ALAPS: Advanced Lidar Atmospheric Profile Sensor, Lidar Applications for Atmospheric Characterization
Document ID: 367
Presentation
1 The Pennsylvania State University, Applied Research Laboratory, University Park, PA, U.S.A.
Introduction
A Lidar Atmospheric Profile Sensor (LAPS) has been developed and tested. The device detects pipeline emissions from an aerial platform. This paper outlines changes that need to be made to the instrument for improved performance.
Summary
FUTURE ALAPS DEVELOPMENTS
The lessons learned from the LAPS development and the requirements for a smaller system have been addressed in a proposed design for an advanced system that will use an eye-safe ultraviolet diode pumped laser transmitter, improved detector, high speed electronics. The features include:
• Diode pumped laser using quasi-CW bar diodes
• GHz electronics - selectable resolution of 3, 7, 15 meter
• Eye-safe transmitted beam at ultraviolet wavelength with 1 kHz repetition rate
• Power required about 20% of LAPS, reduced EMI and environment control
• Size reduction to 20% of LAPS, no radar, smaller environment system
• Automate operation and seif calibration
• Measures on any radial in a 5 km cube to provide spatial information
• Evaporation duct by pointing slightly below horizontal (20 cm height resolution)
• EO propagation, multi-λ optical extinction, aerosol size
• Direct detection technique for wind velocity
Major advances have been made with the development of diode pumped Nd: YAG and Nd: YLF during the past few years. Even though a penalty in power efficiency comes with using the double, triple and quadruple wavelengths, the advantages in scattering cross-section (~1/λ4) and quantum efficiency of detectors still made this an attractive approach. The laser beam can be made eye safe by lowering the peak power and moving to the ultraviolet spectral region where the eye safe radiation flux is much higher. By making the transmitted beam eye safe, the instrument can be used to measure the evaporative ducts by pointing at the sea at a distance of several hundred meters to the side of the ship (thus increasing the vertical resolution from the 3 to 15 meters attained with the new electronics to fraction of one meter). The instrument can be pointed in any direction to determine nearby atmospheric properties. The ALAPS instrument will be covert, that is no visible beam will be observed. The unit will be contained completely in a cube of approximately 1 meter and it will have simple interface connections for power and for data transfer of the final data product to a remote computer. The reduced EMI conditions which can be achieved using a diode pumped Iaser will allow the co-location of the Iaser and the sensitive detectors in the same instrument package. In preparation for the project of fabricating the actual ALAPS instrument, several tasks are outlined in the following section which provide significant steps toward the actual task of developing the ALAPS prototype instrument.