The European Extremely Large Telescope (ELT) is a 39-m Class telescope with active and adaptive capability included into the telescope being developed by the European Southern Observatory (ESO).
The Telescope Secondary (M2) and Tertiary (M3) Mirrors are 4-metre class Zerodur mirrors close to 3.2 Tons that are passively supported by Cells with an 18 points axial whiffletree and a warping harness system that allows to correct low order deformations of the Mirrors. Laterally the Mirrors are supported on 12+2 points by Lateral Supports. In addition, the Cells have alignment capabilities by means of a high precision hexapod.
SENER has been contracted by ESO for the design, construction, validation and delivery of the ELT Secondary Mirror (M2) and Tertiary Mirror (M3) Cells.
The Cells’ mechanisms guarantee the alignment of the Telescope during observation while correcting optics deformations. In this process, a high precision hexapod will be responsible for aligning and tracking the mirrors and an active structure will be used to compensate errors in the mirrors’ surface. These are large-size critical elements of the Telescope that require extremely high precision levels to give the Telescope optimal image quality.
This manuscript describes the preliminary design and key aspects of the ELT M2 and M3 Mirrors Cells mechanisms, in particular the Mirror Suppor.
WEAVE is a new wide-field multi-object spectroscopy (MOS) facility proposed for the prime focus of the 4.2m William Herschel Telescope (WHT), situated on the island of La Palma, Canary Islands, Spain. To allow for the compensation of the effects of temperature-induced and gravity-induced image degradation, the WEAVE prime focus assembly will be translated along the telescope optical axis. The assembly comprises the prime focus corrector (PFC), a central mount for the corrector known as FTS, an instrument rotator and a twin-focal-plane fibre positioner. SENER, that manufactured and delivered the FTS, is also responsible for the final design, manufacturing, integration, alignment and testing of the PFC and its ancillary equipment. This manuscript describes the final design of the PFC along with the analyses and simulations performed and presents the procedures for the integration and alignment of the lenses in the corrector.
We present an X-ray mirror bender that includes multiple spring actuators that introduce a controlled deformation of the
mirror substrate capable of correcting residual figure errors on the mirror, below one nanometer. For usual mirror
dimensions, this requires applying correcting forces with resolution and stability in the order of 0.01 N, and a range up to
20 N, depending on the initial figure error of the mirror. To obtain the required stability, the actuators need to
compensate intrinsic mechanical instabilities, such as thermal drifts or the limited repeatability of parts that move during
the adjustment of the figure. The concept we propose uses weak springs that allow reducing all these effects below
noticeable values. Additional considerations on friction and parasitic components of the force are accounted. The system
also includes two independent bending actuators with a larger force range to generate the mean elliptic figure of the
mirror. Metrology tests of the performances of the system show that the correctors are repeatable within 0.01 N, and
reach much higher resolution. A prototype of the bender has been used to correct the figure error of a 500 mm long
mirror below one nanometer (root mean square). The agreement to the predicted figure is better than 0.08 nm rms.
WEAVE is a new wide-field spectroscopy facility proposed for the prime focus of the 4.2m William Herschel Telescope (WHT), placed in La Palma, Canary Islands, Spain.
To allow for the compensation of the effects of temperature-induced and gravity-induced image degradation, the WEAVE prime focus assembly will be translated along the telescope optical axis. The assembly comprises the prime focus corrector with integrated ADC, a central mount for the corrector, an instrument rotator and a twin-focal-plane fibre positioner. Translation is accomplished through the use of a set of purpose-built actuators; collectively referred to as the Focus Translation System (FTS), formed by four independently-controlled Focus Translation Units (FTUs), eight vanes connecting the FTUs to a central can, and a central can hosting WEAVE Instrument. Each FTU is capable of providing a maximum stroke of ±4mm with sufficient, combined force to move the five-tonne assembly with a positional accuracy of ±20μm at a resolution of 5μm. The coordinated movement of the four FTUs allows ±3mm WEAVE focus adjustment in the optical axis and ±0.015° tilt correction in one axis. The control of the FTS is accomplished through a PLC-based subsystem that receives positional demands from the higher-level Instrument Control System.
SENER has been responsible for designing, manufacturing and testing the FTS and the equipment required to manipulate and store the FTS together with the instrument.
This manuscript describes the final design of the FTS along with the analyses and simulations that were performed, discusses the manufacturing procedures and the results of early verification prior to integration with the telescope. The plans for mounting the whole system on the telescope are also discussed.
