In this paper, the new coronagraph that will be mounted at the Pic du Midi Observatory (IMCCE - T1m telescope) is presented. To optimize the occulting process of a Lyot coronagraph, a compressed mercury (Hg) drop is used as an occulting disk and its size control offers an adaptation to the seeing conditions or to the Airy diameter fraction needed. In addition to the Hg-mask, a variation on the theme is proposed by a diameter and wavelength adaptive phase mask made of a gas bubble in immersion oil between two optical windows. The instrument concept offers a good versatility to test other mask type and pupil apodization techniques.

The Keck Interferometer Nuller (KIN) is one of the major scientific and technical precursors to the Terrestrial Planet Finder Interferometer (TPF-I) mission. KIN's primary objective is to measure the level of exo-zodiacal mid-infrared emission around nearby main sequence stars, which requires deep broad-band nulling of astronomical sources of a few Janskys at 10 microns. A number of new capabilitites are needed in order to reach that goal with the Keck telescopes: mid-infrared coherent recombination, interferometric operation in “split pupil” mode, N-band optical path stabilization using K-band fringe tracking and internal metrology, and eventually, active atmospheric dispersion correction. We report here on the progress made implementing these new functionalities, and discuss the initial levels of extinction achieved on the sky.

We discuss the instrumental and data reduction techniques used to suppress speckle noise with the Simultaneous Differential Imager (SDI) implemented at the VLT and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 $\mu$m methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be significantly attenuated, resulting in photon noise limited data. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our survey of nearby young stars at the VLT and MMT (see Biller et al., this conference), we achieved H band contrasts >25000 (5$\sigma \Delta$F1(1.575 $\mu$m) >10.0 mag, $\Delta$H$\,{>}\,$11.5 mag for a T6 spectral type object) at a separation of 0.5” from the primary star. We believe that our SDI images are among the highest contrast astronomical images ever made from ground or space for methane rich companions.

Here we examine the visible spectra of giant planets in anticipation of the science return of missions like the Terrestrial Planet Finder-Coronagraph and proposed Discovery class space coronagraph missions EPIC and ECLIPSE. Our understanding of extrasolar giant planets is already greatly improving because of our studies of old brown dwarfs (which have effective temperatures similar to young giant planets), transiting hot Jupiters, and the planet Jupiter itself. The first data collected on Jupiter-like extrasolar giant planets will likely consist of magnitudes in a few filters or very low resolution spectra. We investigate diagnostics for determining planetary effective temperature, atmospheric chemical abundances, cloud cover, and mass using such limited data. In general, giant planet science is improved significantly if missions in the visible domain extend to wavelengths as long as possible, within engineering constraints.

Ground and space based coronagraphs have been proposed to suppress the light of the star so a planet nearby can be imaged. But even when starlight has been suppressed by $10^{10}$, the residual starlight is as bright as the planet, and must be subtracted to $2*10^{-11}$ for a 5 sigma detection of the planet. For a ground based AO coronagraph, the problem is even more severe. Typically suppression of starlight to $10^{-5}$ of the star is possible and the residual speckle pattern must not have any “bumps” that mimic a planet at $10^{-7}-10^{-8}$. This paper describes a speckle calibration approach that measures the electric field of the light after it exits the coronagraph, in order to estimate the speckle pattern in the image plane. This technique makes use of the coherence of star light or rather the incoherence of starlight to planet light, and has very significant advantages compared to other techniques.

For a space based coronagraph, an alternative approach is to rotate the telescope /coronagraph and subtract two images. The calibration interferometer described here has the advantage that the temporal stability of the system can be relaxed by several orders of magnitude. For a ground based AO coronagraph system this approach has none of the serious limitations of the techniques based on the radial expansion of the speckle pattern with wavelength and enables ground based AO coronagraphs to approach the photon limit rather than the atmospheric limit. The calibration interferometer is being built for a NASA sounding rocket experiment by BU, JPL, MIT, and GSFC (PICTURE) with a 50cm telescope and a nulling coronagraph to be launched in 2007. It is also part of a design study for an extreme AO coronagraph for the Gemini Telescope, and a conceptual study of an extreme AO coronagraph for the TMT.

We describe the baseline TPF-C instrument design as of October 2005.

