Instrument rotators provide high accuracy instrument rotation at a commanded angle to ensure telescope pupil tracking. Structural support and mechanical interfaces must be provided and services (electrical and communications subsystems) routed from the stationary platform to the rotating platform for heavy instruments (which can exceed 1,500 kg). Cannot transmit vibrations to instruments. The experience gained over the years in working with several types of rotators is summarized in this paper. Not only experimental methods, but also mechanical and control models have allowed us to understand the system in depth. The paper focuses on rotators with two servomotors working together to counteract backlash and rotators with directly coupled motors. For the latter, balanced and unbalanced loads are studied. The mechanical model used to control the servo is explained and analyzed. During the development of the study, different rotator work schedules will be investigated. Tracking will be the focus of the study. The HARMONI rotator and the QUIJOTE telescopes (telescopes built by the Spanish company IDOM) in operation at the Teide Observatory (Tenerife) will therefore be the focus of our attention.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 470nm to 2450nm with resolving powers from 3300 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews.
The core of HARMONI is the Integral Field Spectrograph (IFS) which is composed of different subsystems including the IFS Pre-Optics (IPO). The IPO main objective is to take light from the focal plane relay system and reformat and condition it to be a suitable input for the rest of the instrument. The IPO in HARMONI includes the IFS Pre-Optics Fast Shutter (POFS), a mechanical cryogenic fast shutter which will be used with both the visible and infrared detectors. This mechanism has been designed to be fast and reliable and its design has already passed the Critical Design Review (CDR) but specific issues that require further analysis have been identified. The functioning of this element is a critical part in HARMONI and, consequently, a prototype has been used to analyze possible improvements in the CDR design and to perform extensive testing before the Final Design Review (FDR).
In this work we present the design of the IFS Pre-Optics Fast Shutter and the test results obtained with the prototype developed at the facilities of the Instituto de Astrofísica de Canarias (IAC).
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450 nm to 2450 nm with resolving powers from 3500 to 18000 and spatial sampling from 60 mas to 4 mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews. HARMONI is a work-horse instrument that provides efficient, spatially resolved spectroscopy of extended objects or crowded fields of view. The gigantic leap in sensitivity and spatial resolution that HARMONI at the ELT will enable promises to transform the landscape in observational astrophysics in the coming decade. The project has undergone some key changes to the leadership and management structure over the last two years. We present the salient elements of the project restructuring, and modifications to the technical specifications. The instrument design is very mature in the lead up to the final design review. In this paper, we provide an overview of the instrument's capabilities, details of recent technical changes during the red flag period, and an update of sensitivities.
The High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI) is planned as a first light instrument for the Extremely Large Telescope (ELT). The Instrument Control Electronics (ICE) subsystem plays a vital role in HARMONI, housing all control devices and ensuring they function optimally. However, limited space within the instrument necessitates a unique design approach for the electronic cabinets. This paper details the design of these bespoke cabinets, emphasizing the thermal analysis and insulation technologies implemented to maintain proper operating temperatures for the electronics within the compact instrument volume.
HARMONI is the first light, adaptive optics assisted, integral field spectrograph for the European Southern Observatory’s Extremely Large Telescope (ELT). A work-horse instrument, it provides the ELT’s diffraction limited spectroscopic capability across the near-infrared wavelength range. HARMONI will exploit the ELT’s unique combination of exquisite spatial resolution and enormous collecting area, enabling transformational science. The design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, and provide a summary of the instrument’s design. We also include recent changes to the project, both technical and programmatic, that have resulted from red-flag actions. Finally, we outline some of the simulated HARMONI observations currently being analyzed.
