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Transcript
AO status and perspectives
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
1
List of current AO developments
• Adaptive secondary mirrors *
• First Light AO system (including software) *
• Test tower for secondaries and First Light AO *
• Photon counting CCD detectors
• Site turbulence measurements (g. SCIDAR)
• Second Light Multiconjugate AO (Nirvana) * *
• Sodium line reference stars (Parsec)
• Rayleigh reference stars
[Arcetri]
[Arcetri]
[Arcetri]
[Arcetri+Bologna]
[SO+MPIA]
[MPIA+Arcetri]
[MPE+ESO]
[SO]
. . . Too many for 20 minutes!
I am going to (just) touch only those with a red dot (*)
S. Esposito (*) and Tom Herbst (* *) will describe those with blue dots
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
2
LBT AO milestones and keywords
1992: Decision to (try to) go with adaptive secondaries (AS)
. . . (lot of work on MMT AS, pyramid wfs, lasers, MCAO)
2001: Decision to go with a 672 actuator secondary and (in first light):
• with natural star AO (but upgradeable with a Sodium laser)
• with pyramid WFS (upgradeable with photon counting CCD)
2002: Decision to give “strategic” status as second light instrument
to the “Nirvana” interferometer using on each arm a
natural star MCAO system with the following features:
• Layer Oriented
• Double FoV (~ 6 arcmin outer FoV, ~2 arcmin MCAO FoV)
• Triple conjugate on each arm
(secondary + 2 Xinetics DM with 349 actuator each)
2002: The MMT adaptive secondary seems to work at the telescope!
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
3
AO plans
At the moment we have AO plans for two of the four (double)
Gregorian foci of LBT:
• The “front bent Gregorians” (used by Lucifer)
• The “rear bent Gregorians” (used by Nirvana).
What can we do for the other focal stations? [if we find the money]
• For the “central bent Gregorians” (used by LBTI),
we can easily adapt the “first light AO” system, adding a
“chopped” AO mode (double or multiple Pyramid) [ ~ 0.5 M$]
• For the “direct Gregorians” (used by MODS), we are considering
adapting the “ground layer” wavefront sensor of Nirvana, to
provide “wide field” partial correction of seeing (~1/2) [ ~ 2.5 M$]
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
4
AO summary
The current developments may in principle satisfy the adaptive
requirements of all the planned instruments using natural stars only,
providing:
In the Near (and Thermal) IR:
• Sufficient sky coverage (10% at high Galactic Latitude in J band)
• High Strehl ratio (with relatively faint reference stars)
At shorter wavelengths (R, I):
• Sufficient sky coverage at moderate Strehl (~ 0.2, Nirvana)
• Seeing reduction on “wide” field (~ 2 arcmin) on most of the sky for MODS
Completing LBT adaptivization (without LGS) would cost about 3 M$
The NIR sky coverage could be increased by using two LGS [add ~ 3M$]
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
5
Adaptive secondary mirrors
If these gadgets don’t work
LBT can only use “Prime Focus”,
First requirement therefore is:
Reliability!!!!
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
6
Obtaining reliability
• MMT336 (in this contest) is a “prototype” on which we had
more than two years of testing in the lab and ~3 very important
weeks on MMT (until now)
• All changes wrt MMT336 are being tested on prototypes
(P1, P36) and then all together on the final prototype P45
• LBT672 units will be tested in a special test tower with final
hardware and software reproducing site conditions (the same
holds for the full adaptive system)
• All LBT672 functions can be monitored (and operated) remotely
for test, diagnosis, and software correction or upgrade by experts
• The tower testing hardware and software (Fisba interferometer,
retroreflectors, etc.) will be available at the telescope for
periodic tests, maintenance, re-calibration
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
7
Correcting problems discovered with MMT336
1.
2.
3.
4.
Position jumps (cured with better contacts with backplate)
Cable chaos (cured with distribution boards)
Coolant leaks (cured with heat sink re-design)
Gap contamination by dust, cured with:
• Construction in clean room (and “clean sealing”)
• Soft gaskets on new actuators sealing the gap
• Larger gap (new electronic damping)
5. Various (connectors, power supplies etc.)
(cured by replacement with safer components)
6. Lack of AS figure-test on telescope (cured by adding it)
The testing at system level will be complete in the tower
and repeatable on the telescope in daytime when required
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
8
LBT672 layout
Hexapod
Interface flange and
structural support
3 cooled electronics
boxes
Fixed hexapod
Cold-plate and
actuator support
Astatic levers
50mm thick Zerodur
reference-plate
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
9
New actuator and capacitive sensor
Already tested on P1.
faster to allow
higher electronic damping
easier accessibility
more reliable connections
[email protected]
added “skirt” to better seal the gap
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
10
Electronic damping test
P36 prototype Test
(24 [email protected])
Gap=100mm
No e-damping
Settling time: >8ms
With e-damping
Not only reduces risk of gap
contamination,
it improves performances!
