MICADO, a Multi-AO Imaging Camera for Deep Observations, is a first light imager for the European Large Telescope (ELT). It is being designed and built by a consortium of partners from 6 different countries across Europe and led by the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching. The European Southern Observatory (ESO) is responsible for delivering the near infrared detector subsystem to the instrument. This subsystem includes nine Hawaii-4RG-15 (H4RG-15) near infrared detectors (2.5μm cut-off) mounted in a compact 3x3 mosaic at the heart of the instrument. They will operate at a nominal temperature of 82K using an array of cryogenic preamplifiers located at the back of the focal plane plate, close to the detectors. This paper presents an overview of this detector subsystem, including the measured performance of two of the H4RG-15 science detectors already characterised in a custom-built test facility at ESO. Special readout modes have been developed for the instrument and for AO corrections to one of the ELT mirrors and these are described. The design of the focal plane, its thermal analysis and the focal plane flatness measurement system being setup at ESO is also presented. This paper also provides a brief description of the new detector controllers (NGCII) being developed at ESO for all the ELT and future VLT (Very Large Telescope) science detector systems and presents the specific controller configuration which must be implemented for the MICADO detectors.
The METIS instrument (Mid-infrared ELT Imager and Spectrograph) is one of the three first-light instruments for the ELT. It will work in the mid-infrared with a set of four different focal planes, grouped in three different subsystems: the imager (IMG) and the spectrograph (LMS) are the two scientific focal planes, and the last one, SCAO, is the dedicated adaptive optics system. In total, this instrument requires five H2RG detectors (5.3μm cutoff), one SAPHIRA detector (2.5μm) and one GEOSNAP (13.5μm). All of these detectors will be controlled by the New General Controller, second generation (NGCII). These three separate subsystems require specific tests and development : the IMG needs a fast readout for both N and LM channels, the LMS requires a mosaic of four detectors and SCAO works with one single detector operated fast for AO corrections. In this paper, we will present the challenges for the development of the detector systems of the three detector subunits in METIS. This includes the design, tests and preparations for the AIT/AIV phases that each subsystem has to go through. First, we describe the detector-specifics of all the instruments. In a second part, we go over the design challenges for these detector subunits. In the end, we will report on the current testing.
Common-mode choke inductors are useful tools for resolving grounding issues in large detector systems. Using inductive components on cryogenic pre-amplifier boards has so far been prevented by the poor low-temperature performance of common ferrite materials such as NiZn and MnZn. Recently developed nanocrystalline and amorphous ferrite materials promise improved performance up to the point where using magnetics at liquid nitrogen temperatures becomes feasible. This research applies the work of Yin et al. on characterizing ferrite materials by constructing and testing a common mode choke inductor for use on detector pre-amplifiers for the ELT first generation instruments.
Enrico Marchetti, Paola Amico, Martin Brinkmann, Ralf Conzelmann, Diego Del Valle, Nicola Di Lieto, Max Engelhardt, Christoph Geimer, Josh Hopgood, Ignacio Molina, Eric Mueller, Jutta Quentin, Javier Reyes, Mathias Richerzhagen, Matthias Seidel, Joerg Stegmeier, Mirko Todorovic
The development of the ESO’s ALICE and LISA wavefront sensor cameras is approaching its conclusion.
The cameras will serve the ELT and VLT telescopes and their instrumentation for a variety of wavefront sensing applications: they are built around a common set of components with the only difference being the customizable frontends to support the different type of detector and they have been designed to be fully embedded in the ELT network and control infrastructure.
In this paper we will present a quick overview of the design and the performance of the two cameras as a results of the final review of the compliance to their respective set of requirements and interfaces.
The scientific detector systems for the ESO ELT first-light instruments, HARMONI, MICADO, and METIS, together will require 27 science detectors: seventeen 2.5 μm cutoff H4RG-15 detectors, four 4K x 4K 231-84 CCDs, five 5.3 μm cutoff H2RG detectors, and one 13.5 μm cutoff GEOSNAP detector. This challenging program of scientific detector system development covers everything from designing and producing state-of-the-art detector control and readout electronics, to developing new detector characterization techniques in the lab, to performance modeling and final system verification. We report briefly on the current design of these detector systems and developments underway to meet the challenging scientific performance goals of the ELT instruments.
One of the critical components of the AO systems are the WFS detectors that have very challenging requirements of high Quantum Efficiency (QE), and low read noise at high read out speeds. For several years now, ESO has been very active in gathering requirements, planning, and developing detectors and controllers/cameras for the AO systems of the telescope and instruments of the ELT. There cameras are in development: ALICE, LISA and FREDA. For ALICE and LISA, a single camera design approach is being followed with the only difference being the customizable front-ends to support the different type of detector. For the FREDA camera, a different approach is being followed: C-RED One cameras are being procured from First Light Imaging and will be modified by ESO to comply with ELT standards. An update on the progress of this development and measured results of camera test will be provided.