HARMONI is the Extremely Large Telescope visible and near infrared integral field spectrograph and will be one of the first light instruments. The instrument supports four operational modes called No Adaptive Optics (NOAO), Single Conjugated Adaptive Optics (SCAO), High Contrast Adaptive Optics (HCAO), and Laser Tomography Adaptive Optics (LTAO). These operational modes are closely related to the wavefront correction topology used to support the performance required for each of the science cases. By following a novel function model-based systems engineering (FBSE) methodology in conjunction with observing the software computer system golden rule of design; namely having tight cohesion within software modules and loose coupling between modules, a system architecture has emerged. In this paper, we present the design of the HARMONI Control System (HCS). Although this is not the first time (for example NACO on VLT and NIRC2 on Keck) that the adaptive optics required to correct the atmospheric turbulence is part of a general instrument design, and not tailored for a very specific science case, this will be the first instrument of this size and complexity in the era of extremely large ground-based telescopes. The instrument control design must be compatible with the ELT instrument control system framework while there is also an expectation that the adaptive optics (AO) real-time computer toolkit (RTC-TK) should be used for the realization of the AO real-time control software and hardware. The HCS is composed of the instrument control electronics (ICE), the Instrument Control System (ICS), and the AO Control Sub-system (AOCS). The operation concept of the instrument is also novel in that for each mode the instrument creates an instantiation of a virtual system composed of only the system blocks required to provide the selected mode of operation. Therefore, each mode supports a unique system composition in terms of hardware, software, and the sequencing of activities.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for final design review (FDR). The Natural Guide Star Sensors (NGSS) system of HARMONI provides wavefront and image stabilization sensing for each of the four observing modes of the instrument, LTAO, SCAO, HCAO, and NOAO. It consists of five subsystems, three of which provide wavefront sensing (LOWFS, SCAOS and HCM), the remaining two (ESE and ISB) providing thermal and mechanical functions. To limit thermal background and to ensure the required stability, the sensors operate in a cold, thermally stabilized, dry gas environment. This paper presents the overall design of the system with emphasis on system analysis, assembly and test, and maintenance.
HARMONI is the adaptive optics assisted, near-infrared and visible light integral field spectrograph for the Extremely Large Telescope (ELT). A first light instrument, it provides the work-horse spectroscopic capability for the ELT. As the project approaches its Final Design Review milestone, the design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, provide a summary of the instrument’s design, including plans for operations and calibrations, and provide a brief glimpse of the predicted performance for a specific observing scenario. The paper also provides some details of the consortium composition and its evolution since the project commenced in 2015.
The QUIJOTE Experiment (Q-U-I JOint TEnerife) is a combined operation of two telescopes and three instruments working in the microwave band to measure the polarization of the Cosmic Microwave Background (CMB) from the northern hemisphere, at medium and large angular scales. The experiment is located at the Teide Observatory in Tenerife, one of the seven Canary Islands (Spain). The project is a consortium maintained by several institutions: the Instituto de Astrofísica de Canarias (IAC), the Instituto de Física de Cantabria (IFCA), the Communications Engineering Department (DICOM) at Universidad de Cantabria, and the Universities of Manchester and Cambridge. The consortium is led by the IAC.
