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PHASE_SCREEN

PHASE_SCREEN
Warning: This tasks is encapsulated into the "phaseeen.map" procedure
which enables an easy viewing of the result.
To compute the atmospheric phase errors, this tasks generate a 2-D phase
screen on a grid with sufficient spatial resolution to sample the anten-
na diameter (typically 4-m pixels for ALMA, and 4-m pixels for Bure).
The phase screen is generated in the Fourier plane with the constraint
that its 2nd order structure function is a combination of 3 power laws
in 3 different spatial ranges. The resulting phase screen is averaged
over the effective dish diameter. Because of the size limitation imposed
by the FFT, very long phase screen are built as a linear combination of
independently generated screens. This is correct since atmospheric path-
length variations are completely uncorrelated at large distances.
Dynamic (anomalous) refraction is directly proportional to the phase
gradient. This tasks thus computes the phase gradient associated to the
phase screen, in order to obtain a coherent derivation of the dynamic
refraction term. As the phase screen, the phase gradient is averaged
over the effective dish diameter.

Gildas manager
2014-07-01