16 th Coherent Laser Radar Conference (June 20, 2011, Long Beach CA, USA)

Transcription

1 Novmbr 3, th Cohrnt Lasr adar Confrnc 1/18 16 th Cohrnt Lasr adar Confrnc (Jun, 11, Long Bach CA, USA) Dvlopmnt of Cohrnt -μm Diffrntial Absorption and Wind Lidar with lasr frquncy offst locking tchniqu and column-intgratd CO masurmnt Shokn Ishii 1, Kohi Mizutani 1, Hirotak Fukuoka, Takayoshi Ishikawa 3, Philipp Baron 1, Tomoaki Tanaka 4, *, Isamu Morino 4, Osamu Uchino 4, Hironori Iwai 1, yoko Oda 1, Ttsuo Aoki 1, Toshikazu Itab 1, Atsushi Sato 5, and Kazuhiro Asai 5 1 National Institut of Information and Communications Tchnology Hamamatsu Photonics K.K. 3 Nippon Alph Co. 4 National Institut for Environmntal Studis 5 Tohoku Institut of Tchnology * Prsnt affiliation: Japan Arospac Exploration Agncy

2 Outlin Background and objctivs Frquncy offst-locking tchniqu and spcifications Estimation of XCO Horizontal xprimntal CO masurmnt Exprimntal CO masurmnt for th GOSAT data products validation Summary Novmbr 3, th Cohrnt Lasr adar Confrnc /18

3 Novmbr 3, th Cohrnt Lasr adar Confrnc 3/18 Background and Objctivs Background CO is on of th most important grnhous gass. Spatial and tmporal variations of th CO concntration ar important to undrstand th carbon cycl. Spacborn masurmnt is a promising approach to globally masur th distribution of CO concntration. Passiv snsor mission: GOSAT( 9), OCO- (13). Activ snsor mission: ASCENDS (19?). Intgratd path diffrntial absorption (IPDA) lidar is on of th nxt-gnration spacborn snsors. 1.6-μm and -μm IPDA lidar systms hav bn dvloping by many rsarch groups. Objctivs of dvlopmnt of DIAL systm Dvlopmnt of rliabl stabl singl-frquncy Q-switchd lasr. Dvlopmnt of rliabl dtction tchniqu. Dvlopmnt of algorithm. Dvlopmnt of airborn systm. Prcursor of spacborn IPDA lidar systm. Exprimntal study from moving. Dmonstration of CO masurmnt with a high accuracy.

4 Novmbr 3, th Cohrnt Lasr adar Confrnc 4/18 Frquncy offst-locking tchniqu I: Cntr lasr MO I (λ-cntr) Signal output a to variabl FC +1 ordr ordr -1 ordr 5.967nm Signal outpu + 1 ordr ordr -1 ordr 5.967nm Transmission of CO cll Error signal output (a.u.) PZT divr s DC voltag 3 absorption lin cntr of CO. ISO PZT drivr PBS EOM Oscillator Phas shiftr Dtctor 1 PID controllr Error signal LPF Mixr Cntr lasr: Th cntr lasr is st at th 3 absorption lin cntr of CO by using a CO cll, xtrnal phas modulation and PID controllr for PZT.

5 Novmbr 3, th Cohrnt Lasr adar Confrnc 5/18 Frquncy offst-locking tchniqu I: Cntr lasr Error Signal output (a.u.) + - CO gas cll: Torr Optical Pass:.36 m x 3 pass Frquncy offst from 3 abosoption lin ctr of CO (MHz) 1 MHz 15 MHz 15 MHz 175 MHz MHz t fs o c y n u q fr a t z ro p lo S Frquncy (MHz) Conditions: Frquncy should b slctd to maximiz th slop at around th zro frquncy offst. EOM nds a high frquncy to stablish larg monoton intrval. Lft figur shows th simulatd rsult of th rlation btwn th frquncy offst from th 3 absorption lin cntr for th various frquncy and th rror signal output. ight figur shows th slop at th zro frquncy offst. Th frquncy offst rachs a pak at around 15 MHz. Th EOM oprating at th frquncy of 15 MHz was slctd.