The QUIJOTE (Q-U-I JOint TEnerife) experiment is a scientific collaboration, led by the Instituto de Astrofísica de Canarias (IAC), with the aim of measuring the polarization of the Cosmic Microwave Background (CMB) in the frequency range 10-40 GHz and at large angular scales (around 1°). The project is composed of 2 telescopes and 3 instruments, located in Teide Observatory (Tenerife, Spain). Idom´s contribution for this project is divided in two phases. Phase I consisted on the design, assembly and factory testing of the first telescope (2008), the integration and functional tests for the 5 polarimeters of the first instrument (2009), and the design and construction supervision of the building which protects both telescopes (2009), including the installation and commissioning of the mechanism for domes apertures. Phase II comprised the design, factory assembly and testing, transport and final commissioning on site of the second telescope, which finished in January 2015. The optical design of both telescopes should allow them to reach up to 200 GHz. The required opto-mechanical performance was checked under nominal conditions, reaching a pointing and tracking accuracy lower than 5 arcsec in both axes, 8 times better than specified. Particular inspections and tests were carried out for critical systems, as the rotary joint that transmits fluid, power and signal to the rotary elements, or for the safety system to ensure personnel and hardware protection under emergency conditions. This paper contains a comprehensive description of the power electronics and acquisition/control design required for safely operation under nominal and emergency conditions, as well as a detailed description of the factory and observatory tests required for the final acceptance of the telescope
The PLT-HPT-32, a new cryogenic temperature monitor, has been developed by the Institute of Astrophysics of the Canary Islands (IAC) and an external engineering company (Sergio González Martín-Fernandez). The PLT-HPT-32 temperature monitor offers precision measurement in a wide range of cryogenic and higher-temperature applications with the ability to easily monitor up to 32 sensor channels. It provides better measurement performance in applications where researchers need to ensure accuracy and precision in their low cryogenic temperature monitoring.
The PLT-HPT-32 supports PTC RTDs such as platinum sensors, and diodes such as the Lake Shore DT-670 Series. Used with silicon diodes, it provides accurate measurements in cryo-cooler applications from 16 K to above room temperature. The resolution of the measurement is less than 0.1K. Measurements can be displayed in voltage units or Kelvin units. For it, two different tables can be used. One can be programmed by the user, and the other one corresponds to Lake Shore DT670 sensor that comes standard.
There are two modes of measuring, the instantaneous mode and averaged mode. In this moment, all channels must work in the same mode but in the near future it expected to be used in blocks of eight channels. The instantaneous mode takes three seconds to read all channels. The averaged mode takes one minute to average twenty samples in all channels. Alarm thresholds can be configured independently for each input. The alarm events, come from the first eight channels, can activate the unit’s relay outputs for hard-wired triggering of other systems or audible annunciators. Activate relays on high, low, or both alarms for any input.
For local monitoring, "Stand-Alone Mode", the front panel of the PLT-HPT-32 features a bright liquid crystal display with an LED backlight that shows up to 32 readings simultaneously. Plus, monitoring can be done over a network "Remote Control Mode". Using the Ethernet port on the PLT-HPT-32, you can keep an eye on temperatures, log measurement and configured remotely via a Networked local PC or even remotely over a TCP/IP Internet connection from anywhere.
The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment is operating at the Teide Observatory with the aim of
characterizing the polarization of the CMB and other processes of Galactic and extragalactic emission in the frequency
range of 10–40GHz and at large and medium angular scales. The QUIJOTE CMB experiment consists of two telescopes
installed inside a single enclosure, and three instruments, the MFI (multi-frequency 10–30GHz), the TGI (26–36 GHz)
and the FGI (37–47 GHz). The first QUIJOTE telescope and the MFI instrument have been in operation at the
Observatory since November 2012. In this poster we present the TGI cryostat and optomechanics status, including their
design, MAIT, and thermal clamp developments.
KEYWORDS: Telescopes, Control systems, Polarimetry, Switches, Data acquisition, Human-machine interfaces, Polarimetry, Field programmable gate arrays, Data storage, Data communications, Safety
The QUIJOTE-CMB experiment (Q-U-I JOint TEnerife CMB experiment) has been described in previous publications.
In particular, the architecture of the MFI instrument control system, the first of the three QUIJOTE instruments, was
presented in [1]. In this paper we describe the control system architecture, hardware, and software, of the second
QUIJOTE instrument, the TGI (Thirty GHz Instrument), which has been in the process of commissioning for a few
weeks now. It is a 30 pixel 26-36 GHz polarimeter array mounted at the focus of the second QUIJOTE telescope. The
polarimeter design is based on the QUIET polarimeter scheme, implementing phase switches of 90° and 180° to generate
four states of polarisation. The TGI control system acquires the scientific signal of the four channels for each of the 30
polarimeters, sampled at 160 kHz; it controls the commutation of the 30 x 4 phase switches at 16 kHz or 8 kHz; it
performs the acquisition and monitoring of the health of the complete instrument, acquiring housekeeping from the
various subsystems and also controls the different operational modes of the telescope. It finally, implements a queue
system that permits automation of the observations by allowing the programming of several days of observations with
the minimum of human intervention. The acquisition system is based on a PXI-RT host from NI, the commutations of
the phase switches are performed by a PXI-FPGA subsystem and the telescope control is based on an EtherCAT bus
from Beckhoff.
