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Contents lists available at SciVerse ScienceDirect

Sensors and Actuators B: Chemical

journa l h o mepage: www.elsev ier .com/ locate /snb

reenhouse gas analyzer for measurements of carbon dioxide, methane,nd water vapor aboard an unmanned aerial vehicle

lena S.F. Bermana,∗, Matthew Fladelandb, Jimmy Liema, Richard Kolyerb, Manish Guptaa

Los Gatos Research, 67 East Evelyn Ave, Suite 3, Mountain View, CA 94043, United StatesNASA Ames Research Center, Moffett Field, CA 94035, United States

r t i c l e i n f o

rticle history:eceived 20 December 2011eceived in revised form 5 April 2012ccepted 10 April 2012vailable online xxx

eywords:reenhouse gas

COSAV

a b s t r a c t

A compact, lightweight atmospheric gas analyzer has been integrated into and flown on the NationalAeronautics and Space Administration (NASA) Sensor Integrated Environmental Remote Research Air-craft (SIERRA) unmanned aerial vehicle (UAV) and deployed to make highly accurate, 1 Hz measurementsof methane, carbon dioxide, and water vapor. The analyzer was used to measure gas concentrations inflight and to demonstrate the system for providing measurements at altitudes as low as 10 m and inremote locations. The first flights were conducted at Crows Landing, CA, an agricultural site, with H2Oconcentrations showing distinct structure and sharp features that were well outside of the measurementnoise. The instrument was then deployed in Svalbard, Norway prior to the NASA Characterization ofArctic Sea Ice Experiment (CASIE). During the Svalbard flight, there was minimal variation in the CO2

ptical sensorarbon dioxideethaneater vapor

and CH4 concentrations, but the water concentration changed dramatically, oscillating as the aircraftmoved repeatedly through its racetrack shaped flight pattern. The regions of high water concentrationcorresponded to low-lying areas which collect runoff from the nearby Vestre Broggerbreen glacier. Thisnovel, integrated instrument-aircraft system allows more numerous and efficient measurements of car-bon dioxide, methane, and water vapor concentrations at low-altitudes and in remote or dangerouslocations.

. Introduction

The accurate quantification of greenhouse gases is criticallymportant for determining how the global environment is chang-ng, what drives these changes, and the potential consequencesor human civilization [1]. Ideally, this quantification is providedith high accuracy, fast time response, and high spatial resolu-

ion at relatively low cost. The three most important greenhouseases, in terms of abundance and contribution to the greenhouseffect, are water vapor (H2O), carbon dioxide (CO2), and methaneCH4). Water vapor is the primary driver behind the developmentf weather systems. Moreover, it strongly absorbs terrestrial radia-ion, and thus provides strong positive feedback of the greenhouseffect [1]. Although water vapor measurements are routinely madey ground-based stations and environmental monitoring satellites,ore accurate quantification and spatial precision are required for

limate modeling [2]. Carbon dioxide is the key species in the atmo-

Please cite this article in press as: E.S.F. Berman, et al., Greenhouse gas analaboard an unmanned aerial vehicle, Sens. Actuators B: Chem. (2012), http:

pheric carbon cycle and has been implicated as the foremost gasesponsible for climate change. In order to better understand thelobal carbon cycle and predict future climate change, scientists

∗ Corresponding author. Tel.: +1 650 965 7772x239; fax: +1 650 965 7074.E-mail address: [email protected] (E.S.F. Berman).

925-4005/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.snb.2012.04.036

© 2012 Elsevier B.V. All rights reserved.

need to accurately quantify the spatial and temporal distributionof carbon dioxide. Methane also plays a critical role in global cli-mate change, with a global warming potential that is 72 timeslarger than CO2 in a 20 year time horizon [2]. However, unlike CO2,atmospheric methane is more difficult to measure, often requiringoff-line laboratory analysis using a gas chromatograph coupled to aflame ionization detector [3]. Methane quantification is importantin studying the carbon cycle where vertical profiling and higherresolution provide additional data on key methane sources andsinks.