This paper summarizes the general theory and properties for Apodized Pupil Lyot Coronagraphs which consist of a classical hard-edged Lyot coronagraph with an upstream pupil apodization. The ideal apodization function can be determined from an integral eigenvalue problem which solutions are prolate spheroidal functions. Solutions exist for any geometrty, including rectangular, circular, or elliptical. Formal solutions can be extended to the case of arbitrary apertures, using generalized prolate spheroidal functions for centrally obstructed apertures, spiders, or segmented telescopes. The properties of these coronagraphs enable the possibility of multiple stage coronagraphy and achromatization. The new instrument Gemini Planet Imager (GPI) will include such a coronagraph.

Following the tracks of Malbet, Yu, & Shao (1995) on dark hole algorithms, we present analytical methods to measure and correct the speckle noise behind an ideal coronagraph. We show that, in a low aberration regime, wavefront sensing can be accomplished with only three images, the next image being fully corrected (no iterative process needed). The only hardware required is the coronagraph deformable mirror and an imaging detector in the focal plane, thus there are no non-common path errors to correct. Our first method, speckle field nulling, is a fast FFT-based algorithm requiring the deformable mirror influence functions to have identical shapes. Our second method, speckle energy minimization is more general and based on matrix inversion. Numerical simulations show that these methods can improve the contrast by several orders of magnitude.

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for a spacecraft-borne imaging and nulling interferometer for the near to mid-infrared spectral region. FKSI is a scientific and technological pathfinder to the Darwin and Terrestrial Planet Finder (TPF) missions and will be a high angular resolution system complementary to the James Webb Space Telescope (JWST). There are four key scientific issues the FKSI mission is designed to address. These are: 1.) characterization of the atmospheres of the known extra-solar giant planets, 2.) assay of the morphology of debris disks to look for resonant structures characteristic of the presence of extrasolar planets, 3.) study of circumstellar material around a variety of stellar types to better understand their evolutionary state, and in the case of young stellar systems, their planet forming potential, and 4.) measurement of detailed structures inside active galactic nuclei. We report results of simulation studies of the imaging capabilities of the FKSI, current progress on our nulling testbed, results from control system and residual jitter analysis, and selection of hollow waveguide fibers for wavefront cleanup.

We report 320 to 1020nm disk-averaged Earth reflectance spectra obtained from Moon's Earthshine observations with the EMMI spectrograph on the NTT at ESO La Silla (Chile). The spectral signatures of Earth atmosphere and ground vegetation are observed. A vegetation red-edge of up to 9% is observed on Europe and Africa and ${\approx}2%$ upon Pacific Ocean. The spectra also show that Earth is a blue planet when Rayleigh scattering dominates, or totally white when the cloud cover is large.

Direct detection and spectral characterization of extrasolar planets is one of the most exciting but also one of the most challenging area in modern astronomy. For its second generation instrumentation on the VLT, ESO has supported two phase A studies for a so-called “Planet Finder” dedicated instrument. Based on the results of these two studies, a unique instrument is now considered for first light in early 2010, including a powerful extreme adaptive optics system, various coronagraphs, an infrared differential imaging camera, an infrared integral field spectrograph and a visible differential polarimeter. We will briefly summarize the science objectives and requirements, describe the proposed conceptual design and discuss the main limitations and corresponding instrumental issues of such a system. We will also derive the expected performance of the proposed Planet Finder and present the project organization.

Adaptive optics (AO) systems have significantly improved astronomical imaging capabilities over the last decade, and are revolutionizing the kinds of science possible with 4-5 m class ground-based telescopes. A thorough understanding of AO system performance at the telescope can enable new frontiers of science as observations push AO systems to their performance limits. We look at the understanding we have gained from recent Lyot Project images at the Advanced Electro-Optical System (AEOS) 3.6 m telescope to show how progress made in improving WFR can be measured directly in improved science images. We describe how wave front errors affect the AO point-spread function (PSF), and model details of AEOS AO to simulate a PSF which matches the actual AO PSF in the astronomical H-band. Finally, we estimate the impact of improvements to wave front reconstruction techniques on diffraction-limited coronagraphy with the Lyot Project near-infrared coronagraph.

As of early $\sim$2010's, the Japanese SPace Infrared telescope for Cosmology and Astrophysics (SPICA) space observatory will be launched. This actively cooled, cryogenic (4.5K), 3.5m telescope will operate in the mid and far infrared spectral regions. With its very high sensitivity, one of SPICA's aims will be the direct detection and characterization of extra-solar outer planets of nearby stars. The goal contrast ranges from $10^5$ to $10^6$ up to an angular separation of ${\sim}5$ arcsec. The relatively low angular resolution at MIR (5 to 20 $\mu$m) requires an efficient and robust coronagraphic mode working at cryogenic temperatures. In this presentation we describe several envisaged preliminary designs and assess their performance against the science goals and host telescope specifications. These are compared against numerical simulations and instrumental environment considerations, such as the need for an actively corrected wavefront.

