VLT Laser Guide Star Facility RecoveryVLT Laser Guide Star Facility Recovery

DBO - ESO Status Overview – CfAO meeting 26 March 2007

ESO: E. Allaert, C. Araujo, G.Avila, D.Bonaccini Calia, E.Brunetto, B. Buzzoni, M. Comin, M. Cullum, C.Dichirico, M. Dimmler, I.Guidolin, W. Hackenberg, F.Koch, D. Popovic, M. Quattri, J. Quentin and A.Silber

MPE/MPIA: Davies, S. Hippler, S, Kellner, U.

Neumann, T. Ott, S. Rabien

Oberti - 28.Jan.2006

• Recovery of what? Degraded Im. Quality form LT Mech problems

• Recovery Action? Redesign and Construction LT M1 supports

• Extra Resources: 1.2 FTE + 120 kEUR

• Project Delay: 11 months

• Results: Problem solved, very close to specs

• LGSF Status: Completed Commissioning – Science Phase

LGSF Launch TelescopeLGSF Launch Telescope

Commissioning runs Commissioning runs

3 runs from October to December

Dec and January together with NACO and SINFONI

LGS-AO Doing science, Feb-March-April-May

Issues:

• Pointing of LGS

• Focussing to the optimal height

• LGS fwhm

• LGS flux

• Operation with UT4 and AO systems

• Diagnostics

LGS observed with a side telescope (LGS Monitoring Telescope)

Photometry done using several standards, V-band Johnson filterDone in two different nights in May 06, it gives similar LGS flux results:

LGS flux 2.006x106 phot/m2 on the ground (spec: 1x106 phot/m2 at Nasmyth)

Would correspond to ~3.2x105 cts/subap/sec at the Sinfoni WFS

LGS mv= 8.8 with calibrated photometry. The corresponding WFS magnitude is higher!

LGS FLUX

11 inch Celestron, 0.66”/pxl, 14-bit CCD

LGSM had a 2250m baseline (Residencia)

Average LGS flux depends on the season

Lgs fwhm depends on the uplink wavefront quality, but also on Sodium layer density distribution and on the lower atmospheric turbulence levels

LGS FWHM

lgs fwhm vs ngs fhwm (UT4 guider)

1.00

1.20

1.40

1.60

1.80

2.00

2.20

0.5 0.7 0.9 1.1

NGS fwhm (arcsec)

LG

S f

wh

m (

arcs

ec)

fwhm-x

fwhm-y

Linear (fwhm-x)

• Mostly UT4-M2 flexures with gravity induces LT pointing deviations

• The effect is corrected by moving the fibre on the focal plane of the LT

• To bring the LGS at centerfield we will use the same method as for NGS (tool in prep.)

LGS Pointing

LGS Pointing Model FOS CorrectionsFOS1-2 = -0.0026x2 + 0.0078x - 0.1548

-30.0

-25.0

-20.0

-15.0

-10.0

-5.0

0.0

5.0

10.0

90 85 80 75 70 65 60 55 50 45 40 35 30

Altitude Angle (deg)

FO

S M

oti

on

(a

rcs

ec

)

Azimuth (FOS1-2)

Altitude (FOS3)

Linear (Altitude (FOS3))

Poly. (Azimuth (FOS1-2))

LGS

• Repeatable focusing depends on temperature and sodium layer median altitude

• We have to collect more data during operation for a repeatable calibration.

• A tool for automatic focusing is in preparation, useful to speed up LGS

acquisition

LGS Focussing

BEU ENC(T)

150000

200000

250000

300000

350000

400000

20 16 12 8 4 0

Temp (C)

En

cod

er U

nit

s

BEU ENC(T)

BEU ENC(Z)

20000

25000

30000

35000

40000

45000

0 20 40 60

Zenith Angle (deg)

Encoder Units

Current calibration is not satisfactory

Conclusions

• The LGSF can be used for LGS-AO observations

• Technical time with AO continues, to fine tune operations/performances

• Observing overhead will be reduced with tools to center/focus LGS during acquisition

• The LGS fwhm in our analytical predictions was smaller. We believe it is physical, it is important also for future projects with LGS systems.

• In the coming months LGS data will continue to be accumulated and analyzed

• It has not been a walk, but the team has cumulated very precious experience for the next complex systems