R. Hoyland, M. Aguiar-González, R. Génova-Santosa, F. Gómez-Reñasco, C. López-Caraballo, R. Rebolo-López, J. Rubiño-Martín, V. Sánchez-de la Rosa, A. Vega-Moreno, T. Viera-Curbelo, A. Pelaez-Santos, R. Vignaga, D. Tramonte, F. Poidevin, M. Pérez-de-Taoro, E. Martínez-Gonzalez, B. Aja, E. Artal, J. Cagigas, J. Cano-de-Diego, E. Cuerno, L. de-la-Fuente, A. Pérez, D. Ortiz, J. Terán, E. Villa, L. Piccirillo, M. Hobson
The QUIJOTE TGI instrument is currently being assembled and tested at the IAC in Spain. The TGI is a 31 pixel 26-36 GHz polarimeter array designed to be mounted at the focus of the second QUIJOTE telescope. This follows a first telescope and multi-frequency instrument that have now been observing almost 2 years. The polarimeter design is based on the QUIET polarimeter scheme but with the addition of an extra 90º phase switch which allows for quasiinstantaneous complete QUI measurements through each detector. The advantage of this solution is a reduction in the systematics associated with differencing two independent radiometer channels. The polarimeters are split into a cold front end and a warm back end. The back end is a highly integrated design by the engineers at DICOM. It is also sufficiently modular for testing purposes. In this presentation the high quality wide band components used in the optical design (also designed in DICOM) are presented as well as the novel cryogenic modular design. Each polarimeter chain is accessible individually and can be removed from the cryostat and replaced without having to move the remaining pixels. The optical components work over the complete Ka band showing excellent performance. Results from the sub unit measurements are presented and also a description of the novel calibration technique that allows for bandpass measurement and polar alignment. Terrestrial Calibration for this instrument is very important and will be carried out at three points in the commissioning phase: in the laboratory, at the telescope site and finally a reduced set of calibrations will be carried out on the telescope before measurements of extraterrestrial sources begin. The telescope pointing model is known to be more precise than the expected calibration precision so no further significant error will be added through the telescope optics. The integrated back-end components are presented showing the overall arrangement for mounting on the cryostat. Many of the microwave circuits are in-house designs with performances that go beyond commercially available products.
M. Pérez-de-Taoro, M. Aguiar-González, R. Génova-Santos, F. Gómez-Reñasco, R. Hoyland, C. López-Caraballo, A. Peláez-Santos, F. Poidevin, D. Tramonte, R. Rebolo-López, J. Rubiño-Martín, V. Sánchez-de la Rosa, A. Vega-Moreno, T. Viera-Curbelo, R. Vignaga, E. Martínez-Gonzalez, B. Aja, E. Artal, J. Cagigas, J. Cano-de-Diego, E. Cuerno, L. de-la-Fuente, A. Pérez, J. Terán, E. Villa, L. Piccirillo, A. Lasenby
The QUIJOTE-CMB experiment (Q-U-I JOint TEnerife CMB experiment) is an ambitious project to obtain polarization measurements of the sky microwave emission in the 10 to 47 GHz range. With this aim, a pair of 2,5μm telescopes and three instruments are being sited at the Teide Observatory, in Tenerife (Canary Islands, Spain). The first telescope and the first instrument (the MFI: Multi Frequency Instrument) are both already operating in the band from 10 to 20 GHz, since November 2012. The second telescope and the second instrument (TGI: Thirty GHz instrument) is planned to be in
commissioning by the end of summer 2014, covering the range of 26 to 36 GHz. After that, a third instrument named FGI (Forty GHz instrument) will be designed and manufactured to complete the sky survey in the frequency range from 37 to 47 GHz. In this paper we present an overview of the whole project current status, from the technical point of view.
