The polarimetric and helioseismic imager instrument for the Solar Orbiter mission from the European Space Agency requires a high stability while capturing images, specially for the polarimetric ones. For this reason, an image stabilization system has been included in the instrument. It uses global motion estimation techniques to estimate the jitter in real time with subpixel resolution. Due to instrument requirements, the algorithm has to be implemented in a Xilinx Virtex-4QV field programmable gate array. The algorithm includes a 2-D paraboloid interpolation algorithm based on 2-D bisection. We describe the algorithm implementation and the tests that have been made to verify its performance. The jitter estimation has a mean error of 125 pixel of the correlation tracking camera. The paraboloid interpolation algorithm provides also better results in terms of resources and time required for the calculation (at least a 20% improvement in both cases) than those based on direct calculation.
MIRADAS is a near-infrared multiobject echelle spectrograph operating at spectral resolution R = 20,000 over the 1 to 2.5 μm bandpass for Gran Telescopio Canarias. It possesses a multiplexing system with 12 cryogenic robotic probe arms, each capable of independently selecting a user-defined target in the instrument field of view. The arms are distributed around a circular bench, becoming a very packed workspace when all of them are in simultaneous operation. Therefore, their motions have to be carefully coordinated. We propose here a motion planning method for the MIRADAS probe arms. Our offline algorithm relies on roadmaps comprising alternative paths, which are discretized in a state-time space. The determination of collision-free trajectories in such space is achieved by means of a graph-search technique. The approach considers the constraints imposed by the particular architecture of the probe arms as well as the limitations of the commercial off-the-shelf motor controllers used in the mechanical design. We test our solution with real science targets and a typical MIRADAS scenario presenting some instances of the two identified collision conflicts that can arise between any pair of probe arms. Experiments show the method is versatile enough to compute trajectories fulfilling the requirements.
MIRADAS (Mid-resolution InfRAreD Astronomical Spectrograph) is the facility near-infrared multi-object echelle spectrograph for the Gran Telescopio Canarias (GTC) 10.4-meter telescope. MIRADAS operates at spectral resolution R=20,000 over the 1-2.5µm bandpass), and provides multiplexing (up to N=12 targets) and spectro-polarimetry. The MIRADAS consortium includes the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de Canarias, Institut d'Estudis Espacials de Catalunya and Universidad Nacional Autonoma de Mexico, as well as partners at A-V-S (Spain), New England Optical Systems (USA), and IUCAA (India). MIRADAS completed its Final Design Review in 2015, and in this paper, we review the current status and overall system design for the instrument, with scheduled delivery in 2018. We particularly emphasize key developments in cryogenic robotic probe arms for multiplexing, a macro-slicer mini-IFU, an advanced cryogenic spectrograph optical system, and a SIDECAR-based array control system for the 1x2 HAWAII-2RG detector mosaic.
Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS), a near-infrared multi-object spectrograph for Gran Telescopio Canarias (GTC), has 12 deployable optomechanical Integral Field Units (IFU). Based on a robotic probe arm with a pick-off mirror, each of these units can observe a different user-defined sky object. MIRADAS can work with target sets where their components are spread over such a wide area so that all of them do not fit in the field-of-view of the instrument. Therefore, data sets of that kind require, prior to capturing them, some arrangement that groups its elements in different subsets where the distance between the two most remote elements is inferior to the field-of-view diameter. This field segmentation is achieved using a hierarchical clustering technique. Our method relies on determining mutual nearest-neighbors, which will be merged if they show a given degree of similarity known beforehand. Moreover, we also compute a geometric center for these clusters, information to be delivered to the telescope’s pointing process. This step is formulated as the minimum bounding disk problem, which founds the center of the smallest radius circle enclosing all points of a cluster. Finally, we consider several real science cases and analyze the performance of the proposed solution.
The tip/tilt driver is part of the Polarimetric and Helioseismic Imager (PHI) instrument for the ESA Solar Orbiter (SO), which is scheduled to launch in 2017. PPHI captures polarimetric images from the Sun to better understand our nearest star, the Sun. The paper covers an analog amplifier design to drive capacitive solid state actuator such ass piezoelectric actuator. Due to their static and continuous operation, the actuator needs to be supplied by high-quality, low-frequency, high-voltage sinusoidal signals. The described circuit is an efficiency-improved Class-AB amplifier capable of recovering up to 60% of the charge stored in the actuator. The results obtained after the qualification model test demonstrate the feasibility of the circuit with the accomplishment of the requirements fixed by the scientific team.
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle spectrograph operating at spectral resolution R=20,000 over the 1-2.5μm bandpass) was selected by the Gran Telescopio Canarias (GTC) partnership as the next-generation near-infrared spectrograph for the world's largest optical/infrared telescope, and is being developed by an international consortium. The MIRADAS consortium includes the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de Canarias, and Institut d'Estudis Espacials de Catalunya, as well as probe arm industrial partner A-V-S (Spain), with more than 45 Science Working Group members in 10 institutions primarily in Spain, Mexico, and the USA. In this paper, we review the overall system design and project status for MIRADAS during its early fabrication phase in 2016.
