Laser ceilometer with pseudo random code modulation for cloud high measurements

Abstract

This paper present a CW low power ceilometer designed for cloud base high measurements. The 500mW CW IR laser of the ceilometer is modulated by a pseudo noise sequence. The scattered and delayed light signal is received by a correlation system with output bandwidth of only 3,5 Hz. This enables to obtain the ranges of 1.2 km to the clouds and the accuracy of the order of +/- 2.5 m to the solid objects. The following issues are discussed: principle of operation, deice architecture and error estimation. Some measurement results are also enclosed.