James Abshire

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Papers by James Abshire

A highly sensitive multi-element HgCdTe e-APD detector for IPDA lidar applications

Proceedings of SPIE, May 21, 2013

An HgCdTe electron avalanche photodiode (e-APD) detector has been developed for lidar receivers, ... more An HgCdTe electron avalanche photodiode (e-APD) detector has been developed for lidar receivers, one application of which is integrated path differential absorption lidar measurements of such atmospheric trace gases as CO 2 and CH 4. The HgCdTe APD has a wide, visible to mid-wave-infrared, spectral response, high dynamic range, substantially improved sensitivity, and an expected improvement in operational lifetime. A demonstration sensor-chip assembly consisting of a 4.3 lm cutoff HgCdTe 4 9 4 APD detector array with 80 lm pitch pixels and a custom complementary metal-oxide-semiconductor readout integrated circuit was developed. For one typical array the APD gain was 654 at 12 V with corresponding gain normalized dark currents ranging from 1.2 fA to 3.2 fA. The 4 9 4 detector system was characterized at 77 K with a 1.55 lm wavelength, 1 ls wide, laser pulse. The measured unit gain detector photon conversion efficiency was 91.1%. At 11 V bias the mean measured APD gain at 77 K was 307.8 with r/mean uniformity of 1.23%. The average, noise-bandwidth normalized, system noise-equivalent power (NEP) was 1.04 fW/Hz 1/2 with a r/mean of 3.8%. The measured, electronics-limited, bandwidth of 6.8 MHz was more than adequate for 1 ls pulse detection. The system had an NEP (3 MHz) of 0.4 fW/Hz 1/2 at 12 V APD bias and a linear dynamic range close to 1000. A gain-independent quantum-limited SNR of 80% of full theoretical was indicative of a gain-independent excess noise factor very close to 1.0 and the expected APD mode quantum efficiency.

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A Laser Sounder for global measurements of CO2 from space

Lasers, Sources, and Related Photonic Devices, 2012

ABSTRACT We have developed a laser technique for the remote measurement of the tropospheric CO2 c... more

Retrieval Algorithm for the Column CO2 Mixing Ratio from Pulsed Multi-Wavelength Lidar Measurements

The retrieval algorithm for the column mixing ratio of CO2 from the measurements of a pulsed mult... more The retrieval algorithm for the column mixing ratio of CO2 from the measurements of a pulsed multi-wavelength integrated path differential absorption (IPDA) lidar is described. The lidar samples the shape of the 1572.33 nm CO2 absorption line at 15 or 30 wavelengths. The algorithm uses a least-squares fit between the CO2 line shape computed from a layered atmosphere model to that sampled by the lidar. In addition to the column average CO2 dry air mole fraction (XCO2), several other parameters are also solved simultaneously from the fit. These include the Doppler shift in the received laser signal wavelengths, the product of the surface reflectivity and atmospheric transmission and a linear trend in the lidar receiver's spectral response. The algorithm can also be used to solve for the average water vapor mixing ratio, which causes a secondary absorption in the wings of the CO2 absorption line under high humidity conditions. The least-squares fit is linearized about the expected XCO2 value which allows the use of a standard linear least-squares fitting method and software tools. The standard deviation of the retrieved XCO2 is obtained from covariance matrix of the fit. An averaging kernel is defined similarly to that used for passive trace-gas sounding. Examples are presented of using the algorithm to retrieve XCO2 from the measurements from NASA Goddard's airborne CO2 Sounder lidar made at a constant altitude and during spiral-down maneuvers. 1 Introduction Accurate remote sensing of atmospheric CO2 from Earth orbiting satellites is a key component in the long-term carbon-climate observing system (Sellers et al., 2018). Airborne and spaceborne lidar can be used to remotely monitor the global CO2 and other trace-gas concentrations under conditions that are inaccessible to passive space-borne CO2 measurement missions, such as GOSAT (Kuze et al., 2016), OCO-2 (Crisp, 2017), and OCO-3 (Eldering et al., 2017; 2019). Studies have shown (Kawa et al., 2018) that a polar orbiting integrated path differential absorption (IPDA) lidar can measure XCO2 with low bias and high precision at all sun angles, seasons and latitudes using a constant nadir-zenith illumination and observing geometry. A pulsed IPDA lidar provides the range-resolved atmospheric backscatter profiles, so that return signals from the surface, clouds, and aerosols can be uniquely separated. This allows pulsed IPDA lidar to measure XCO2 to the surface, cloud tops, or both (Ramanathan et al., 2015). Because the laser pulses reflected from clouds, aerosols and surface are separated in time, the XCO2 retrievals to the ground surface are not affected by multiple scattering from clouds and aerosols (Mao et al., 2018).

