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LBT External Review December 4 2002
AO status and perspectives P. Salinari
1
AO status and perspectives
LBT External Review December 4 2002
AO status and perspectives P. Salinari
2
List of current AO developments
• Adaptive secondary mirrors * [Arcetri]• First Light AO system (including software) * [Arcetri]• Test tower for secondaries and First Light AO * [Arcetri]• Photon counting CCD detectors [Arcetri+Bologna]• Site turbulence measurements (g. SCIDAR) [SO+MPIA]• Second Light Multiconjugate AO (Nirvana) * * [MPIA+Arcetri]• Sodium line reference stars (Parsec) [MPE+ESO]• Rayleigh reference stars [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
3
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
4
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
5
AO summary
The current developments may in principle satisfy the adaptiverequirements 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
6
Adaptive secondary mirrors
If these gadgets don’t workLBT can only use “Prime Focus”,First requirement therefore is:
Reliability!!!!
LBT External Review December 4 2002
AO status and perspectives P. Salinari
7
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
8
Correcting problems discovered with MMT336
1. Position jumps (cured with better contacts with backplate)2. Cable chaos (cured with distribution boards)3. Coolant leaks (cured with heat sink re-design)4. 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
9
LBT672 layout
Hexapod
Interface flange andstructural support
3 cooled electronicsboxes
Fixed hexapodCold-plate and
actuator supportAstatic levers
50mm thick Zerodurreference-plate
LBT External Review December 4 2002
AO status and perspectives P. Salinari
10
New actuator and capacitive sensor
Already tested on P1.
faster to allowhigher electronic damping
easier accessibility
more reliable connections
added “skirt” to better seal the gap
90kHz@-3dB
LBT External Review December 4 2002
AO status and perspectives P. Salinari
11
Electronic damping test
P36 prototype Test(24 kHz@-3db)
Gap=100m
Settling time: >8ms
Settling time: 0.5ms
Not only reduces risk of gapcontamination,
it improves performances!
No e-damping
With e-damping
LBT External Review December 4 2002
AO status and perspectives P. Salinari
12
Curing “position jumps”: Au versus Cr
Gold is the therapy!
(but the first attempt Of deposition on the P45Backplate was not really successful)
LBT External Review December 4 2002
AO status and perspectives P. Salinari
13
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
14
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
15
Secondary mirrors comparison
r0=15cm@500nm 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
16
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
17
Testing the adaptive secondary
15m optical bench to simulate the telescope
Arcetri Solar Tower
Reference optics
Tube supported byIsolators
Optical Bench (WFS unit)
LBT External Review December 4 2002
AO status and perspectives P. Salinari
18
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 (3kW@ΔT=30K)
LBT External Review December 4 2002
AO status and perspectives P. Salinari
19
Scope of the test
Adaptive Secondary Tests:•Optical Flattening and calibration•Optical behavior at “mountain” ambient temperature•Dynamical Behavior at “mountain” atmospheric pressureWFS 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
20
Concept
F2
F1
F/15.0
F/1.22
13713mm
1064.7mm911mm
The ellipsoidal secondaryis illuminated by theinterferometer from one of itsfoci, light is retro-reflectedat the other one.
a spherical mirror is sufficientfor simple “flattening”, necessary for “passive” use
LBT External Review December 4 2002
AO status and perspectives P. Salinari
21
Some optical details
WFS needs exit pupil on the AdSec mirror!No simple reference sphere:Collimating optics+flat on the pupil image
Parabola+flat Single Aspheric lens+flat
Spheric obj+flat
LBT External Review December 4 2002
AO status and perspectives P. Salinari
22
More details
Fisba interferometer
Movable beam-splitter
Beam to/from AdSec
Beam to WFS
LBT External Review December 4 2002
AO status and perspectives P. Salinari
23
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
24
A more detailed schedule
LBT External Review December 4 2002
AO status and perspectives P. Salinari
25
The End
Any question?
LBT External Review December 4 2002
AO status and perspectives P. Salinari
26
Photoncounting CCDs
The new E2V (ex-Marconi)back illuminated LLLCCD 60delivered to Arcetri on Nov. 21st
Its features:high internal gain (>1000)high QE (~ 90% in R)fast (16 Mpix/s, 1000frames/s)128x128 pix24x24 μm pix
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