Bridging the gap between JWST and ALMA, the far-infrared wavelength range between 30 and 300 micron, contains a wealth of spectral features enabling deep studies of galaxy evolution and planet forming systems. One of the key diagnostic tools used by far-IR astronomers is spectroscopy, employing low resolution (R~100) grating modules to achieve the highest possible spectroscopic sensitivity and mapping speed. The next generation of space missions in this field, as exemplified by the Origins Space Telescope (OST), and recently proposed concepts like the PRIMA, FIRSST and SALTUS, will utilize grating spectrometers combined with ultra-sensitive large-format KID detector arrays. Such grating modules will enable a variety of instrument architectures offering powerful observing capabilities including post-dispersed Fourier Transformation Spectrometer (FTS), long-slit spectroscopic mapping, and high-resolution Fabry-Perot or a Virtually Imaged Phased Array (VIPA) based spectroscopy, where the grating is used for order-sorting. To fully exploit the astronomical potential these instruments require compact, cryogenic and wideband grating spectrometers with a large telecentric field of view.
In this paper we present the opto-mechanical design and realization of a multi-purpose Grating Module Breadboard (GMBB), which supports arbitrary one-octave bandwidth diffraction gratings in the 25-400 micron wavelength band. The purpose of realizing this GMBB is to aid experimental verification of blazed grating developments, and to verify the optical interfaces and spectral characteristics of KID detector arrays.
The driving concepts, methodologies, engineering solutions and finally the realization are discussed and supported by optical verification results. A simple and modular configuration containing a collimator unit and camera bay optics allows for easy adaptation to different wavelength/dispersion combinations by exchanging the grating and/or detector array. The opto-mechanical design is monolithic with highly accurate and reproducible kinematic optical mounts, while allowing mirror realization with the highest optical performance. Special attention is given to the development of grating production methods for high-efficiency blazed gratings optimized for specific wavelength bands.
PLATO (PLAnetary Transits and Oscillations of stars)1 is the M3 class ESA mission dedicated to the discovery
and study of extrasolar planetary systems by means of planetary transits detection. PLATO Payload Camera
units are integrated and vibrated at CSL before being TVAC tested for thermal acceptance and performance
verification at 3 different test facilities (SRON, IAS and INTA). 15 of the 26 Flight Cameras were integrated,
tested and delivered to ESA for integration by the Prime between June 2023 and June 2024, with the remaining
flight units to be tested by the end of 2024. In this paper, we provide an overview of our serial testing approach,
some of the associated challenges, key performance results and an up-to-date status on the remaining planned
activities.
Proposed for a late 2031 launch, PRIMA, the Probe far-Infrared Mission for Astrophysics, closes the gap between JWST and ALMA, offering unprecedented sensitivity and spectroscopic mapping capability in the 24-264 μm range for detailed studies of galactic evolution, planetary atmospheres, and dust-metal dynamics. Onboard PRIMA, the PRIMAger camera operates in the 25-80 μm bands utilizing advanced MKID detector modules for hyperspectral imaging enabled by Linear Variable Filters. This paper presents a graded resonant metal-mesh filter technology, demonstrating very promising efficiency in the short wavelength range. Overcoming dielectric loss limitations, an innovative dual-layer LVF design on thin membranes achieves a transmission of 80-90% at 12 THz. Rigorous electromagnetic modeling, optimization, and position-dependent spectral response measurements validate the filter performance. We present a comprehensive set of simulation and experimental results, including environmental pre-qualification tests, strongly supporting the suitability of this technology for future space applications.
Deposited dielectrics with low mm-submm loss will be of great benefit to on-chip superconducting circuits for mm-submm astronomy. Compared with planar chip designs, multilayer structures with deposited dielectrics allow for more compact circuit elements, and eliminate radiation losses at high frequencies. While recently hydrogenated amorphous silicon carbide has been demonstrated to exhibit low dielectric losses at mm-submm wavelengths, the origin of the mm-submm loss in hydrogenated amorphous silicon carbide remains unknown.