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Space Borne Swath Mapping Laser Altimeters - Comparison of Measurement Approaches

AGU Fall Meeting Abstracts, Dec 1, 2007

ABSTRACT Laser altimetry is an important technique for studying the surface topography of the pla... more ABSTRACT Laser altimetry is an important technique for studying the surface topography of the planets and the Earth from orbit. Presently orbital laser altimeters profile surface height along a single ground track, such as the Geoscience Laser Altimeter System (GLAS) on Ice, Cloud, and land Elevation Satellite (ICESat). NASA is developing new technologies for an orbiting swath mapping laser altimeter with faster pulse rate and smaller footprint size to provide an instantaneous 3-dimentional measurement of the of icesheets, land topography and vegetation structure. The goal is to provide a greater than 200 m wide swath with 5 to 10 m diameter laser footprint from a 400 km altitude orbit. To achieve these goals, we have to use more efficient laser transmitters and more sensitive detectors to allow simultaneous multi-channel measurement with a reasonable instrument size and electrical power requirement. The measurement efficiency in terms of electrical energy needed per laser ranging measurement needs to be improved by more than an order of magnitude. Several different approaches were considered, including the use of fiber lasers, shorter laser pulse widths, lower noise analog detectors and photon counting detectors. The receiver sensitivity was further improved by averaging the results from a number of laser pulse measurements. Different laser pulse modulation formats, such as the pseudo random noise code modulation used in the Global Position System (GPS), were investigated to give more flexibility in laser selection and to further improve the ranging performance. We have analyzed and compared measurement performance for several different approaches using the receiver models that was validated with GLAS in orbit measurement data. We compared measurement performance with the traditional high-power low-pulse-rate laser transmitters to those with low-energy high-pulse-rate laser transmitters. For this work we considered laser characteristics representative of Microchip lasers at 1064 and 532 nm, and for pulsed Ytterbium fiber lasers at about 1?m wavelength. We considered Si APDs for analog detection, InGaAsP photocathode hybrid photomultiplier tubes for photon counting at 1?m, and Si APD single photon counting modules at 532 nm. For all cases we evaluated the probability of detection and the standard deviation of the ranging error as a function of the apparent surface reflectance defined as the product of the surface reflectance times the two-way atmosphere transmission. We also conducted several photon counting laser ranging experiments in the lab and in the field to validate our model and measurement techniques with various photon counting detectors. The results of the analysis and the experiments will be summarized and compared for parameters representative of future missions recommended by the National Research Council (NRC), such as ICESat II, LIST, and DESDynl.

Comparison of measured and theoretical performance of a maximum likelihood laser ranging receiver (A)

Journal of the Optical Society of America, Dec 1, 1980

The design and construction of a circular microphone array (CMA) that has a wide frequency range ... more The design and construction of a circular microphone array (CMA) that has a wide frequency range suitable for human hearing is presented. The design of the CMA was achieved using a technique based on simulated directivity index (DI) curves. The simulated DI curves encapsulate the critical microphone array performance limitations: spatial aliasing, measurement noise, and microphone placement errors. This paper demonstrates how the non-regularized DI curves for a given beamforming order clearly define the bandwidth of operation, in other words, the frequency band for which the beamformer has relatively constant and maximum directivity. Detailed and comprehensive experimental data that characterizes the CMA beamformer are also presented.

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Data Analysis for the Recent Flight Campaigns towards Future NASA Space Mission ASCENDS

