Preliminary optical design for the common fore optics of METIS

METIS is the Mid-infrared E-ELT Imager and Spectrograph, which will provide outstanding observing capabilities, focusing on high angular and spectral resolution. It consists of two diffraction-limited imagers operating in the LM and NQ bands respectively and an IFU fed diffraction-limited high-resolution (R=100,000) LM band spectrograph. These science subsystems are preceded by the common fore optics (CFO), which provides the following essential functionalities: calibration, chopping, image de-rotation, thermal background and stray light reduction. We show the evolution of the CFO optical design from the conceptual design to the preliminary optical design, detail the optimization steps and discuss the necessary trade-offs

High-Performance Motion Control of the METIS Cold Chopper Mechanism

We present the main results of the performance test campaign of the Mid-Infrared European Extremely Large Telescope Imager and Spectrograph (METIS) Cold Chopper Demonstrator (MCCD). This tip/tilt mirror, which operates at a temperature of 77 K, is one of the critical components in the METIS for the European Extremely Large Telescope. The performance requirements of the MCCD relate to the field of fast and very accurate reference tracking. We discuss the applicability of different high-performance motion control strategies and describe the control synthesis of a repetitive and of a novel hybrid controller. We identified the presence of nonlinearities in the plant, which limits the performance of the hybrid controller. The repetitive controller shows very promising results and can handle the nonlinearities in the system. This experimental phase concludes the MCCD program, which was initiated to verify the feasibility of a high-performance cryogenic tip/tilt mirror at an early stage in the METIS development. Because of the very promising test results, no significant changes to the hardware will be implemented. We believe that minor adjustments will suffice to meet all requirements of the final hardware after integration with the METIS instrument.Astrodynamics & Space Mission

The Mid-Infrared Instrument for the James Webb Space Telescope, VI: The Medium Resolution Spectrometer

We describe the design and performance of the Medium Resolution Spectrometer (MRS) for the JWST-MIRI instrument. The MRS incorporates four coaxial spectral channels in a compact opto-mechanical layout that generates spectral images over fields of view up to 7.7 × 7.7" in extent and at spectral resolving powers ranging from 1300 to 3700. Each channel includes an all-reflective integral field unit (IFU): an "image slicer" that reformats the input field for presentation to a grating spectrometer. Two 1024 × 1024 focal plane detector arrays record the output spectral images with an instantaneous spectral coverage of approximately one third of the full wavelength range of each channel. The full 5-28.5 mum spectrum is then obtained by making three exposures using gratings and pass-band-determining filters that are selected using just two three-position mechanisms. The expected on-orbit optical performance is presented, based on testing of the MIRI Flight Model and including spectral and spatial coverage and resolution. The point spread function of the reconstructed images is shown to be diffraction limited and the optical transmission is shown to be consistent with the design expectations.published in PASP, vol. 127, issue 953, pp.623-632, 2015status: publishe

The wide field monitor onboard the Chinese-European x-ray mission eXTP

The eXTP (enhanced X-ray Timing and Polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS), with a large involvement of Europe. The scientific payload of eXTP includes four instruments: the SFA (Spectroscopy Focusing Array) and the PFA (Polarimetry Focusing Array) - led by China - the LAD (Large Area Detector) and the WFM (Wide Field Monitor) - led by Europe (Italy and Spain). They offer a unique simultaneous wide-band X-ray timing and polarimetry sensitivity. The WFM is a wide field X-ray monitor instrument in the 2-50 keV energy range, consisting of an array of six coded mask cameras with a field of view of 180ºx90ºat an angular resolution of 5 arcmin and 4 silicon drift detectors in each camera. Its unprecedented combination of large field of view and imaging down to 2 keV will allow eXTP to make important discoveries of the variable and transient X-ray sky and is essential in detecting transient black holes, that are part of the primary science goals of eXTP, so that they can be promptly followed up with other instruments on eXTP and elsewhere

The enhanced x-ray timing and polarimetry mission – eXTP: an update on its scientific cases, mission profile and development status

The enhanced x-ray timing and polarimetry mission (eXTP) is a flagship observatory for x-ray timing, spectroscopy and polarimetry developed by an international consortium. Thanks to its very large collecting area, good spectral resolution and unprecedented polarimetry capabilities, eXTP will explore the properties of matter and the propagation of light in the most extreme conditions found in the universe. eXTP will, in addition, be a powerful x-ray observatory. The mission will continuously monitor the x-ray sky, and will enable multi-wavelength and multi-messenger studies. The mission is currently in phase B, which will be completed in the middle of 2022