Layer Oriented: scienc e with MAD and beyondrobertoragazzoni.it/Repository/[PAPERS-CONF]C205-70150I_1... · 2015-07-27 · performances drops by a factor two, turned out to be about

Layer Oriented: science with MAD and beyond

R. Ragazzoni*a, Y. Almomanya, C. Arcidiaconoa, R. Falomoa, J. Farinatoa, M. Gullieuszika, E. Diolaitib, M. Lombinib, A. Morettia, G. Piottoc, E. Marchettid, R. Donaldsond, R. Turollac

aINAF – Astronomical Obsevatory of Padova, v.lo dell’Osservatorio 5, I - 35122 Padova (Italy);

bINAF – Astronomical Obsevatory of Bologna, via Ranzani 5, I - 40127 Bologna (Italy); cDept. of Astronomy, Univ. degli Studi di Padova, v.lo dell’Osservatorio 3, 35122 Padova (Italy);

dEuropean Southern Observatory, Karl-Schwarzschild-Strasse 2, D - 85748 Garching bei München (Germany).

ABSTRACT

The Layer Oriented Wavefront Sensor for MAD has been used in the sky to achieve science. The preliminary results from a six night run and the perspectives in terms of achieved performances and projections of sky coverage for slightly more sophisticated system like the Multiple Field of View one are shown indicating that the sensor is keeping its promises.

Keywords: Adaptive Optics, Wide Field, Multi Conjugated Adaptive Optics

1. INTRODUCTION The Layer Oriented approach has been introduced [1, 2] as an optical means to perform Multi Conjugated Adaptive Optics [3]. It implies the use of a number of pupil plane wavefront sensors foreoptics, namely pyramids if such a kind of wavefront sensor is used [4] and it has the feature to co-add optically the light from, ideally, a number of individually faint star into the same detector. The detector is optically conjugated to the layer where the correction is willing to be applied. It has been shown [5] that the layer oriented approach is close to the optimum when the stars fill uniformly the Field of View where the correction is required to be applied. The key role of the LO approach, however, is not in the optical computation issue, but rather in the possibility to use efficiently the light from a number of fain stars in order to improve the sky coverage with the declared aim to be competitive with Laser Guide Stars in terms of achievable sky coverages in areas where NGS are scarce, like close to the Galactic Poles. Subsequently an enhanced version of the LO approach, namely the Multiple Field of View approach, has been introduced [6] in order to select a larger Field of View of the narrower and stronger ground layer turbulence, leaving to a second stage the correction for the high altitude layers, confined to the Field of View of scientific interest.

2. THE WAVEFRONT SENSOR In the framework of the Multi Conjugated Adaptive Optics Demonstrator [7, 8 MAD, Marchetti et al. ] we developed [9, 10, 11, 12, 13, 14] a wavefront sensor to drive the two DMs in this device. In order to reach such a goal we build a four reference stars prototype [15], later used for further optical bench experiments [16, 17]. We also developed a Layer Oriented Simulation Tool [18, 19, 20] to anticipate the expected performances in the sky of MAD in LO mode.

* [email protected]; phone +39 049 8293517; www.oapd.inaf.it

Adaptive Optics Systems, edited by Norbert Hubin, Claire E. Max, Peter L. Wizinowich,Proc. of SPIE Vol. 7015, 70150I, (2008)

0277-786X/08/$18 · doi: 10.1117/12.790412

Proc. of SPIE Vol. 7015 70150I-1

Downloaded From: http://proceedings.spiedigitallibrary.org/ on 07/14/2015 Terms of Use: http://spiedl.org/terms

The system has been extensively tested in laboratory in Garching with a turbulence simulator and the main result found there is that, in spite of a (less than 10%) marginal loss of performances with respect to the Shack Hartmann sensing in terms of peak achieved Strehl (partially due to the small Field of View of each individual pyramids) the limiting magnitude, defined as the equivalent magnitude where the performances drops to one half of he bright ends one, turned out to be about 1.5 magnitude deeper than the conventional approach, as correctly foreseen [21, 22], see also Fig. 1.