AGUFM, Dec 1, 2010

ABSTRACT NASA launched science flight campaigns in summers 2009 and 2010 for future space mission... more ABSTRACT NASA launched science flight campaigns in summers 2009 and 2010 for future space mission ASCENDS (the Active Sensing of CO2 Emissions over Nights, Days and Seasons). Three NASA laser approaches currently under development in the Goddard Space Flight Center (GSFC), the Langley Research Center and the Jet Propulsion Laboratory flew and tested during the campaigns as candidates of ASCENDS toward high-precision global CO2 concentration measurement from space. For the first time, GSFC flew O2 lidar during summer 2010 campaign together with CO2 laser sounder in order to measure CO2 and dry air density simultaneously for estimating CO2 concentration, a mixing ratio with regards to dry air, as required by ASCENDS mission for global carbon cycle studies. In this presentation we will report our data analysis and retrieval results from both campaigns and will address issues associated with data acquisition, calibration, spectroscopy, forward calculations and retrieval processing. Campaigns were conducted from east coast to west coast, over land and oceans, over vegetation covers and deserts, in clear and cloudy sky, and measurements were made from 3 km to as high as 13 km. Measurement sensitivity to surface reflectivity, meteorological parameters, and CO2 variations will be assessed and studied. The lessons we learned from these flight campaigns will direct our future improvements and development and also help us better understand and define ASCENDS&#39; measurement requirements and mission goals.

Profiling tropospheric CO2 using the Aura TES and TCCON instruments

Monitoring the global distribution and long-term variations of CO 2 sources and sinks is required... more Monitoring the global distribution and long-term variations of CO 2 sources and sinks is required for characterizing the global carbon budget. Although total column measurements will be useful for estimating large regional fluxes, model transport error remains a significant error source, particularly for local sources and sinks. To improve the capability of estimating regional fluxes, we estimate near-surface CO 2 values from ground-based near infrared (NIR) measurements with space-based thermal infrared (TIR) measurements. The NIR measurements are obtained from the Total Carbon Column Observing Network (TCCON) of solar measurements which provide an estimate of the total CO 2 atmospheric column amount. Estimates of tropospheric CO 2 that are co-located with TCCON are obtained by assimilating Tropospheric Emission Spectrometer (TES) free-tropospheric CO 2 estimates into the GEOS-Chem model. Estimates of the boundary layer CO 2 are obtained through simple subtraction, as the CO 2 estimation problem is linear. We find that the calculated random uncertainties in total column and boundary layer estimates are consistent with actual uncertainties as compared to aircraft data. For the total column estimates the random uncertainty is about 0.55 ppm with a bias of −5.66 ppm, consistent with previously published results. After accounting for the total column bias, the bias in the boundary layer CO 2 estimates is 0.26 ppm with a precision of 1.02 ppm This precision is sufficient for capturing the winter to summer variability of approximately 12 ppm in the lower troposphere; double the variability of the total column. This work shows that a combination of NIR and IR measurements can profile CO 2 with the precisions and accuracy needed to quantify near-surface CO 2 variability. 1 Introduction Our ability to infer surface carbon fluxes depends critically on interpreting spatial and temporal variations of atmospheric CO 2 and relating them back to surface fluxes. For

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<title>Mars Observer laser altimeter investigation</title>

Proceedings of SPIE, Oct 15, 1993

The primary objective of the Mars Observer laser altimeter (MOLA) investigation is to determine g... more The primary objective of the Mars Observer laser altimeter (MOLA) investigation is to determine globally the topography of Mars at a level suitable for addressing problems in geology and geophysics. Secondary objectives are to characterize the 1064-nm wavelength surface reflectivity of Mars to contribute to analyses of global surface mineralogy and seasonal albedo changes, to assist in addressing problems in atmospheric circulation, and to provide geodetic control and topographic context for the assessment of possible future Mars landing sites. The principal components of MOLA are a diode-pumped, neodymium-doped yttrium aluminum garnet laser transmitter that emits 1064-nm wavelength laser pulses, a 0.5-m-diameter telescope, a silicon avalanche photodiode detector, and a time interval unit with 10-ns resolution. MOLA will provide measurements of the topography of Mars within approximately 160-m footprints and a center-to-center along-track footprint spacing of 300 m along the Mars Observer subspacecraft ground track. The elevation measurements will be quantized with 1.5 m vertical resolution before correction for orbit-and pointing-induced errors. MOLA profiles will be assembled into a global 0.2 ø x 0.2 ø grid that will be referenced to Mars' center of mass with an absolute accuracy of approximately 30 m. Other data products will include a global grid of topographic gradients, corrected individual profiles, and a global 0.2 ø x 0.2 ø grid of 1064-nm surface reflectivity. INTRODUCTION Surface topography is one of the fundamental measurements required to understand the structure and evolution of solid planetary bodies. Topographic measurements referenced to the planetary center of mass provide a basis for interpreting the gravity field in the context of a planet's internal structure and state of stress. Regional-scale topography and derived topographic gradients are frequently required in investigations of tectonic, volcanic, impact, and surface modification processes. Topography also provides a necessary constraint for atmospheric circulation and climate models. Because of its general importance to so many geoscience disciplines, global characterization of topography was advanced as one of the fundamental goals of NASA's Mars Observer (MO) Mission [Mars Observer Science Working Group, 1987]. The topographic objective of the Mars Observer mission will be accomplished using data from the Mars Observer laser altimeter (MOLA). Specific measurement objectives of the MOLA investigation are (1) to derive a global, geodetically referenced 0.2 ø x 0.2 ø topographic grid of Mars with a vertical accuracy of better than 30 m suitable for addressing problems in geophysics, geology, and atmospheric circulation; (2) to acquire globally distributed topographic profiles of the Martian surface on short baselines (-100 km) with a vertical precision of better than 2 m suitable for addressing a

