SPHERE (Spectro-Polarimetric High Contrast Exoplanet Research) is one of the first instruments which aim for the direct detection from extra-solar planets. SPHERE commissioning is foreseen in 2013 on the VLT. ZIMPOL (Zurich Imaging Polarimeter) is the high contrast imaging polarimeter subsystem of the ESO SPHERE instrument. ZIMPOL is dedicated to detect the very faint reflected and hence polarized visible light (600-900 nm) from extrasolar planets. It is located behind an extreme AO system (SAXO) and a stellar coronagraph. We present the first high contrast polarimetric results obtained for the fully integrated SPHERE-ZIMPOL system. We have measured the polarimetric high contrast performance of several coronagraphs: a Classical Lyot on substrate, a suspended Classical Lyot and two 4 Quadrant Phase Mask coronagraphs. We describe the impact of crucial system parameters – Adaptive Optics, Coronagraphy and Polarimetry - on the contrast performance.
The imaging polarimeter ZIMPOL is one of three focal plane instruments of the SPHERE / VLT planet finder. ZIMPOL
measures the linear polarization based on a fast modulation – demodulation principle using a charge-shifting technique
on a masked CCD for separating the photons with opposite polarization direction. This paper describes the on-chip
demodulation and the different detector read-out modes which are implemented for the ZIMPOL polarimeter. Test
results are presented which allow an evaluation of the performance of the ZIMPOL CCD detectors. The achievable
polarization efficiency is close to expectation and the charge trap correction with the two-phase demodulation mode
works well. Other detector effects like bias level variations and read-out patterns can be corrected in the data reduction
process. The tests demonstrate that the demodulating CCDs fulfill the requirements for the SPHERE project.
SPHERE (Spectro-Polarimetric High Contrast Exoplanet Research) is one of the first instruments which aim for the
direct detection from extra-solar planets. The instrument will search for direct light from old planets with orbital periods
of several months to several years as we know them from our solar system. These are planets which are in or close to the
habitable zone. ZIMPOL (Zurich Imaging Polarimeter) is the high contrast imaging polarimeter subsystem of the ESO
SPHERE instrument. ZIMPOL is dedicated to detect the very faint reflected and hence polarized visible light from
extrasolar planets. The search for reflected light from extra-solar planets is very demanding because the signal decreases
rapidly with the orbital separation. For a Jupiter-sized object and a separation of 1 AU the planet/star contrast to be
achieved is on the order of 10-8 for a successful detection. This is much more demanding than the direct imaging of
young self-luminous planets. ZIMPOL is located behind an extreme AO system (SAXO) and a stellar coronagraph.
SPHERE is foreseen to have first light at the VLT at the end of 2012. ZIMPOL is currently in the subsystem testing
phase. We describe the results of verification and performance testing done at the NOVA-ASTRON lab. We will give an
overview of the system noise performance, the polarimetric accuracy and the high contrast testing. For the high contrast
testing we will describe the impact of crucial system parameters on the contrast performance. SPHERE is an instrument
designed and built by a consortium consisting of IPAG, MPIA, LAM, LESIA, Fizeau, INAF, Observatoire de Genève,
ETH, NOVA, ONERA and ASTRON in collaboration with ESO.
ZIMPOL is the high contrast imaging polarimeter subsystem of the ESO SPHERE instrument. ZIMPOL is dedicated to
detect the very faint reflected and hence polarized visible light from extrasolar planets. ZIMPOL is located behind an
extreme AO system (SAXO) and a stellar coronagraph. SPHERE is foreseen to have first light at the VLT at the end of
2011. ZIMPOL is currently in the manufacturing, integration and testing phase. We describe the optical, polarimetric,
mechanical, thermal and electronic design as well as the design trade offs. Specifically emphasized is the optical quality
of the key performance component: the Ferro-electric Liquid Crystal polarization modulator (FLC). Furthermore, we
describe the ZIMPOL test setup and the first test results on the achieved polarimetric sensitivity and accuracy. These
results will give first indications for the expected overall high contrast system performance. SPHERE is an instrument
designed and built by a consortium consisting of LAOG, MPIA, LAM, LESIA, Fizeau, INAF, Observatoire de Genève,
ETH, NOVA, ONERA and ASTRON in collaboration with ESO.
SPHERE is a second generation instrument for the Very Large Telescope (VLT) which will aim at directly
detecting the intrinsic flux of young giant exoplanets thanks to a dedicated extreme adaptive optics system
and coronagraphs. Exoplanet detection in the near-infrared will be performed in parallel with an integral
field spectrograph and a differential imager, IRDIS. IRDIS main mode for exoplanet detection will be Dual-
Band Imaging (DBI) where two images are acquired simultaneously at close wavelengths around expected sharp
features in cold planetary objects spectra. We present here the end-to-end simulations performed to obtain
realistic data for IRDIS in DBI mode with temporal evolution of the quasi-static speckle pattern. Data cubes
have been generated to represent 4 hour observations in IRDIS filter pairs for various star magnitudes and planets
at angular separations from 0."2 to 2".0. Using this unique set of data, we present a comparison of various data
analysis methods for high-contrast imaging with IRDIS in DBI mode both in terms of detection limits and of
estimation of the exoplanet flux after speckle noise attenuation.
