MICADO will enable the ELT to perform diffraction limited near-infrared observations at first light. The instrument’s capabilities focus on imaging (including astrometric and high contrast) as well as single object spectroscopy. This contribution looks at how requirements from the observing modes have driven the instrument design and functionality. Using examples from specific science cases, and making use of the data simulation tool, an outline is presented of what we can expect the instrument to achieve.
MICADO will equip the ELT with a first light capability for diffraction limited imaging at near-infrared wave- lengths. The instrument’s observing modes focus on various flavours of imaging, including astrometric, high contrast, and time resolved. There is also a single object spectroscopic mode optimised for wavelength coverage at moderately high resolution.1 Due to ESO’s technology standards evolution from VLT to ELT, MICADO will manifest the combined, PLC based soft- and hardware control. The evolution of ESO’s technology design guidelines is on the one hand triggered by the ongoing developments in modern days industry and consumer tech- nology. On the other hand, ELT’s sheer dimensions request increasingly complex and smart solutions onwards controlling and monitoring such huge instruments. ESO’s control concept is based on a two layer approach: PLCs are responsible for low-level hardware control (in a real-time fashion, if necessary), while software running on a Linux workstation implements the astronomic business logic of the control system. Development is eased by the fact that ESO delivers libraries for the control of many standard hardware components. A very interesting feature of this approach is the possibility to run C++ code natively inside a PLC real-time environment. This will be used for the control of complex mechanisms like the MICADO Atmoshperic Dispersion Corrector (ADC).
This contribution provides an overview of the key functionality of the instrument focusing on the mechanisms inside the cryostat, and an overview of the cryogenic control. Because of hardware and cryogenic safety reasons, the cryostat control PLC system will be designed as a closed PLC based control system. Hence commands will only be accepted from a human machine interface located next to the cryostat itself. All cryostat parameters and according sensor readings will be published via OpcUA, allowing for full remote cryostat monitoring. In contrast, the instrument control PLC system will interact with the higher level software using the advantages of the industrial OpcUA communication standard and will therefore allow for remote control. Further configuration and commissioning of those mechanisms is made conveniently accessible via this approach. All this is based on ESO’s concept for Line replaceable Units (LRU), which utilizes Beckhoff PLC units to ensure maintainability, availability.
We present the new LN2 continuous- ow test cryostat of the Universitats-Sternwarte Munchen, procured within the context of the Multi-Adaptive Optics Imaging Camera for Deep Observations (MICADO) for the Extremely Large Telescope. The cryostat will be used to perform tests of mechanical, optical and electronic components at high vacuum condition and cryogenic temperature, for the development of the cryogenic Main Selection Mechanism of the MICADO instrument. In this paper we give an overview of the cryostat design and we report about the temperature stability the cryostat can achieve, as well as the temperature gradient over its cold plate. We also report about the impact of adding extra loads on the system after integrating a cold curved shutter in the cryostat and on characterizing the thermal coupling of cryogenic assemblies.
MICADO, the Multi AO Imaging Camera for Deep Observations, is one of the first light instruments for the ELT, currently under construction by the European Southern Observatory (ESO) on Cerro Armazones in Chile. It is built by a huge consortium with partners from the Netherlands, Austria, France, Italy, Finland and Germany under the lead of the Max-Planck-Institute for extraterrestrial Physics in Garching. The instrument will operate in the NIR wavelength range, thus is developed as a cryogenic instrument to work under vacuum conditions. It can be used as an imaging camera in a high and low resolution mode, a spectrometer and also as a coronagraph. For calibration purposes a so called ”pupil imager” mode will also be implemented. To switch between the operational modes MICADO will use the MSM to insert different optical modules to the fixed components of the High Resolution Imager (HRI) inside the cryostat. All moving parts have to operate under vacuum and at cryogenic temperatures. The MSM consists of a rotating platform, where the optical modules are mounted on. To lower the friction inside the mechanism we decided to use several small bearings to support the platform instead of a central big one. The small bearings are placed in a way, that the movement of the platform is limited to a rotation. Some of the bearings will be preloaded by springs to take also CTE differences or temperature gradients during the cool down and warm up phases into account. The mechanism will be driven by a cryogenic Phytron stepper motor with an integrated planetary gear box. Switches will be used to limit the rotation of the platform to the necessary range. Because of the challenging requirements on repositioning of the optical modules inside the science beam, we will use an indent mechanism. We are still investigating if the indent mechanism has to be actively driven or can be implemented as a passive version. The necessary optics to switch between the operational modes are designed as individual pre-aligned modules, each with a defined mechanical and thermal interface to the rotating platform. The Low Resolution Imager (LRI) consists of two flat mirrors, blocking some of the fixed components of the HRI. The spectrometer will use two reflective gratings, one acting as the main and one as a cross disperser. The cross disperser separates the overlaying orders on the focal plane array. The pupil viewer consists like the LRI module of two flat mirrors and an additional lens imaging the pupil to the focal plane. In this paper we will present the current mechanical design and first results of the structural and thermal FEM analyses we performed. We will also highlight first ideas on integration and alignment. A second paper (A. Monna et al., same proceedings) concentrates on the cryogenic setups we perform inside a cryostat to proof proper functionality of the chosen components and designs.