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
Settling time: 0.5ms
11
Curing “position jumps”: Au versus Cr
Gold is the therapy!
(but the first attempt
Of deposition on the P45
Backplate was
not really successful)
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
12
Distribution boards (curing “cable chaos”)
“in principio erat caos”
Now we have
distribution boards
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
13
On LBT672 performances . . .
There is also some progress in other fields, beyond reliability,
that are worth mentioning:
• The new, much faster, communication lines, the new
32 bit floating point DSPs allow to handle more data in less time
• The incresed computing power allow wavefront reconstruction
“on board”
• The new faster analog electronics allows faster settling AND
wider gap (therefore larger chopper throw, piston correction
in interferometry etc.)
• The new Gigabit Ethernet connection allows parallel (not real time)
data processing and system monitoring
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
14
Secondary mirrors comparison
[email protected]
MMT
LBT
Diameter
641 mm
911 mm
N act
336
672
Fitting error
72 nm
64 nm
Act efficency
0.5 N/W1/2
0.5 N/W1/2
Power (act)
0.41 W/act
0.19 W/act
Power (crate)
4.7 W/act
3.8 W/act
Comm. link
160 Mbit/s
2.9 Gbit/s
Comm. diagnostic
No dedicated
400 Mbit/s
DSP
40 Mmac/s (16 bit int)
160 Mmac/s (32 bit float)
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
15
Where are we with LBT672?
• Mirror 1 manufacturing started in Summer 2002
• Pre-production of magnets, analog electronics, actuators mechanics
tested and accepted in summer 2002. Ready for mass production.
• P45 to be delivered in December 2002 (with “old” digital cards to
complete the test of the new actuators and of the distribution boards)
• New pre-production digital cards (BCU and DSP) due in Feb. 2003
• Full test of new hardware/software in spring 2003
• Mass production of components in spring/summer 2003
• Assembly in clean room and test in tower in autumn 2003
• Full AO system test in tower in winter 2003-2004
• Transportation to site in spring 2004
Still (marginally) in time for “first light” in June 2004
(but AO is not officially a first light capability)
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
16
Testing the adaptive secondary
15m optical bench to simulate the telescope
Arcetri Solar Tower
Reference optics
Tube supported by
LBT External Review
Isolators
December 4 2002
AO status and perspectives
P. Salinari
17
Optical Bench (WFS unit)
Thermal control
Goals:
0.2 K stability (in open air)
ΔT=25 K wrt ambient
Double cylinder with ~ 20mbar
pressure in the gap (Acetone:
liquid-vapor phases in equilibrium
like in “heat pipes”)
4cm hd polyurethane outer skin
([email protected]ΔT=30K)
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
18
Scope of the test
Adaptive Secondary Tests:
•Optical Flattening and calibration
•Optical behavior at “mountain” ambient temperature
•Dynamical Behavior at “mountain” atmospheric pressure
WFS Optical Test:
•Optical interaction with LBT672
•Optical Closed loop operation
Main target:
Test and characterization of the Optical
Closed Loop for the Complete and Final
AO System before 1st light
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
19
Concept
1064.7mm
911mm
F/1.22
F/15.0
LBT External Review
December 4 2002
F2
13713mm
F1
The ellipsoidal secondary
is illuminated by the
interferometer from one of its
foci, light is retro-reflected
at the other one.
a spherical mirror is sufficient
for simple “flattening”,
necessary for “passive” use
AO status and perspectives
P. Salinari
20
Some optical details
WFS needs exit pupil on the AdSec mirror!
No simple reference sphere:
Collimating optics+flat on the pupil image
Parabola+flat
LBT External Review
December 4 2002
Single Aspheric
AO status and perspectives
lens+flat
P. Salinari
Spheric
obj+flat
21
More details
Beam to/from
AdSec
Beam to WFS
Movable
beam-splitter
Fisba
interferometer
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
22
Where are we with the assembly and test facilities?
• The clean room is in operation (but used for LBC till summer 03)
• Bids for Civil Work and “Heat Pipe” are out (offers due 12/20/02)
• Orders of components done (Fisba interferometer, vibration insulators)
or being done (winch, special o-rings . . .)
All the subsystems should be installed and go trough acceptance
tests in June 2003
As the test tower is a fairly complex system in itself, we think
of spending a few more months in tuning up the test tower
LBT672 should go in the test tower in October 2003
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
23
A more detailed schedule
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
24
The End
Any question?
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
25
Photoncounting CCDs
The new E2V (ex-Marconi)
back illuminated LLLCCD 60
delivered to Arcetri on Nov. 21st
Its features:
high internal gain (>1000)
high QE (~ 90% in R)
fast (16 Mpix/s, 1000frames/s)
128x128 pix
24x24 μm pix
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
26
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
27
LBT External Review
December 4 2002
AO status and perspectives
P. Salinari
28