HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 1 LIDAR Atmospheric corrections determined using Raman/backscatter lidar measurements Valentin Mitev Observatory of Neuchâtel Rue de l’Observatoire 58, CH2000 Neuchâtel Switzerland Tel.: +41–32–

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 2 LIDAR Content: Measurement requirements Concept for the Lidar set-up Extinction derivation, vibrational Raman Numerical performance simulations for Extinction derivation, Raman lidar Extinction derivation, elastic backscatter Temperature derivation, pure Rotational Raman Conclusion Annex: Compact backscatter lidar in field measurements

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 3 LIDAR ~7km Total transmission Range-resolved transmission (extinction coefficient) Zenith angle 0°-60° Measurement requirements Direction of probing Temperature profile

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 4 LIDAR Raman-elastic backscatter lidar – Concept: One laser with two/optional three separate receivers for increased dynamic range and decrease of the « blind » range Transmitted wavelength: 355nm, 532nm, 3rd/2nd harmonics of Nd:Yag laser Receiverd wavelengths: 355nm (elastic); 387nm (Raman N 2 ), 532nm elastic + polarisation/depolarisation; Rotational Raman at (533nm, 531nm)+ (529nm, 535nm) Lidar on pointing platform for collocation of the direction of probing with te line-of-sight of the Cerenkov camera; Optical&Laser part in environmental housing

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 5 LIDAR Raman backscatter lidar: Basics One laser line transmitted (UV/ vis) Received Raman vibrational: N2, O2, H2O/Rorational Determined: extinction, water vapours, temperature Development and use: since early 1980s / in atmospheirc probing for aerosol extinction and microphysics, humidity, temperature, …

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 6 LIDAR

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 7 LIDAR 1.Laser; 2a, 2b, 2c. Telescope long/med/short range 3a, 3b, 3c. Spectral selection 4a, 4b, 4c. Detectors 5. Pointing platform/environnmental housing 6. Synchronisation: Acqusition and Laser pulse& Main Experiment 7.Signal acquisition electronics Synch out 1 5 2a3a4a 2b3b4b 6 7 Data out 2c3c4c

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 8 LIDAR 532nm, 355nm 532nm 387nm 532nm-s 532nm -p 355nm RR1…RR4 532nm (e) 355nm (e) 356/8nm (2*RR-S) 352/4nm (2*RR-aS) aS1/ aS2/ 355nm/ S1/ S2 Laser Receiver Coupling optics 2-Dichroic beamsplitter 3-Interference filter 4-Depolarisation beamsplitter 5-Grating spectrometer 2

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 9 LIDAR Extinction derivation from vibrational Raman backscatter … two times the averaged value of the extinction coefficient in the spectral range 355nm – 387nm

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 10 LIDAR Inputs for the performance simulations: Lidar subsystems specifications Pulse energy at 355nm: 300mJ/PRR : 20Hz Telescope diameter of the « long-range » receiver: 80cm Efficiency transmitter/receiver (without filter): 07./07 Transmission, filter: 0.6 Detector, Quantum efficiency: 0.2 Lidar measurement parameters Integration time: 600sec Zenith angle (from zenith): 60° Range resolution: 120m at 60 Ambient optical background: full moon – 7*10 -4 Wm -2  m -1

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 11 LIDAR Atmosphere: Molecular model: hydrostatic Aerosol model: PBL/dust, km tropospheric layer, 3 - 5km cirrus cloud, ,4km PBL/Dust layer, 0-2km Tropopsphere/Desert Dust, 3-5km Cirrus cloud, 9 – 10.4km

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 12 LIDAR Vibrational -Raman signal – simulated, at slant path 60 deg

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 13 LIDAR Extinction from the vibrational Raman signal

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 14 LIDAR Error of the extinction coefficient obtained from the vibrational Raman signal

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 15 LIDAR Error of the extinction coefficient obtained from the vibrational Raman signal - ZOOM Range x10 4 zenith angle

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 16 LIDAR Total atmospheric transmission of the marked layers, derived from the simulated Raman signal « TRmod » = model value; « TRmeas » = derived value TRmodel = TRmeasured = PBL/Dust layer Tropopsphere/Desert Dust Cirrus cloud TRmodcloud = TRmeas cloud =

