Greenhouse Gas Monitoring by Lidar in Space

PHF XVI CLRC Long Beach, CA, June 20-23, 2011 1

Greenhouse Gas Monitoring by Lidar in SpaceGreenhouse Gas Monitoring by Lidar in SpaceMERLIN Initiative for MethaneMERLIN Initiative for Methane

Pierre H. FlamantPierre H. Flamant11 & Gerhard Ehret & Gerhard Ehret22

MERLIN Scientific Advisory Group (CNES-DLR)A-SCOPE Scientific Advisory Group (ESA)

1Laboratoire de Métérologie Dynamique, École Polytechnique, Palaiseau, France2Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen, Germany


Dial activity on GHG i.e. CO2 and CH4, get started in early 2000 We, scientits, gained experience by our (leading) contribution to

various studies funded by ESA We had a phase “0” study by industry for the CO2 mission A-

SCOPE More recently in 2010 the EXCALIBUR proposal for CO2

mission was submitted in response to call for ideas for ESA EE-8 mission opportunity

Today, we built on this common long term expertise to conduct theFranco-German climate mission MERLIN for CH4

FORWORDFORWORD


Needs on GHG for Climate Change IssueNeeds on GHG for Climate Change Issue

Better understanding of climate change direction in near future isbased on assessment of carbon sources and sinks strengths withtime and locations and atmospheric GHG fluxes

3 main Greenhouse Gases: water vapor (H2O), carbon dioxide(CO2), methane (CH4)

Monthly GHG fluxes at global scales call for accurate and evenlydistributed GHG concentration that in turn call for remote sensingtechniques (passive and active) for flexibility to overcome inherentsparse and limited deployment of surface network, TCCON sitesand airborne in situ probes and flask measurements

Passive missions already in space (GOSAT/JAXA), ready to go(OCO-2/NASA), or in preparation (CarbonSat/ESA EE-8,MiniCarb/CNES)

Active remote sensing technique i.e. DiAL technique in spacealready studied: A-SCOPE/ESA (phase 0) and MERLIN/CNES-DLR(phase A)


High potential ofhazardousness⇒ methanisationof atmosphere

• Sources ?. « C »cycle,radiationbudget

. Low variabilityaround 1,7 ppmvBUT …. ± 2 %

. ABL

. Troposphere

. UTLS, lowstratosphere

. Natural &Anthropogenic. Highlyreactive (withOH)

MethaneCH4

Slow continuousraising ⇒temperatureincrease

. Sinks?

. « C »cycle,radiationbudget

. Low variabilityaround 380 ppmv. ± 1 ppmv (0,3 %)

. ABL

. Troposphere


. Anthropogenic

. Passive

. Diurnal cycle

CarbondioxideCO2

Indirect: rain &fresh wateravailability, …

. Primaryvariable. Water cycle,radiation buget

≈ 0 to 20 g/Kg. Large variabilityin space & time. ± 10 %

. ABL,

. Troposphere


. Natural

. Weaklyreactive. Gas, liquid,solid

Watervapor H2O

Potential climatichazardousness

Importance inMeteorology

Climate

ConcentrationPrecision

Verticaldistribution

Origine &Reactivity

Specie

a priori : GHG measurements from space assume broad representativity distribution inspace and time ⇒ sampling the atmosphere at random is adequate

MOTIVATIONS & OBJECTIVESMOTIVATIONS & OBJECTIVES


Lidar signal strength (W)• Laser energy per pulse (E)• Receiver collecting area (A)• Photo detector efficiency (q <1), detection noise, inherent electronic

noise (NEP), background light, speckles effect• Ideally : signal detection noise only• The photodetector play a key role !!!• Target reflectivity ⇒ lidar signal strength ⇒ SNRWall plug efficiency. 2 effects on output energy and duty cycle,

dimensioning of cooling system

Time allocated for one measurement (t) : Vsat = 7 km/s ⇒ t =7/14 s⇒ horizontal resolution ≈ 50/100 km

Number of independent samples N to reduce the random error ⇒ √Nwith N= F x t, where F is the pulse pair repetition rate

Detailed spectroscopy of few absorption lines

Key elements for a GHG Mission


• Pulsed emission for accurate ranging (3 m) and preferred shortpulse duration

• Tunable laser at at least 2 wavelengths λabs (λon) and λref (λoff)in less than a 1ms for efficient pair correlation

• Accurate spectral tuning. Stable operation and high spectralstability at λon ⇒ absorption cross section Δσ ⇒ bias.

