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.