Lidar activities at CEReS Center for Environmental Remote Sensing (CEReS), Chiba University Hiroaki Kuze

Transcription

1 Lidar activities at CEReS Center for Environmenta Remote Sensing (CEReS), Chiba University Hiroaki Kuze

2 Lidar activities at CEReS Portabe Automated Lidar (PAL) Micro Puse Lidar (MPL) Four-waveength Lidar Look-up Tabe approach for the determination of aeroso profies Imaging Lidar Appication of the wide FOV teescope of the Ashra-I project

3 Portabe Automated Lidar (PAL) Automatic aignment

4 PAL (Portabe Automated Lidar) Observation of tropospheric aerosos and couds

5 A-scope of PAL

6 Aeroso concentration in the boundary ayer: comparison between PAL data and ground data

7 Micro-Puse Lidar and Portabe Automated Lidar MPL Dispay W. Chen et a., Atmospheric Environment, (2001). µ µ

8 Autonomous monitoring of coud base height with MPL Sukhothai, Thaiand, Juy, 1997

9 Aeroso profie measurement with the CEReS 4-waveength idar 355, 532, 756, and 1064 nm 80 cm teescope with 4 photomutipiers Kinjo et a., Jpn.J. App.Phys., 40, (2001); Yabuki et a. Jpn.J.App.Phys., 42, (2003).

10 Lidar Equation cτ G( R) = R P( R) P AK R R dr R 0 β( )exp 2 α( ) R target range [m] P (R ) detected power [W] P 0 emitted power [W] (R ) backscattering coefficient [m -1 sr -1 ] (R ) extinction coefficient [m -1 ] c ight speed [m/s] aser puse duration [s] A teescope area [m 2 ] K optica efficiency G (R ) overapping function

11 Soution of the idar equation (Fernad method) dσ ( R) = α1( R) / β1( R) = σ 1( R), S2 ( R) = α2( R)/ β2( R) = dω sr 1 S1 / θ = π α 1 ( R ) = S 1 S ( R ) 2 α 2 ( R ) + α S S 1 1 1( R ) X ( R ) exp I ( R ) X ( Rc ) + J ( ) ( ) ( R ) Rc α 2 Rc + ( R ) S c 2 2 X ( R) = R P( R), I J ( R) ( R ) R S = c 1 2 R 1 α 2 d S 2 R c ( R ) R ( R) = S ( R ) X( R ) expi( R ) dr 2 1 R

12 Time evoution of the aeroso vertica profie , 13: , 3:00) Aeroso extinction coefficient and the Angstrom parameter

13 Look-up tabe (LUT) method Size distribution [R. Jaenicke, 1993] s (u) : u = 0 to 10 Logarithmic division of the Urban and Maritime aeroso modes Compex refractive index rea part m ( j 1 ): j 1 = 0 to (0.01) imaginary part k ( j 2 ): j 2 = 0 to (0.0001) Waveength ( ) : =1 to 4 355, 532, 756, 1064 nm S 1 (LUT) (, j 1, j 2, u ) : S 1 parameter 1 (LUT) (, j 1, j 2, u ) : Extinction coefficient Aeroso size distribution for LUT. s =0 corresponds to the urban mode, and s =10 to the maritime mode.

14 Theory of Mie scattering Scattered radiance Scattering ampitude 2 2 I 0 dσ I F 0 1( θ) + F2 ( θ) scat I( θ) = = R dω R 2k Differentia cross section F ( θ ) = a cos cos π θ bτ = 1 { ( ) ( θ )} ( ) π 1 sinθ F ( θ ) = cos 2 = 1 () 1 ( cosθ ) ( cosθ ) P { b ( cos ) + ( )} ( + 1) π θ a τ θ d dθ () 1 = τ ( cosθ ) = ( cosθ ), P Associated Legendre functions

15 Constants determined by the boundary conditions: a, b a b ψ = ~ ( nka) ψ ( ka) nψ ( nka) ψ ( ka) ( nka ~ ) ς ( ka) n~ ψ ( nka ~ ) ς ( ka) ψ = n~ ψ n~ ψ ~ ~ ( nka) ψ ( ka) ψ ( nka) ψ ( ka) ( nka ~ ) ς ( ka) ψ ( nka ~ ) ς ( ka) ~ ~ n ~ compex refractive index k =2π/λ a radius of the dieectric sphere ψ χ ς d sinξ ( ξ ) = ( 1) ξ ξ dξ ξ 1 d cosξ ξ dξ ξ + 1 ( ξ ) = ( 1) ξ n ( ξ ) = ψ ( ξ ) + iχ ( ξ ) θ

16 Phase functions (Anguar dependence of the differentia cross section)

17 3000 Extinction and S 1 profies derived from the smoothed parameters (LUT method) Atitude (m) nm 532nm 756nm 1064nm 355nm 532nm 756nm 1064nm Extinction coefficient (km -1 ) Extinction coefficient parameter (sr) 1 S 1 parameter (extinction/backscattering)

18 3000 Vertica profies of the compex refractive index and size distribution as derived from actua idar data Atitude (m) LUT resut Smoothed LUT resut Smoothed LUT resut Smoothed 1500 (a) (b) (c) Rea part Imaginary part (U) Mode (M) Rea part Imaginary part Size distribution mode

19 3000 Comparison of aeroso extinction profies between the LUT and conventiona methods 3000 Atitude (m) nm 532nm 756nm 1064nm Atitude (m) nm 532nm 756nm 1064nm Extinction coefficient (km -1 ) Extinction coefficient (km -1 ) LUT method Fernad method Waveength (nm) S 1 (sr)

