Title:

General Formulation for Imaging through Atmospheric
Turbulence using Large Ground-Based Telescopes


T. Stewart McKechnie
ITT Industries Inc., Advanced Engineering & Sciences Div.
5901 Indian School Road, 
Albuquerque, New Mexico 87110




ABSTRACT 

A general formulation for light propagation and imaging through turbulence 
is described in which no specific form is assumed for the turbulence 
structure function, Kolmogorov or otherwise. Instead, turbulence structure 
is described in terms of a general, initially unknown function. Turbulence 
introduces Optical Path Difference (OPD) fluctuations in the wavefronts 
arriving at the telescope. The OPD fluctuations fully and uniquely determine 
the properties of images formed through the turbulence. Measurements of certain 
key statistical properties of point-object images allow us to obtain the 
statistical properties of the OPD fluctuations. In turn, these OPD properties 
allow us to obtain the statistical properties of the turbulence. In particular, 
they allow us to establish the previously unknown form of the turbulence 
structure function.

The measurement procedures provide essential information about the integrated 
effect of all mechanisms in the propagation path that affect the wavefronts. 
In addition to atmospheric turbulence, these mechanisms can include, but are 
not limited to, dome turbulence, telescope aberrations, and the (corrective) 
effect of Adaptive Optics (AO). The measurement procedures enable full 
end-to-end characterization of the entire propagation path between object and 
image, and they take account of amplitude scintillation as well as phase 
variation in the wavefronts. Once the entire path has been characterized, 
telescope resolution can be established as a function of wavelength. A wavelength 
region can also be identified that offers highest resolution. The measurement 
procedures enable performance characterization of ground-based telescopes of 
any size, with or without AO capability, even next generation telescopes with 
100-meter apertures.


Biography:
Stewart McKechnie's interest in imaging through turbulence dates back to his 
postdoctoral research work in light scattering at Imperial College, London, 
in the mid-1970s. In 1981, he moved to the US where he now holds US citizenship. 
He is currently Chief Scientist at ITT Industries where he is involved in 
developing LIDAR and other types of remote sensing systems.