hand profile from a late afternoon flight on December 7, 2008. The black dots are measurements made during the aircraft's direct ascent, and the blue dots are those measured during the altitude-stepped decent, where the aircraft sampled CO2 while flying horizontally for 5–10 min per altitude. The spread in blue dots at the altitude bands is caused by the spatial variability of CO2 concentrations at the altitude. The red lines are the functions used to approximate the concentration profiles.
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We report initial measurements of atmospheric CO2 column density using a pulsed airborne lidar operating at 1572 nm. It uses a lidar measurement technique being developed at NASA Goddard Space Flight Center as a candidate for the CO2 measurement in the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) space mission. The pulsed...
Citations
... With the aim of developing a space-borne IPDA lidar for carbon dioxide monitoring, several studies have highlighted the utility of using a multiple-frequency CO 2 IPDA lidar [42]. In the frame of the ASCENDS project, different flight tests have been conducted with a different number of wavelengths between 8 to 20 and with a frequency spacing in the order of 1 GHz to sample the CO 2 absorption line at 1572.34 nm [1,14]. ...
... Thus, averaging over a large number of pulses to obtain a precise time-of-flight measurement was possible. Nevertheless, in scenarios of varying path length, fast, precise, and accurate time-of-flight monitoring is required [42]. After processing 1.5 × 10 5 spectrograms, we obtained a path length of 696 m with a standard deviation of 5 m. ...
In the context of greenhouse gas monitoring, previous studies have highlighted the potential benefits of using dual-comb spectroscopy (DCS) for integrated-path differential absorption (IPDA) lidar measurements. Unlike traditional IPDA lidars, in which the probing wavelengths are emitted sequentially over time, DCS enables the simultaneous emission of precisely evenly spaced wavelengths. This can help mitigate errors in the gas concentration measurement, especially in moving platform scenarios. However, several challenges must be addressed before considering the extension of DCS for air or spaceborne applications. This thesis presents the development and performance assessment of a ground-based IPDA lidar based on a dual-comb spectrometer for greenhouse gas monitoring, specifically carbon dioxide. We addressed the issue of implementing DCS for atmospheric gas measurements using the lidar returns from topographic targets at long distances (in the order of 1 km). This involved developing a lidar architecture, an inversion method, and signal processing suitable to the high optical losses and speckle noise inherent to the lidar measurement. A performance model to anticipate and optimize the measurement was developed, and a dual-comb IPDA lidar prototype was implemented. The prototype can operate at two different wavelengths, 1544 nm (with 100 µJ pulses) and 1572 nm (20 µJ), for H2O and CO2 sensing, respectively. The use of electro-optic combs enables easy tuning of the number of comb lines (below 10) and the comb line spacing within a range of up to 10 GHz. The ability of the lidar to monitor (non-simultaneously) water vapor and carbon dioxide concentrations, with a precision of 3% and 5%, respectively, using a non-cooperative target located 700 m away, was demonstrated. Excellent agreement with in-situ measurements was observed. These results may open the way for new concepts of robust, tunable multi-spectral gas lidars.
... Although these missions have not been finished, several groups have participated in the development of potential IPDA lidar methods and technologies utilizing various detection techniques. High accuracy in measuring atmospheric XCO 2 was validated [15][16][17][18][19]. The Methane Remote Sensing Lidar Mission (MERLIN) is being executed by the German Aerospace Center in collaboration with the French Space Agency. ...
In contrast to the passive remote sensing of global CO2 column concentrations (XCO2), active remote sensing with a lidar enables continuous XCO2 measurements throughout the entire atmosphere in daytime and nighttime. The lidar could penetrate most cirrus and is almost unaffected by aerosols. Atmospheric environment monitoring satellite (AEMS, also named DQ-1) aerosol and carbon dioxide detection Lidar (ACDL) is a novel spaceborne lidar that implements a 1572 nm integrated path differential absorption (IPDA) method to measure the global XCO2 for the first time. In this study, special methods have been developed for ACDL data processing and XCO2 retrieval. The CO2 measurement data products of ACDL, including the differential absorption optical depth between the online and offline wavelengths, the integral weighting function, and XCO2, are presented. The results of XCO2 measurements over the period from 1st June 2022 to 30th June 2022 (first month data of ACDL) are analyzed to demonstrate the measurement capabilities of the spaceborne ACDL system.