We measured the 270-600 GHz dielectric losses of hydrogenated amorphous silicon carbide in superconducting microstrip lines. Furthermore, we measured the complex dielectric constant of the hydrogenated amorphous silicon carbide in the 3-100 THz range using Fourier transform spectroscopy. We modeled the loss data from 0.27-100 THz using a Maxwell-Helmholtz-Drude dispersion model. Our results demonstrate that phonon modes above 10 THz dominate the mm-submm losses in deposited dielectrics.
Robert Huisman, Marcel Bruijn, Silvia Damerio, Martin Eggens, Syed Naveed Kazmi, Anja E. Schmerbauch, Heino Smit, Marco Vasquez-Beltran, Ewout Van der Veer, Mónica Acuautla, Bayu Jayawardhana, Beatriz Noheda
We present the conceptual design and initial development of the hysteretic deformable mirror (HDM). The HDM is a completely new approach to the design and operation of deformable mirrors (DMs) for wavefront correction in advanced imaging systems. The key technology breakthrough is the application of highly hysteretic piezoelectric material in combination with a simple electrode layout to efficiently define single actuator pixels. The set-and-forget nature of the HDM, which is based on the large remnant deformation of the newly developed piezomaterial, facilitates the use of time division multiplexing to address the single pixels without the need for high update frequencies to avoid pixel drift. This, in combination with the simple electrode layout, paves the way for upscaling to extremely high pixel numbers (≥128 × 128) and pixel density (100 / mm2) DMs, which is of great importance for high spatial frequency wavefront correction in some of the most advanced imaging systems in the world.
In this article the immersed gratings for the ESA Copernicus Sentinel-5 mission are presented. The manufacturing approach is shown and the optical performance of the SWIR-3 immersed gratings as well as the results of the environmental tests are discussed. The immersed gratings show an average efficiency of 60% and a wavefront error of 200 nm rms. The total integrated scatter over the complete stray-light hemisphere excluding ghosts from internal reflections is found to be 0.2% using a conservative estimate. A method for the derivation of the wavefront error from separate surface measurements is presented and the results are compared to measurements with an experimental Shack- Hartmann setup. The immersed gratings are produced by bonding a prism to a wafer with a grating. Environmental tests and testing at operational temperatures show the suitability of this approach for complex space optical components. The article concludes with possible improvements in the optical performance of future immersed gratings.
In context of wavefront control for high-contrast coronagraphy, we present the spectral characterization of speckles generated by deformable mirrors (DMs) at various distances downstream of the pupil plane. We have measured the focal-plane electric field at 600 to 690nm of speckles generated with an in- and out-of-pupil DM on a highcontrast testbed using a self-coherent camera. These measurements are analyzed analytically and are compared to numerical end-to-end simulations of the setup. This will aid in the design of wavefront correction algorithms with multiple DMs.
The Heterodyne Instrument for the Far-Infrared (HIFI) of the ESA cornerstone mission Herschel is required to operate at wavelengths between 157 and 625 μm. Because of the long-wavelength character, and the complexity and modularity of the optical design, there is a clear need for accurate electromagnetic simulations supported by experimental verification. The need for a compact layout in order to reduce mass and volume as far as possible has important optical consequences. Several mirrors are illuminated in the propagating near-field rather than in the far-field. Consequently the classical geometrical design and analysis approach is inadequate. The long-wavelength character of the system can not be ignored and the associated diffraction effects inevitably become important. In this paper we describe the results of electromagnetic simulations of the optical system for band 1 of HIFI at a wavelength of 625 μm. In order to verify the results of the front-to-end coherent propagation of the detector beams, near-field facilities capable of measuring both amplitude and phase of the electromagnetic field have been developed. A unique feature of these facilities is that the absolute coordinates of the measured field components are known within a fraction of a wavelength. Therefore a true comparison with theoretical predictions can be made. We compare measurement data taken at 625 μm with simulations and discuss to what extent measured and simulated results may be expected to agree. We conclude by presenting the consequences of our observations in terms of system performance.