Experiment QUIJOTE (Q-U-I JOint TEnerife) is a scientific collaboration, leaded by the Instituto de Astrofísica de Canarias (IAC), which can measure the polarization of the Cosmic Microwave Background (CMB) in the range of frequency up to 200 GHz, at angular scales of 1°. The project is composed of 2 telescopes and 3 instruments, located in Teide Observatory (Tenerife, Spain).
After the successful delivery of the first telescope (operative since 2012), Idom is currently involved on the turn key supply of the second telescope (phase II). The work started in June 2013 and it will be completed in a challenging period of 12 months (operative at the beginning of July 2014), including design, factory assembly and testing, transport and final commissioning on site.
This second unit will improve the opto-mechanical performance and maintainability. The telescope will have an unlimited rotation capacity in azimuth axis and a range of movement between 25°-95° in elevation axis. An integrated rotary joint will transmit fluid, power and signal to the rotary elements. The pointing and tracking accuracy will be significantly below to specification: 1.76 arcmin and 44 arcsec, respectively.
This project completes Idom´s contribution during phase I, which also comprises the integration and functional tests for the 5 polarimeters of the first instrument in Bilbao headquarters, and the design and supervision of the building which protects both telescopes, including the installation and commissioning of the mechanism for shutters aperture.
The QUIJOTE-CMB project has been described in previous publications. Here we present the current status of the
QUIJOTE multi-frequency instrument (MFI) with five separate polarimeters (providing 5 independent sky pixels): two
which operate at 10-14 GHz, two which operate at 16-20 GHz, and a central polarimeter at 30 GHz. The optical
arrangement includes 5 conical corrugated feedhorns staring into a dual reflector crossed-draconian system, which
provides optimal cross-polarization properties (designed to be < −35 dB) and symmetric beams. Each horn feeds a novel
cryogenic on-axis rotating polar modulator which can rotate at a speed of up to 1 Hz. The science driver for this first
instrument is the characterization of the galactic emission. The polarimeters use the polar modulator to derive linear
polar parameters Q, U and I and switch out various systematics. The detection system provides optimum sensitivity
through 2 correlated and 2 total power channels. The system is calibrated using bright polarized celestial sources and
through a secondary calibration source and antenna. The acquisition system, telescope control and housekeeping are all
linked through a real-time gigabit Ethernet network. All communication, power and helium gas are passed through a
central rotary joint. The time stamp is synchronized to a GPS time signal. The acquisition software is based on PLCs
written in Beckhoffs TwinCat and ethercat. The user interface is written in LABVIEW. The status of the QUIJOTE MFI
will be presented including pre-commissioning results and laboratory testing.
The QUIJOTE-CMB experiment has been described in previous publications. Here we describe the architecture of the
control system, hardware and software, of the QUIJOTE I instrument (MFI). It is a multi-channel instrument with five
separate polarimeters: two of which operate at 10-14 GHz, two of which operate at 16-20 GHz, and a central polarimeter
at 26-36 GHz. Each polarimeter can rotate at a speed of up to 1 Hz and also can move to discrete angular positions which
allow the linear polar parameters Q, U and I to be derived. The instrument is installed in an alt-azimuth telescope which
implements several operational modes: movement around the azimuth axis at a constant velocity while the elevation axis
is held at a fixed elevation; tracking of a sky object; and raster of a rectangular area both in horizontal and sky
coordinates. The control system of both, telescope and instrument, is based in the following technologies: an LXI-VXI
bus is used for the signal acquisition system; an EtherCAT bus implements software PLCs developed in TwinCAT to
perform the movement of the 5 polarimeters and the 2 axes of the telescope. Science signal, angular positions of the 5
polarimeters and telescope coordinates are sampled at up to 4000 Hz. All these data are correlated by a time stamp
obtained from an external GPS clock implementing the Precise Time Protocol-1588 which provides synchronization to
less than 1 microsecond. The control software also acquires housekeeping (HK) from the different subsystems.