6 Novmbr 3, th Cohrnt Lasr adar Confrnc 6/18 Frquncy offst-locking tchniqu I: Cntr lasr 13.4 hours Long-trm lasr frquncy fluctuation of th λ cntr lasr xamind by rcording th rror signal using a data loggr. Charactristics of λ cntr lasr Wavlngth : nm Frquncy stability : <16KHz (-157 to +138 KHz) Tim to locking : 6 msc Modulation frquncy : 15.6 MHz CO gas cll : Torr,.36 m x 3 pass + Adjusting rang PZT DC Swping signal Error signal Tuning rang of th λ cntr lasr invstigatd using th rror signal, and PZT divr s DC voltag. Frquncy of th cntr lasr changs in proportion to MHz/ 1mV PZT drivr s DC. ΔPZT_DC= 16.6 mv 361 MHz Frquncy offst : -361 MHz to +361 MHz - Short wavlngth sid Long wavlngth sid 3 absorption lin cntr of CO.

7 Frquncy offst-locking tchniqu II: On lasr λ-cntr Charactristics of λ on lasr Wavlngth : nm Frquncy stability : <1KHz (-157 to +138 KHz) Frquncy offst by PZT drivr : -543 MHz to +448 MHz Frquncy offst :.5 GHz to 6.5 GHz Tim to locking : 7 msc λ-on lasr is controlld to b lockd for th λ-cntr lasr. Diffrnc in th frquncy btwn th λ-cntr and th λ-on lasrs is dtrmind by th htrodyn and phas snsitiv dtctions. Cavity lngth of th λ-on lasr is controlld by adjusting PZT divr s DC voltag. Th phas lockd loop (PLL) is usd to control th DC voltag with a good prcision. amp and fir tchniqu is usd to stablish th singl-frquncy Q-sw lasr. Th frquncy stabilization of th singl-frquncy Q-sw lasr was about 1MHz. Total absolut frquncy stability of th on-lin lasr dpnds on th frquncy stability of th λ cntr lasr, λ on lasr, and puls lasr. 1. MHz Total absolut frquncy stablitiy.16mhz.1mhz 1MHz Novmbr 3, th Cohrnt Lasr adar Confrnc 7/18

8 Novmbr 3, th Cohrnt Lasr adar Confrnc 8/188 Spcifications of CoDiaWiL Transmittr Lasr : Tm:Ho:YLF Wavlngth : 51.4 to 51.6 nm (On) : 51.5 nm (Off) Puls nrgy : 8 mj/puls Puls width : 14 nsc Puls ptition : 3 Hz civr Clar diamtr : 1 cm Dtctor : InGaAs Balancd rcivr Data Procssing Signal procssing : 8 Bit A/D Sampling frquncy : 5 MHz Sampling points : 1317 Scannr Clar diamtr : 1 cm Elvation angl : -- Azimuth angl : Scanning spd : -6/sc W us a InGaAs PIN photodiod (DET 1 ).

9 Novmbr 3, th Cohrnt Lasr adar Confrnc 9/18 Exampls of CN for various lasr frquncy offsts 9 shots 3Hz CN (db) Off-lin.5 GHz from 3 lin cntr (On-lin) 4.8 GHz from 3 lin cntr (On-lin) 5.8 GHz from 3 lin cntr (On-lin) ang (km) Exampl of atmosphric rturns corrsponding to th off-lin lasr and th on-lin lasr for thr lasr frquncy offsts,.5, 4.8, and 5.8 GHz. Th CN of th on-lin lasr dcrass mor modratly with incrasing th lasr frquncy offst.

10 Horizontal xprimntal CO masurmnt (3 m-column rang) CO concntration (ppm) : 1:45 13:3 14:15 Tim (JST) + symbols show 1-minut DIAL rsults and black lin shows 3-min running avrag of th DIAL rsults. Gray lin shows data masurd by th in-situ snsor. Th prcision for th 3-m column rang from 616 to 5614 m (998 m) and 9 shot pairs was 1%-%. Th root-man-squar of th absolut valus of th diffrncs btwn th 3-min avrags by th two snsors was 3.5 ppm. Surfac data indicatd that it was clar sky in th morning and cloudy in th aftrnoon. Convction was activ in th morning, but lss sunlight supprssd convction in th aftrnoon. 15: 15:45 16:3 Novmbr 3, th Cohrnt Lasr adar Confrnc 17:15 18: 18:45 1/18