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Prelaunch testing of the GEOS-3 laser reflector array

NASA STI/Recon Technical Report N, 1978

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Airborne measurements of CO&lt;sub&gt;2&lt;/sub&gt; column concentrations made with a pulsed IPDA lidar using a multiple-wavelength-locked laser and HgCdTe APD detector

Atmospheric Measurement Techniques, Apr 10, 2018

Here we report on measurements made with an improved CO 2 Sounder lidar during the ASCENDS 2014 a... more Here we report on measurements made with an improved CO 2 Sounder lidar during the ASCENDS 2014 and 2016 airborne campaigns. The changes made to the 2011 version of the lidar included incorporating a rapidly wavelength-tunable, step-locked seed laser in the transmitter, using a much more sensitive HgCdTe APD detector and using an analog digitizer with faster readout time in the receiver. We also improved the lidar's calibration approach and the XCO 2 retrieval algorithm. The 2014 and 2016 flights were made over several types of topographic surfaces from 3 to 12 km aircraft altitudes in the continental US. The results are compared to the XCO 2 values computed from an airborne in situ sensor during spiral-down maneuvers. The 2014 results show significantly better performance and include measurement of horizontal gradients in XCO 2 made over the Midwestern US that agree with chemistry transport models. The results from the 2016 airborne lidar retrievals show precisions of ∼ 0.7 parts per million (ppm) with 1 s averaging over desert surfaces, which is an improvement of about 8 times compared to similar measurements made in 2011. Measurements in 2016 were also made over fresh snow surfaces that have lower surface reflectance at the laser wavelengths. The results from both campaigns showed that the mean values of XCO 2 retrieved from the lidar consistently agreed with those based on the in situ sensor to within 1 ppm. The improved precision and accuracy demonstrated in the 2014 and 2016 flights should benefit future airborne science campaigns and advance the technique's readiness for a spacebased instrument.

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The NASA Goddard CO2 Sounder Lidar: 2017 Airborne Campaign as a Demonstration toward a Future Space Mission

NASA Goddard Space Flight Center has developed an integrated-path, differential absorption (IPDA)... more NASA Goddard Space Flight Center has developed an integrated-path, differential absorption (IPDA) lidar approach to measure atmospheric column-averaged CO2 mole fraction (XCO2). This pulsed laser approach uses a step-locked laser diode source, a fiber laser amplifier, and a high-sensitivity detector. The approach allows measurements of CO2 absorption and time-resolved laser backscatter profiles. These enable accurate estimates of XCO2 and range to the Earth's surface and cloud tops under a wide variety of conditions, including darkness, at low sun angles, through broken cloud fields, and the presence of aerosols. The CO2 Sounder lidar team has demonstrated airborne measurements during several campaigns over the past decade. Here we use the data from the summer 2017 airborne campaign in Alaska to further demonstrate the capabilities of this technique. We validated the XCO2 retrievals from the lidar against in situ measurements made from the aircraft during spiral-down maneuvers. The results show that this lidar approach provides XCO2 measurements with low bias and high precision under a wide variety of measurement conditions. The campaign showed the lidar's capability to resolve the vertical and horizontal gradients of CO2 and to quantify CO2 enhancements from wildfires. The results show it is an attractive candidate for future airborne science campaigns and, with more laser power, for a space mission like NASA's planned Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) mission.

