Optimized background suppression in near field lidar telescopes

It is shown that a tilted slit in the focal plane of the lidar telescope limits the telescopes field of view efficiently and suppresses the background in the lidar signal by up to an order of magnitude better than a circular diaphragm

Lidar Rayleigh-fit criteria

The talk explains how aerosol-free regions in a lidar signal can be determined by means of the so-called Rayleigh-fit. Criteria based on statistical analyses of the residuals are proposed and explained in detail, which allow to assess the quality of the Rayleigh-fit. Some of the methods can be used to develop quantitative criteria for the uncertainty in the retrieved reference value for the lidar signal inversion

Polarizing lidars and the instrument function

Although the determination of the linear depolarization ratio with lidar seems to be a simple task at first sight, systematic errors can skew the results a great deal. Different unknown systematic errors in different instruments make it difficult to compare the results and to compile a consistent picture of the aerosol properties from measurements around the globe. For the correction of known systematic errors and for the estimation of the uncertainty of the correction we first need a model of the lidars with a mathematical description of the measurements which contribute to the determination of the linear depolarization ratio. This lecture will introduce the model that has recently been published for this purpose [1]. An important part deals with the relative calibration of the signal channels which contribute to the linear depolarization ratio. A basic understanding of the Mueller-Stokes formalism [2,3] will facilitate to follow the lecture

About the effects of polarising optics on lidar signals and the Delta 90 calibration

This paper provides a model for assessing the effects of polarising optics on the signals of typical lidar systems, which is based on the description of the individual optical elements of the lidar and of the state of polarisation of the light by means of the Muller-Stokes formalism. General analytical equations are derived for the dependence of the lidar signals on polarisation parameters, for the linear depolarisation ratio, and for the signals of different polarisation calibration setups. The equations can also be used for the calculation of systematic errors caused by non-ideal optical elements, their rotational misalignment, and by non-ideal laser polarisation. We present the description of the lidar signals including the polarisation calibration in a closed form, which can be applied for a large variety of lidar systems

About the effects of polarising optics on lidar signals and the Delta 90 calibration

This paper provides a model for assessing the effects of polarising optics on the signals of typical lidar systems, which is based on the description of the individual optical elements of the lidar and of the state of polarisation of the light by means of the Muller-Stokes formalism. General analytical equations are derived for the dependence of the lidar signals on polarisation parameters, for the linear depolarisation ratio, and for the signals of different polarisation calibration setups. The equations can also be used for the calculation of systematic errors caused by non-ideal optical elements, their rotational misalignment, and by non-ideal laser polarisation. We present the description of the lidar signals including the polarisation calibration in a closed form, which can be applied for a large variety of lidar systems

How to Support More Flexible Learning Settings in Second Life

Together with advanced technologies, learning environments in today’s education context are becoming more and more sophisticated. The learning requirements and options for students and instructors are also changing with different types and combination of learning modes (face-to-face, online learning, and blended learning). In addition, students are also located at different geographical regions and these students have to be given the opportunity to choose a mode of learning that suit their lifestyle and location. Virtual 3D Worlds can support such options bytaking advantage of the multiple communication channels and the social engagement associated with presence and awareness. There exist a number of learning settings which are designed for traditional learning approaches that donot support flexible environment. This situation has motivated us to initiate research towards a flexible system which supports configuration and adaptation of virtual learning environment according to the learners’ needs. In this paper, we will present the concept of reuse of resources which were invested to support flexible learning settings. Preliminary findings based on the virtual world Second Life are also discussed