LINC-NIRVANA is an imaging interferometer for the Large Binocular Telescope (LBT) and will make use of multi-conjugated adaptive optics (MCAO) with two 349 actuators deformable mirrors (DM), two 672 actuator deformable secondary mirrors and a total of 4 wavefront sensors (WFS) by using 8 or 12 natural guide stars each. The goal of the MCAO is to increase sky coverage and achieve a medium Strehl-ratio over the 2 arcmin field of view. To test the concepts and prototypes, a laboratory setup of one MCAO arm is being built. We present the layout of the MCAO prototype, planned and accomplished tests, especially for the used Xinetics DMs, and a possible setup for a test on sky with an existing 8m class telescope.

On the way to the Extremely Large Telescopes (ELT) the Large Binocular Telescope (LBT) is an intermediate step. The two 8.4m mirrors create a masked aperture of 23m. LINC-NIRVANA is an instrument taking advantage of this opportunity. It will get, by means of Multi-Conjugated Adaptive Optics (MCAO), a moderate Strehl Ratio over a 2 arcmin field of view, which is used for Fizeau (imaging) interferometry in J,H and K. Several MCAO concepts, which are proposed for ELTs, will be proven with this instrument. Studies of sub-systems are done in the laboratory and the option to test them on sky are kept open. We will show the implementation of the MCAO concepts and control aspects of the instrument and present the road map to the final installation at LBT. Major milestones of LINC-NIRVANA, like preliminary design review or final design review are already done or in preparation. LINC-NIRVANA is one of the few MCAO instruments in the world which will see first light and go into operation within the next years.

Layer Oriented represented in the last few years a new and promising aproach to solve the problems related to the limited field of view achieved by classical Adaptive Optics systems. It is basically a different approach to multi conjugate adaptive optics, in which pupil plane wavefront sensors (like the pyramid one) are conjugated to the same altitudes as the deformable mirrors. Each wavefront sensor is independently driving its conjugated deformable mirror thus simplifying strongly the complexity of the wavefront computers used to reconstruct the deformations and drive the mirror themselves, fact that can become very important in the case of extremely large telescopes where the complexity is a serious issue. The fact of using pupil plane wavefront sensors allow for optical co-addition of the light at the level of the detector thus increasing the SNR of the system and permitting the usage of faint stars, improving the efficiency of the wavefront sensor. Furthermore if coupled to the Pyramid wavefront sensor (because of its high sensitivity), this technique is actually peforming a very efficient usage of the light leading to the expectation that, even by using only natural guide stars, a good sky coverage can be achieved, above all in the case of giant telescopes. These are the main reasons for which in the last two years several projects decided to make MCAO systems based on the Layer Oriented technique. This is the case of MAD (an MCAO demonstrator that ESO is building with one wavefront sensing channel based on the Layer Oriented concept) and NIRVANA (an instrument for LBT). Few months ago we built and successfully tested a first prototype of a layer oriented wavefront sensor and experiments and demonstrations on the sky are foreseen even before the effective first light of the above mentioned instruments. The current situation of all these projects is presented, including the extensive laboratory testing and the on-going experiments on the sky.

We are currently working on four projects employing Multi Conjugate Adaptive Optics in a Layer-Oriented fashion. These ranges from experimental validations, to demonstration facility or full instrument to be offered to an astronomical community and involves telescopes in the range of 4m to 24m equivalent telescope aperture. The current status of these projects along with their brief description is here given.

LINC-NIRVANA is a Fizeau interferometer which will be built for the Large Binocular Telescope (LBT). The LBT exists of two 8.4m mirrors on one mounting with a distance of 22.8m between the outer edges of the two mirrors. The interferometric technique used in LINC-NIRVANA provides direct imaging with the resolution of a 23m telescope in one direction and 8.4m in the other. The instrument uses multi-conjugated adaptive optics (MCAO) to increase the sky coverage and achieve the diffraction limit in J, H, K over a moderate Field of View (2 arcmin in diameter). During the preliminary design phase the team faced several problems similar to those for an instrument at a 23m telescope. We will give an overview of the current design, explain problems related to 20m class telescopes and present solutions.

We present the design of and recent results from the Large Binocular Telescope (LBT) facility SCIDAR. To our knowledge, this work will produce the first SCIDAR designed as a user instrument for routine seeing measurements in support of telescope operations. Using a commercial, off-the-shelf approach, we have minimized the resources required for system construction.

