ING is installing a system to measure the strength of separate
turbulent layers in the atmosphere. These measurements will assist
adaptive optics observations, in particular the use of the Rayleigh
laser guide star. The altitude and strength of atmospheric turbulence
layers determine the quality of correction attainable by adaptive
optics, so that having this information will be very
useful for planning adaptive optics observations.
There are different techniques to measure atmospheric turbulence.
One such technique has been developed by A. Tokovinin (CTIO) and
is called Multi-Aperture Scintillation Sensing (MASS).
By correlating scintillation patterns in different annular
pupils in a telescope the altitude and strength of turbulent
motions in the atmosphere, where the scintillation originates,
can be deduced. For details on this technique see this page at CTIO.
Advantages of this technique are that it requires only a single star
for the measurement and it can be carried out with a relatively small
aperture telescope.
Schematic MASS diagram by A. Tokovinin.
MASS systems are now being used by various observatories as a site
characterisation tool. The MASS instrument, designed and built at
CTIO, will be attached to a small commercial telescope.
The system will deliver on-line actual turbulence strength measurements
as a function of height in the atmosphere in a completely autonomous
fashion. The telescope has been located on the existing DIMM-tower
close to the WHT building, next to the existing RoboDIMM telescope.
Future location of the MASS instrument.
This project has been made possible thanks to the kind collaboration
of CTIO.