... Speckle reduction using partially coherent sources or multiple distinct laser modules with different wavelengths has been reported for laser projection and holographic displays [27][28][29][30][31]. Particular attention has been paid to reducing speckle for green-light sources [32,33], as traditionally green laser light is produced with narrow-linewidth second harmonic generation. Speckle noise was identified as a concern in atmospheric Integrated Path Differential Absorption (IPDA) lidar measurements, but since single-frequency operation is integral to the method, spatial averaging and a loss of spatial resolution are accepted in airborne and spaceborne approaches [26,[34][35][36][37]. We have not found reports of using laser linewidth broadening for high-precision reflectance measurements in the infrared. ...
The low obliquity of the Moon leads to challenging solar illumination conditions at the poles, especially for passive reflectance measurements aimed at determining the presence and extent of surface volatiles. A nascent alternate method is to use active laser illumination sources in either a multispectral or hyperspectral design. With a laser spectral source, however, the achievable reflectance precision may be limited by speckle noise resulting from the interference effects of a coherent beam interacting with a rough surface. Here, we have experimentally tested the use of laser linewidth broadening to reduce speckle noise and, thus, increase reflectance precision. We performed a series of speckle imaging tests with near-infrared laser sources of varying coherence, compared them to both theory and speckle pattern simulations, and measured the reflectance precision using calibrated targets. By increasing the laser linewidth, we observed a reduction in speckle contrast and the corresponding increase in reflectance precision, which was 80% of the theoretical improvement. Finally, we discuss methods of laser linewidth broadening and spectral resolution requirements for planetary laser reflectance spectrometers.
... Typically, in IPDA systems, two wavelengths are used to probe the atmosphere and estimate the average gas concentration. Yet having multiple differential absorption measurements at several wavelengths can help mitigate systematic errors in the gas concentration estimation and even provide additional information about the absorption line shape and the spatial distribution of the gas [1][2][3][4]. However, the precise knowledge and control of the emitted wavelengths can pose important technical challenges. ...
... It is worth noting that the lidar enables the emission and identification of 5 (or even more) wavelengths in a single 1 µs pulse, which is considerably faster than other IPDA lidar approaches where the different wavelengths are sent and detected one after the other over time with a typical frequency of 10 kHz [3,5]. ...
... It is worth noting that the lidar enables the emission and identification of 5 (or even more) 223 wavelengths in a single 1 s pulse, which is considerably faster than other IPDA lidar approaches 224 where the different wavelengths are sent and detected one after the other over time with a typical 225 frequency of 10 kHz [3,5]. In order to improve the measurement precision, different measurements with statistically 248 independent speckle noise must be averaged [17]. ...
We present the development of a multi-spectral, integrated-path differential absorption (IPDA) lidar based on a dual-comb spectrometer for greenhouse gas monitoring. The system uses the lidar returns from topographic targets and does not require retroreflectors. The two frequency combs are generated by electro-optic modulation of a single continuous-wave laser diode. One of the combs is pulsed, amplified, and transmitted into the atmosphere, while the other acts as a local oscillator for coherent detection. We discuss the physical principles of the measurement, outline a performance model including speckle effects, and detail the fiber-based lidar architecture and signal processing. A maximum likelihood algorithm is used to estimate simultaneously the gas concentration and the central frequency of the comb, allowing the system to work without frequency locking. H2O (at 1544 nm) and CO2 (at 1572 nm) concentrations are monitored with a precision of 3% and 5%, respectively, using a non-cooperative target at 700 m. In addition, the measured water vapor concentrations are in excellent agreement with in-situ measurements obtained from nearby weather stations. To our knowledge, this is the first complete experimental demonstration and performance assessment of greenhouse gas monitoring with a dual-comb spectrometer using lidar echoes from topographic targets.
... In the CO2 differential absorption measurement, it is common practice to choose two or more wavelengths (Abshire et al., 2010;Lin et al., 2013;Refaat et al., 2015). One wavelength, referred to as the offline wavelength, is selected far from the 80 center of the absorption line where the CO2 absorption is insignificant, serving as a baseline reference. ...