The Mid-infrared E-ELT Imager and Spectrograph, or METIS, is foreseen as an early instrument for the European
Extremely Large Telescope (E-ELT). A key part of METIS is the Cold Chopper (MCC) which switches the optical beam
between the target and a nearby reference sky during observation for characterization of the fluctuating IR background
signal in post-processing. This paper discusses the development and characterization of the realized MCC demonstrator.
The chopper mirror (Ø64mm) should tip/tilt in 2D with a combined angle of up to 13.6mrad with 1.7μrad stability and
repeatability within 5ms (95% duty cycle at 5Hz) at 80K. As these requirements cannot be met in the presence of friction
or backlash, the mirror is guided by a monolithically integrated flexure mechanism. The angular position is actuated by
three linear actuators and measured by three linear position sensors, resulting in a fast tip, tilt, and focus mirror. Using
the third actuator introduces symmetry, and thus homogeneity in forces and heat flux.
In an earlier paper, Ref. [1], the design of the chopper and the breadboard level testing of the key components were
discussed. Since then, the chopper design has been revised to implement the lessons learned from the breadboard test and
a demonstrator has been realized. This demonstrator has undergone an elaborate test program for characterization and
performance validation in a cryogenic environment, as discussed in this paper.
SAFARI is a far-infrared camera to be launched in 2021 onboard the SPICA satellite. SAFARI offers imaging
spectroscopy and imaging photometry in the wavelength range of 34 to 210 μm with detector NEP of 2•10-19 W/√Hz.
A cryogenic test facility for SAFARI on-ground calibration and characterization is being developed. The main design
driver is the required low background of a few attoWatts per pixel. This prohibits optical access to room temperature and
hence all test equipment needs to be inside the cryostat at 4.5K. The instrument parameters to be verified are interfaces
with the SPICA satellite, sensitivity, alignment, image quality, spectral response, frequency calibration, and point spread
function. The instrument sensitivity is calibrated by a calibration source providing a spatially homogeneous signal at the
attoWatt level. This low light intensity is achieved by geometrical dilution of a 150K source to an integrating sphere. The
beam quality and point spread function is measured by a pinhole/mask plate wheel, back-illuminated by a second
integrating sphere. This sphere is fed by a stable wide-band source, providing spectral lines via a cryogenic etalon.
The Mid-infrared E-ELT Imager and Spectrograph, or METIS, is foreseen as the third instrument for the European
Extremely Large Telescope (E-ELT). A key part of METIS is the Cold Chopper (MCC) which switches the optical beam
between the target and a nearby reference sky during observation for elimination of the fluctuating IR background signal
in post-processing. This paper discusses the development of the MCC demonstrator.
The chopper mirror (Ø64mm) has to tip/tilt in 2D with a combined angle of up to 13.6mrad with 1.7μrad stability and
repeatability within 5ms (95% duty cycle at 5Hz) at 80K. As these requirements cannot be met in the presence of friction
or backlash, the mirror is guided by a monolithically integrated flexure mechanism. The angular position is actuated by
three linear actuators and measured by three linear position sensors, resulting in a fast tip, tilt, and focus mirror. Using
the third actuator to introduce symmetry, homogeneity in forces and heat flux is obtained.
Both the actuators and the sensors are key components. A voice coil actuator had to be custom designed, to achieve the
required acceleration force within the specified 1W heat load. The requirements for the displacement measurement can
be met with a commercially available, fiber interferometry system. For integration of this system, stray light elimination
is a critical design aspect and retro-reflectors have been used to reflect sufficient power into the fiber at large tip/tilt
angles.
METIS: "Mid-infrared ELT Imager and Spectrograph" is the mid-infrared (3 - 14 microns) instrument for imaging and
spectroscopy for the European Extremely Large Telescope (E-ELT). To ensure high detection sensitivity the internal
radiation of the instrument needs to be eliminated (sufficiently reduced) and thus needs to be operated at cryogenic
temperatures.