20 Aeroso characteristics over the urban Chiba area Variation of Angstrom parameter and optica thickness

21 Detection of VHE cosmic-ray partices Air-shower emission of Fuorescence/ Cherenkov ights ( nm) gamma proton atmosphere neutrino earth Ashra (a-sky survey high resoution air-shower) teescope

22 Ashra Teescope

23 Regiona atmospheric monitoring with an imaging idar System configuration Wide FOV, highresoution teescope Scanning aser Monitoring of urban atmosphere Distribution of SPM - Mie scattering idar Trace gases (poutants) - Raman idar - Differentia Absorption idar DIAL -DOAS Rea time, 3-dim. measurement in a range of 100m10km Observation with an imaging idar

24 Imaging idar vs. conventiona idar Conventiona idar (narrow FOV) Anguar scan is time consuming Target may change during the measurement Time-Height indication (vertica profie) FOV of imaging idar FOV of conventiona idar Anguar scan of a portabe idar Imaging idar Wide Fied-of-view 50 deg50 deg Ony the aser beam is scanned Capabiity of quick measurement

25 Eye-safety Laser power must be under the Maximum Permissibe Exposure (MPE) (JIS C6802 safety standard) Operation waveength of the Ashra teescope is between nm. (Waveength range of the air-shower fuorescence) For a puse width of 20 ns with 2 khz repetition frequency, MPE = 4 J/m 355 nm (about 300 µj/puse for a beam diameter of 10 mm) cf. MPE = 5 mj/m 532 nm

26 2/3 scae prototype 1/3 scae portabe mode Two modes

27 Geometry of bistatic measurement Line of sight Laser Beam Ashra sub-teescope θ scat θ aser Range θ view L 2.1m

28 Ashra teescope 1/3 scae mode Bistatic measurement Backscattering measurement

29 Lidar equation for bistatic measurement P = P A r 0 K ds β θ 2 scat ) P Received power [W] P 0 K ( T T Transmitted power [W] Optica efficiency of the teescope A Effective area of main mirror [m 2 ] r Range to the target [m] ds Laser path ength in one pixe [m] Scattering coefficient [m -1 sr -1 ] T t T r where ds = r θ FOV sin( θ scat Transmittance from aser to target Transmittance from target to teescope ) t r scat

30 Comparison of Lidar Parameters

31 Parameters for 100 m range measurement Laser : Photonics Industries (DC30-351YLF) Waveength 351 nm, Power µj Frequency 1-2 khz, Puse Width 20 ns Background [Wm -2 sr -1 nm nm (Nighttime) (Ten times as bright as the new moon case) FOV/pixe Fiter Bandwidth 3 nm Shot counts (10 s) 7 mrad ( pixes), 0.29 mrad ( pixes)

32 Mode profie of the atmosphere

33 Laser power dependence L = 100 m, Gate time = 1µs, night time background 50µJ/puse 150µJ/puse θ aser is varied between 5 deg and 85 deg.

34 Anguar resoution dependence L = 100 m, Laser power = 50 µj/puse, Gate time = 1µs 7 mrad ( pixes) 0.29 mrad ( pixes)

35 Atitude & Range (L = 100 m) Atitude Range

36 Parameters for 5 km range measurement Laser : Spectra Physics (GCR-130) Waveength 355 nm, Power 80 mj/puse Frequency 10 Hz, Puse Width 5 ns Background [Wm -2 sr -1 nm -1 ] for 355nm (Nighttime) (Ten times as bright as the new moon case) FOV/pixe Fiter Bandwidth 3 nm Shot Counts 100 (10 s) 0.29 mrad ( pixes)

37 L=5 km (nighttime) Inteigent trigger 33µs 100 ns Because of the sma background, onger gate time does not resut in the S/N degradation. Gate time of 100 ns is roughy equa to the eapsed time in which the aser beam passes through a macro ce 2424 pixes with the viewing ange of 0at the range of 5 km.

38 Modtran Simuation θview=75 deg Oct.10, 15:00

39 L=5 km (daytime) 33s Inteigent trigger 100ns Sky radiance at 355 nm is assumed to be 0.1 Wm -2 sr -1 nm -1 on the basis of the MODTRAN simuation. Inteigent trigger is quite usefu for the daytime measurement with a arge background.

40 Atitude & Range (L = 5 km) Atitude Range

41 Summary for the imaging idar project In the Ashra-I project, EHE cosmic-ray partices wi be measured using wide-fov, high-resoution teescopes. The FOV of 50 deg, resoution of 1 arcmin (0.29 mrad), inteigent high-speed shutter, and 1 khz repetition rate indicate that the system has superior quaity aso for the teescope of an imaging idar. The overa ampification factor of the detection system is 10 6, equivaent to that of a conventiona PMT. The greatest advantage of this teescope for an imaging idar is that it provides a wide receiving ange, as opposed to very narrow acceptance ange of the conventiona idar teescopes. In the receiving ange of 50 deg, idar observation can be carried out by scanning the aser beam. At CEReS, we are going to deveop a Mie-scattering imaging idar for the twodimensiona detection of aeroso partices.

42 Lidar activities at CEReS Summary Lidar : Light detection and ranging Deveopment of idar observation of aerosos Muti-waveength measurement of tropospheric aerosos Automated measurement with PAL and MPL Imaging idar system using a wide FOV teescope

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44 Singe Component Atmosphere Two Component Atmosphere Mutipe-to-Singe Scattering Ratio (MSS)