Currently, greenhouse gases are measured primarily at a net-work of atmospheric monitoring sites around the globe, such asthe NOAA Mauna Loa Observatory, which provide single-locationmeasurements of greenhouse gas concentrations at the Earth’s sur-face [2]. These measurements are complemented by satellite-basedsounding systems which measure greenhouse gases in various lay-ers of the atmosphere such as the NASA Atmospheric InfraredSounder [4] and the JAXA GOSAT which measures total column con-centrations using infrared spectroscopy [5,6]. These measurementstrategies have several advantages including wide global coverage

yzer for measurements of carbon dioxide, methane, and water vapor//dx.doi.org/10.1016/j.snb.2012.04.036

and multi-species detection. However, as a complement to thesemeasurements, in situ monitoring with higher accuracy, faster timeresponse, and more spatial resolution is required for a more com-plete understanding of climate change [7]. For example, current

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ARTICLE IN PRESSG Model

SNB-14074; No. of Pages 8

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ig. 1. Schematic of the unmanned aerial vehicle greenhouse gas analyzer showing tpproximately 30.5 cm × 30.5 cm × 28 cm and weighs 19.5 kg.

atellite instrumentation, like the Microwave Limb Sounder (MLS),rovides a best-case 1.5 km of vertical resolution and 200 km oforizontal resolution for water vapor measurements [8], which is

nsufficient to resolve Stratospheric–Tropospheric exchange (STE)echanisms (tropopause folding) [9–11]. Likewise, accurate verti-

al profiling is necessary to study large carbon sinks and sourcese.g. Amazon forest), where satellite data is insufficient for currentlimate modeling efforts [2]. Finally, in situ data can also be usedo provide verification of satellite observations.

In the past, most such airborne measurements have been madesing comprehensive, large-scale, field campaigns on piloted air-raft, such as the DC-8, WB-57F, and ER-2 (e.g. [7,10–12]). In anffort to make these measurements more efficient and cost effec-ive, research is underway to use smaller, unmanned aircraft [13].hus, new instrumentation is required that can autonomouslyeasure greenhouse gases while meeting the size, weight, and

ower limitations of UAV’s. For example, NASA’s Sensor Integratednvironmental Remote Research Aircraft (SIERRA) UAV is mid-ize UAV with a 6.1 m wing span, 3.6 m long and 1.4 m high.he SIERRA has a cruising speed of 28 m/s and a maximum alti-ude of 3600 m. The SIERRA can carry a 40 kg payload measuring0.5 cm × 40.5 cm × 30.5 cm and can provide up to 200 W of aircraftower.

In order to meet these stringent requirements for autonomousirborne deployments, we have exploited near infrared Off-Axisntegrated Cavity Output Spectroscopy (Off-Axis ICOS) [14,15].riefly, Off-Axis ICOS employs a high-finesse optical cavity asn absorption cell for laser spectroscopic measurements. Theechnique uses an off-axis trajectory of the laser beam throughhe optical cavity to produce an effective path length of severalilometers, allowing sensitive spectroscopic measurements whilevoiding excessive noise due to constructive/destructive interfer-nces. The sensitivity of Off-Axis ICOS makes possible the accurate

Please cite this article in press as: E.S.F. Berman, et al., Greenhouse gas anaaboard an unmanned aerial vehicle, Sens. Actuators B: Chem. (2012), http:

easurement of atmospheric quantities of H2O, CO2, and CH4 in lightweight and miniaturized package suitable for UAV deploy-ent. Besides its high sensitivity, Off-Axis ICOS is also inherently

obust and self-calibrating. Since the pathlength only depends on

(a) bottom (c) and assembled (b) UAV GGA. The fully assembled UAV GGA measures

losses in the cavity and not on the exact beam alignment, it isnot necessary to stringently align the optical cavity or the inputbeam. This allows the Off-Axis ICOS technique to tolerate a veryhigh degree of mechanical vibration and promotes its use as aflight instrument (see [12] for example). Moreover, this uniqueplatform permits self-calibration by rapidly switching the laser offand measuring the decay of light out of the cavity (similar to thewell-established technique of cavity ringdown spectroscopy) [16].Due to the robustness and sensitivity of Off-Axis ICOS technology,researchers routinely measure absorptions as small as 10−10 cm−1

and have applied this technique to a variety of industrial and envi-ronmental problems [15].

In this report, we detail the development and deployment of aminiaturized sensor for quantification of H2O, CO2, and CH4 thatmeets the physical requirements for UAV operation aboard theNASA SIERRA.

