AO review meeting, Florence, November 10-11 2005. FLAO operating Modes Presented by: S. Esposito Osservatorio Astrofisico di Arcetri / INAF.

AO review meeting, Florence, November 10-11 2005.

FLAO operating Modes

Presented by: S. Esposito Osservatorio Astrofisico di Arcetri / INAF

AO review meeting, Florence, November 10-11 2005.

Fixed Mode

• A seeing limited mode where Adaptive secondary mirror holds a fixed shape defined by a pre-calibrated mirror command vector “flat”.– AO supervisor is on for LBT672 operation diagnostics

– The baseline flat is the LBT672 AO flat measured during AT

– Flat quality for AO is specified as 65nm rms i.e. over specified for SL

– Flat optimization for M1 & non common path aberration• Two different flats for LUCIFER with ADC on/off

• Each LBT instrument could use its own flat, adjusting for non common path aberrations (low order wavefront modes).

AO review meeting, Florence, November 10-11 2005.

Tip Tilt Mode (TTM)

•It is an AO mode with two corrected modes.-Tip tilt is measured using the AO WFS and corrected by the secondary mirror-FoV for tip tilt correction is about 3x2 arsmin i.e. 6 arcmin^2-Reference source as dim as 18 R mag i. e. close to full Sky coverage-Binning by 5x5 or larger can be used to reduce RON sqrt(36x4xRON^2) = 42e-

•This mode can be used for:-AO correction on very faint objects-Field stabilization using non isoplanatic reference stars against

--dome seeing--telescope flexure --telescope vibrations --telescope tracking errors (with mode offloading)--Tip Tilt mode for LGS (?)

Mag 17.5 gives 40phot/ tint on LBTDlambda = 0.3Eta = 0.5Tint = 1ms

Mag 18.5 gives 160 phot/ tint on LBTDlambda = 0.3Eta = 0.5Tint = 10msSky background in R 19.5 / arcsec^2

AO review meeting, Florence, November 10-11 2005.

Tip Tilt Mode (TTM)

•Input data:• Reference star co-ordinates (3x2 arcmin FoV)•Reference star magnitude

•Main configured parameters (automated)•Integration time•Tip Tilt loop gain

•Tip tilt commands from other instruments, MODS, PEPSI..

AO review meeting, Florence, November 10-11 2005.

AO Auto-Configured Mode I

• It is the full AO correction mode

• Input data:– R0 value

– Averaged wind speed (measured from OL data)

– Ref. Star co-ordinates

– Ref. Star magnitude (and color)

• AO loop parameters are automatically selected by the AO Supervisor SW considering the above input data.

• Main selected parameters are:– Integration Time– Binning mode– Number of corrected modes– Pyramid modulation

AO review meeting, Florence, November 10-11 2005.

FLAO CL configuration

1x1 2x2 3x3

K band

H band

J band

• Ref. Star mag => photon flux• Photon flux => binning•Binning, Photon flux => int time• r0, photon flux => Nmodes•Nmodes => Modulation

AO review meeting, Florence, November 10-11 2005.

From flux & binning to Nmodes

Propagated noise on reconstructed modesis computed from r0, photon flux and pre-calibrated noise propagation coefficients [rad^2/phot]

Turbulence modal coefficients aremeasured or computed from r0 value

Maximum number of modes is defined by the binning value i.e. number of subaperture

Modes radial degree

Rad^2

Optimal numberof modes identified

r0

Photon flux

AO review meeting, Florence, November 10-11 2005.

AO Auto-configured Mode II

• Scientific instrument LBT672 best flat & WFS slope null vector.– The AO client instrument flat have to be measured maximising the instrument SR for low

order modes. Slope null vector is recorded at the same time.

• High SR Long exposure > 10min. Differential flexures (LUCIFER-AO WFS) correction is required.

– Flexure correction using AO supervisor look-up table

– LUCIFER internal tip-tilt sensor

• Mode offloading to telescope via TCSOffloading of tip, tilt, defocus and other low order modes is required expecialy for long exposures. Time averaged LBT672 modal commands are sent at low frequency from the AO supervisor to the TCS for offloading to (telescope arbitrator, TCS):

--hexapod

--primary

--telescope pointing

• Optical loop gain control PSF FWHM ?????

AO review meeting, Florence, November 10-11 2005.

AO Auto-configured Interactive Mode II

• Do we have situations where performance evaluation is ambiguous ?– Photon flux close to binning mode discontinuity.

– Two reference stars in the isoplanatic patch: far and bright close and dim.

• Main adjustable parameters from TCS AO GUI using pre-defined values:– Integration time

– Binning mode

– Number of corrected modes

– Pyramid modulation

AO review meeting, Florence, November 10-11 2005.

Operation diagnostic

• Fixed mode

– Diagnostic for LBT672 can be provided using cap sensors reading and applied forces.

• Tip-Tilt mode

– Diagnostic can be provided by the

Optimal perfomance on startOptimal performance sustained, LUCIFER integration time