• High spectral purity at λon for low bias. Spectral purity isdictated by bias

• Several λabs according to range of concentration• Several λref according to spectral dependence of scattering

properties (in particular NIR)• Energy per pulse ⇒ SNR (in DD) ⇒ random error• SLM emission and good M2

• PRF for accumulation of independent samples in a given time‘or horizontal distance ⇒ measurement accuracy

LaserLaser Characteristic Characteristic for for DiAL DiAL ApplicationApplication


All solid pulsed laser ⇒ several solutions

Lasers for COLasers for CO22 & CH & CH44 DiALsDiALs

MissionsDiALs airborneDiALs on groundLaser

EXCALIBUR-COWI 2-µm (LMD)(see F. LeMounier)- NASA-LaRC 2µm

Diodes laser ⇒ 1st Tm fiberlaser ⇒ 2nd Ho laser in freespace cavity

2 µm Qinetiq/ESADiodes laser ⇒ fiber laser

A-SCOPEMERLINMERLIN

CHARM-F (DLR)1,57 et 1,64 µminjection seeded

PULSNIR 2 µm« DROPO »ONERA/ESA

Diodes laser ⇒ 1st laser ⇒OPO+ APO(s)

A-SCOPENASA LaRC 2µmDiodes laser ⇒ laser


DiAL DiAL TechniquesTechniques

DiALpulsed laserlarge E A q

Range resolved

IPDAPulsed lasersmall E A q

ColumnWeighting Fct

Laser (E)Telescope (A)Detector (q)

Laser, TelescopeDetector

Laser, Telescope,Detector

Molecules &particlesβ(x,z) . Δz

Surface ρ/π

Retroreflector

Laser

TelescopeDetector

Nadir Nadir

Zenith

WALES (ESA)A-SCOPE (ESA)

MERLIN (CNES/DLR)

ACCURATE (ESA)

ADEOS (JAXA)

Limb

IPDAPulsed lasersmall E A q

ColumnWeighting

Fct

IPDADiode laser

small E A qUTLS

Weighting Fct

Methodology:Molecular absorption ⇒measurement signatureTarget reflectivities ⇒measurements support


WALES / ESAWALES / ESA

4 Lidar(s)configurationparaxiale

Télescope(s) ≈ 2 m

4 wavelengths (3On- and 1 Off- inthe 940 nmspectral range



CH4

CO2

Molecular SpectroscopyMolecular Spectroscopy


Call for Earth Explorer Core missionLetter of Intent mid 2005Phase « 0 » in 2007-2008 with 5other missionsESA report WP 1313/1 2008UCM in January 2009


mini-sat

Rx TxRx


Overlap


On Range accuracy for surface pressure• 1 hPa corresponds to about 10 m. Sampling at 3 m resolutionWhat acceptable angular fluctuations on LOS pointing to result in

range unknown variation ≤ 3 m?For 600 km orbit• At nadir Δθ≈ 3 mrad• For θo = 1° (X=9 km) and Δθ≈ 0.3 mrad• For θo = 10° (X=88 km) and Δθ≈ 30 µrad

On Beam overlapping at ground• Overlap of On- and Off wavelength beams at surface is critical

for bias for surface with characteristics. It needs to be very goodto results in negligible bias (10-3) on DAOD and XCH4 after 50km accumulation

• How good it needs to be depends on i) surface reflectivitygradient (Δρ(X,Y)) within the beam footprints and ii) beamintensity distribution (linked to laser M2)

Pointing IssuesPointing Issues


A-SCOPE SAGA-SCOPE SAG

A-SCOPE got excellent review but due to low TRL for some key elementsA-SCOPE was not selected for phase A!

At UCM in Lisbon, January 2009


“EXCALIEXCALIBURBUR” “EXPERIMENT ON CARBON DIOXIDE (CO2) BY LIDAR FOR

BIOSPHERE AND CLIMATE URGENCY”

IN RESPONSE TO ESA CALL FOR PROPOSALS FOR EARTH EXPLORER

OPPORTUNITY MISSION EE-8

by

Pierre H. FLAMANT

and

Dr. Philippe CIAIS Pr. John DAVID Dr. Kenneth DAVIS

Dr. Gerhard EHRET Dr. Fabien GIBERT Pr. Nicolas GRUBER

Dr. Ir. Sander

HOUWELING

Jason HYON Dr. Xavier MARCADET

Dr. Robert T. MENZIES Pr. Anna M. MICHALAK Dr. Marko SCHOLZE

Dr. Upendra N. SINGH Dr. Jirong YU

ESA Call for idea in 2009 forMission Opportunity EE-8- 100 M euros Budget cape forpayload and dedicated missionground segment- Letter of Intent due Dec. 2009- Full proposal June 2010.