2. System design and construction

The UAV Greenhouse Gas Analyzer (GGA), schematically shownin Fig. 1, is based upon Los Gatos Research’s Off-Axis ICOS technol-ogy [15]. The instrument is fabricated on two 30.5 cm square opticalbreadboards. The bottom breadboard houses power and gas han-dling components including the battery, inverter, switching powersupply, and 2-head diaphragm pump. The instrument uses a single,rechargeable Lithium-Polymer battery (Powerizer) that measures185 mm × 170 mm × 70 mm, weighs 3.5 kg, and provides 560 W hof capacity at 11.1 V (nominal). The instrument requires about 70 Wof power, so the battery is capable of continuously operating theunit for 8 h, comparable to the typical SIERRA flight time. A 12 Vinverter (PowerBright, Coral Springs, FL) is employed to transformthe battery voltage into 110 VAC with > 90% efficiency after whicha switching power supply (Condor Electronics, Sunnyvale, CA) is

lyzer for measurements of carbon dioxide, methane, and water vapor//dx.doi.org/10.1016/j.snb.2012.04.036

used to transform the 110 VAC into all required voltages (e.g. ±12 V,+5 V). A small, 2-head diaphragm pump (KNF Neuberger, Trenton,NJ) that measures 129 mm × 105 mm × 49 mm, weighs 0.9 kg, andprovides 500 sccm of flow is used to direct sampled gas through the

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ig. 2. UAV greenhouse gas analyzer (left) integrated into the SIERRA nosecone rea

ff-Axis ICOS cavity. The cavity volume is approximately 400 cc,nd the pump rate gives a flow response time at 18.7 kPa of about

s. At the standard SIERRA cruise speed of 28 m/s, this responseime corresponds to an approximately 250 m horizontal resolution.

small voltage driven switch is included to activate the pump onlyhen the software is operational to save power.

The top breadboard houses the Off-Axis ICOS cavity, PC/104omputer, laser driver boards, lasers, and pressure controller. Theff-Axis ICOS subsystem includes the 2 in. (5 cm) diameter cav-

ty, highly reflective, multi-layer dielectric mirrors (R = 0.99995nd 0.999925 at 1650 nm and 1603 nm, respectively), laser launchount, and custom amplified InGaAs detector (3 mm diameter).

he laser launch mount is equipped with a custom launch blockhat enables 2 lasers to be simultaneously coupled into the cell,

1650 nm laser for CH4 measurements and a 1603 nm laser forimultaneous measurements of CO2 and H2O. The absorptionsue to CO2 and H2O are well-separated in the spectrum near603 nm, permitting simultaneous, separate measurements of thewo species. The cavity is insulated to prevent thermal gradientscross the measurement. A 10k thermistor (Measurement Special-ies, Dayton, OH) and pressure gauge (Honeywell, Morristown, NJ)re inserted into the sample to measure gas temperature and pres-ure respectively. The entire system is operated by an onboardC/104 computer. The system includes the processor board, datacquisition card, interfacing board, and solid state hard drive forata storage. The computer provides voltages to drive the lasers,eads the relevant signals (e.g. detector, temperature, and pres-ure), and stores the measured data to the hard drive for post-flightnalysis. An external KVM can be connected to change the controlettings or diagnose the analyzer’s operation.

Two custom, miniature laser driver boards are used to con-rol the laser current and temperature. These parameters are usedo provide fine and coarse control over the laser operating fre-uency, respectively. The driver boards are also equipped with aast laser disable switch (<200 ns) to permit rapid cavity ringdown

easurements of effective pathlength. Based on cavity ringdowneasurements, the optical path lengths through the cavity are

pproximately 3000 m at 1603 nm and approximately 4000 m at650 nm. The near-infrared distributed feedback diode lasers areoused in a 14-pin butterfly package that is directly mountednto the laser driver board. The laser temperatures are activelyontrolled via their internal thermo-electric coolers to maintain


avelength stability. The pressure in the cell is controlled atpproximately 18.4 kPa via a proportional solenoid valve (Parkeraniffin Pneutronics, Hollis, NH) that feeds back from the pressureauge. Note that the setpoint pressure is substantially lower than

flight (right). The instrument measures approximately 30.5 cm × 30.5 cm × 28 cm.

the ambient pressure for all SIERRA flight altitudes (i.e. 0–3600 m),and the cell pressure is actively controlled throughout the flight.

