Publications (10)0 Total impact
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Article: Innovative Technologies for Optical and Infrared Astronomy
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ABSTRACT: Advances in astronomy are often enabled by adoption of new technology. In some instances this is where the technology has been invented specifically for astronomy, but more usually it is adopted from another scientific or industrial area of application. The adoption of new technology typically occurs via one of two processes. The more usual is incremental progress by a series of small improvements, but occasionally this process is disruptive, where a new technology completely replaces an older one. One of the activities of the OPTICON Key Technology Network over the past few years has been a technology forecasting exercise. Here we report on a recent event which focused on the more radical, potentially disruptive technologies for ground-based, optical and infrared astronomy.07/2012; -
Article: Optical performance of the JWST MIRI flight model: characterization of the point spread function at high-resolution
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ABSTRACT: The Mid Infra Red Instrument (MIRI) is one of the four instruments onboard the James Webb Space Telescope (JWST), providing imaging, coronagraphy and spectroscopy over the 5-28 microns band. To verify the optical performance of the instrument, extensive tests were performed at CEA on the flight model (FM) of the Mid-InfraRed IMager (MIRIM) at cryogenic temperatures and in the infrared. This paper reports on the point spread function (PSF) measurements at 5.6 microns, the shortest operating wavelength for imaging. At 5.6 microns the PSF is not Nyquist-sampled, so we use am original technique that combines a microscanning measurement strategy with a deconvolution algorithm to obtain an over-resolved MIRIM PSF. The microscanning consists in a sub-pixel scan of a point source on the focal plane. A data inversion method is used to reconstruct PSF images that are over-resolved by a factor of 7 compared to the native resolution of MIRI. We show that the FWHM of the high-resolution PSFs were 5-10% wider than that obtained with Zemax simulations. The main cause was identified as an out-of-specification tilt of the M4 mirror. After correction, two additional test campaigns were carried out, and we show that the shape of the PSF is conform to expectations. The FWHM of the PSFs are 0.18-0.20 arcsec, in agreement with simulations. 56.1-59.2% of the total encircled energy (normalized to a 5 arcsec radius) is contained within the first dark Airy ring, over the whole field of view. At longer wavelengths (7.7-25.5 microns), this percentage is 57-68%. MIRIM is thus compliant with the optical quality requirements. This characterization of the MIRIM PSF, as well as the deconvolution method presented here, are of particular importance, not only for the verification of the optical quality and the MIRI calibration, but also for scientific applications. Comment: 13 pages, submitted to SPIE Proceedings vol. 7731, Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave06/2010; -
Article: Wavelength calibration of the JWST-MIRI medium resolution spectrometer
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ABSTRACT: We present the wavelength and spectral resolution characterisation of the Integral Field Unit (IFU) Medium Resolution Spectrometer for the Mid-InfraRed Instrument (MIRI), to fly onboard the James Webb Space Telescope in 2014. We use data collected using the Verification Model of the instrument and develop an empirical method to calibrate properties such as wavelength range and resolving power in a portion of the spectrometer's full spectral range (5-28 microns). We test our results against optical models to verify the system requirements and combine them with a study of the fringing pattern in the instrument's detector to provide a more accurate calibration. We show that MIRI's IFU spectrometer will be able to produce spectra with a resolving power above R=2800 in the wavelength range 6.46-7.70 microns, and that the unresolved spectral lines are well fitted by a Gaussian profile. Comment: 12 pages, submitted to SPIE Proceedings vol. 7731, Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave06/2010; -
Article: Extreme Adaptive Optics in the mid-IR: The METIS AO system