The instrument is divided in a cold and warm system. The cold system, the actual heart of the system, is subdivided into
five main opto-mechanical modules located within a common cryostat (part of the warm system). The warm system
provides the crucial environment for the cold system, including the instrument control and maintenance equipment. The
end 2009 finished Phase-A study carried out within the framework of the ESO sponsored E-ELT instrumentation studies
has been performed by an international consortium with institutes from Netherlands (PI: Bernhard Brandl - NOVA),
Germany, France, United Kingdom and Belgium. During this conference various aspects of the METIS instrument
(design) are presented in several papers, including the instrument concept and science case, and the system engineering
and optical design.
This paper describes the design constraints and key issues regarding the packaging of this complex cryogenic instrument.
The design solutions to create a light, small and fully accessible instrument are discussed together with the specific
subdivision of the cold and warm system to ensure concurrent development at various different institutes around Europe.
In addition the paper addresses the design and development studies for the special, challenging units such as the large
optical image de-rotator, the (2D) chopper mechanism and the special cryogenic drives.
7010-5Thijs de Graauw, Nick Whyborn, Frank Helmich, Pieter Dieleman, Peter Roelfsema, Emmanuel Caux, Tom Phillips, Jürgen Stutzki, Douwe Beintema, Arnold Benz, Nicolas Biver, Adwin Boogert, Francois Boulanger, Sergey Cherednichenko, Odile Coeur-Joly, Claudia Comito, Emmanuel Dartois, Albrecht de Jonge, Gert de Lange, Ian Delorme, Anna DiGiorgio, Luc Dubbeldam, Kevin Edwards, Michael Fich, Rolf Güsten, Fabrice Herpin, Netty Honingh, Robert Huisman, Herman Jacobs, Willem Jellema, Jon Kawamura, Do Kester, Teun Klapwijk, Thomas Klein, Jacob Kooi, Jean-Michel Krieg, Carsten Kramer, Bob Kruizenga, Wouter Laauwen, Bengt Larsson, Christian Leinz, Rene Liseau, Steve Lord, Willem Luinge, Anthony Marston, Harald Merkel, Rafael Moreno, Patrick Morris, Anthony Murphy, Albert Naber, Pere Planesas, Jesus Martin-Pintado, Micheal Olberg, Piotr Orleanski, Volker Ossenkopf, John Pearson, Michel Perault, Sabine Phillip, Mirek Rataj, Laurent Ravera, Paolo Saraceno, Rudolf Schieder, Frank Schmuelling, Ryszard Szczerba, Russell Shipman, David Teyssier, Charlotte Vastel, Huib Visser, Klaas Wildeman, Kees Wafelbakker, John Ward, Roonan Higgins, Henri Aarts, Xander Tielens, Peer Zaal
This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI), to be launched onboard of ESA's Herschel Space Observatory, by 2008. It includes the first results from the instrument level tests. The instrument is designed to be electronically tuneable over a wide and continuous frequency range in the Far Infrared, with velocity resolutions better than 0.1 km/s with a high sensitivity. This will enable detailed investigations of a wide variety of astronomical sources, ranging from solar system objects, star formation regions to nuclei of galaxies.
The instrument comprises 5 frequency bands covering 480-1150 GHz with SIS mixers and a sixth dual frequency band, for the 1410-1910 GHz range, with Hot Electron Bolometer Mixers (HEB). The Local Oscillator (LO) subsystem consists of a dedicated Ka-band synthesizer followed by 7 times 2 chains of frequency multipliers, 2 chains for each frequency band. A pair of Auto-Correlators and a pair of Acousto-Optic spectrometers process the two IF signals from the dual-polarization front-ends to provide instantaneous frequency coverage of 4 GHz, with a set of resolutions (140 kHz to 1 MHz), better than < 0.1 km/s. After a successful qualification program, the flight instrument was delivered and entered the testing phase at satellite level. We will also report on the pre-flight test and calibration results together with the expected in-flight performance.
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