Requirements for AO-ELT operation and AO site monitor. Andrei Tokovinin NOAO/CTIO. Three ways to schedule AO. CS – classical scheduling (fixed nights) SQS – standard queue scheduling (on seeing) AQS – advanced queue scheduling (on relevant parameter).
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operation and AO site monitor
ELT and its AO instruments are such a huge investment
that even a small gain in performance is important.
Optimum scheduling will increase AO science output
At large telescopes, dominant AO error comes
from the high-altitude turbulence
Fourier code to compute PSF (fast, 0.2s/profile!)
Median on-axis Strehl: 0.95 (NGS), ~0.2 (LGS)
Cone effect and tilt anisoplanatism dominate
Similar data exist for:
6 TMT sites
[ArXiv:0904.1183 Schoeck et al.]
Cerro Pachon, etc.
On-axis Strehl ratio
Best 25% nights
Queue scheduling on 0 gives nearly guaranteed Strehl
Nights with good 0 also have “slow” seeing
The worst offender is
Laser tomography will be used almost always.
This case is sensitive to high-altitude turbulence,
also relevant to tomography
On-axis Strehl, best 25% of nights
0 is not as good as
in the VLT case, but
better than other
100% time coverage
on top of the dome
Two (or more) collimated 5-cm laser beams
from top-end to focus
will measure (r0, L0) of internal turbulence without
perturbing normal telescope operation
(fringe period 0.22”)