LabVIEW implements the instrument user interface.
The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment will operate at the Teide Observatory with the aim
of characterizing the polarisation of the CMB and other processes of Galactic and extragalactic emission in the
frequency range of 10-40GHz and at large and medium angular scales. The first of the two QUIJOTE telescopes
and the first multi-frequency (10-30GHz) instrument are already built and have been tested in the laboratory.
QUIJOTE-CMB will be a valuable complement at low frequencies for the Planck mission, and will have the
required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger
than r = 0.05.
KEYWORDS: Actuators, Photoacoustic tomography, Electronics, Computer programming, Mirrors, Control systems, Prototyping, Sensors, Large telescopes, Lead
European Extremely Large Telescope (E-ELT) based in 984 primary mirror segments achieving required
optical performance; they must position relatively to adjacent segments with relative nanometer accuracy.
CESA designed M1 Position Actuators (PACT) to comply with demanding performance requirements of EELT.
Three PACT are located under each segment controlling three out of the plane degrees of freedom (tip, tilt,
piston). To achieve a high linear accuracy in long operational displacements, PACT uses two stages in series.
First stage based on Voice Coil Actuator (VCA) to achieve high accuracies in very short travel ranges, while
second stage based on Brushless DC Motor (BLDC) provides large stroke ranges and allows positioning the
first stage closer to the demanded position.
A BLDC motor is used achieving a continuous smoothly movement compared to sudden jumps of a stepper.
A gear box attached to the motor allows a high reduction of power consumption and provides a great
challenge for sizing. PACT space envelope was reduced by means of two flat springs fixed to VCA. Its main
characteristic is a low linear axial stiffness.
To achieve best performance for PACT, sensors have been included in both stages. A rotary encoder is
included in BLDC stage to close position/velocity control loop. An incremental optical encoder measures
PACT travel range with relative nanometer accuracy and used to close the position loop of the whole actuator
movement. For this purpose, four different optical sensors with different gratings will be evaluated.
Control strategy show different internal closed loops that work together to achieve required performance.
The Wind Evaluation Breadboard (WEB) is a primary mirror and telescope simulator formed by seven aluminium
segments, including position sensors, electromechanical support systems and support structures. WEB has been
developed to evaluate technologies for primary mirror wavefront control and to evaluate the performance of the control
of wind buffeting disturbance on ELT segmented mirrors. For this purpose WEB electro-mechanical set-up simulates the
real operational constrains applied to large segmented mirrors. This paper describes the WEB assembly, integration and
verification, the instrument characterisation and close loop control design, including the dynamical characterization of
the instrument and the control architecture. The performance of the new technologies developed for position sensing,
acting and controlling is evaluated. The integration of the instrument in the observatory and the results of the first
experiments are summarised, with different wind conditions, elevation and azimuth angles of incidence. Conclusions are
extracted with respect the wind rejection performance and the control strategy for an ELT. WEB has been designed and
developed by IAC, ESO, ALTRAN and JUPASA, with the integration of subsystems of FOGALE and TNO.
