1. HEAPnet meeting, 19-20 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.: +41–32–889 8813 E-mail: valentin.mitev@ne.ch

2. HEAPnet meeting, 19-20 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

3. HEAPnet meeting, 19-20 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

4. HEAPnet meeting, 19-20 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

5. HEAPnet meeting, 19-20 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, …

6. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 6 LIDAR

7. HEAPnet meeting, 19-20 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

8. HEAPnet meeting, 19-20 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 1 2 3 3 4 5 1-Coupling optics 2-Dichroic beamsplitter 3-Interference filter 4-Depolarisation beamsplitter 5-Grating spectrometer 2

9. HEAPnet meeting, 19-20 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

10. HEAPnet meeting, 19-20 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

11. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 11 LIDAR Atmosphere: Molecular model: hydrostatic Aerosol model: PBL/dust, 0 - 2 km tropospheric layer, 3 - 5km cirrus cloud, 9 - 10,4km PBL/Dust layer, 0-2km Tropopsphere/Desert Dust, 3-5km Cirrus cloud, 9 – 10.4km

12. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 12 LIDAR Vibrational -Raman signal – simulated, at slant path 60 deg

13. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 13 LIDAR Extinction from the vibrational Raman signal

14. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 14 LIDAR Error of the extinction coefficient obtained from the vibrational Raman signal

15. HEAPnet meeting, 19-20 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 m, @60° zenith angle

16. HEAPnet meeting, 19-20 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 = 0.5836 TRmeasured = 0.5830 PBL/Dust layer Tropopsphere/Desert Dust Cirrus cloud TRmodcloud = 0.9498 TRmeas cloud = 0.9508

17. HEAPnet meeting, 19-20 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

18. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 18 LIDAR Extinction from Elastic backscatter signal - simultion reference Aerosol layer (Cirrus cloud)

19. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 19 LIDAR The elastic-backscatter lidar equation

20. HEAPnet meeting, 19-20 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)

21. HEAPnet meeting, 19-20 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

22. HEAPnet meeting, 19-20 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

23. HEAPnet meeting, 19-20 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%

24. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 24 LIDAR

25. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 25 LIDAR Uncertainty - ZOOM 60° zenith angle Integration time: 30min Range resolution: 120m

26. HEAPnet meeting, 19-20 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

27. HEAPnet meeting, 19-20 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

28. HEAPnet meeting, 19-20 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

29. HEAPnet meeting, 19-20 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

30. HEAPnet meeting, 19-20 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

31. HEAPnet meeting, 19-20 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 (2001-2002). The lidar was remotely operated from ON Example for 24h- measurement of the aerosol load above Basel in project BUBBLE 600mmx600mmx700mm

32. HEAPnet meeting, 19-20 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 …)

33. HEAPnet meeting, 19-20 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)

34. HEAPnet meeting, 19-20 February 2007, Amsterdam Atmospheric corrections determined using Raman/backscatter lidar measurements 34 LIDAR Thank you! Valentin Mitev (valentin.mitev@ne.ch) Observatory of Neuchâtel Rue de l’Observatoire 58, CH2000 Neuchâtel Switzerland