MICADO will equip the E-ELT with a first light capability for diffraction limited imaging at near-infrared wavelengths. The instrument’s observing modes focus on various flavours of imaging, including astrometric, high contrast, and time resolved. There is also a single object spectroscopic mode optimised for wavelength coverage at moderately high resolution. This contribution provides an overview of the key functionality of the instrument, outlining the scientific rationale for its observing modes. The interface between MICADO and the adaptive optics system MAORY that feeds it is summarised. The design of the instrument is discussed, focusing on the optics and mechanisms inside the cryostat, together with a brief overview of the other key sub-systems.
Together with the ongoing major instrument upgrade of the Hobby-Eberly Telescope (HET) we present the planned upgrade of the HET Segment Control System (SCS) to SCS2. Because HET's primary mirror is segmented into 91 individual 1-meter hexagonal mirrors, the SCS is essential to maintain the mirror alignment throughout an entire night of observations. SCS2 will complete tip, tilt and piston corrections of each mirror segment at a significantly higher rate than the original SCS. The new motion control hardware will further increase the system's reliability. The initial optical measurements of this array are performed by the Mirror Alignment Recovery System (MARS) and the HET Extra Focal Instrument (HEFI). Once the segments are optically aligned, the inductive edge sensors give sub-micron precise feedback of each segment's positions relative to its adjacent segments. These sensors are part of the Segment Alignment Maintenance System (SAMS) and are responsible for providing information about positional changes due to external influences, such as steep temperature changes and mechanical stress, and for making compensatory calculations while tracking the telescope on sky. SCS2 will use the optical alignment systems and SAMS inputs to command corrections of every segment in a closed loop. The correction period will be roughly 30 seconds, mostly due to the measurement and averaging process of the SAMS algorithm. The segment actuators will be controlled by the custom developed HET Segment MOtion COntroller (SMOCO). It is a direct descendant of University Observatory Munich's embedded, CAN-based system and instrument control tool-kit. To preserve the existing HET hardware layout, each SMOCO will control two adjacent mirror segments. Unlike the original SCS motor controllers, SMOCO is able to drive all six axes of its two segments at the same time. SCS2 will continue to allow for sub-arcsecond precision in tip and tilt as well as sub-micro meter precision in piston. These estimations are based on the current performance of the segment support mechanics. SMOCO's smart motion control allows for on-the-y correction of the move targets. Since SMOCO uses state-of-the-art motion control electronics and embedded decentralized controllers, we expect reduction in thermal emission as well as less maintenance time.
We present a Θ - Φ-style fiber-positioner prototype, which will be controlled via the EMI-robust CAN-Bus. Our positioner points without iterations or a metrology system. Due to the overlapping patrol disc of 17.3 mm diameter, we reach a filling factor of 100 %. The positioners diameter is 14.6 mm, containing the control electronics on a contemporary PCB of 13.5 mm width. While moving, the power consumption does not lead to a significant rise in temperature. Given a mechanical reference point measured by stall detection, the absolute accuracy is 27 μm (1σ = 14 µm) and pointings are repeatable with 7 μm (1σ = 4 μm). Better positioning may be reachable with upcoming calibration.