The Wind Evaluation Breadboard (WEB) for the European Extremely Large Telescope (ELT) is a primary mirror and
telescope simulator formed by seven segments simulators, including position sensors, electromechanical support systems
and support structures. The purpose of the WEB is to evaluate the performance of the control of wind buffeting
disturbance on ELT segmented mirrors using an electro-mechanical set-up which simulates the real operational
constrains applied to large segmented mirrors. The instrument has been designed and developed by IAC, ALTRAN,
JUPASA and ESO, with FOGALE responsible of the Edge Sensors, and TNO of the Position Actuators. This paper
describes the mechanical design and analysis, the control architecture, the dynamic model generated based on the Finite
Element Model and the close loop performance achieved in simulations. A comparison in control performance between
segments modal control and actuators local control is also presented.
WEB, the Wind Evaluation Breadboard, is an Extremely Large Telescope Primary Mirror simulator, developed with the
aim of quantifying the ability of a segmented primary mirror to cope with wind disturbances. This instrument supported
by the European Community (Framework Programme 6, ELT Design Study), is developed by ESO, IAC, MEDIA-ALTRAN,
JUPASA and FOGALE. The WEB is a bench of about 20 tons and 7 meter diameter emulating a segmented
primary mirror and its cell, with 7 hexagonal segments simulators, including electromechanical support systems.
In this paper we present the WEB central control electronics and the software development which has to interface with:
position actuators, auxiliary slave actuators, edge sensors, azimuth ring, elevation actuator, meteorological station and air
balloons enclosure. The set of subsystems to control is a reduced version of a real telescope segmented primary mirror
control system with high real time performance but emphasizing on development time efficiency and flexibility, because
WEB is a test bench. The paper includes a detailed description of hardware and software, paying special attention to real
time performance.
The Hardware is composed of three computers and the Software architecture has been divided in three
intercommunicated applications and they have been implemented using Labview over Windows XP and Pharlap ETS
real time operating system. The edge sensors and position actuators close loop has a sampling and commanding
frequency of 1KHz.
We present EDiFiSE, a prototype instrument for the observation of high-contrast systems, combining an adaptive
optics (AO) system and an equalized integral field unit (EIFU). The design of the AO system takes into account
the statistical behaviour of the atmospheric turbulence structure at the Canary Islands (Spain) astronomical
observatories: Roque de los Muchachos (ORM) on the island of La Palma and Teide observatory (OT) in
Tenerife. The AO will have the capability of adapting to the prevailing turbulence conditions; in this sense,
the EDiFiSE AO unit will be an 'adaptable' adaptive optics system. The corrected beam feeds an hexagonal
integral field unit formed by 331 micro-lenslets, which focus the intensity distribution at the focal plane into 331
optical fibers. The central seven fibers of the bundle include variable attenuators for the equalization of these
fibers output intensities, matching them to the dynamical range of the detector and reducing the optical cross
talk inside the spectrograph. This technique, called equalized integral field spectroscopy (Arribas, Mediavilla &
Fuensalida 19981), permits to obtain spectral and spatial information of the equalized object and its surroundings
as well as accurate relative photometry and astrometry.
Real-time control has been clearly identified as a separate challenging field within Adaptive Optics, where a lot of computations have to be performed at kilohertz rate to properly actuate the mirror(s) before the input wavefront information has become obsolete. When considering giant telescopes, the number of guide stars, wavefront samples and actuators rises to a level where the amount of processing is far from being manageable by today's conventional processors and even from the expectations given by Moore's law for the next years. FPGA (Field Programmable Gate Arrays) technology has been proposed to overcome this problem by using its massively parallel nature and its superb speed. A complete laboratory test bench using only one FPGA was developed by our group [1], and now this paper summarizes the early results of a real telescope adaptive optics system based in the FPGA-only approach. The system has been installed in the OGS telescope at "Observatorio del Teide", Tenerife, Spain, showing that a complete system with 64 Shack-Hartmann microlenses and 37 actuators (plus tip-tilt mirror) can be implemented with a real time control completely contained within a Xilinx Virtex-4 LX25 FPGA. The wavefront sensor has been implemented using a PULNIX gigabit ethernet camera (714 frames per second), and an ANDOR IXON camera has been used for the
evaluation of the overall correcting behavior.