New proposal wrt A-SCOPE- New 2-µm photodetector to bedevelopped in Europe- New 2-µm pulsed lasertransmitter to be provided byNASA

- Excellent review (again) butnot selected late 2010 forphase A


MERLIN is the Franco-German climatemission initiated in late 2009 for a launch in2014 and for three years of operation.

It is dedicated to atmospheric methane (CH4). Itwill contribute/complement global GHGObserving System (i.e. networks, aircraft,passive missions) through accurate CH4 spatialand temporal distribution, globally.

It is a Micro-Sat class mission with "small" OPOlidar (90 -130 W, 80-100 kg) on the MYRIADEplatform to demonstrate IPDA using an activeinstrument is a powerful technique in space

It will provide weighted CH4 column content innadir direction relying on signal strengthsassociated to surface reflectivity (soils,vegetation, water)

The primary data product will be methane dryair mixing ratio XCH4

CHCH44 & MERLIN Mission Context & MERLIN Mission Context

Artist view of the spacecraft MYRIADE fromCNES carrying the CH4 IPDA lidar instrumentfrom DLR

Mission status

• successful Mission DefinitionReview end of 2010

• Phase A since Jan. 2011


• A Franco-German Climate initiative was put on the table in 2009 duringone of the regular Franco-German Ministry meeting

• Before that, DLR had already conducted a paper study (CHARM) onsmall CH4 mission, and a proposal (OMÉLIE) has been submitted toCNES in view of a Seminar of Prospective

• Budget: 120 M euros total equally shared between France and Germany• MYRIADE platform to be provided by CNES• OPO Lidar to be provided by DLR• MERLIN project under supervision of a Steering Committee (2 + 2

members from CNES and DLR)• One single integrated Project Team led by CNES• One Merlin Scientific Advisory Group in charge of mission objectives,

User Requirement Document, preparatory studies for trade-off,processing algorithms and products definition

• Phase « 0 » in 2010. First cost estimate (really) too high!• Officially in phase « A » since January 2010, but actually still in an

intermediate phase for cost reduction and so called « descoping »activity to get closer (if not equal or lesser) to the budget cape

MERLIN MERLIN OrganisationOrganisation


Co-Principal Investigators: Pierre Flamant (1), Gerhard Ehret (2)

Co-Investigators: Philippe Bousquet (3), John P. Burrows (4)Frederic Chevallier (3), Philippe Ciais (3), Cyril Crevoisier (1),Andreas Fix (2), Fabien Gibert (1), Martin Heimann (5), Hans-Wolfgang Hubberten (6), Kathy Law (7), Alexander Löw (11),Martin Wirth (1)

Observers: Jim Abshire (8), Christian Frankenberg (9), SanderHouweling (10), Patrick Jöckel (1), Julia Marshall (5), CatherinePrigent (12), Marko Scholze (13)

Contributors: Christoph Kiemle (1), Mathieu Quatrevalet (1)

MERLIN SAGMERLIN SAG

(7) LATMOS, University Pierre et Marie Curie,Paris, France(8) GSFC, NASA, Greenbelt, USA(9) JPL, NASA, Pasadena, USA(10) IMAU, University of Utrecht, Utrecht, theNetherlands(11) MPI for Meteorology, Hamburg, Germany(12) Observatoire de Paris, France(13) DES, University of Bristol, Bristol, UK

(1) Laboratoire de Météorologie Dynamique, ÉcolePolytechnique, Palaiseau, France(2) Institute for Atmospheric Physics, DLROberpfaffenhofen, Germany(3) LSCE, IPSL, Gif sur Yvette, France(4) IUP, University of Bremen, Germany(5) MPI BGC, Jena, Germany(6) AWI, Potsdam, Germany


• Measurement of the column-integrated dry-air volume mixingratio of methane XCH4 using the IPDA technique with followingspecifications on XCH4:

Threshold, breakthrough, targetRandom error < 36, 18, 8 ppb

Systematic error: < 3, 2, 1 ppbHorizontal resolution: 50 km

• Global coverage Day/Night including high latitudes in wintertime

• No bias from aerosol and cloud scattering due to range-gatedinstrument operation near the surface

MERLIN ScienceMERLIN Science


Level 2: column-integrated drymixing ratio i.e. XCH4Weighting function WF usingspectroscopy information

!