Comparison of the CO2 column averaged mixing ratio from a Laser Sounder and LICOR measurements from the Boulder Atmospheric Observatory

AGUFM, Dec 1, 2008

We will present a description of a retrieval algorithm, which extracts the column-average CO2 vol... more We will present a description of a retrieval algorithm, which extracts the column-average CO2 volume-mixing ratio from atmospheric observations from our Laser Sounder. We will also present results from a direct comparison between a ground-based version of the laser sounder and the Boulder Atmospheric Observatory (BAO) Tower. The laser sounder was operated in parallel with the height-resolved LICOR measurements from

Laser Limb Sounding Approach for Planetary Atmospheres Using CubeSats or SmallSats

LPICo, Oct 1, 2016

Introduction: We describe an approach for an efficient and sensitive way to map trace gas abundan... more Introduction: We describe an approach for an efficient and sensitive way to map trace gas abundances in planetary atmospheres. The approach uses a pair of small satellites flying in formation, in a circular polar orbit. Each satellite carries several tunable single frequency diode lasers and a sensitive optical detector. The laser beam from each satellite is pointed through the limb of the planetary atmosphere to illuminate the other satellite. Tuning the diode laser's wavelengths through trace gas absorption lines allows the gas abundance in the path to be measured at the other satellite's receiver. Application for Mars Atmosphere: NASA's 2013 Planetary Science Decadal Survey identified mapping gas abundance in planetary atmospheres as an important goal. This new laser limb sounding approach allows the concentration of many key trace gases (such as CH4, H2O, HDO and CO2) to be measured simultaneously and continuously with very high sensitivity. Recent observations of Mars [1-3] suggest that CH4 varies in longitude, latitude, and season, but the details are sparsely measured and are poorly understood. The proposed concept will enable mapping the global atmospheric CH4 concentrations. The technique also allows probing water isotopic ratios (e.g., D/H), a proxy to sub-surface release and water loss. Earthbased observations show strong variations in the D/H ratio in column water vapor, and aspects of their seasonal changes [4]. Measurements from orbit are expected to provide new insights into the processes that control their distribution and ratio. The targeted gases also vary with altitude and one may vary the limb tangent altitude by changing the spacecraft spacing. Benefits of Approach: There are several important benefits to this novel approach. Unlike solar occultation, which can measure only during sunrise or sunset events, this approach allows continuous measurements, permitting full planetary mapping from polar orbit, even in darkness. The measurement sensitivity is high because the optical path length through the atmosphere is long (1000's of km). The geometry allows the measurement to be made with modest (10-20 mW) laser power using compact diode lasers and sensitive infrared detector [5]. Measurement Scenario: A mission can be accomplished with two smallsats, or 6U cubesats. After deployment the distance between them is adjusted so that they co-orbit with the primary spacecraft and the optical path between the two cubesats passes through the

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MOLA 1064nm Radiometry Measurements: Status and Prospects in Extended Mission

Lunar and Planetary Science Conference, Apr 1, 2002

ABSTRACT The Mars Orbiting Laser Altimeter (MOLA) instrument has measured the brightness of the M... more ABSTRACT The Mars Orbiting Laser Altimeter (MOLA) instrument has measured the brightness of the Mars surface at 1064 nm in a passive mode, from background noise counts, since 1997. After ceasing altimetry collection July 2001, MOLA has taken &gt;50 million high-resolution radiometer observations. Additional information is contained in the original extended abstract.

Modified PN Codes for Laser Remote Sensing Measurements

We describe a modified pseudo noise code for laser remote sensing measurements. Our experiments s... more

NASA’s Space Lidar Measurements of Earth and Planetary Surfaces

ABSTRACT

MERLIN: A French-German Space Lidar Mission Dedicated to Atmospheric Methane

Remote Sensing, Oct 16, 2017

The MEthane Remote sensing Lidar missioN (MERLIN) aims at demonstrating the spaceborne active mea... more The MEthane Remote sensing Lidar missioN (MERLIN) aims at demonstrating the spaceborne active measurement of atmospheric methane, a potent greenhouse gas, based on an Integrated Path Differential Absorption (IPDA) nadir-viewing LIght Detecting and Ranging (Lidar) instrument. MERLIN is a joint French and German space mission, with a launch currently scheduled for the timeframe 2021/22. The German Space Agency (DLR) is responsible for the payload, while the platform (MYRIADE Evolutions product line) is developed by the French Space Agency (CNES). The main scientific objective of MERLIN is the delivery of weighted atmospheric columns of methane dry-air mole fractions for all latitudes throughout the year with systematic errors small enough (<3.7 ppb) to significantly improve our knowledge of methane sources from global to regional scales, with emphasis on poorly accessible regions in the tropics and at high latitudes. This paper presents the MERLIN objectives, describes the methodology and the main characteristics of the payload and of the platform, and proposes a first assessment of the error budget and its translation into expected uncertainty reduction of methane surface emissions.