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ABSTRACT: Adaptive Optics at mid-IR wavelengths has long been seen as either not necessary or easy. The impact of atmospheric turbulence on the performance of 8-10 meter class telescopes in the mid-IR is relatively small compared to other performance issues like sky background and telescope emission. Using a relatively low order AO system, Strehl Ratios of larger than 95% have been reported on 6-8 meter class telescopes. Going to 30-42 meter class telescopes changes this picture dramatically. High Strehl Ratios require what is currently considered a high-order AO system. Furthermore, even with a moderate AO system, first order simulations show that the performance of such a system drops significantly when not taking into account refractivity effects and atmospheric composition variations. Reaching Strehl Ratios of over 90% at L, M and N band will require special considerations and will impact the system design and control scheme of AO systems for mid-IR on ELTs. In this paper we present an overview of the effects that impact the performance of an AO system at mid-IR wavelengths on an ELT and simulations on the performance and we will present a first order system concept of such an AO system for METIS, the mid-IR instrument for the E-ELT. Comment: 5 pages, 7 figures; Proceedings of the AO4ELT Conference, Paris, France (22-26 June 2009)09/2009; -
Article: Mid-Infrared Instrumentation for the European Extremely Large Telescope
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ABSTRACT: MIDIR is the proposed thermal/mid-IR imager and spectrograph for the European Extremely Large Telescope (E-ELT). It will cover the wavelength range of 3 to at least 20 microns. Designed for diffraction-limited performance over the entire wavelength range, MIDIR will require an adaptive optics system; a cryogenically cooled system could offer optimal performance in the IR, and this is a critical aspect of the instrument design. We present here an overview of the project, including a discussion of MIDIR's science goals and a comparison with other infrared (IR) facilities planned in the next decade; top level requirements derived from these goals are outlined. We describe the optical and mechanical design work carried out in the context of a conceptual design study, and discuss some important issues to emerge from this work, related to the design, operation and calibration of the instrument. The impact of telescope optical design choices on the requirements for the MIDIR instrument is demonstrated. Comment: for publication in SPIE Proceedings vol. 6692, Cryogenic Optical Systems and Instrumentation XII, eds. J.B. Heaney and L.G. Burriesci, San Diego, Aug 200708/2007; -
Article: Instrument concept and science case of the mid-IR E-ELT imager and spectrograph METIS
SPIE, v.7735 (2010). -
Article: A Direct Measurement of Atmospheric Dispersion in N-band Spectra: Implications for Mid-IR Systems on ELTs
http://dx.doi.org/10.1051/ao4elt/201005019. -
Article: Modeling the Chromatic Correction Error in Adaptive Optics: Application to the Case of Mid-Infrared Observations in Dry to Wet Atmospheric Conditions
http://dx.doi.org/10.1051/ao4elt/201005021. -
Article: METIS: system engineering and optical design of the mid-infrared E-ELT instrument
Proc. SPIE, v.7735 (2010). -
Article: The METIS AO system: bringing extreme adaptive optics to the mid-IR
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ABSTRACT: METIS (Mid-infrared E-ELT Imager and Spectrometer) is the mid-infrared instrument proposed for the European Extremely Large Telescope (E-ELT). METIS will be the first instrument in the mid-IR that will actually require an Adaptive Optics system in order to reach a performance close to the diffraction limit. Extending Adaptive Optics for the mid-IR from the current generation of telescopes to 30-42 meter telescopes is technically challenging, but appears at first sight significantly easier than at visible and near infrared wavelengths. Adaptive Optics has been demonstrated to deliver Strehl Ratios exceeding 95% on 6-8 meter class telescopes at 10 microns, but achieving this performance on E-ELTs under normal observation conditions, requires that several higher order effects are taken into account. The performance of a mid-IR AO system drops significantly if refractivity effects and atmospheric composition variations are not compensated. Reaching Strehl Ratios of over 90% in the L, M and N band will require special considerations and will impact the system design and control scheme of AO systems for mid-IR on ELTs. The METIS instrument has finalized its preliminary design phase and in this paper we present the results of our performance estimates of the METIS AO system. We have included the effects of refractivity and composition fluctuations on the performance of the AO system and we have investigated how these effects impact the science cases for mid-IR instrumentation on an ELT.Ellerbroek, Brent L.; Hart, Michael; Hubin, Norbert; Wizinowich, Peter L.: Adaptive Optics Systems II, SPIE, 77363G-77363G-10 (2010).
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Institutions
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2010
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Universiteit Leiden
Leiden, South Holland, Netherlands
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