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) is a near-infrared multi-object echelle spectrograph for the 10.4-meter Gran Telescopio Canarias. The instrument has 12 pickoff mirror optics on cryogenic probe arms, enabling it to concurrently observe up to 12 user-defined objects located in its field-of-view. In this paper, a method to compute collision-free trajectories for the arms of MIRADAS is presented. We propose a sequential approach that has two stages: target to arm assignment and motion planning. For the former, we present a model based on linear programming that allocates targets according to their associated priorities. The model is constrained by two matrices specifying the targets’ reachability and the incompatibilities among each pair of feasible target-arm pairs. This model has been implemented and experiments show that it is able to determine assignments in less than a second. Regarding the second step, we present a prioritized approach which uses sampled-based roadmaps containing a variety of paths. The motions along a given path are coordinated with the help of a depth-first search algorithm. Paths are sequentially explored according to how promising they are and those not leading to a solution are skipped. This motion planning approach has been implemented considering real probe arm geometries and joint velocities. Experimental results show that the method achieves good performance in scenarios presenting two different types of conflicts.
The Polarimetric and Helioseismic Imager (PHI) instrument is part of the remote instruments for the ESA Solar Orbiter
(SO), which is scheduled to launch in 2017. PHI captures polarimetric images from the Sun to better understand our
nearest star, the Sun. A set of images is acquired with different polarizations, and afterwards is processed to extract the
Stokes parameters. As Stokes parameters require the subtraction of the image values, in order to get the desired quality it
is necessary to have good contrast in the image and very small displacements between them. As a result an Image
Stabilization System (ISS) is required. This paper is focused in the behavior and the main characteristics of this system.
This ISS is composed of a camera, a tip-tilt mirror and a control system. The camera is based on a STAR1000 sensor that
includes a 10 bits resolution high-speed Analog-to-Digital Converter (ADC). The control system includes a Correlation
Tracking (CT) algorithm that determines the necessary corrections. The tip-tilt mirror is moved based on this corrections
to minimize the effects of the spacecraft (S/C) drift and jitter with respect to the Sun. Due to its stringent requirements, a
system model has been developed in order to verify that the required parameters can be satisfied. The results show that
the ISS is feasible, although the margins are very small.
A very high precision Image Stabilization System has been designed for the Solar Orbiter mission. The different components that have been designed are the Correlation Tracking Camera (CTC), Tip-Tilt controller (TTC) and the system control in order to achieve the specified requirements. For the CTC, in order to achieve the required resolution of 12 bits and reduced power consumption, we used an external ADC. For the TTC, a special focus has been dedicated to a 55 V linear regulator in a QUASI-LDO configuration and a Tip-Tilt driver in a transconductance amplifier architecture. Results show that the full system reaches an attenuation of 1/10th of a pixel at 10Hz. The TTC provides a high voltage span, enough slew-rate and the needed stability levels.
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) is a near-infrared (NIR) multi-object
spectrograph for the Gran Telescopio Canarias (GTC). It can simultaneously observe multiple targets selected by
20 identical deployable probe arms with pickoff mirror optics. The bases of the arms are fixed to the multiplexing
system (MXS) plate, a circular platform, and arranged in a circular layout with minimum separation between
elements of the arms. This document presents the MXS prototype P2a, a full-scale, fully operational prototype
of a MIRADAS probe arm. This planar closed-loop mechanism compared to other previous designs offers some
advantages specially in terms of stability and from the point of view of optics. Unfortunately, these benefits come
at the expense of a more complicated kinematics and an unintuitive arm motion. Furthermore, the cryogenic
motor controllers used in prototyping impose severe restrictions in path planing. They negatively impact in the
slice of pie approach, a collision-avoidance patrolling strategy that can gives good results in other scenarios. This
study is a starting point to define collision-free trajectory algorithms for the 20 probe arms of MIRADAS.
We describe the design, development, and laboratory test results of cryogenic probe arms
feeding deployable integral field units (IFUs) for the Mid-resolution InfRAreD Astronomical
Spectrograph (MIRADAS) - a near-infrared multi-object echelle spectrograph for the 10.4-meter
Gran Telescopio Canarias. MIRADAS selects targets using 20 positionable pickoff mirror optics
on cryogenic probe arms, each feeding a 3.7x1.2-arcsec field of view to the spectrograph
integral field units, while maintaining excellent diffraction-limited image quality. The probe arms
are based on a concept developed for the ACES instrument for Gemini and IRMOS for TMT.
We report on the detailed design and opto-mechanical testing of MIRADAS prototype probe
arms, including positioning accuracy, repeatability, and reliability under fully cryogenic
operation, and their performance for MIRADAS. We also discuss potential applications of this
technology to future instruments.
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle
spectrograph operating at spectral resolution R=20,000 over the 1-2.5μm bandpass) was selected in 2010 by the Gran
Telescopio Canarias (GTC) partnership as the next-generation near-infrared spectrograph for the world's largest
optical/infrared telescope, and is being developed by an international consortium. The MIRADAS consortium includes
the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de
Canarias, Institut de Física d'Altes Energies, Institut d'Estudis Espacials de Catalunya and Universidad Nacional
Autonoma de Mexico, as well as probe arm industrial partner A-V-S (Spain). In this paper, we review the overall system
design for MIRADAS, as it nears Preliminary Design Review in the autumn of 2012.