By utilizing progress in millijoule-level pulsed fiber lasers operating in the 1.96 µm spectral range, we introduce a concept utilizing a differential absorption barometric lidar designed to operate within the 1.96 µm CO2 absorption band for remote sensing of Martian atmospheric properties. Our focus is on the online wavelength situated in the trough region of two absorption lines, selected due to its insensitivity to laser frequency variations, thus mitigating the necessity for stringent laser frequency stability. Our investigation revolves around a compact lidar configuration, featuring reduced telescope dimensions and lower laser pulse energies. These adjustments are geared towards minimizing costs for potential forthcoming Mars missions. The core measurement objectives encompass the determination of column CO2 absorption optical depth, columnar CO2 abundance, surface air pressure, as well as vertical distributions of dust and cloud layers. Through the amalgamation of surface pressure data with atmospheric temperature insights garnered from sounders and utilizing the barometric formula, the prospect of deducing atmospheric pressure profiles becomes feasible. Simulation studies validate the viability of our approach. Notably, the precision of Martian surface pressure measurements is projected to surpass 1 Pa when the aerial dust optical depth is projected to be under 0.7, a typical air borne dust scenario on Mars, considering a horizontal averaging span of 10 km.
... Lidar measurements can provide valuable information on the vertical distribution of aerosol, cloud, and gas properties, including their optical and microphysical properties. Lidar measurements have been used in a variety of atmospheric studies, including monitoring air quality (Lolli et al., 2008, studying the vertical structure of clouds (Campbell et al., 2016(Campbell et al., , 2018Lolli et al., 2017;Lolli, 2023), and measuring greenhouse gases such as carbon dioxide (Abshire et al., 2010) and methane (Ehret et al., 2017). The very high spatial and temporal resolution of lidar measurements makes them particularly valuable for studying atmospheric processes on regional and local scales. ...
Aerosols are one of the most important pollutants in the atmosphere and have been monitored for the past few decades by remote sensing and in situ observation platforms to assess the effectiveness of government-managed reduction emission policies and assess their impact on the radiative budget of the Earth's atmosphere. In fact, aerosols can directly modulate incoming short-wave solar radiation and outgoing long-wave radiation and indirectly influence cloud formation, lifetime, and precipitation. In this study, we quantitatively evaluated long-term temporal trends and seasonal variability from a climatological point of view of the optical and microphysical properties of atmospheric particulate matter at the Universitat Politècnica de Catalunya (UPC), Barcelona, Spain, over the past 17 years, through a synergy of lidar, sun photometer, and in situ concentration measurements. Interannual temporal changes in aerosol optical and microphysical properties are evaluated through the seasonal Mann–Kendall test. Long-term trends in the optical depth of the recovered aerosol; the Ångström exponent (AE); and the concentrations of PM10, PM2.5, and PM1 reveal that emission reduction policies implemented in the past decades were effective in improving air quality, with consistent drops in PM concentrations and optical depth of aerosols. The seasonal analysis of the 17-year average vertically resolved aerosol profiles obtained from lidar observations shows that during summer the aerosol layer can be found up to an altitude of 5 km, after a sharp decay in the first kilometer. In contrast, during the other seasons, the backscatter profiles fit a pronounced exponential decay well with a well-defined scale height. Long-range transport, especially dust outbreaks from the Sahara, is likely to occur throughout the year. During winter, the dust aerosol layers are floating above the boundary layer, while during the other seasons they can penetrate the layer. The analysis also revealed that intense, short-duration pollution events during winter, associated with dust outbreaks, have become more frequent and intense since 2016. This study sheds some light on the meteorological processes and conditions that can lead to the formation of haze and helps decision makers adopt mitigation strategies to preserve large metropolitan areas in the Mediterranean basin.
... Using the approach outlined above, we recorded spectra for atmospheric CO 2 in Boulder, Colorado, USA, on October 12, 2022. The measurement targeted the R16 transition of the 30012 ← 00001 CO 2 band near 1572.33 nm, which has been the subject of past remote sensing missions [18] and advanced spectroscopic characterization [19]. Figure 1(b) shows the measured CO 2 spectrum after averaging for nearly 5 h. ...
We report precision atmospheric spectroscopy of CO2 using a laser heterodyne radiometer (LHR) calibrated with an optical frequency comb. Using the comb calibrated LHR, we record spectra of atmospheric CO2 near 1572.33 nm with a spectral resolution of 200 MHz, using sunlight as a light source. The measured CO2 spectra exhibit frequency shifts by approximately 11 MHz over the course of the 5-h measurement, and we show that these shifts are caused by Doppler effects due to wind along the spectrometer line of sight. The measured frequency shifts are in excellent agreement with an atmospheric model, and we show that our measurements track the wind-induced Doppler shifts with a relative frequency precision of 2 MHz (3 m·s⁻¹) for a single 10 s measurement, improving to 100 kHz (15 cm·s⁻¹) after averaging (equivalent to a fractional precision of a few parts in 10¹⁰). These results demonstrate that frequency comb calibrated LHR enables precision velocimetry that can be of use in applications ranging from climate science to astronomy.