Fig. 1. Comparison between the limiting magnitude of the Shack Hartmann and the Pyramid sensors installed onboard MAD

and tested with a turbulence simulator in ESO-Garching. The limiting magnitude, defined as the magnitude where performances drops by a factor two, turned out to be about 1.5mag deeper for the pyramid case.

Fig. 2. A direct comparison of an HST and a MAD-LO image of an extragalactic jet. Given the similar diffaction limited

size and the greater collected flux, against a stronger background, NIR, MCAO images are directly comparable to the HST visible ones.

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Finally, the system has been exposed to true starlight in a nine night shift in the period September and October 2007. In this occasion the first three nights have been under the ESO responsibility, while the latter six were under our one, classified as Guaranteed Observing Time.

In order to make the system running as smoothly as possible at the telescope a total of five technical team member assisted in the observations, while some were on the mountain for integration and testing in advance for a few weeks. ESO provided assistance in terms of three units of personnel in their integration phase and of one during the observing phase.

It is remarkable that the interaction matrix in the LO mode are independent from the used asterism so these were collected during daytime. At the beginning of the run we undergo a few times in the problem of colliding the stars enlarger, the devices able to pick up the starlight to the detectors, as the control software has wrong margin size. After this has been fixed we almost never experience problems of this form. Nevertheless we limited ourselves to a maximum of five pyramids per observation.

3. SCIENTIFIC OBSERVATION In the six scientific nights we carried out a number of observations. These includes:

• The Globular Cluster NGC6388. Thanks to solving the confusion due to the crowding thanks to the improved resolution we have been able to produce Infrared/Visible Color Magnitude Diagram. These are being used in order to confirm or deny the existence of two different populations in such a cluster, preliminarily recently claimed from solely HST data.

• The nearby Galaxy UKS2323-326 where thanks to the improved resolution and to the deeper ability of the instrument with respect to the existing observations, we achieved the highest SNR and deeper in infrared magnitude Color Magnitude Diagram for this galaxy [23].

• The field of a couple of Neutron Stars in order to search for a counterpart [24]. This approach had some chances of success given that in some cases a disk of dust is present around such objects making them particularly bright in the Infrared. Unfortunately we have only been able to place upper limit in the fluxes in the NIR wavelengths.

• The jet of the BL-Lac PKS 0521-365 where, further to find out high SNR images of the jet, in very good agreement with the radio observations of the same, we also find a blob of infrared luminous material aligned with the jet, not visible neither at visible neither at radio wavelengths. Such a blob is clearly a resolved object and so it is ruled out the chance that is a normal foreground star of our Galaxy.

• Other Globular Clusters and a few QSO, together with some low-z galaxies. These observations are still pending a detailed analysis and any kind of astrophysical diagnostics.

Given the high productivity in scientific terms of a relatively short run, we also focused onto a couple of other crucial points, namely which is the accuracy of photometric and astrometric measurements of the LO approach compared to the SO one, and the projected sky coverage given the actual and laboratory results obtained so far.

About the first we analyzed in parallel the data of Omega-Cen taken from the SO-MAD, of public domain, and a set of NGC6388 data we taken during our run. The initial seeing conditions were more favorable to the SO, Omega-Cen case, leading to a closed loop image that is about 25% narrower. Also, in the same covered frames, the number of stars from Omega-Cen is larger (this, however, means also a somehow larger crowding effect). In spite of this a through analysis leads to a cumulative distribution error of the photometric magnitude that is about 10% more accurate for the Layer Oriented approach, and, vice versa, the inverse case for the astrometric precision, pointing, essentially, to the conclusions that the two approach have basically similar performances in terms of astrophysical measurements in crowded fields.



.11*-S

Fig. 3. A comparison between the two sensor has been made on data available of two different Globular Clusters: NGC 6388

and Omega Cen.

Regarding sky coverage [25, 26] we took two reference limiting magnitudes. The first is the typical magnitude to which we obtained a large fraction of data that is an integrated one of about 14. The second is the limiting one found in the laboratory characterization, that turned out, as already mentioned, to be about 16.5. These two figures represent, we think, the range in which the instrument is expected to achieve real good performances, and we plotted these over the published integrated star magnitude for given Field of View in the case of the Multiple Field of View concept.