We are currently investigating the possibilities for a high-contrast, adaptive optics assisted instrument to be placed as a 2nd-generation instrument on ESO's VLT. This instrument will consist of an "extreme-ao" system capable of producing very high Strehl ratios, a contrast-enhancing device and two differential imaging detection systems. It will be designed to collect photons directly coming from the surface of substellar companions - ideally down to planetary masses - to bright, nearby stars and disentangle them from the stellar photons.We will present our current design study for such an instrument and discuss the various ways to tell stellar from companion photons. These ways include the use of polarimetric and/or spectroscopic information a's well as making use of knowledge about photon statistics. Results of our latest simulations regarding the instrument will be presented and the expected performance discussed. Derived from the simulated performance we will also give details about the expected science impact of the planet finder. This will comprise the chances of finding different types of exo-planets - notably the dilemma of going for hot planets marginally separated from their parent stars or cold, far-away plamnets delivering very little radiation, the scientific return of such detections and follow-up examinations, as well as other topics like star-formation, debris disks, and planetary nebulae where a high-resolution, high-contrast system will trigger new break-throughs.

We report near-infrared and optical follow-up observations of the afterglow of the GRB 000418 starting 2.5 days after the occurrence of the burst and extending over nearly 7 weeks. GRB 000418 represents the second case for which the afterglow was initially identified by observations in the near-infrared. During the first 10 days its R-band afterglow was well characterized by a single power-law decay with a slope of 0.86. However, at later times the temporal evolution of the afterglow flattens with respect to a simple power-law decay. Attributing this to an underlying host galaxy, we find its magnitude to be R = 23.9 and an intrinsic afterglow decay slope of 1.22. The afterglow was very red with R-K ≈ 4 mag. The observations can be explained by an adiabatic, spherical fireball solution and a heavy reddening due to dust extinction in the host galaxy. This supports the picture that (long) bursts are associated with events in star-forming regions.

We report near-infrared and optical follow-up observations of the afterglow of the Gamma-Ray Burst 000418 starting 2.5 days after the occurrence of the burst and extending over nearly seven weeks. GRB 000418 represents the second case for which the afterglow was initially identified by observations in the near-infrared. During the first 10 days its R-band afterglow was well characterized by a single power-law decay with a slope of 0.86. However, at later times the temporal evolution of the afterglow deviates from this simple power-law decay. Attributing this to an underlying host galaxy we find its magnitude to be R=23.9 and an intrinsic afterglow decay slope of 1.22. The afterglow was very red with R−K ≈4 mag. This color can be forced to agree with the observed power-law decline slope if we assume that the observations were carried out at a time when the light curve was represented by the adiabatic, spherical fireball solution and the afterglow was reddened due to dust extinction in the host galaxy. This supports the picture that (long) bursts are associated with events in star-forming regions. Subject headings: gamma-rays: bursts Based on observations collected at the Bologna Astronomical Observatory in Loiano, Italy; at the TNG, Canary Islands, Spain; at the German-Spanish Astronomical Centre, Calar Alto, operated by the Max-Planck-Institut for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy; at the U. S. Naval Observatory and at the UK Infrared Telescope. Thüringer Landessternwarte Tautenburg, D–07778 Tautenburg, Germany. Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy. US Naval Observatory, Flagstaff station, P.O. Box 1149, Flagstaff, AZ 86002-1149. Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-1911. Astrophysikalisches Institut und UniversitätsSternwarte, Schillergässchen 2, D–07745 Jena, Germany. Danish Space Research Institute, Juliane Maries Vej 30, DK–2100 Copenhagen, Denmark. Laboratorio de Astrof́ısica Espacial y F́ısica Fundamental (LAEFF-INTA), P.O. Box 50727, E–28080 Madrid, Spain. Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, D–85748 Garching, Germany. Max-Planck-Institut für Astronomie, Königstuhl 17, D–69117 Heidelberg, Germany. Instituto de Astrof́ısica de Andalućıa (IAA-CSIC), P.O. Box 03004, E–18080 Granada, Spain. Astrophysikalisches Institut Potsdam, D–14482 Potsdam, Germany. Dipartimento di Astronomia, Universitá di Bologna, Via Ranzani 1, I-40127 Bologna, Italy. Telescopio Nazionale Galileo, Centro Galileo Galilei, Calle Alvarez de Abreu 70, E-38700 Santa Cruz de La Palma, Canary Islands, Spain. University of California at Berkeley, Space Sciences Laboratory, Berkeley, CA 94720-7450. NASA Goddard Space Flight Center, Greenbelt, MD 20771. Applied Physics Laboratory, Johns Hopkins University,

The Max-Planck institutes for astronomy and for extraterrestrial physics run a high order adaptive optics system with a laser guide star facility at the Calar Alto 3.5-m telescope in southern Spain. This system, called ALFA, saw first light in September 1996. Today, ALFA can compensate for atmospheric turbulences with natural guide stars as faint as 13.5th magnitude in R-band. ALFA recently succeeded in overcoming this limiting magnitude with the deployment of its laser guide star. This paper briefly reviews the ALFA project and its progress over the last 3 years. We further discuss the impact of sodium-layer laser guide stars on wavefront sensing and present results obtained with both kinds of guide stars.