README - file describing the files in the "StrehlCampaignNoise" directory, 
as created to support the ongoing study of Strehl measurements. Simulated
data were created using IDL 5.6 on a SunBlade 100 workstation at the Space
Telescope Science Institute, Fall 2003.

For questions, please contact Russ Makidon (makidon@stsci.edu, 410.338.4946).


Initial images were created assuming a set of five independent 512x512
Kolmogorov-spectrum phase screens with D/r_0 = 12.0 across a Palomar
geometry pupil of 256 pixels across.  PSFs were created by co-adding
the five PSFs due to individual phase screens with a lambda/8D
sampling.

I have provided the file "TelescopePupil.fits", which is the exact
telescope pupil used for these simulations.

'Parabolic' AO correction has been assumed, as described by Eq. 9
of Sivaramakrishnan et al. 2001, ApJ, 552, 397.  Variations in
Strehl ratio between images were achieved by varying the number of
AO actuators across the telescope pupil.

Final FITS image filenames follow the nomenclature

  Palomar.strehlXX.rXnb.fits
  
where 'Palomar' describes the primary and secondary mirror geometry
assumed for these simulations, 'strehlXX' is a number corresponding to
the Strehl ratio simulated (with one file per Strehl ratio at each
sampling), 'rX' denotes the original image at lambda/8D sampling was
rebinned to lambda/XD (e.g., 'r2' for lambda/2D rebinning, 'r4' for
lambda/4D rebinning).  'n' denotes Gaussian read noise and Poisson
noise (from background and star) have been added, and 'b' denotes the
final image has been background subtracted.

This directory contains the two subdirectories 'oversamp2n' and
'oversamp4n', corresponding to PSFs with lambda/2D sampling and lambda/4D
sampling respectively.  Both sets of data have a constant RMS noise level
from detector read noise and background.

The directory 'oversamp2n' has twelve FITS files

  Palomar.strehl01.r2nb.fits
  Palomar.strehl02.r2nb.fits
  Palomar.strehl03.r2nb.fits
  Palomar.strehl04.r2nb.fits
  Palomar.strehl05.r2nb.fits
  Palomar.strehl06.r2nb.fits
  Palomar.strehl07.r2nb.fits
  Palomar.strehl08.r2nb.fits
  Palomar.strehl09.r2nb.fits
  Palomar.strehl10.r2nb.fits
  Palomar.strehl11.r2nb.fits
  Palomar.strehl12.r2nb.fits

with each of these files being a 256x256 image of a non-perfect PSF
with a lambda/2D pixel scale.  These images started their lives as a
series of 1024x1024 images at lambda/8D pixel scale and then rebinned
using the IDL task 'rebin' to a lambda/2D pixel scale.

The images have been scaled to try and simulate a realistic number of
photons acquired from an 8th magnitude star at Palomar at a wavelength
of lambda = 1.635 microns.  An educated guess was made to calculate
the fractional transmission loss of photons reaching the detector due to
atmospheric and instrumental losses.  Detector gain for these images was
set to 1.  Read noise was set to 12 electrons.

A constant background was added to each image (i.e., all images have the
same added background level) and Poisson noise added based on the number
of counts in the star and background.  The constant background was then
subtracted, leaving an image with (close to) zero mean background.

The directory 'oversamp4n' has twelve FITS files

  Palomar.strehl01.r2nb.fits
  Palomar.strehl02.r2nb.fits
  Palomar.strehl03.r2nb.fits
  Palomar.strehl04.r2nb.fits
  Palomar.strehl05.r2nb.fits
  Palomar.strehl06.r2nb.fits
  Palomar.strehl07.r2nb.fits
  Palomar.strehl08.r2nb.fits
  Palomar.strehl09.r2nb.fits
  Palomar.strehl10.r2nb.fits
  Palomar.strehl11.r2nb.fits
  Palomar.strehl12.r2nb.fits

with each of these files being a 512x512 image of a non-perfect PSF
with a lambda/4D pixel scale.  These images started their lives as a
series of 1024x1024 images at lambda/8D pixel scale and then rebinned
using the IDL task 'rebin' to a lambda/4D pixel scale.

The images have been scaled to try and simulate a realistic number of
photons acquired from an 8th magnitude star at Palomar at a wavelength
of lambda = 1.635 microns.  An educated guess was made to calculate
the fractional transmission loss of photons reaching the detector due to
atmospheric and instrumental losses.  Detector gain for these images was
set to 1.  Read noise was set to 12 electrons.

In addition, I have included the following two (resampled)
perfect PSF FITS files in their respective directories...

  Palomar.perfect.r2.fits
  Palomar.perfect.r4.fits

...to help enable comparisions.  These 'perfect' images have also been
scaled by the same number of photons reaching the detector for the
lambda/2D and lambda/4D images respectively.