We compute theoretical infrared light curves for several known extrasolar planets. We have constructed a set of routines to calculate the orbital parameters for a given planet and integrate over the planetary disk to determine the total flux density of the planet as it orbits the parent star. We have further developed a spectral synthesis routine to calculate theoretical spectra of extrasolar giant planets from 3–24 $\mu$m. The code requires a temperature-pressure profile as input, calculated by solving the radiative transfer equation; it then calculates continuous opacities and line opacities for water, carbon monoxide, and methane, and finally integrates over the layers of the atmosphere to determine the emergent flux. By integrating the theoretical spectrum over the bandpass of a particular instrument and including realistic instrument noise, we produce a set of multi-wavelength, infrared light curves. Using these light curves, we predict whether a particular known planet can be observed and characterized using the Spitzer Space Telescope, as well as other proposed space-based instruments, such as the Fourier-Kelvin Stellar Interferometer (FKSI) and the James Webb Space Telescope (JWST).

We present two new phase mask coronagraphs implemented with subwavelength diffractive optical elements. The first one is an evolution of the four quadrant phase mask coronagraph (FQPM), which resolves the $\pi$ phase shift chromaticity issue: the four quadrant zeroth order grating (4QZOG). The second one is a totally new design consisting of an optical vortex induced by a space-variant grating: the annular groove phase mask (AGPM) coronagraph is fully symmetric and free from any “shaded zones”. The potential performances of the 4QZOG and AGPM coronagraph are very good, ensuring, for instance, a theoretical contrast of $1.4 \times 10^{-7}$ at 3$\lambda/D$ over the whole K band. These coronagraphs could be used alone on single-pupil telescopes either in space or on the ground (with an adaptive optics system) to detect exoplanets.

This paper presents the scientific case for a next generation adaptive optics instrument at the VLT, temporarily named “Planet Finder”, that is aimed at detecting and characterizing extrasolar planets through the direct analysis of their emitted photons in the visible and at near-IR wavelengths. We discuss the observational niche of such an instrument to have first light in 2010, in complement to other planet search methods. To improve the efficiency (and consistency) of the search for planets with the PF, the observations will need to be organized in the form of an extensive survey of hundreds of nearby stars, predicted outputs of which are also described here. This summarizes the study phase of the instrument, conducted by two competitive teams and the recent merging of both studies, regarding the scientific impact of Planet Finder.

We study the application of a predictive control law based on a Kalman filter for an extreme adaptive optics system. In particular, we discuss the minimization of temporal error and show the evolution of prediction errors with the order of the model. We also discuss the choice of the optimal temporal frequency as a function of the control law and the level of noise. Finally, the gain expected with respect to a non-predictive law is presented.

In this communication, we study the statistical properties of the light intensity in direct and coronagraphic images, in the context of ground-based Extreme Adaptive Optics observations. The same approach can also be used for space observations with different scales. We show that a coronagraph only affects the perfect part of the wave and leaves the uncorrected part of the wavefront almost unaffected. This statistical model can explain the ‘speckle pinning’ effect (presence of speckles at the position of the diffraction rings), as an amplification of the speckle noise. This statistical approach can be verified on real adaptive optics data.

As we prepare to undertake the observational search for extrasolar terrestrial planets, theoretical modeling studies can help to prepare us for the likely diversity of the extrasolar terrestrial planets. This diversity may arise as a function of planetary system architecture and formation history, which results in a variety of initial planetary properties, as well as stellar, planetary and biological evolutionary processes. Modeling of the physical and chemical processes of the planetary environment, and their interaction with the parent star, allows us to understand the nature of the planetary characteristics that indicate habitability and life, and how these manifest in the planetary spectra. Here we present disk-averaged spectra of planets in our own solar system, and models of the Earth through several eons to understand the types of planetary characteristics that are likely to be observed by planned planet detection and characterization missions.

This communication is devoted to data processing of images obtained using an extreme adaptive optics (AO) system and a coronagraph. Specific attention is given to the following degrading factors: the residuals of atmospheric turbulence after AO correction and the “side” effects of the coronagraph. Relying on a statistical modeling of the measurements a test based on short exposure images is proposed. This processing, which generalizes the dark-speckle technique, takes into account the “local” variance of the complex amplitude residuals and the deterministic response of the system (i.e. without atmospheric turbulence).