The fully assembled UAV GGA is shown in Fig. 2a and mea-sures approximately 30.5 cm × 30.5 cm × 28 cm and weighs 19.5 kg,allowing for it to fit within the SIERRA nosecone and displace mostof the ballast weight. The instrument contains no moving parts,other than the internal workings of the diaphragm pump, allowingit to tolerate a high degree of mechanical vibration. Nevertheless,the top breadboard is vibrationally isolated from the bottom bread-board using inline vibrational isolators with tension springs (BarryControls, Hopkinton, MA). The UAV GGA interfaces with the SIERRAnosecone via a baseplate allowing simple drop-in integration withfour anchor points. The gas inlet line is routed through the bottomplate and fastened to the bottom of the nosecone such that the inletgas stream is directed opposite the plane’s movement. This config-uration helps prevent particulates from entering the system andclogging the included filters. Fig. 2b shows the UAV GreenhouseGas Analyzer fully integrated into the SIERRA nosecone.

3. Results and discussion

3.1. Laboratory testing

Prior to flight, the UAV Greenhouse Gas Analyzer was labora-tory tested to determine its accuracy, precision, linearity, dynamicrange, and thermal stability. The instrument’s performance wastested for CO2 using a NIST-calibrated set of standards that spansfrom 372 to 944 ppm CO2/air. The measured data (Fig. 3a) is withinthe cylinder accuracy of ±1 ppm (1�), even for the highest molefraction, demonstrating high accuracy (defined as the residual fromthe best fit line) and linearity (R2 = 0.999994) over the atmosphericrange. Note that much higher levels of CO2 (e.g. >1%) can be mea-sured using the instrument with appropriate non-linear calibration.The instrument’s performance on CH4 was determined by using 3calibrated gas cylinders containing mixtures that span from 1.738to 5.021 ppm CH4/air. The results are shown in Fig. 3b and showthat the instrument is highly linear (R2 = 0.999998) and accurate to±1.7 ppb (1�) over the atmospherically relevant range of CH4 con-centrations. The instrument’s performance was tested for watervapor by measuring the output of a dewpoint generator (LICOR LI-610). The measured data (Fig. 3c) is within the specified accuracyof the dewpoint generator (0.2 ◦C) and highly linear (R2 = 0.99987)


over the entire atmospheric range from 7000 to 20,000 ppm.The instrument precision for CO2 and CH4 was determined by

measuring a continuously flowing gas sample of constant com-position from an air cylinder for approximately 8 h at a 1 Hz

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Fig. 3. (a) Measured carbon dioxide mole fractions versus the actual, certified cylinder value. The instrument is accurate and linear (R2 = 0.999994) to better than thec action( entrat( 20,00

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ylinder uncertainty (±1 ppm) from 0 to 1000 ppm. (b) Measured methane mole frR2 = 0.999998) to ±1.7 ppb (1�) from 0 to 5 ppm. (c) Measured water vapor concR2 = 0.99987) to better than the dewpoint generator accuracy (0.2 ◦C) from 7000 to

easurement rate. The resulting Allan deviation plots are shownn Fig. 4. The 1 Hz precision for CO2 is ±0.6 ppm (1�) and improves

ith averaging time, to a limit of ±0.08 ppm (1�) in 2000 s. The Hz precision for CH4 is ±2 ppb (1�) and the Allan deviation plothows that better precision can be readily obtained by further aver-ging, reaching a limit of ±0.2 ppb (1�) in 1000 s. The instrumentrecision for H2O was determined by measuring the output of aewpoint generator for approximately 8 h at a 1 Hz measurementate. The resulting Allan deviation plot is shown in Fig. 4c; the 1 Hzrecision is ±35 ppm (1�) and improves with averaging time to a

imit of ±5 ppm (1�) in 100 s.One of the presumed challenges of deploying instrumentation

board an UAV was the large ambient thermal excursion as thelane changes altitude. For example, prior to flight, the temperature

n the SIERRA nosecone can reach 35 ◦C (depending on deploy-ent location) but, as the plane approaches its maximum altitude

f 3600 m, the ambient temperature can be as low as 0–5 ◦C. Inrder to mimic these conditions, the analyzer was placed in annvironmental test chamber and continuously measured a con-tant gas stream as the ambient temperature was varied. Note that


he analyzer is not actively thermally controlled. The temperatureas varied over 2.5 days: first the temperature was ramped over

ts extremes of 40 ◦C to −5 ◦C. Then, in order to emphasize thexpected highest-altitude cruising temperature, the temperature

s versus the actual, certified cylinder value. The instrument is accurate and linearions versus the dewpoint generator value. The instrument is accurate and linear0 ppm.

was held at 5 ◦C and finally brought back to room temperature (seeFig. 5).

