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• 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 90s
• 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, )

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Specifications from SESI (MPL Manufacturer) web
site (http//www.sesi-md.com)
Transmitter  Laser Diode Pumped NdYLF
laser  Wavelength 523 nm  Output Pulse Energy
10 micro-Joule  Pulse Repetition Frequency 2500
Hz  Pulse Duration 10 ns  Polarization
gt1001  Transmitter Field of View 50 µrd  
Receiver  Telescope 20 cm diameter, F/10,
Schmidt-Cassegrain  Field of View 100 µrd  
(full angle) Detector  Type Geiger Mode
Avalanche Photodiode  Quantum Efficiency 40  
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Specifications from SESI (MPL Manufacturer)
Physical Dimensions  Lidar 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 
Other  System 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  
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Nighttime
Daytime
Example of quick-look provided for ARM/SGP data
range corrected data normalized to energy and
time resolution
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Example of quick-look obtained from ARM/Barrow
data
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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_at_5kHz Spinhirne, 1993
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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.
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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)