Artificial guide stars for adaptive imaging

Pilkington, J. D. H.

doi:10.1038/330116a0

Cited by 36 publications

(27 citation statements)

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“…All the mentioned above concepts lead to the speculation that, provided all these conditions (tuning of spatial and temporal sampling to a restricted volume of atmosphere, large number of references and additional gain introduced by the closed loop operations on a pyramid WFS) are successfully met and combined positively, good sky coverages could be obtained with the usage of NGSs alone, solving istantaneously (as a plus, in case this would be necessary) the tip-tilt indetermination problem (Pilkington 1987;Rigaut & Gendron 1992) and of course all the technical issues of reliability and efficiency related to the massive use of a significant number of artificial reference beacons. This approach is completely different from a previous conjecture (Ragazzoni 1999b) that assumed the global reconstructor MCAO had to be adopted, leading to very large FoVs.…”

Section: The Layer-oriented Conceptmentioning

confidence: 99%

Multiple field of view layer-oriented adaptive optics

Ragazzoni

Diolaiti

Farinato

et al. 2002

A&A

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Abstract. In layer-oriented adaptive optics, multiconjugation is performed in a much more efficient way than conventional wavefront sensing. This improved efficiency is impressive for high altitude layers and moderate for ground ones. On the other hand, high altitude layers can be covered with only a limited field of view (where one can search for natural guide stars) while for ground layers the usable field of view is limited essentially by practical reasons. We introduce the further concept of multiple field of view layer-oriented adaptive optics where a combination of sampling and covered field leads easily to sky coverages for 8 m class telescopes that nearly approach the whole sky with the usage solely of natural guide stars. The extension of the concept to much larger apertures is also discussed.

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Section: The Layer-oriented Conceptmentioning

confidence: 99%

Multiple field of view layer-oriented adaptive optics

Ragazzoni

Diolaiti

Farinato

et al. 2002

A&A

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“…Projecting a Laser Guide Star (LGS in the following) inside of the isoplanatic patch, as proposed by Foy and Labeyrie (1985), is convenient when correcting the higher order terms of the perturbation, but it must be considered that tilt alone represents nearly 87% of the wavefront phase variance (Noll 1976). The feasibility of using a LGS as a reference source, apart from the problem of focal anisoplanatism (Tallon & Foy 1990), is fundamentally constrained by the tilt indetermination problem (Pilkington 1987). As regard to the latter, it is known that due to reciprocity in the upward and downward path of the projected laser, the tilt of an LGS is almost completely compensated, at least when the telescope has the same diameter of the projector.…”

Section: Introductionmentioning

confidence: 99%

Isokinetic patch measurements on the edge of the Moon

Ghedina¹,

Ragazzoni²,

Baruffolo³

1998

Astron. Astrophys. Suppl. Ser.

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Abstract. By imaging the edge of the Moon we have tested a seeing monitor able to evaluate the isokinetic patch size. These measurements have a relevant interest because of several Laser Guide Star (LGS) tilt recovery schemes that have been proposed. In our approach the edge of the Moon mimics a LGS as seen far from the laser projector. The conceptual design of the instrument, the data reduction techniques and the preliminary results obtained at the Asiago Astronomical Observatory are given. Because, as a by product, the instrument is able to evaluate r 0 , a comparison with seeing data collected at the 1.82 m telescope of Cima Ekar during the three nights test of the described instrument is also given.

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“…Because of the tilt or tilts between the emitting laser and the receiving wavefront sensor, the location of the laser spot in the mesosphere is unknown [2].…”

Section: (Lgs)mentioning

confidence: 99%

ELP-OA : status report of the setup of the demonstrator of the polychromatic laser guide star at Observatoire de Haute Provence

et al. 2008

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Abstract.We report the status of ELP-OA (Étoile Laser polychromatique pour l'Optique Adaptative), the full demonstrator which we are building at OHP 1.52m telescope. The goal is to open adaptive optics to the domain of visible wavelengths at large telescopes, which is almost not feasible today because of the tiny isoplanatic patch. ELP-OA relies on the 2-photon excitation of sodium in the mesosphere, through 589 and 569 nm transitions. We use 2 pulsed dye lasers (on loan from CEA) pumped with NdYAGs. The average power at the mesosphere will be 2 × 22W. The twin laser beams are projected to the mesosphere by a 3-aperture interferometer. The backscattered spots in NaI lines at 330, 569 and 589nm are oberved through an adaptive optics at the telescope coudé focus, derived from the ONERA's BOA device. The differential tilt measurement channel is equipped with an EMCCD. We use a correlation algorithm to extract it. From our end to end model we expect tilt Strehl ratios of 35% at 550nm (see Meilard et al in this conference). First lasers launches are planned early 2010, with the full experiment running 2011.

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Artificial guide stars for adaptive imaging

Cited by 36 publications

References 0 publications

Multiple field of view layer-oriented adaptive optics

Multiple field of view layer-oriented adaptive optics

Isokinetic patch measurements on the edge of the Moon

ELP-OA : status report of the setup of the demonstrator of the polychromatic laser guide star at Observatoire de Haute Provence

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