System description

The instrument was developed and built for NSF and NCAR by the University of Wisconsin’s lidar group led by Dr. Edwin Eloranta.  The principles of HSRL and some early systems are described in Piironen and Eloranta (1994), Shipley et al. (1983), and Sroga et al. (1983). The evolution of the current system is described by Razenkov et al. (2002, 2008) and Eloranta and Razenkov (2006) describes the locking technique.  The high-repetition, low-pulse energy laser is expanded to fill the telescope aperture so it meets the eye-safety criteria of the American National Standards Institute (ANSI) at all ranges.  The design uses a shared telescope which gives the same field-of-view (FOV) to both the transmitter and receiver so the lidar alignment is very stable.  When on-board an aircraft, the telescope can be rotated between zenith and nadir pointing in few seconds during flight.  A safety interlock insures that the outgoing laser shutter is open only when the telescope is locked in either the nadir or zenith position. 

Figure 1. An optical block diagram of GVHSRL

The HSRL is a calibrated lidar.  A simple block diagram of the instrment is given in Figure 1. It separates molecular backscattering from aerosol and cloud particle backscatter based on their Doppler spectrum widths.  The molecular backscatter is used to calibrate the aerosol backscatter cross section from the ratio between the molecular signal and the aerosol signal.  The aerosol extinction is calculated by comparing the expected molecular return to the actual molecular return signal.  Table 1 lists some of the technical specifications of the HSRL.

Internal users: For more information see http://wiki.eol.ucar.edu/rafscience/HSRL (last edited 2012-12-08)