HiCIAO is a near-infrared, high contrast instrument which is specifically designed for searches and studies for
extrasolar planets and proto-planetary/debris disks on the Subaru 8.2 m telescope. A coronagraph technique
and three differential observing modes, i.e., a dual-beam simultaneous polarimetric differential imaging mode,
quad-beam simultaneous spectral differential imaging mode, and angular differential imaging mode, are used
to extract faint objects from the sea of speckle around bright stars. We describe the instrument performances
verified in the laboratory and during the commissioning period. Readout noise with a correlated double sampling
method is 15 e- using the Sidecar ASIC controller with the HAWAII-2RG detector array, and it is as low as 5 e-
with a multiple sampling method. Strehl ratio obtained by HiCIAO on the sky combined with the 188-actuator
adaptive optics system (AO188) is 0.4 and 0.7 in the H and K-band, respectively, with natural guide stars that
have R ~ 5 and under median seeing conditions. Image distortion is correctable to 7 milli-arcsec level using
the ACS data as a reference image. Examples of contrast performances in the observing modes are presented
from data obtained during the commissioning period. An observation for HR 8799 in the angular differential
imaging mode shows a clear detection of three known planets, demonstrating the high contrast capability of
The ESO planet finder instrument SPHERE will search for the polarimetric signature of the reflected light from
extrasolar planets, using a VLT telescope, an extreme AO system (SAXO), a stellar coronagraph, and an imaging
polarimeter (ZIMPOL). We present the design concept of the ZIMPOL instrument, a single-beam polarimeter
that achieves very high polarimetric accuracy using fast polarization modulation and demodulating CCD detectors.
Furthermore, we describe comprehensive performance simulations made with the CAOS problem-solving
environment. We conclude that direct detection of Jupiter-sized planets in close orbit around the brightest nearby
stars is achievable with imaging polarimetry, signal-switching calibration, and angular differential imaging.
Direct detection and spectral characterization of extra-solar planets is one of the most exciting but also one of the most
challenging areas in modern astronomy. The challenge consists in the very large contrast between the host star and the
planet, larger than 12.5 magnitudes at very small angular separations, typically inside the seeing halo. The whole design
of a "Planet Finder" instrument is therefore optimized towards reaching the highest contrast in a limited field of view and
at short distances from the central star. Both evolved and young planetary systems can be detected, respectively through
their reflected light and through the intrinsic planet emission. We present the science objectives, conceptual design and
expected performance of the SPHERE instrument.
SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) is the second-generation VLT instrument
devoted primarily to direct imaging and characterization of exoplanets, and allowing a large number of promising
observation modes. In this framework, an IDL-based end-to-end numerical tool has been developed within the
problem-solving environment CAOS (or CAOS "system"): the Software Package SPHERE, dedicated to the complete and detailed simulation of the whole instrument. It hence includes detailed instrumental modeling of the extreme adaptive optics system SAXO, the dual-band imaging camera IRDIS, the Integral Field Spectrograph (IFS), and the Zürich IMaging POLarimeter (ZIMPOL). The status of the whole package (which has now reached version 3.0) is exposed. An example of application is also detailed: a sub-system study aspect concerning the near-infrared apodized Lyot coronagraph.
We present a method based on Mueller calculus to calibrate linear polarimetric observations. The key advantages
of the proposed way of calibration are: (1) that it can be implemented in a data reduction pipeline, (2) that it is possible
to do accurate polarimetry also for telescopes/instruments with polarimetric non-friendly architecture (e.g. Nasmyth
instruments) and (3) that the proposed strategy is much less time consuming than standard calibration procedures. The
telescope/instrument will polarimetrically be described by a train of Mueller matrices. The components of these matrices
are dependent on wavelength, incident angle of the incoming light and surface properties.
The result is, that an observer gets the polarimetrically calibrated data from a reduction pipeline. The data will be
corrected for the telescope/instrumental polarisation off-set and with the position angle of polarisation rotated into sky
coordinates. Up to now these two calibration steps were mostly performed with the help of dedicated and time consuming
night-time calibration measurements of polarisation standard stars.
The SPHERE is an exo-solar planet imager, which goal is to detect giant exo-solar planets in the vicinity of bright stars
and to characterize them through spectroscopic and polarimetric observations. It is a complete system with a core made
of an extreme-Adaptive Optics (AO) turbulence correction, pupil tracker and interferential coronagraphs. At its back
end, an Infra-Red Dual-beam Imaging and Spectroscopy science module and an integral field spectrograph work in
the Near Infrared (NIR) Y, J, H and Ks bands (0.95 - 2.32μm) and a high resolution polarization camera covers the
visible (0.6 - 0.9 μm) region. We describe briefly the science goals of the instrument and deduce the top-level
requirements. This paper presents the system architecture, and reviews each of the main sub-systems. The results of the
latest end-to-end simulations are shown and an update of the expected performance is given. The project has been
officially kicked-off in March 2006, it is presently undergoing Preliminary Design Review and is scheduled for 1st
light in early 2011. This paper reviews the present design of SPHERE but focuses on the changes implemented since
this project was presented the last time to this audience.
The Exo-Planets Imaging Camera and Spectrograph (EPICS), is the Planet Finder Instrument concept for the European
Extremely Large Telescope (ELT). The study made in the frame of the OWL 100-m telescope concept is being up-dated
in direct relation with the re-baselining activities of the European Extremely Large Telescope.
We present results from a phase A study supported by ESO for a VLT instrument for the search and investigation of extrasolar planets.
The envisaged CHEOPS (CHaracterizing Extrasolar planets by Opto-infrared Polarization and Spectroscopy) instrument consists of an extreme AO system, a spectroscopic integral field unit and an imaging polarimeter. This paper describes the conceptual design of the imaging polarimeter which is based on the ZIMPOL (Zurich IMaging POLarimeter) technique using a fast polarization modulator combined with a demodulating CCD camera. ZIMPOL is capable of detecting polarization signals on the order of p=0.001% as demonstrated in solar applications. We discuss the planned implementation of ZIMPOL within the CHEOPS instrument, in particular the design of the polarization modulator. Further we describe strategies to minimize the instrumental effects and to enhance the overall measuring efficiency in order to achieve the very demanding science goals.