The instrument readings show slight correlation with exter-nal temperature. Since the instrument constantly measures thegas temperature, a linear compensation factor can be readilyimplemented to account for gas temperature. The compensateddependence of the CO2 and CH4 readings on ambient temperatureis shown in Fig. 6; the readings change by less than ±0.36% and±0.37% (1�) respectively over the entire −5 to 40 ◦C range. Thistype of compensation scheme has been validated for the full atmo-spheric range of gas concentrations. However, during flight testing(see Section 3.2) it was found that the internal gas temperature var-ied by a much smaller amount, reducing the temperature-relatedvariation of the concentration readings and eliminating the needfor temperature compensation.

3.2. Flight deployments


The UAV Greenhouse Gas Analyzer was integrated into thenosecone of the SIERRA as shown in Fig. 2. Two separatedeployments demonstrated the airborne performance of theinstrument.

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Fig. 4. The CO2 (a), CH4 (b), and H2O (c) Allan deviation plots show a 1 Hz preci-sion of ±0.6 ppm (1�) for CO2, ±2 ppb (1�) for CH4, and ±35 ppm (1�) for H2O anddemonstrate that the measurement uncertainty decreases with averaging time toa limit of ±0.08 ppm (1�) in 2000 s for CO2, ±0.2 ppb (1�) in 1000 s for CH4, and±5 ppm (1�) in 100 s for H2O. The dashed lines represent perfect averaging.

Fig. 5. Environmental chamber testing temperature profile designed to exceed theexpected extremes and mimic the highest-altitude cruising temperature in the UAV.

3.2.1. Crow’s Landing, CaliforniaCrows Landing is a 1500 acre (607 ha) former NASA facility in

Stanislaus County, in a highly agricultural area of the central valleyof California (Lat: 37.4 Lon: 121.1). It is used by NASA for flight test-ing of the SIERRA among other uses. The UAV GGA was flown forapproximately 40 min around 6 pm local time, 9 June 2009 (01:00UTC, 10 June) during which time CO2 and H2O data were collected ata 1 Hz data rate. During flight, internal gas temperature (30–35 ◦C)and pressure (18.36 kPa ± 0.2%) remained in a very narrow range,and based on the findings of the laboratory measurements shownabove, should have a negligible effect on the measurements. Mea-sured dry CO2 mole fraction was relatively constant during the


constant altitude portion of the flight. Measured H2O vapor fluc-tuated with spatial position along the racetrack shaped flight path.The measured H2O vapor concentration was generally higher inthe more southerly regions of the flight path, possibly correlated

Fig. 6. Linearly compensated CO2 (a) and CH4 (b) concentrations from the analyzer,which is not temperature stabilized, as a function of gas temperature. Note that thereadings change less than 0.36% and 0.37% (1�), respectively over the entire −5 to40 ◦C range.

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Fig. 9. Measured CO2 mole fraction (dry) shows large spikes due to sampling ofengine exhaust prior to takeoff. During the flight in Svalbard, Norway (inset) CO2

mole fraction is relatively stable and is consistent with levels measured by NOAAscientists from flask samples taken at the Zeppelin station the day after the flight(dashed line) [17] and hourly samples taken by researchers from Stockholm Uni-versity (marker) [data courtesy of Stockholm University].

ig. 7. Aerial photo taken a few days prior to the test flight showing the locationsf the airstrip, glacier, and glacial runoff collection area.

ith agricultural activity such as increased irrigation. CH4 was noteasured during this flight.

.2.2. Svalbard, NorwayThe Svalbard archipelago is located midway between mainland

orway and the North Pole and primarily consists of arctic wilder-ess. The area of the Svalbard deployment near Ny Ålesund (Lat:8.9 Lon: 11.9) is shown in an aerial photograph in Fig. 7 taken aew days prior to the test flight. In the photograph one can see thehoreline, airstrip, and Vestre Broggerbreen glacier. The area to theouth of the runway is a collection area for glacial runoff.

