Title: Lidar and the Lunar Scintillation Instrument 

Thomas Pfrommer, University of British Columbia

Abstract: I will first talk about the UBC 6m Liquid Mirror
Telescope and its current LIDAR experiment with which we
investigate the variability of the sodium layer at high
spatio-temporal resolution in support of adaptive optics
(AO) systems of extremely-large optical telescopes (ELTs).
These will employ laser guide stars (LGS) to achieve wide
sky coverage and excite the mesospheric sodium layer at
~ 90 km height on the Na I D2 resonance hyperfine trans-
mission. The finite thickness of the sodium layer and
temporal variations in its density structure produce
elongation and varying internal structure in the LGS. This
degrades the performance of the AO system due to degeneracy
between effects of atmospheric and sodium layer variations.
In order quantify this and assess the impact on future
extremely large telescopes our system provides more than
an order of magnitude improvement in signal-to-noise ratio
as well as spatio-temporal resolution compared to previous
work.

After this quick introduction about my normal day-time work,
I will talk about our current experiment here at CFHT where
we are measuring boundary layer seeing from inside the dome
as well as outside by using integrated moonlight with a
lunar scintillometer, the Portable Turbulence Profiler
(PTP). We are measuring light from the integrated moon disk
with photo diodes and read out the intensity at 1kHz. These 
diodes are located on a 2m long bar and are separated such
that they all have different separations (baselines) between
each other. Due to the extended disk of the moon, the line
of sight from each diode to the moon shares the same path
above a distinct height layer. By disentangling cross-
correlated time series intensity fluctuations from the
smallest to the largest baseline, turbulence information
from each individual layer can be obtained. Our height
resolution is hereby restricted from 2 m to about 250 m and
we are therefore very sensitive to boundary layer turbulence.
I will describe our experiment, background information and
will present first preliminary results from last week.