FPGA (Field Programmable Gate Array) technology has become a very powerful tool available to the electronic designer, specially after the spreading of high quality synthesis and simulation software packages at very affordable prices. They also offer high physical integration levels and high speed, and eases the implementation of parallelism to obtain superb features. Adaptive optics for the next generation telescopes (50-100 m diameter) -or improved versions for existing ones- requires a huge amount of processing power that goes beyond the practical limits of today's processor capability, and perhaps tomorrow's, so FPGAs may become a viable approach. In order to evaluate the feasibility of such a system, a laboratory adaptive optical test bench has been developed, using only FPGAs in its closed loop processing chain. A Shack-Hartmann wavefront sensor has been implemented using a 955-image per second DALSA CA-D6 camera, and a 37-channel OKO mirror has been used for wavefront correcting. Results are presented and extrapolation of the behavior for large and extremely large telescopes is discussed.
In the frame of the SILEX project, the European Space Agency (ESA) has put into orbit two Laser Communication Terminals, to establish an experimental free space optical communication link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV), to relay earth observation data. In order to perform In Orbit Testing (IOT) of these, and other, optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for building the Optical Ground Station (OGS), in the Teide Observatory of the IAC. With ARTEMIS placed in a circular parking orbit at about 31000 kilometres, its optical payload has been preliminary tested with the OGS. First results and analysis are presented on the space-to-ground bi-directional link, including pointing acquisition and tracking performance, Bit-Error Rate (BER) and transmitted beam divergence effects related with atmospheric models and predictions. Future plans include deeper optical bi-directional communication tests of OGS, not only with ARTEMIS but also with OSCAR-40 (downlink) and SMART-1 (up-link) satellites, in order to do a full characterisation of the performances of laser beam propagation through atmospheric turbulence and a comparison with theoretical predictions.
The European Space Agency (ESA) has undertaken the development of Optical Data Relay payloads, aimed at establishing free space optical communication links between satellites. The first of such systems put into orbit is the SILEX project, in which an experimental link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV) will be used to relay earth observation data. In order to perform In Orbit Testing (IOT) of these and future optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for the building of the Optical Ground Station (OGS) in the IAC Teide Observatory, which consists basically of a 1-meter telescope and the suitable instrumentation for establishing and testing bi-directional optical links with satellites. The presence of the atmosphere in the data path posses particular problems, with an impact on the instrumentation design. The transmission, reception and measurement functions, along with the overall control of the instruments, are performed at OGS by the Focal Plane Control Electronics (FPCE). The design and performance of this instrumentation is presented, emphasizing the Pointing, Acquisition and Tracking, the Tuneable Laser and the Master Control.
KEYWORDS: Satellites, Optical communications, Data communications, Acquisition tracking and pointing, Space operations, Satellite communications, Observatories, Polarization, Signal attenuation, Scintillation
ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreemenet for building the Optical Ground Station (OGS), in the IAC Teide Observatory, in order to perform In Orbit Testing (IOT) of Optical Data Relay payloads onboard communication satellites, the first being ARTEMIS. During its recent launch, ARTEMIS was put into a degraded orbit due to a malfunction on the launcher's upper stage. ESA rapidly adopted a recovery strategy aimed to take the satellite to its nominal geostationary position. After completion of the first manoeuvres, ARTEMIS was successfully positioned in a circular parking orbit, at about 31,000 kilometers, and turned into full operation. In this orbit, its optical payload has been tested with the OGS, before establishing the link with SPOT IV. New tracking algorithms were developed at OGS control system in order to correct for ARTEMIS new orbit. The OGS has established a bi-directional link to ARTEMIS, behaving, seen from ARTEMIS, as a LEO terminal. Preliminary results are presented on the space-to- ground bi-directional link, including pointing acquisition and tracking (PAT) performance, received beam characterization and BER measurements.
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