The UAV GGA was integrated into SIERRA prior to the NASAharacterization of Arctic Sea Ice Experiment (CASIE) and operated

or approximately 45 min on the ground while the plane was pre-ared and taxied, around 06:00 UTC, 11 July 2009. The SIERRA washen flown for approximately 25 min in a racetrack shaped flightath traversed 8 times during which the analyzer measured CO2,H4, and H2O mole fractions at 1 Hz. The internal gas tempera-ure (21.8–22.5 ◦C) and pressure (18.36 kPa ± 0.2%) again remainedn a very narrow range during flight, and should have a negligi-le effect on the measurements. The measured CH4 mole fraction

s relatively stable throughout the short flight and consistent with


OAA and Norwegian Institute for Air Research (NILU) measure-ents (Fig. 8). NOAA scientists collect flask samples approximatelyeekly at Zeppelin Station (475 m ASL) near Ny Ålesund, Norway

nd measure greenhouse gasses from these flasks, including CH4

ig. 8. Measured CH4 mole fraction is relatively stable during the flight in Svalbard,orway and is consistent with levels measured by NOAA scientists from flask sam-les taken at the Zeppelin station the day after the flight (dashed line) [18] andeasurements taken by the Norwegian Institute for Air Research (marker) [data

ourtesy of NILU].

Fig. 10. Water vapor mole fraction measured with the UAV GGA fluctuates withspatial position along the racetrack shaped flight path (4 traversals) as seen super-imposed on a satellite map of the Svalbard flight area. The areas of high water
concentration correspond to low-lying areas which collect runoff from the nearbyVestre Broggerbreen glacier. Satellite images© GoogleMaps, DigitalGlobe, GeoEye,Norwegian Polar Institute. Map produced by GPS Visualizer.
and CO2, at the NOAA laboratories in Boulder, Colorado [17,18].The NOAA measured CH4 mole fraction the day after the flight isshown by the dashed line in Fig. 8 [18]. In the two weeks immedi-ately surrounding the flight, the CH4 levels at the site are relativelyconstant, changing by a maximum of 8 ppb [18]. The NorwegianInstitute for Air Research measures CH4 on an hourly basis usingan automated GC at the Zeppelin Station; the CH4 mole fractionmeasured at the flight time is shown by the marker in Fig. 8 [datacourtesy of NILU].

The measured CO2 (dry mole fraction) shows large spikes priorto takeoff due to sampling of engine exhaust (Fig. 9). During flight,mole fractions are relatively stable at expected ambient levels


and consistent with the NOAA measurement taken the day afterthe flight (dashed line) [17] and hourly data taken by researchersfrom the Department of Applied Environmental Science, Stockholm

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niversity, Sweden (marker) (Fig. 9, inset). NOAA data shows aecreasing trend in CO2 levels over the two weeks immediatelyurrounding the flight, with an overall change in that time periodf 7 ppm [17]. Stockholm University measures CO2 hourly using aifferential, non-dispersive, infrared gas analyzer (LiCOR LI-7000).oth NOAA and Stockholm University data were taken at the Zep-elin Station.

Fig. 10 shows the water vapor mole fraction measured by theAV GGA during 4 constant altitude traversals of the racetrack

haped flight path overlaid on a satellite map of the Svalbard flightrea. The correlation of water vapor mole fraction with spatialosition is obvious, with areas of high water concentration corre-ponding to low-lying areas which collect runoff from the nearbyestre Broggerbreen glacier.

. Conclusions

A compact, lightweight atmospheric analyzer has been inte-rated into the NASA Sensor Integrated Environmental Remoteesearch Aircraft (SIERRA) unmanned aerial vehicle (UAV) andeployed to make highly accurate, 1 Hz measurements of methane,arbon dioxide, and water vapor. The integrated analyzer was usedo monitor gas concentrations in flight, providing atmospheric

easurements at altitudes as low as 10 m in a remote location.he first flights were conducted at Crows Landing, CA, an agri-ultural site, with H2O concentrations showing distinct structurend sharp features that were well outside of the measurementoise. The instrument was then deployed in Svalbard, Norwayhere minimal variation in the CO2 and CH4 concentrations were

