The GTC primary mirror control system

Lefort, Bertrand; Castro, Jordi

doi:10.1117/12.789382

Cited by 18 publications

(6 citation statements)

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“…This stabilization loop works normally with a sampling frequency of 20Hz. The bandwidth rejection to perturbations obtained is 2Hz [3]. The observed noise at the edge sensors within the control band is 3-4 nm rms.…”

Section: Primary Mirror Active Control Systemmentioning

confidence: 98%

The GTC project: under commissioning

et al. 2008

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The GTC (Gran Telescopio Canarias) is an optical/IR telescope, with a 10,4 meter segmented primary, installed at the Observatorio del Roque de Los Muchachos (ORM), at La Palma.Past July 2007 it saw its First Light showing a very promising behaviour. The very good image quality achieved at that an early stage of telescope commissioning is a direct consequence of the quality of its optics, the high performances of its primary mirror control system, and the highly engineered telescope structure and servo system.At present, we are advancing with the telescope commissioning whose first results are presented here. The two Day One science instruments: OSIRIS and CanariCam are being prepared for installation and commissioning on the telescope. Science verification are planned to be initiated by the end of 2008 and regular operation by March 2009.

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Section: Primary Mirror Active Control Systemmentioning

confidence: 98%

The GTC project: under commissioning

et al. 2008

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“…The actuators suitable to handle segmented mirror can be classified in two broad categories: hard actuator and the soft actuator. Actuators used in existing segmented mirror telescope such as, W. M. Keck Observatory (Keck) [1], Gran Telescopio Canarias (GTC) [2], Southern African Large Telescope (SALT) [3], Hobby-Eberly Telescope (HET) [4] and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) [5] are rigid actuators and found to have extremely high axial stiffness. The disadvantage of rigid actuator is that it support only low control bandwidth.…”

Section: Introductionmentioning

confidence: 99%

Precision controller for segmented mirror telescope actuator: Control and tuning

Deshmukh

Parihar

2016

2016 Indian Control Conference (ICC)

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The segmented mirror telescopes are built using small hexagonal mirrors positioned and aligned by the three actuators and six edge sensors per segment to maintain the shape of the primary mirror. The global loop controller does this by sending commands to the actuators to move within few nanometers. These commands are executed at individual actuator locally by a precision controller. The paper describes our effort to develop a precision actuator controller at India TMT Coordination Centre (ITCC) laboratory, Indian Institute of Astrophysics, Bangalore. The actuator controller is implemented around a single board computer called SBC6845. We have also designed and developed a customized actuator drive board which comprises power electronics to handle the voice coil motor (VCM), off-loader as well as snubber stepper motors. In addition to this, drive board also contains a decoder, current sensor and related circuitry to get the position and other feedbacks. The closed loop proportional-integralderivative controller (PID controller) is implemented for position loop using the feedback from linear optical encoder. Another closed loop is introduced around off-loader with the feedback from current sensor. The tuning of position loop is done by two different methods based on Relay Auto tuning and System Identification. By making use of above controller and the optimum gain, several experiments have been conducted to test the performance of prototype soft actuator. The Actuator along with its best tuned controller gives the steady state position error around 2.44nm RMS. At the tracking rate of 300nm/s, we could achieve RMS position error of 4.04nm, which is better than what is required. These results and other details of controller and its tuning are presented.

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“…The current standard for observatories to control the alignment of a segmented primary mirror is by using capacitance-based edge sensors, [2][3][4][5] which are capable of electrically detecting any physical displacement between two segments which share a common edge. 6 Using these systems, the alignment of the primary is, ideally, set by the electrical noise of the sensors.…”

Section: Introductionmentioning

confidence: 99%

Strategies and considerations for the on-sky implementation of the controllable segmented primary mirror with AO WFS feedback

Calvin,

Fitzgerald,

Ragland

et al. 2023

Techniques and Instrumentation for Detection of Exoplanets XI

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Maintaining the co-phasing of the primary mirror segments is a critical aspect to the operation of segmented telescopes. However, speckle-based measurements of the phasing of the Keck primary estimated static aberrations of approximately 90 nm rms that are not sensed by the current edge-sensing segment control system. We propose directly sensing and controlling the primary via the wavefront sensor of the adaptive optics system, as a Controllable Segmented Primary (CSP), to actively correct its phasing. In this work, we consider strategies for implementing and calibrating the CSP system on-sky.

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The GTC primary mirror control system

Cited by 18 publications

References 0 publications

The GTC project: under commissioning

The GTC project: under commissioning

Precision controller for segmented mirror telescope actuator: Control and tuning

Strategies and considerations for the on-sky implementation of the controllable segmented primary mirror with AO WFS feedback

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