11 Novmbr 3, th Cohrnt Lasr adar Confrnc 11/18 Estimation of XCO XCO 1 n CO 1 (r) WF(r) dr WF(r) dr CO IWF 1 HO, n (r) dr air CO H O 1 P log P On Off 1 POff 1 POn x CO : n air n CO : Dry-air volum mixing ratio of carbon dioxid : Dry-air numbr dnsity :CO numbr dnsity τ CO : Diffrntial absorption optical dpth (DAOD) CO absorption in th rang btwn 1 and. τ HO : DAOD du to th H O absorption in th rang btwn 1 and WF : Wighting function IWF : Intgratd wighting function Δσ : Diffrnc in th absorption cross sctions at wavlngths of th on- and off-lin lasrs Error ΔXCO is givn using th DAOD, th WF, and mtorological data: XCO CO IWF CO IWF IWF CO IWF CO IWF IWF IWF P IWF IWF T IWF IWF H. W usd a radiosond (Vaisala, S9-SGP) to masur vrtical profil of mtorological data. Total rror of XCO stimatd from accuracy of th radiosond was <. %.

12 Slant and vrtical CO masurmnts for th GOSAT data products validation Column-intgratd CO masurmnts wr conductd to contribut to th GOSAT projct snsors on Fbruary 14,, and 3, 1, and January 8, 31, Fbruary 3, and 7, 11. Instrumnts at NICT CO DIAL 4 hours opration EL= dg (5 min), 16 dg (5 min), 9 dg ( min) (1) EL= 16 dg (1 min), 9 dg ( min) (11) Mi Lidar, Cilomtr GPS Sond (1JST, 1JST, 14JST) Prssur, Tmpratur, H, Wind spd and dirction Automatic wathr station Prssur, Tmpratur, H, Wind spd and dirction In-situ NDI 4 hours opration National institut for nvironmntal studis (NIES) GOSAT Projct conductd an airborn CO masurmnt with Japan Arospac Exploration Agncy (JAXA). Novmbr 3, th Cohrnt Lasr adar Confrnc 1/18

13 7. 6. Vrtical profil of CO, masurd by th airborn in-situ snsor on Fbruary 14 and, 1 Fbruary 14, 9 Fbruary, 9 7. NICT NICT Kumagya 6. Kumagaya / Altitud (km) Altitud (km) / CO concntraion ppm (in-situ) CO concntraion ppm (in-situ) Airborn in-situ data providd by GOSAT validation tam (NIES) Pictur from GOSAT JAXA/NIES/MOE Altitud -4m: data masurd by ground-basd in-situ snsor Altitud 4m-3km: data takn by airborn in-situ snsor ovr NICT (35.7N,139.5E). Altitud 3km-7 km: data by airborn in-situ snsor ovr Kumagaya (36.N,139.3E). Novmbr 3, 11 16Altitud th Cohrnt >7 km: constant Lasr valu adar masurd Confrnc at altitud of 7km 13/18

14 Novmbr 3, th Cohrnt Lasr adar Confrnc 14/18 Vrtical profil of DAOD and SN obsrvd on Fbruary 14,, and 3, 1 15 /14/1 4:8-4:33 UT SN (db) OD calculatd from EL=16 OD calculatd from EL=9 Off-lin SN EL=9 On-lin SN EL=9 Off-lin SN EL=16 On-lin SN EL=16 //1 3:5-4:7 UT SN (db) OD calculatd from EL=16 OD calculatd from EL=9 15 Off-lin SN EL=9 On-lin SN EL=9 Off-lin SN EL=16 On-lin SN EL=16 /3/1 3:14-4:13 JST SN (db) OD calculatd from EL=16 OD calculatd from EL=9 15 Off-lin SN EL=9 On-lin SN EL=9 Off-lin SN EL=16 On-lin SN EL=16 ) m (k d1 ltitu A * ) m (k d1 ltitu A ) m (k d1 ltitu A DAOD DAOD DAOD Slant masurmnt : EL=16 dg Vrtical masurmnt : EL=9 dg SN i j N L N C P i P j i j P N,i. P i j : Man powr of th backscattrd signal P N,i : Man nois powr, N C : Numbr of cohrnt cll N L : Numbr of on- and off-lin lasr shots

15 Novmbr 3, th Cohrnt Lasr adar Confrnc 15/18 XCO masurmnt mad on Fbruary 14,, and 3, 1 and stimat of various rror sourcs Intgral intrval Fbruary 14, 1 Fbruary, 1 Fbruary 3, 1 In-Situ DIAL GOSAT In-Situ DIAL GOSAT In-Situ DIAL ± ±4.6 No data 399.9± ±4. No data 44.4± ± No data 397.9± ±5.1* - - No data * Cirrus Error sourc Uncrtainty Masurmnt Error Mtorological lmnts Prssur Tmpratur H Frquncy stability of Lasr On-lin Off-lin ±1 hpa ±.5 ºC ±5% 1. MHz 1. MHz.% <.1% <.1% <.1%.% GOSAT data JAXA/NIES/MOE