XCH4 "

[CH4]WF(p)dp

0

psurf

#

WF(p)dp

0

psurf

#=

DAOD

WF(p)dp

0

psurf

#

Level 1b1: range (R) to scatteringthe surface. Surface height abovegeoid zloc to determine localsurface pressure psurf usinghydrostatic equation

Spin-off product: canopy,surface reflectivity

orbitRLidar

R

zloc, psurf

zNWP, pNWP

Data ProductsData Products

Level 1b2: Differential AbsorptionOptical Depth (DAOD) of CH4

!

DAOD =1

2ln

Soff / Eoff

Son / Eon

"

# $

%

& '


Sun Lighting & EclipsesSun Lighting & Eclipses

Problem associated to amicrosat and low orbit


Line selectioncriteria

• sufficient opticaldepth

• low interferencewith other GHG

• low temperaturedependency

• sufficient weight inABL

CH4

H2O

CO2

Selected absorption CH4 LineSelected absorption CH4 Line


soundingat troughpositionfavorable

!"

" )DAOD(

Selected on-line wavelengthSelected on-line wavelength

• Substantial relaxation of instrumentand platform stability requirement

airOH

air

OH

offon

Mg)T,p(M

M1

)T,p()T,p(

2

2 !!""#

$%%&

'(+

)*)= T)WF(p,

• MERLIN WF enables highmeasurement sensitivity inthe low troposphere


Global Map of Global Map of Surface Surface Reflectance at 1.64 Reflectance at 1.64 µµmmLand surface:

MODIS 16-d compositefor 4 seasonsJan/Apr/Jul/Oct

Sea surface:

refl. ~ 1/wind

sources:30-yr mean w,Menzies 1998, Hu 2008,Josset 2010.

July C. Kiemle and A. Amediek, DLR


Preliminary PerformancePreliminary PerformanceInstrument and Auxiliary ParametersInstrument and Auxiliary Parameters

Cal. Device

Linearity

Bgr.

Freq. TXPointing

BWTXSp. Purity

Very small instrument error budget of0.8 ppb which compares to 1ppb/3ppbof the systematic target/threshold errorfor MERLIN

Sensitivity ofInstrument Parameter

Small random error budget ~2.4 ppbdue to uncertainties of meteorologicalparameter (psurf,T,q) which compares to8/36 ppb for the random target/thresholderror for MERLIN

Sensitivity of MeteorologicalParameter


Substantial error reduction in keyregions with respect to the presentknowledge of CH4-fluxes on regionalscale for July

Preliminary Inverse CH4 Flux Modeling ResultsPreliminary Inverse CH4 Flux Modeling ResultsM. Heimann, J. Marshall, MPI-BGC, Jena

1

pri,xpri,d1T1

post,x CJCJC !!!+=

aggregation of 50 km lidarobservations along track:

calculation of posterior fluxcovariance matrix

Use of TM3 model resolutionof 3hr x 8° x 10° x 9

1-(σpost/σpri)

Assumption• Standard scenario using a priori flux and

flux uncertainty based on Mikaloff-Fletcheret al., 2004 with updated, process based,global totals from IPCC AR4

• Neglecting of- possible biases and error correlations

of observations- Transport model error- "Representation” error


SummarySummary• The French-German Climate mission MERLIN has successfully passed MDR and

is now further investigated in Phase “A”

• MERLIN is a Micro-SAT mission based on an active OPO optical instrument forthe first time

• Initial results from Phase “0” performance studies are encouraging:

- measurements over land and water surfaces at all latitudes possible

- very small instrument error thanks to soundings in the trough region of theselected methane line

- little impact from uncertainties of the meteorological parameter (T,q,psurf)

- inverse modelling using synthetic MERLIN observations will yieldsignificant error reduction of CH4 fluxes over most of the interestingregions of the globe

• The total efficiency of the laser head remains the largest uncertainty with respectto the final SNR budget of the lidar signals which drives the random errorperformance of MERLIN. A predevelopment model is currently constructed in theLab.

Documents

Greenhouse Gas Monitoring by Lidar in Space