Lidar Remote Sensing Applications: Ready and Waiting
- PDF / 864,721 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 98 Downloads / 275 Views
FF8.2.1
Lidar Remote Sensing Applications: Ready and Waiting John F. Hahn Optech Incorporated / Space and Atmospheric Division Toronto, Ontario Canada M3J 2Z9 ABSTRACT In this note, lidar materials, ready and waiting, will be discussed. Most lidar applications depend upon "Ready" materials, conventional materials that are part of a design solution to the application. Lidar systems already operating and serving the needs of communities in atmospheric, earth and planetary sciences, include airborne terrain mapping, airborne bathymetric mapping, ground-based imaging rangefinding and ceilometry are included in this category. Even in space application, "Ready" spaceborne applications include orbital rendezvous and docking, precision landing/hazard avoidance and Martian atmospheric evaluation. Other applications, however, have particular materials needs and constitute "Waiting" systems. These include in particular spaceborne differential absorption lidar (DIAL) for the measurement of important trace species such as ozone and water vapor in the Earth's atmosphere (ORACLE, WALES). An evaluation of critical issues facing mission-enabling lidar materials development will be presented, based upon Optech Incorporated's direct experience in these areas. LIDAR BASICS The fundamental physics of lidar remote sensing are described by the lidar equation. The lidar equation defines the optical power collected by the system is expressed as in Equation (1): ⎡ R ⎤ P(λ , R ) = E 0 (λ )(c / 2)( A / R 2 )Qtr (λ )Qr (λ )β (λ , R ) exp⎢− 2 α (λ , z ) dz ⎥ + PB (λ ) ⎣⎢ 0 ⎦⎥
∫
(1)
where E0(λ) is the laser output pulse energy at wavelength, λ, c is the speed of light, A is the receiver aperture area, R is the retrieval range, z is the range free variable, Qtr is the transmitter optical transmission efficiency, Qr is the receiver optical transmission efficiency, α(λ,z) is the total extinction coefficient at wavelength λ , as varying over range z, β(λ,z) is the total volume backscatter coefficient at wavelength λ , as varying over range z and PB(λ) is the background optical power at wavelength λ. The background radiance is further broken down in Equation (2) as: B
⎛ π ⋅θ ⎞ PB (λ ) = L( λ ) ⋅ A ⋅ ⎜ ⎟ ⋅ Q r ⋅ Δλ ⎝ 2 ⎠ 2
(2)
FF8.2.2
where L(λ) is the background solar spectral irradiance, θ is the full-angle receiver field of view, Qr is the receiver optical transmission efficiency and Δλ is the receiver optical bandwidth. The lidar equation is the basic building block of many lidar retrieval techniques, such as simple backscattering, differential absorption lidar (DIAL), Raman lidar, laser induced fluorescence and so forth. The lidar application encompassing the lidar instrument as well as the medium under investigation, and also incorporating the parameters listed above, is affected by the environmental conditions of operation. The parameters appearing in the lidar equation pertain either to the lidar instrument hardware or to the scattering environment and consequently can be mapped into the various hardware assemblies and the scattering m
Data Loading...