These figures leads to a range of sky coverages in the range of 7% to 25% at the North Galactic Poles.

In the timescale of a few years, however, it is unlikely to make from scratch a Multiple-Field of View instrument, neither it is not realistic to upgrade MAD to a full 6 arcmin Field of View. The adoption of extremely low noise CCDs could lead simply to the implementation of such a concept using a number of WaveFront Sensor, but usually the system that are under design in these days made reference to a few Laser Guide Stars so the overall sky coverage will be nevertheless very limited. A small window of opportunity comes with NIRVANA onboard LBT where the two arms illuminating the common, interferometric camera, are equipped with a Multiple-Field of View system [27, 28, 29]. However, these systems are not optimized for the Infrared and, as in MAD, have refractive optics in the relay beam, at ambient temperature. Anyway, given the small additional burden to make a camera and maybe a small Integral Field Unit on the two arms, this could represent a viable solution.

On a longer timescale Laser Guide Stars should assess their reliability and effectiveness. As recently we found options for Wavefrtont Sensing that allow for simultaneous sensing of a few LGS and NGS together we just mention this option here.

Omega Cen (public data)NGC6388 (LO data)



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Fig. 4. Cumulative errors in photometry and astrometry of the two globular cluster measured with the Star Oriented and the

Layer Oriented Wavefront Sensors.

Fig. 5. The sky coverage of the ground (left) and high (right) layer shown together with the prediction originally carried out

when the concept has been devised (continuous line) compared with the actual ones, assuming they lies somewhere between the typical integrated magnitude at which most of the science has been carried out (dotted – dashed line) and the one derived from the laboratory measurements (double dotted – dashed line).

4. CONCLUSIONS Finally, we would like to conclude stating that the Layer-Oriented approach is within its expectations and that there are a number of options that has never been considered or studied in detail. Among the others we like to cite the two that sounds more promising in principle, that is the usage of the Taylor hypothesis to greatly enlarge the integration time of

Layer Oriented

Star Oriented

Layer oriented

Star Oriented



the sensing, and hence pushing further the limiting magnitude) and the non linear coaddition of the information coming from portions of the Field of View. The latter, in particular, promised to break the rules such that a larger Field of View translates into a more limited thickness of turbulence correction, allowing, provided a large Field of View is attained in the telescope optics, to push in another way for deeper sky coverage.

REFERENCES

[1] Ragazzoni R., “Adaptive optics for giant telescopes: NGS vs. LGS”, Proc. of the Backaskog workshop on extremely large telescopes, ESO conference and workshop proceedings, 57, 175, (2000).

[2] Ragazzoni R., Farinato J., Marchetti E., “Adaptive optics for 100-m-class telescopes: new challenges require new solutions”, Proc. SPIE 4007, 1076-1087, (2000).

[3] Ragazzoni, R., Marchetti E., Valente G., “Adaptive-optics corrections available for the whole sky”, Nature, Vol. 403, 6765, 54-56, (2000).

[4] Ragazzoni R., “Pupil plane wavefront sensing with an oscillating prism”, Journal of Modern Optics, Vol. 43, n.2, 289-293, (1996).

[5] Tokovinin A., Viard E., “Limiting precision of tomographic phase estimation," J. Opt. Soc. Am. A 18, 873-882, (2001).

[6] Ragazzoni R., Diolaiti E., Farinato J., Fedrigo E., Marchetti E., Tordi M., Kirkman D., “Multiple field of view layer-oriented adaptive optics. Nearly whole sky coverage on 8 m class telescopes and beyond”, Astronomy and Astrophysics, 396, 731-744, (2002).

[7] Marchetti E., Hubin N., Fedrigo E., Brynnel J., Delabre B., Donaldson R., Franza F., Conan R., Le Louarn M., Cavadore C., Balestra A., Baade D., Lison J. L., Gilmozzi R., Monnet G., Ragazzoni R., Arcidiacono C., Baruffolo A., Diolaiti E., Farinato J., Viard E., Butler D., Hippler S., Amorim A., “MAD the ESO multi-conjugate adaptive optics demonstrator”, Proc. SPIE 4839, 317-328, (2003).

