Direct detection of nearby habitable zone planets using slicer based integral field spectrographs and epics on the E-ELT

Early design studies for the future Exo-Planet Imaging Camera and Specrotgraph (EPICS) on the European Extremely Large Telescope (E-ELT) show the ability to probe the region of super-Earths in the habitable zone of stars within 5pc (including Gilese 581d). However, these planets will be lost to us if the correct choice of integral field spectrograph (IFS) technology is not selected for such an instrument the ability to fit and remove the speckle noise that remains is crucial to reaching these contrasts. We conclusively demonstrate, though the use of an experimental setup producing an artificial speckle, that slicer based IFSs and post-processing using spectral deconvolution can achieve speckle rejection factors exceeding 103. Contrary to popular belief, we do not find any evidence that this choice of IFS technology limits the achievable contrast. Coupled with extreme adaptive optics and high performance coronographs, a slicer based integral field spectrograph could achieve contrasts exceeding 109, enabling these super-Earths to be detected in the habitable zone of nearby stars, making it an attractive option for the next generation of instruments being designed for the direct detection of extra solar planets. Copyright © International Astronomical Union 2014

Coronagraphic capability for HARMONI at the E-ELT

HARMONI is a proposed visible and near-infrared integral field spectrograph for the European Extremely Large Telescope. We are exploring the merits of adding a coronagraphic capability to HARMONI, specifically targeted at enabling observations of faint, nearby companions (primarily extra-solar planets) that require high contrast. Although HARMONI is not fed by extreme adaptive optics, we show that substantial contrasts can be achieved by post-processing of the hyperspectral data cube using spectral deconvolution. We make predictions of achievable contrast as a function of coronagraph design, based on realistic models of the telescope's aberrations. © 2010 Copyright SPIE - The International Society for Optical Engineering

LUCIFER-MOS: A cryogenic multi object infrared spectrograph for the let

LUCIFER-MOS is a liquid nitrogen cooled near infrared multi object spectrograph imaging 20 freely selectable sub-fields of about 2.2" x 1.8" and 6 x 4 image elements each on the entrance slit of the LUCIFER spectrograph. The image elements are re-arranged by 480 fused silica fibers of 50 mu m core diameter and 100 mu m total diameter with integrated, hexagonal lenslets of 0.6 mm width corresponding to a 0.3" field. The pre-optics magnifies the telescope image by a factor 3.3, thus adapting the telescope plate scale to the lenslet scale, and additionally providing a cold stop. The post-optics converts the f/3 fiber output beam to the f/15 beam accepted by the spectrograph. Each of the 20 6 x 4 fiber arrays together with its pre-optics is mounted in a spider arm which can be freely positioned within the 200 mm diameter field of view by a cryogenic robot. The robot performs three rotational movements to position the spider arms and is driven by cold stepper motors. The spider arms are locked in their positions by two permanent magnets each. Their magnetic field can be compensated by coils to unlock the arms and move them across the field of view

Improving the observing efficiency of SINFONI and KMOS at the VLT by factors of 2 to 4: sophisticated sky subtraction algorithms

Accurate subtraction of the bright night sky emission lines in the near-infrared is crucial, given that the object being observed is often several magnitudes fainter than the sky background. Most integral field spectrographs (IFS) have a modest field of view (FoV), and it is often not possible to achieve good sky subtraction by nodding the object within the FoV, as is common practice for long slit spectrographs. In principle, it should be possible to use sky background information from one part of the FoV (typically the periphery) to subtract the sky from all other parts of the IFS FoV. However, this has never been achieved in practice. We show that the reason on-IFU sky subtraction does not work is that the spectrograph spectral response function (line spread function, or LSF) varies strongly with wavelength, position within the field of view, and telescope pointing (flexure). By micro-stepping the grating of the SINFONI IFS at the ESO-VLT, we have been able to hyper-sample the spectral PSF and reconstruct detailed LSF profiles for all wavelengths and all field points for SINFONI H band data. Using this information, we can conclusively demonstrate improvements in observing efficiency by over a factor of two. Our technique not only removes the need for separate sky exposures, but can also improve the noise of the sky background measurement itself, providing further potential gain over pairwise frame subtraction. We explain our algorithms, including non-parametric descriptions of the LSF, and present the results from applying our method to archival SINFONI data. © 2012 SPIE

High-contrast observations with slicer-based integral field spectrographs 1: Simulations

As part of the Phase A study for the EPICS instrument, we investigate if there are any contrast limitations imposed by the choice of the integral field spectrograph (IFS) technology, and if so, to determine the contrast limits applicable to each technology. In this document we investigate (through simulations) the contrast limitations inherent in a slicer based IFS. Current results show the achievable contrast with the slicer to be promising when taking into consideration the fact that the central region of the apodized PSF has not been masked. Limiting the maximum intensity by a factor of 100-1000 using an obscuring focal plane mask should also reduce the intensity of the secondary speckles by an equivalent factor. Furthermore, the secondary speckles created in the slicer spectrograph only influence the few slices where the bright central core is imaged. By orienting these slices to lie along the spider arms of the E-ELT secondary, the fraction of the field of view affected can be minimized. © 2010 Copyright SPIE - The International Society for Optical Engineering

Opto-mechanical design of the KMOS spectrograph module - art. no. 62694G

We present the optical and mechanical design of the KMOS spectrograph module together with a detailed analysis of its performance. KMOS is a cryogenic near-infrared multi-object spectrograph being developed as a second-generation instrument for the VLT by a consortium of UK and German institutes. Three identical spectrograph modules provide Nyquist sampled spectra in the wavelength range covering the atmospheric bands z, J, H, and K with a resolving power exceeding 3200. The spectrographs are fully achromatic over the bands and the single mirror collimator and six-element camera, together with six high efficiency gratings provide high throughput. The optical performance analysis includes amongst others the spectral resolving power and variation of the PSF as a function of the pupil illumination

KMOS: an infrared multiple object integral field spectrograph for the ESO VLT

We describe the design of a 2nd generation instrument for the ESO VLT which will deliver a unique multiple deployable integral field capability in the near-infrared (1-2.5μm). The science drivers for the instrument are presented and linked to the functional specification. The baseline instrument concept is described with emphasis on technological innovations. Detailed discussions of specific technologies, and ongoing prototype studies, are described in separate papers