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 17 LIDAR Concept for derivation of the extinction coefficient inside aerosol layer using elastic backscatter Assumptions: - The layer contains the same type of aerosol (e.g.,subvisible cirrus cloud) - Aerisol-free atmosphere above the cloud - Total layer (cloud) transmision is determined from the Raman signal

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 18 LIDAR Extinction from Elastic backscatter signal - simultion reference Aerosol layer (Cirrus cloud)

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 19 LIDAR The elastic-backscatter lidar equation

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 20 LIDAR The Fernald's inversion method for derivation of the backscatter coefficient; is omitted Additional conditions: “ lr ” is constant (extinction to backscatter ratio, initial approximation taken from model values, here the depolarization ratio may help to classify the cloud particles), “ r f ” is a reference range “  (r f ) ” is known ( typically, the molecular backscatter)

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 21 LIDAR Assuming: “  (r) ” is derived from elastic lidar Total double trip transmission “DT” is derived from Raman lidar, Molecular backscatter is known/type of particles may be “guessed” Then we may determine “ lr ” from And the profile of the aerosol extinction in the cloud

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 22 LIDAR Derivation of the atmospheric temperature profile using pure rotational Raman backscatter Rotational Raman Spectra of N2 and O2, Excitation at 532nm

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 23 LIDAR Spectral intervals in pure RR where the scattering cross-sections derivative has opposite sign A calibration of the lidar is critical. « + » « - » Temperature derivative of the Rotational Raman lines of N2 (red) and O2 (black) « + » R(T)=exp(  –  /T) Typically dR/dT ~0.05%

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 24 LIDAR

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 25 LIDAR Uncertainty - ZOOM 60° zenith angle Integration time: 30min Range resolution: 120m

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 26 LIDAR Summary: A Raman-backscatter Lidar for CTA-site is a technically feasible solution for the requirements in CTA: Advantages: « Real time » and « Real direction » coinciding with the pointing direction the Cherenkov Telescope(s) The necessary lidar methods and algorithms are developed, adaptation to the tasks will be possible ; Realistic subsystem specifications, compatible with the commercially available hardware; Additional /Optional lidar tasks: laser backscatter for calibration of the Cherenkov telescope; Remark: This presentation is not with system optimisation. The final specifications may be different from the specifications used for numerical simulations

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 27 LIDAR Next step for the Raman lidar - a design study with the following objectives: Detailed numerical simulations of the various detection modes with respect to the finalised detection requirements Concept design and optimisation; Algorithm developments; Optional 1: Participation in atmospheric characterisation at the potential CTA sites; Optional 2: Raman lidar bread-board/ lower aperture and power

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 28 LIDAR ANNEX: Possibility for atmospheric characterisation at potential CTA sites with a compact elastic backscatter lidars

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 29 LIDAR Micro-pulse lidars on stratospheric aircraft (M55) MAL 1MAL 2 MAL-1MAL-2 32 cm

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 30 LIDAR Micro-pulse lidars on stratospheric aircraft (M55) SCOUT O3/ Brunei - Darwin, 12 November 2005 Backscatter Ratio= (  a +  m )/  m

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 31 LIDAR Ground-based LIDAR, transportable development, observations, data analysis The lidar on the balcony of the 5th floor of the University of Basel; Project BUBBLE ( ). The lidar was remotely operated from ON Example for 24h- measurement of the aerosol load above Basel in project BUBBLE 600mmx600mmx700mm

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 32 LIDAR Ground-based three-wavelength elastic Raman LIDAR, in Observatory of Neuchatel Operational, Presently under refurbishment Concerning the CTA-activity: Not transportable May be a base for the Raman lidar bread- board/test bench wrt the CTA requirements Possibility to be deployed on site (with limitations for steering, schedule …)

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 33 LIDAR Summary for the “compact lidar” capabilities: - Possibility for qualitative characterisation of the aerosol vertical/slant path profile: Backscatter coefficient profile (~30% uncertainty, systematic), altitude of layers, -Convenient transportation and implementation on the field - Limitations: The qualitative evaluation is not adequate to the requirements in CTI, i.e., NOT a replacement for the Raman lidar)

HEAPnet meeting, February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 34 LIDAR Thank you! Valentin Mitev Observatory of Neuchâtel Rue de l’Observatoire 58, CH2000 Neuchâtel Switzerland