Global coverage of internet access is essential for digitalization in society, becoming a disruptive technology in industry, education or political participation for example. Satellite communications is a complementary approach to the terrestrial fiber network, which can provide world-wide coverage with few satellites in geostationary orbit or with low-earth-orbit constellations. Optical wavelengths offer multiple THz of available spectrum that can be used to connect satellites to the ground network with high-throughput links, solving the radiofrequency bandwidth bottleneck, without regulations. Cloud covereage and atmospheric turbulence are the main challenge in guaranteeing the same availability as in terrestrial fiber-based systems. While the former can be addressed by site diversity, for the latter, other mitigation strategies are required. Adaptive optics is a common approach to correct for atmospheric phase distortions and ensure stable fiber coupling. However, this approach requires a relatively complex active setup and therefore a collaboration between DLR Institute of Communications and Navigation and Cailabs has been formed to investigate alternative passive solutions for low-complexity ground stations. Coupling into multimode fibers does not require adaptive optics due to the large fiber core, however the coupled signal is distributed into multiple fiber-modes and is therefore incompatible with standard telecommunications components. Cailabs Multi-Plane Light Conversion (MPLC) technology overcomes this issue, selectively demultiplexing the fibermodes into single-mode fibers. Here, DLR’s adaptive optics system and the MPLC technology in a turbulence-relevant environment for GEO communications are compared, investigating the advantages of the MPLC approach for compensating strong turbulence. This paper presents an overview of the measurement setup and analyzes the single-mode fibers outputs of the spatial demultiplexer and the measured phase-distortions from a wavefront sensor.
For the next generation of very high throughput communication satellites, TNO and DLR envision optical free-space communication between ground stations and geostationary telecommunication satellites to replace the traditional RF links. To mitigate atmospheric turbulence, an Adaptive Optics (AO) system will be used to apply uplink pre-correction. OFELIA, an ground terminal breadboard was developed to demonstrate the pre-correction principle over an realistic link. Currently, integration tests have been performed to verify the AO performance. Also a laser link experiment over 10 km distance has already been established, in a scenario relevant to ground-to-satellite links. The paper shows that AO is clearly beneficial for the downlink performance. In addition the first preliminary experimental results of the pre-correction show it is also beneficial for the uplink.
For the next generation of very high throughput communication satellites, free-space optical (FSO) communication between ground stations and geostationary telecommunication satellites is likely to replace conventional RF links. To mitigate atmospheric turbulence, TNO and DLR propose Adaptive Optics (AO) to apply uplink pre-correction. In order to demonstrate the feasibility of AO pre-correction an FSO link has been tested over a 10 km range. This paper shows that AO pre-correction is most advantageous for low point ahead angles (PAAs), as expected. In addition, an optimum AO precorrection performance is found at 16 AO modes for the experimental conditions. For the specific test site, tip-tilt precorrection accounted for 4.5 dB improvement in the link budget. Higher order AO modes accounted for another 1.5 dB improvement in the link budget. From these results it is concluded that AO pre-correction can effectively improve high-throughput optical feeder links.
Broadband internet access has become a vertex for the future development of society and industry in the digital era. Geostationary orbit (GEO) satellite can provide global broadband coverage, becoming a complementary solution to optical fiber network. Low-earth-orbit (LEO) constellations have been proposed in the last years and they may become a reality soon, but still based on radiofrequency for the ground-to-satellite links. Optical technologies offer multiple THz of available spectrum, which can be used in the feeder link. The DLR’s Institute of Communications and Navigation has demonstrated Terabit-per-second throughput in relevant environment for GEO communications, in terms of the turbulent channel. In 2016 DLR set the world-record in freespace communications to 1.72 Tbit/s, and in 2017 to 13.16 Tbit/s. Two terminals, emulating the satellite and the ground station have been developed. Bi-directional communications link with single-mode-fiber coupling at both ends was demonstrated. Adaptive optics for the downlink and uplink (pre-distortion) improved the fiber-coupling in downlink and decreased signal fluctuations in uplink. A 80 Gbit/s QPSK system based on digital homodyne reception was also developed, demonstrating the use of coherent communications under strong turbulence conditions. These activities were performed in the frame of two internal DLR projects, THRUST and Global Connectivity Synergy project. Several measurement campaigns took place in the last years in a valley-to-mountain-top test-link. Turbulence has been monitored at both ends and the point-ahead-angle has been emulated by separating the downlink beacon from the receiving aperture. An overview of the system and the main results will be presented.
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