84 research outputs found
Analysis of isoplanatic high resolution stellar fields by Starfinder code
We describe a new code for the deep analysis of stellar fields, designed for
Adaptive Optics Nyquist-sampled images with high and low Strehl ratio. The
Point Spread Function is extracted directly from the image frame, to take into
account the actual structure of the instrumental response and the atmospheric
effects. The code is written in IDL language and organized in the form of a
self-contained widget-based application, provided with a series of tools for
data visualization and analysis. A description of the method and some
applications to AO data are presented.Comment: 10 pages, 13 figures. Accepted for publication in Astron.& Astrophys.
Sup. Se
StarFinder: an IDL GUI based code to analyze crowded fields with isoplanatic correcting PSF fitting
StarFinder is a new code for the deep analysis of stellar fields, designed
for well-sampled images with high and low Strehl ratio. It is organized in the
form of a self-contained IDL widget-based application, with a 'user-friendly'
graphic interface. We give here a general description of the code along with
some applications to real data with space-invariant Point Spread Function
(PSF). We present also some methods to handle anisoplanatic effects in
wide-field Adaptive Optics (AO)observations.Comment: 9 pages, to to be published on "Proceeedings of Adaptive Optical
Systems Technology",Proc.of SPIE,Vol.4007,2000. In pres
Optimization of cw sodium laser guide star efficiency
Context: Sodium laser guide stars (LGS) are about to enter a new range of
laser powers. Previous theoretical and numerical methods are inadequate for
accurate computations of the return flux and hence for the design of the
next-generation LGS systems.
Aims: We numerically optimize the cw (continuous wave) laser format, in
particular the light polarization and spectrum.
Methods: Using Bloch equations, we simulate the mesospheric sodium atoms,
including Doppler broadening, saturation, collisional relaxation, Larmor
precession, and recoil, taking into account all 24 sodium hyperfine states and
on the order of 100 velocity groups.
Results: LGS return flux is limited by "three evils": Larmor precession due
to the geomagnetic field, atomic recoil due to radiation pressure, and
transition saturation. We study their impacts and show that the return flux can
be boosted by repumping (simultaneous excitation of the sodium D2a and D2b
lines with 10-20% of the laser power in the latter).
Conclusions: We strongly recommend the use of circularly polarized lasers and
repumping. As a rule of thumb, the bandwidth of laser radiation in MHz (at each
line) should approximately equal the launched laser power in Watts divided by
six, assuming a diffraction-limited spot size.Comment: 15 pages, 12 figures, to be published in Astronomy & Astrophysics,
AA/2009/1310
Extragalactic Fields Optimized for Adaptive Optics
In this paper we present the coordinates of 67 55' x 55' patches of sky which
have the rare combination of both high stellar surface density (>0.5
arcmin^{-2} with 13<R<16.5 mag) and low extinction (E(B-V)<0.1). These fields
are ideal for adaptive-optics based follow-up of extragalactic targets. One
region of sky, situated near Baade's Window, contains most of the patches we
have identified. Our optimal field, centered at RA: 7h24m3s, Dec: -1deg27'15",
has an additional advantage of being accessible from both hemispheres. We
propose a figure of merit for quantifying real-world adaptive optics
performance, and use this to analyze the performance of multi-conjugate
adaptive optics in these fields. We also compare our results to those that
would be obtained in existing deep fields. In some cases adaptive optics
observations undertaken in the fields given in this paper would be orders of
magnitude more efficient than equivalent observations undertaken in existing
deep fields.Comment: 28 pages, 15 figures, 1 table; accepted for publication in PAS
- …