... 2. Regions with elevations close to sea level. Gaseous CO 2 is denser than other atmospheric gases, and ambient CO 2 concentration levels decline at higher elevations (Abshire et al., 2010). 3. Proximity to high quality sedimentary basins for CO 2 storage. ...
Low temperature geothermal resources, ranging from 80° to 120°C, may substantially lower both the cost and the CO2 emissions footprint of CO2 direct air capture (DAC) systems. This paper provides a model for determining a region-specific economic analysis for DAC with solid sorbent (S-DAC) using geothermal resources (S-DAC-GT).
This paper provides a model for calculating estimated cost and carbon emissions for potential S-DAC facilities on a region-specific basis. The paper outlines the necessary region-specific characteristics required as parameters for the techno-economic model. The region-specific characteristics are then applied to an S-DAC energy and cost model based on existing literature to calculate the levelized cost per tonne of CO2 captured and stored. Further, the model provides a reasonable approximation of the carbon intensity of the S-DAC-GT system. These calculations allow selecting and prioritizing regions appropriate for potential S-DAC-GT facilities operating at a scale of ~1 Mt CO2 captured and stored per year.
Existing DAC techno-economic analyses are region agnostic and do not account for geothermal energy as the primary thermal energy source. The novelty of this paper is its deeper technical and economic analysis using geothermal energy as the thermal resource for the S-DAC process. This paper provides a model for customization of the techno-economic model specific to the target region. Further, the paper provides a consistent methodology for differentiating S-DAC-GT costs and carbon intensity by region.
... Lidar measurements can provide valuable information on the vertical distribution of aerosol, cloud, and gas properties, including their optical and microphysical properties. Lidar measurements have been used in a variety of atmospheric studies, including monitoring air quality (Lolli et al., 2008, studying the vertical structure of clouds (Campbell et al., 2016(Campbell et al., , 2018Lolli et al., 2017;Lolli, 2023), and measuring greenhouse gases such as carbon dioxide (Abshire et al., 2010) and methane (Ehret et al., 2017). The very high spatial and temporal resolution of lidar measurements makes them particularly valuable for studying atmospheric processes on regional and local scales. ...
Aerosols are one of the most important pollutants in the atmosphere and have been monitored for the past few decades by both remote sensing and in situ observation platforms to assess the effectiveness of government-managed reduction emission policies and assess their impact on the radiative budget of the Earth's atmosphere. In fact, aerosols can directly modulate incoming short-wave solar radiation and outgoing long-wave radiation and indirectly influence cloud formation, lifetime, and precipitation. In this study, we quantitatively evaluated long-term temporal trends and seasonal variability from a climatological point of view of the optical and microphysical properties of atmospheric particulate matter at the Universitat Politècnica de Catalunya, Barcelona, Spain, over the past 17 years, through a synergy of lidar, sunphotometer, and in situ concentration measurements. Interannual temporal changes in aerosol optical and microphysical properties are evaluated through the seasonal Mann-Kendall test. Long-term trends in the optical depth of the recovered aerosol, the Ångström exponent (AE) and the concentrations of PM10, PM2.5 and PM1 reveal that emission reduction policies implemented in the last decades were effective in improving air quality, with consistent drops in PM concentrations and optical depth of aerosols. The seasonal analysis of the 17-year average vertically resolved aerosol profiles obtained from lidar observations shows that during summer the aerosol layer can be found up to an altitude of 5 km, after a sharp decay in the first km. In contrast, during the other seasons, the backscatter profiles fit a pronounced exponential decay well with a well-defined scale height. Long-range transport, especially dust outbreaks from the Sahara Desert, is likely to occur throughout the year. During winter, the dust aerosol layers are floating above the boundary layer, while during the other seasons they can penetrate the layer. This study sheds some light on meteorological processes and conditions that can lead to haze formation and helps decision makers adopt mitigation strategies to preserve large metropolitan areas in the Mediterranean basin.
... 2. Regions with elevations close to sea level. Gaseous CO 2 is denser than other atmospheric gases, and ambient CO 2 concentration levels decline at higher elevations (Abshire et al., 2010). 3. Proximity to high quality sedimentary basins for CO 2 storage. ...