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New Examination of the Traditional Raman Lidar Technique: 1; Temperature Dependence and the Calculation of Atmospheric Transmission

In a companion paper, the temperature dependence of Raman scattering and its influence on the Ram... more In a companion paper, the temperature dependence of Raman scattering and its influence on the Raman water vapor signal and , f the lidar equations was examined. _w forms of the lidar equation were developed to account for this temperature sensitivity. Here we use those results to derive the temperatue dependent forms of the equations for the aerosol scattering ratio, aerosol backscatter coefficient, extinction to backscatter ratio and water vapor mixing ratio.Pertinent analysis examples are presented to illustrate each calculation. OCIS # 010.3640, 010.3920, 999.9999

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NASA/GSFC Scanning Raman Lidar Measurements of Water Vapor and Cirrus Clouds during WVIOP2000 and AFWEX

ABSTRACT The NASA/GSFC Scanning Raman Lidar (SRL) was deployed to the Southern Great Plains CART ... more ABSTRACT The NASA/GSFC Scanning Raman Lidar (SRL) was deployed to the Southern Great Plains CART site from September - December, 2000 and participated in two field campaigns devoted to comparisons of various water vapor measurement technologies and calibrations. These campaigns were the Water Vapor Intensive Operations Period 2000 (WVIOP2000) and the ARM FIRE Water Vapor Experiment (AFWEX). WVIOP2000 was devoted to validating water vapor measurements in the lower atmosphere while AFWEX had similar goals but for measurements in the upper troposphere. The SRL was significantly upgraded both optically and electronically prior to these field campaigns. These upgrades enabled the SRL to demonstrate the highest resolution lidar measurements of water vapor ever acquired during the nighttime and the highest S/N Raman lidar measurements of water vapor in the daytime; more than a factor of 2 increase in S/N versus the DOE CARL Raman Lidar. Examples of these new measurement capabilities along with comparisons of SRL and CARL, LASE, MPI-DIAL, in-situ sensors, radiosonde, and others will be presented. The profile comparisons of the SRL and CARL have revealed what appears to be an overlap correction or countrate correction problem in CARL. This may be involved in an overall dry bias in the precipitable water calibration of CARL with respect to the MWR of approx. 4%. Preliminary analysis indicates that the application of a temperature dependent correction to the narrowband Raman lidar measurements of water vapor improves the lidar/Vaisala radiosonde comparisons of upper tropospheric water vapor. Other results including the comparison of the first-ever simultaneous measurements from four water vapor lidar systems, a bore-wave event captured at high resolution by the SRL and cirrus cloud optical depth studies using the SRL and CARL will be presented at the meeting.

Attenuated atmospheric backscatter profiles measured by the CO2 Sounder lidar in the 2017 ASCENDS/ABoVE airborne campaign

Earth System Science Data, Aug 26, 2022

A series of attenuated atmospheric backscatter profiles were measured at 1572 nm by the CO 2 Soun... more A series of attenuated atmospheric backscatter profiles were measured at 1572 nm by the CO 2 Sounder lidar during the eight flights of the 2017 ASCENDS/ABoVE (Active Sensing of CO 2 Emission over Nights, Days, and Seasons, Arctic Boreal Vulnerability Experiment) airborne campaign. In addition to measuring the column average CO 2 mixing ratio from the laser signals reflected by the ground, the CO 2 Sounder lidar also recorded the height-resolved attenuated atmospheric backscatter profiles beneath the aircraft. We have recently processed these vertical profiles with a 15 m vertical spacing and 1 s integration time along the flight path (∼ 200 m) for all the 2017 flights and have posted the results at NASA Distributed Active Archive Center (DAAC) for Biogeochemical Dynamics https://doi.org/10.3334/ORNLDAAC/2051 (Sun et al., 2022). This paper describes the measurement principles, the data processing technique, and the signal to noise ratios.

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