JEM-EUSO is a space observatory that will be attached to the Japanese module of the International Space Station (ISS) to observe the UV photon tracks produced by Ultra High Energy Cosmic Rays (UHECR) interacting with atmospheric nuclei. The observatory comprises an Atmospheric Monitoring System (AMS) to gather data about the status of the atmosphere, including an infrared camera (IRCAM) for cloud coverage and cloud top height detection. This paper describes the design and characterization tests of IRCAM, which is the responsibility of the Spanish JEM-EUSO Consortium. The core of IRCAM is a 640x480 microbolometer array, the ULIS 04171, sensitive to radiation in the range 7 to 14 microns. The microbolometer array has been tested using the Front End Electronics Prototype (FEEP). This custom designed electronics corresponds to the Breadboard Model, a design built to verify the camera requirements in the laboratory. The FEEP controls the configuration of the microbolometer, digitizes the detector output, sends data to the Instrument Control Unit (ICU), and controls the microbolometer temperature to a 10 mK stability. Furthermore, the FEEP allows IRCAM to preprocess images by the addition of a powerful FPGA. This prototype has been characterized in the laboratories of Instituto de Astrofisica de Canarias (IAC). Main results, including detector response as a function of the scene temperature, NETD and Non-Uniformity Correction (NUC) are shown. Results about thermal resolution meet the system requirements with a NETD lower than 1K including the narrow band filters which allow us to retrieve the clouds temperature using stereovision algorithms.
JPCam is designed to perform the Javalambre-PAU Astrophysical Survey (J-PAS), a photometric survey of the northern
sky with the new JST telescope being constructed in the Observatorio Astrofísico of Javalambre in Spain by CEFCA
(Centro de Estudios de Física del Cosmos de Aragón).
SENER has been responsible for the design, manufacturing, verification and delivery of the JPCam Actuator System
that will be installed between the Telescope and the cryogenic Camera Subsystem. The main function is to control the
instrument position to guarantee the image quality required during observations in all field of view and compensate
deformations produced by gravity and temperature changes.
The paper summarizes the main aspects of the hexapod design and earliest information related of integration and
performances tests results.
The Japanese Experiment Module (JEM) Extreme Universe Space Observatory (EUSO) will be launched and attached to the Japanese module of the International Space Station (ISS). Its aim is to observe UV photon tracks produced by ultra-high energy cosmic rays developing in the atmosphere and producing extensive air showers. The key element of the instrument is a very wide-field, very fast, large-lense telescope that can detect extreme energy particles with energy above 1019 eV. The Atmospheric Monitoring System (AMS), comprising, among others, the Infrared Camera (IRCAM), which is the Spanish contribution, plays a fundamental role in the understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. It is used to detect the temperature of clouds and to obtain the cloud coverage and cloud top altitude during the observation period of the JEM-EUSO main instrument. SENER is responsible for the preliminary design of the Front End Electronics (FEE) of the Infrared Camera, based on an uncooled microbolometer, and the manufacturing and verification of the prototype model. This paper describes the flight design drivers and key factors to achieve the target features, namely, detector biasing with electrical noise better than 100μV from 1Hz to 10MHz, temperature control of the microbolometer, from 10°C to 40°C with stability better than 10mK over 4.8hours, low noise high bandwidth amplifier adaptation of the microbolometer output to differential input before analog to digital conversion, housekeeping generation, microbolometer control, and image accumulation for noise reduction. It also shows the modifications implemented in the FEE prototype design to perform a trade-off of different technologies, such as the convenience of using linear or switched regulation for the temperature control, the possibility to check the camera performances when both microbolometer and analog electronics are moved further away from the power and digital electronics, and the addition of switching regulators to demonstrate the design is immune to the electrical noise the switching converters introduce. Finally, the results obtained during the verification phase are presented: FEE limitations, verification results, including FEE noise for each channel and its equivalent NETD and microbolometer temperature stability achieved, technologies trade-off, lessons learnt, and design improvement to implement in future project phases.
This paper summarizes the main aspects of the design and qualification test results of the ALMA Amplitude Calibration
Device Robotic Arm (ACD). The design aspects of the ACD, including a detailed description of the components selected to achieve the expected performances are presented in the first part of the paper. Also the system performances results measured in the first prototype units are summarized at the last part of the paper.
This paper summarizes the main aspects of the design and qualification test results of the secondary mirror mechanism
for the VISTA Telescope. A design overview is presented, with detailed description of the main aspects of the system
including the electromechanical part and the control system. Also a description of the test facilities and test
methodologies is provided prior to the presentation and discussion of the performance test results.
The GTC Acquisition Cameras and Wavefront Sensors are based on a modular design with remote, low-profile and lightweight CCD heads and a compact CCD controller. The cameras employ E2V Technologies Peltier cooled CCD47-20 and CCD39-01 detectors, which achieve 1Hz and 200Hz full frame readouts, respectively. The CCD controller is a modified version of the Magellan CCD controller (Greg Burley - OCIW), which is linked to the GTC control system. We present the detailed design and first performance results of the cameras.
This paper summarizes the main aspects of the design and qualification test results of the secondary mirror mechanism for the 10.4-m Gran Telescopio Canarias (GTC). The design of the M2DS consists of a two stage mechanism, a hexapod for alignment using six linear actuators and a compensated tilt/chop stage with three voice coils taking its base on the hexapod mobile plate. The system has been tested after servos adjustment and calibration and the latest results are presented, which illustrate the quality and accuracy of this mechanism in both alignment and chop performances. Finally, the results and experiences are summarized in order to provide useful information for new developments of such systems.