[8] Marchetti E., Brast, R., Delabre B., Donaldson R., Fedrigo E., Frank C., Hubin N., Kolb J., Le Louarn M., Lizon J. L., Oberti S., Reiss R., Santos J., Tordo S., Ragazzoni R., Arcidiacono C., Baruffolo A., Diolaiti E., Farinato J., Vernet-Viard E., “MAD status report”, Proc. SPIE 5490, 236-247, (2004).

[9] Farinato J., Ragazzoni R., Diolaiti E., Vernet-Viard E., Baruffolo A., Arcidiacono C., Ghedina A., Cecconi M., Rossettini P., Tomelleri R., Crimi G., Ghigo M., “Layer oriented adaptive optics: from drawings to metal”, Proc. SPIE 4839, 588-599, (2003).

[10] Ragazzoni R., Soci R., Arcidiacono C., Baruffolo A., Baumeister H., Bisson R., Böhnhardt H., Brindisi A., Coyne J., Diolaiti E., Farinato J., Gässler W., Herbst T., Lombini M., Meneghini G., Mohr L., Rohloff R.R., Vernet-Viard, E., Weiss R., Xompero M., Xu W., “Layer-oriented MCAO projects and experiments: an update”, Proc. SPIE 5169, 181-189, (2003).

[11] Farinato J., Ragazzoni R., Arcidiacono C., Bagnara P., Baruffolo A., Baumeister H., Bisson R., Böhnhardt H., Brindisi A., Brynnel J., Cecconi M., Coyne J., Delabre B., Diolaiti E., Donaldson R., Fedrigo E., Franza F., Gässler W., Ghedina A., Herbst T. M., hubin N. N., Kellern S., Kolb J., Lizon J. L., Lombini M., Marchetti E., Meneghini G., Mohr L., Rohloff R.R., Soci R., Vernet-Viard, E., Weiss R., Xompero M., Xu W., “Layer-oriented on paper, laboratory, and soon on the sky”, Proc. SPIE 5382, 578-587, (2004).

[12] Lombini M., Ragazzoni R., Arcidiacono C., Baruffolo A., Bisson R., Brindisi A., Coyne J., Diolaiti E., Farinato J., Le Roux B., Lombardi G., Marchetti E., Meneghini G., Vernet-Viard E., Xompero M., “Assembly, integration, and test of the layer-oriented wavefront sensor for MAD”, Proc. SPIE 5490, 1247-1255, (2004).

[13] Arcidiacono C., Lombini M., Diolaiti E., Farinato J., Ragazzoni R., “Laboratory testing the layer oriented wavefront sensor for the multiconjugate adaptive optics demonstrator”, Proc. SPIE 6272, 70, (2006).

[14] Farinato J., Ragazzoni R., Arcidiacono C., Gentile G., Diolaiti E., Foppiani I., Lombini M., Schreiber L., Lorenzetti D., D'Alessio F., Li Causi G., Pedichini F., Vitali F., Herbst T., Kürster M., Bizenberger P., Briegel F., De Bonis F., Egner S., Gässler W., Mohr L., Pavlov A., Rohloff R. R., Soci R., “The MCAO wavefront sensing system of LINC-NIRVANA: status report”, Proc. SPIE 6272, (2006).

[15] Vernet-Viard E., Ragazzoni R., Arcidiacono C., Baruffolo A., Diolaiti E., Farinato J., Fedrigo E., Marchetti E., Falomo R., Esposito S., Carbillet M., Vérinaud C., “Layer-oriented wavefront sensor for MAD: status and progress report”, Proc. SPIE 4839, 344-353, (2003).



[16] Egner S. E., Gaessler W., Herbst T., Ragazzoni R., “A closed loop layer-oriented adaptive optics test”, The Publications of the Astronomical Society of the Pacific 119, Issue 860, 1114-1125, (2007).

[17] Egner S., Gaessler W., Ragazzoni R., LeRoux B., Herbst T., Farinato J., Diolaiti E., Arcidiacono C., “MANU-CHAO: a laboratory ground-layer adaptive optics experiment”, Proc. SPIE 6272, 62724X, (2006).