KMOS is a multi-object near-infrared integral field spectrograph built by a consortium of UK and German institutes for
the ESO Paranal Observatory. We report on the on-sky performance verification of KMOS measured during three
commissioning runs on the ESO VLT in 2012/13 and some of the early science results.
KMOS is a multi-object near-infrared integral field spectrograph being built by a consortium of UK and German
institutes. We report on the final integration and test phases of KMOS, and its performance verification, prior to
commissioning on the ESO VLT later this year.
4MOST<sup>1</sup> is a multi object spectrograph facility for ESO’s NTT or VISTA telescope. 4MOST is one of the two projects selected for a conceptual design study by ESO. The 4MOST instrument will be able to position < 1500 fibres in the focal plane and collect spectra in a high resolution (R=20000)<sup>2</sup> and a low resolution (R=5000) mode (HRM, LRM). The spectral coverage for the LRM is 400-900 nm, the HRM covers 390-459 nm and 564-676 nm. We will present one of the possible positioner designs and first tests of some components for the focal plane array. The design follows the LAMOST<sup>3</sup> positioner and has two rotational axes to move the fibre inside the patrol disc. Each axis consists of a stepper motor attached to micro harmonic drive (MHD). The small outer dimensions and high gear ratios of the MHD-stepper motor package, makes them perfectly suitable for our application. The MHD is also backlash free and self-locking what gives us the opportunity to minimize power consumption and heat dissipation during observation without loosing the position of the fibre on sky. The control electronics will also be miniaturized and part of the positioner unit.
The KMOS Instrument is built to be one of the second generation VLT instruments. It is a highly complex multi-object
spectrograph for the near infrared. Nearly 60 cryogenic mechanisms have to be controlled. This includes 24 deployable
Pick-Off arms, three filter and grating wheels as well as three focus stages and four lamps with an attenuator wheel.
These mechanisms and a calibration unit are supervised by three control cabinets based on the VLT standards. To follow
the rotation of the Nasmyth adaptor the cabinets are mounted into a Co-rotating structure. The presentation will highlight
the requirements on the electronics control and how these are met by new technologies applying a compact and reliable
signal distribution. To enable high density wiring within the given space envelope flex-rigid printed circuit board designs
have been installed. In addition an electronic system that detects collisions between the moving Pick-Off arms will be
presented for safe operations. The control system is designed to achieve two micron resolution as required by optomechanical
and flexure constraints. Dedicated LVDT sensors are capable to identify the absolute positions of the Pick-
Off arms. These contribute to a safe recovery procedure after power failure or accidental collision.
KMOS is a near-infrared multi-object integral-field spectrometer which is one of a suite of second-generation
instruments under construction for the VLT. The instrument is being built by a consortium of UK and German
institutes working in partnership with ESO and is now in the manufacture, integration and test phase. In this paper
we present an overview of recent progress with the design and build of KMOS and present the first results from the
subsystem test and integration.
KMOS is a near-infrared multi-object integral field spectrometer which has been selected as one of a suite of second-generation instruments to be constructed for the ESO VLT in Chile. The instrument will be built by a consortium of UK and German institutes working in partnership with ESO and is currently at the end of its preliminary design phase. We present the design status of KMOS and discuss the most novel technical aspects and the compliance with the technical specification.
Multi-integral-field spectrographs for near-infrared observations require a large number of complex cryogenic mechanisms to select source images in the telescope field of view which are then re-format on the spectrograph entrance slit. Source selection can be achieved in several ways, but the two methods most adequate for large fields and cryogenic environment are positioning of an optical element in the telescope field to pick off the source image, or steering a mirror located in a pupil image to deflect the light from a source into relay optics. The first solution permits high flexibility in source selection at the cost of large mechanical travels. The second solution limits the source selection to one per pre-defined sub-field, but gets by with small mirror tilts. Higher flexibility can be regained for the second solution by assigning different sub-field sizes to the steering mirrors in the central and in the peripheral areas of the field of view. We present a solution for a cryogenic steering mirror unit with a mirror diameter of about 20 mm and tilt angles of a few degrees, appropriate for source selection in a 1 arc minute field of an 8 m class telescope. The gimbaled mirror can be tilted about two perpendicular axes in the tangential plane of the mirror apex. The mirror is driven by two Nanomotors, and the motor strokes are measured by LVDTs. Motors and sensors are specified for operation at LHe temperatures.