bserved during flight, but the water concentration changed dra-atically, oscillating as the aircraft moved repeatedly through its

acetrack shaped flight pattern. Importantly, it was demonstratedhat measurements can be correlated with environmental fea-ures, as the regions of high water concentration corresponded toow-lying areas which collect runoff from the nearby Vestre Brog-erbreen glacier. This novel, integrated instrument-aircraft systemill allow more numerous and efficient measurements of carbonioxide, methane, and water vapor concentrations at low-altitudesnd in remote or dangerous locations. Specific application targetsnclude deployment in forest fire plumes to measure greenhouseas generation and additional deployments in remote areas suchs those undertaken in Norway. Future work will consist of mul-iple tracks of continued instrument development. A smaller andighter instrument for measuring CO2, H2O, and CH4 is under devel-pment to allow deployment aboard smaller UAV platforms. Inddition, a faster analyzer (20 Hz) will allow airborne eddy fluxovariance measurements, effectively turning the SIERRA into aobile flux tower. Finally, we are designing additional instrumentshich will be capable of measuring other important greenhouse

asses, including N2O and CO, aboard UAVs. Future instrumentsill also be equipped with on-board calibration cylinders for real

ime, in flight calibration of the instrument.

cknowledgements

The authors would like to thank all the members of the NASAASIE team, especially Lesli Monforton, Brad Lobitz, Mark Sumich,ike Gaunce, Randy Berthold, and Don Herlth. The authors would

lso like to thank the researchers at the Norwegian Institute forir Research, especially Ove Hermansen, and researchers at the


epartment of Applied Environmental Science, Stockholm Uni-ersity, especially Birgitta Noone, for their assistance and these of their data. This work was supported by NASA SBIR GrantNNX09CC17P.

PRESStuators B xxx (2012) xxx– xxx 7

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Biographies

Elena S.F. Berman is a senior scientist and principal investigator at Los GatosResearch, a leader in the development of innovative, laser-based measurementstrategies for non-destructive analyses of gases, liquids, and solids. Her current


research interests include airborne and terrestrial measurements of greenhousegasses and medical diagnostic and hydrological applications of water isotope mea-surements. Prior to joining LGR, Dr. Berman received her PhD in Physical Chemistryfrom Stanford University and was a postdoctoral associate at Lawrence LivermoreNational Laboratory.

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atthew Fladeland is a research scientist at NASA Ames Research Center servings the Airborne Science Manager within the Earth Science Division. He is the projectanager for the SIERRA UAV flight project and is interested in the use of unmanned

ircraft as platforms to support and complement NASA satellite observations andeasurements. Mr. Fladeland received his Masters degree from the Yale School

f Forestry and Environmental Studies and served as a Presidential Managementellow at NASA Headquarters prior to taking a position at Ames Research Center.

immy Soeseno Liem is a mechanical design engineer who has over 20 years ofxperience in product development and manufacturing. His experience includes


esigning automation for assembly lines, developing test/measurement productsnvolving ultra-precise mechanical and optical designs, and managing technicalperations of multi-discipline and cross-department projects. Presently, he servess Vice President of Operations at Los Gatos Research. He received a Masters Degreen Mechanical Engineering from University of Wisconsin in 1990.

PRESStuators B xxx (2012) xxx– xxx

Richard Kolyer is a payload integration specialist with NASA Ames Research Center.He has extensive experience in the fields of in situ and remote sensing instrumentdesign & payload integration on both manned and unmanned aircraft. He is cur-rently the SIERRA UAV avionics lead and payload integration manager. His currentinterests center on developing medium class unmanned aircraft for use in remoteand dangerous environments.

Manish Gupta is the Vice-President of R&D at LGR and a pioneer in the developmentand application of cavity-enhanced optical absorption techniques to gas, liquid, andfiber sensing. He has over 18 years of experience in laser spectroscopy and has served


as PI on over 20 projects funded by EPA, DoD, NASA, NSF, and DOE. Dr. Gupta hashelped developed a suite of Off-Axis ICOS instrumentation for environmental, indus-trial, medical, and military applications. Prior to joining LGR, Dr. Gupta received hisPh.D. in Physical Chemistry from Harvard University and a postdoctoral fellowshipfrom Stanford University.

dx.doi.org/10.1016/j.snb.2012.04.036

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