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
Transmitter   Laser: 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  
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%  

3. 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 resolution Data 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
75 m,
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)