16 Vrtical profil of DAOD and SN obsrvd on January 8, 31, and Fbruary 7, 11 Novmbr 3, th Cohrnt Lasr adar Confrnc 16/18 15 ) 1 m (k d ltitu A 1/8/11 3:39-4:39 UT SN (db) OD calculatd from EL=16 OD calculatd from EL=9 Off-lin SN EL=9 On-lin SN EL=9 Off-lin SN EL=16 On-lin SN EL=16 15 ) 1 m (k d ltitu A 1/31/11 :4-3:4 UT SN (db) OD calculatd from EL=16 OD calculatd from EL=9 Off-lin SN EL=9 On-lin SN EL=9 Off-lin SN EL=16 On-lin SN EL=16 15 ) 1 m (k d ltitu A /7/11 :35-3:35 UT SN (db) OD calculatd from EL=16 OD calculatd from EL=9 Off-lin SN EL=9 On-lin SN EL=9 Off-lin SN EL=16 On-lin SN EL= DAOD DAOD DAOD Slant masurmnt : EL=16 dg Vrtical masurmnt : EL=9 dg SN i j N L N C P i P j i j P N,i. P i j : Man powr of th backscattrd signal P N,i : Man nois powr, N C : Numbr of cohrnt cll N L : Numbr of on- and off-lin lasr shots

17 Novmbr 3, th Cohrnt Lasr adar Confrnc 17/18 XCO masurmnts mad on January 8, 31, and Fbruary 7, 11 Intgral intrval January 8 January 31 Fbruary ± ± ± ± ±9.5* 4.9± ± ± ±6.4** * Intgral intrval is btwn.4 km and 1.9 km. ** Cirrus Error sourc Uncrtainty Masurmnt Error Mtorological lmnts Prssur Tmpratur H Frquncy stability of Lasr On-lin Off-lin ±1 hpa ±.5 ºC ±5% 1. MHz 1. MHz.% <.1% <.1% <.1%.%

18 Novmbr 3, th Cohrnt Lasr adar Confrnc 18/18 Summary A cohrnt -μm diffrntial absorption and wind lidar with lasr offst locking tchniqu was dvlopd to mak th long-rang CO masurmnt. W xamind th th frquncy stabilization of th λ-cntr and λ-on lasrs and th singl-frquncy Q-switchd lasr. Th frquncy stabilization of th λ-cntr lasr was lockd within about ±16 KHz. Th frquncy stabilization of th λ-on lasr was lockd within about ±1 KHz for th λ-cntr lasr. Th frquncy stabilization of th singl-frquncy Q-switchd lasr with th ramp-and-fir tchniqu was within about ±1 MHz. Th absolut frquncy stability of th singl-frquncy Q-switchd lasr bam is <1. MHz. W mad horizontal xprimntal CO masurmnts to dtction snsitivity of th CoDiaWil. Th prcisions for th 9 shot pairs and 3-m column rangs wr in th rang of 1%-%. Th root-man-squar of th absolut valus of th diffrncs btwn th 3-min avrags by th two snsors for th 3-m column rang was 3.5 ppm. Total rrors du to th mtorological data was <.5 % in th concntration on th CO masurmnt. W mad slant and vrtical CO masurmnts for th GOSAT validation in 1 and 11. Prcision of XCO masurmnt in th boundary layr was 1 to %. W stimatd XCO using th two cass of clouds obsrvd in th uppr troposphr: Clouds obsrvd around at altitud of 1.5 km on Fbruary 14, 1: 39.6±5.1 ppm. Clouds obsrvd around at altitud of 8.5 km on Fbruary 7, 11: 397.±6.4 ppm. W usd th radiosond (S9-SGP) to masur vrtical profil of mtorological data. Total rror of XCO stimatd from accuracy of th radiosond was <. %. Futur plans Last April, nw 5-yar trm program startd. W startd to dvlop th airborn systm for CO and wind masurmnts and a fibr-lasr-pumpd lasr systm with middl/high rptition. W will contribut to th Japans ISS-JEM lidar obsrvation of vgtation nvironmnt. W ar organizing a working group on spac-born Dopplr lidar as on of following spacborn lidar missions.