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Micro-Pulse Lidar (MPL) Specifications and performance History :

Micro-Pulse Lidar (MPL) Specifications and performance History : First eye-safe lidar operating in the visible developed at NASA/GSFC by J. Spinhirne in the early 90’s Industrial version commercialized by a small US Company (SESI) Several systems now implemented on ARM sites

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Micro-Pulse Lidar (MPL) Specifications and performance History :

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  1. Micro-Pulse Lidar (MPL) • Specifications and performance • History : • First eye-safe lidar operating in the visible developed at NASA/GSFC by J. Spinhirne in the early 90’s • Industrial version commercialized by a small • US Company (SESI) • Several systems now implemented on ARM sites • Involved in several campaigns for aerosol characterisation (ACE2, INDOEX, ACE-ASIA, …)

  2. Specifications from SESI (MPL Manufacturer) web site (http://www.sesi-md.com) TransmitterLaser: Diode Pumped Nd:YLF laser  Wavelength: 523 nm  Output Pulse Energy: 10 micro-Joule  Pulse Repetition Frequency: 2500 Hz  Pulse Duration: 10 ns  Polarization: >100:1  Transmitter Field of View: 50 µrd   ReceiverTelescope: 20 cm diameter, F/10, Schmidt-Cassegrain  Field of View: 100 µrd   (full angle) DetectorType: Geiger Mode Avalanche Photodiode  Quantum Efficiency: 40%  

  3. Specifications from SESI (MPL Manufacturer) Physical DimensionsLidar Controller and Computer Display: User selected computer  Optical Transceiver: 30 x 30 x 84 cm  MPL Scaler & Control Unit: 49 x 10 x 33 cm  Diode Laser Power Supply: 49 x 14 x 31 cm  OtherSystem Control: via Pentium based IBM compatible PC  Photon Counting System: SESI Multichannel Scaler (200 ns / 500 ns / 1 us / 2 us dwell time selectable)  corresponding to 30 m-300 m vertical resolutionData Acquisition Software: Windows 95 based disk/CD versions  Power Requirements: 115/230 VAC,  50/60 Hz, ~ 5/3A  System Weight: 50 kg  

  4. Nighttime Daytime Example of quick-look provided for ARM/SGP data : range corrected data normalized to energy and time resolution

  5. Example of quick-look obtained from ARM/Barrow data

  6. Calculated Performance 1-2 µJ 7.5 cm 2- 10 µJ 20 cm 3- 25 µJ 20cm Overall efficiency 0.08-0.1-0.2 75 m, 2s@5kHz Spinhirne, 1993

  7. Refering to the standard acquisition procedure (300 m vertical resolution and 60 s acquisition time), a multiplicative factor equal to 10 is to be applied to the obtained SNR values. This leads to SNR values larger than 100 up to 10 km for nighttime operation. Experimental limitations : overlap factor and detector response In a more recent paper (Welton and Campbell, 2002), the uncertainty analysis is discussed with reference to afterpulse corrections. The signal shown in this paper are corresponding to version 1 signal of Campbell et al., so that a SNR of 40 at 10 km altitude for nighttime operation and a 60s integration time. Overlap factor is also further revisited to extend up to 6.2 km. Signal processing now includes correction of afterpulse and overlap factor.

  8. CONCLUSION • Very impressive system in operation : fast profiling up to high • Altitudes, narrow field of view (for multiple scattering), but • Temperature stabilization required • High cost • New system being developed at NASA/GSFC • Smaller laser divergence • Otherwise similar but looking for an improved temperature Stability (correction of overlap including alignment drifts)

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