[18] Arcidiacono C., Diolaiti E., Ragazzoni R., Farinato J., Vernet-Viard E., “Sky coverage for layer-oriented MCAO: a detailed analytical and numerical study”, Proc. SPIE 5490, 563-573, (2004).

[19] Arcidiacono C., Diolaiti E., Ragazzoni R., Baruffolo A., Brindisi A., Farinato J., Vernet-Viard E., “Sky coverage and Strehl ratio uniformity in layer-oriented MCAO systems”, Proc. SPIE 5169, 169-180, (2003).

[20] Vérinaud C., Arcidiacono C., Carbillet M., Diolaiti E., Ragazzoni R., Vernet-Viard E., Esposito S., “Layer Oriented multi-conjugate adaptive optics systems: performance analysis by numerical simulations”, Proc. SPIE 4839, 524-535, (2003).

[21] Ragazzoni R., Farinato J., “Sensitivity of a pyramidic Wave Front sensor in closed loop Adaptive Optics”, Astronomy and Astrophysics 350, L23-L26, (1999).

[22] Esposito S., Riccardi A., “Pyramid Wavefront Sensor behavior in partial correction Adaptive Optic systems” [23] Gullieuszik M., Greggio L., Held E. V., Moretti A., Arcidiacono C., Bagnara P., Baruffolo A., Diolaiti E., Falomo

R., Farinato J., Lombini M., Ragazzoni R., Brast R., Donaldson R., Kolb J., Marchetti E., Tordo S., “Resolving stellar populations outside the Local Group: MAD observations of UKS 2323-326”, Astronomy and Astrophysics 483, Issue 1, L5-L8, (2008).

[24] Mignani R. P., Falomo R., Moretti A., Treves A., Turolla R., Sartore N., Zane S., Arcidiacono C., Lombini M., Farinato J., Baruffolo A., Ragazzoni R., Marchetti E., “Observations of Isolated Neutron Stars with the ESO Multi-Conjugate Adaptive Optics Demonstrator”, Astronomy and Astrophysics, accepted, (2008)

[25] Ragazzoni R., Diolaiti E., Farinato J., Fedrigo E., Marchetti E., Tordi M., Kirkman D., “Sky coverage in layer-oriented adaptive optics”, Proc. SPIE 4494, 52-59, (2002)

[26] Marchetti E., Ragazzoni R., Diolaiti E., “Which range of magnitudes for layer oriented MCAO?”, Proc. SPIE 4839, 566-577, (2003).

[27] Lombini M., Ragazzoni R., Arcidiacono C., Baruffolo A., Cresci G., Diolaiti E., Falomo R., Gaessler W., Mannucci F., Vernet E., Vernet J., Xompero M., “Layer-Oriented MCAO projects for 8-m class telescopes and possible scientific outcome”, Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century, ESO Astrophysics Symposia, European Southern Observatory series, Springer-Verlag, 59, (2007).

[28] Egner S., Gaessler W., Herbst T., Ragazzoni R., Stuik R., Andersen D. A., Arcidiacono C., Baumeister H., Beckmann U., Behrend J., Bertram T., Bizenberger P., Boehnhardt H., Diolaiti E., Driebe T., Eckhardt A., Farinato J., Kuerster M., Laun W., Ligori S., Naranjo V., Nußbaum E., Rix, H. W., Rohloff R. R., Salinari P., Soci R., Straubmeier C., Vernet-Viard E., Wigelt G. P.; Weiss R., Xu W., “LINC-NIRVANA: the single arm MCAO experiment”, Proc. SPIE 5490, 924-933, (2004).

[29] Ragazzoni R., Herbst T, Gaessler W., Andersen D., Arcidiacono C., Baruffolo A., Baumeister H., Bizenberger P., Diolaiti E., Esposito S., Farinato J., Rix H. W., Rohloff R. R., Riccardi A., Salinari P., Soci R., Vernet-Viard E., Xu W., “A visible MCAO channel for NIRVANA at the LBT”, Proc. SPIE 4839, 536-543, (2003).



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Layer Oriented: scienc e with MAD and beyondrobertoragazzoni.it/Repository/[PAPERS-CONF]C205-70150I_1... · 2015-07-27 · performances drops by a factor two, turned out to be about