Active optics primary mirror support system for the 26m VST telescope

Schipani, P.; D’Orsi, Sergio; Ferragina, L.; Fierro, Davide; Marty, Laurent; Molfese, C.; Perrotta, Francesco

doi:10.1364/ao.49.001234

Cited by 40 publications

(22 citation statements)

References 28 publications

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“…The VST is currently the largest telescope in the world specially designed for surveying the sky in visible light; it is the ESO work-horse totally dedicated to visible survey programmes. The telescope is a F/5.5 with an alt-azimuth mount, equipped with an active optics system (Schipani et al 2010(Schipani et al , 2012. VST is equipped with the wide field camera OmegaCAM, spanning a 1×1 degree 2 field of view, in the optical wavelength range from 0.3 to 1.0 micron (Kuijken 2011 band and 1.4 hours in the i band.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

A forming wide polar-ring galaxy at z ~ 0.05 in the VST Deep Field of the Fornax cluster

Iodice

Capaccioli

Spavone

et al. 2015

A&A

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We present the first deep photometry of a good candidate for a forming polar ring galaxy at redshift z 0.05. This object, named FCSS J033710.0-354727, is a background galaxy in the VST deep field of the Fornax cluster. The deep exposures combined with the high angular resolution of the OmegaCAM at VST allow us to carry out the first detailed photometric analysis for this system in the g and i bands to derive the galaxy structure and colors. Results show that the central object resembles a disk galaxy, surrounded by a ring-like structure 2 times more extended than the central disk. The warped geometry and the presence of bright knots observed along the polar direction, as well as the several debris detected on the NW side with colors comparable to those of the galaxy, suggest that the polar structure is still forming. We argue that the wide polar ring/disk is the result of the ongoing disruption of a companion galaxy in the potential of the central object, which is 2-3 times more massive than the accreting galaxy.

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Section: Observations and Data Reductionmentioning

confidence: 99%

A forming wide polar-ring galaxy at z ~ 0.05 in the VST Deep Field of the Fornax cluster

Iodice

Capaccioli

Spavone

et al. 2015

A&A

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“…Further increase of mirror lateral displacement doesn't change the load on fixed points. For a detailed description of the primary mirror support system see Schipani et al [13].…”

Section: Primary Mirror Support Systemmentioning

confidence: 99%

“…On the axial actuators points an external force equal to mirror weight divided by support number has been applied, in order to simulate active optics contribution. As reported by Schipani et al [13], axial actuators are force controlled: they exert for each altitude angle a predetermined force plus a F needed to correct mirror aberrations (induced by incorrect polishing, or by gravity and thermal effects). A common force value for each actuator has been set in the simulation, to be as general as possible.…”

Section: Transient Analysismentioning

confidence: 99%

A simulation model for a telescope earthquake analysis: the VST primary mirror safety system

Perrotta

Schipani

2011

Exp Astron

Self Cite

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The VST (VLT Survey Telescope) is a wide field survey telescope going to be commissioned at Cerro Paranal (Chile). Due to the geological nature of the area, telescopes in Chile can be submitted to unpredictable and sometimes severe earthquake conditions. The commonly used response spectrum analysis has proven to be not suitable to evaluate the behavior of the VST telescope during an earthquake, due to the high number of devices with a nonlinear force-displacement characteristic in the primary mirror cell. Therefore, a nonlinear transient analysis based on a mixed Finite ElementSimulink approach has been carried out. A linear Finite Element (FE) model of the telescope has been developed and exported to Simulink, using a space state model representation. Then all nonlinear devices have been properly modeled and artificial accelerograms based on seismic history of the site have been applied. The paper focuses on the Simulink model, while giving an overview of the whole procedure.

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“…2 This general problem is an interesting topic. [3][4][5][6][7][8][9][10][11][12][13][14] In the past, researchers were only able to make a rough estimate of the numbers and optimum locations of the support points based on the theory of deflections of thin plates. 1,[3][4][5]11 In the last decade, based on finite element method (FEM), structural optimization technology is used to design support of astronomical telescopes.…”

Section: Introductionmentioning

confidence: 99%

Hybrid optimization methodology of variable densities mesh model for the axial supporting design of wide-field survey telescope

et al. 2016

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Hybrid optimization methodology of variable densities mesh model for the axial supporting design of wide-field survey telescope," Opt. Eng. 55(3), 035105 (2016), Abstract. The optimization of a primary mirror support system is one of the most critical problems in the design of large telescopes. Here, we propose a hybrid optimization methodology of variable densities mesh model (HOMVDMM) for the axial supporting design, which has three key steps: (1) creating a variable densities mesh model, which will partition the mirror into several sparse mesh areas and several dense mesh areas;(2) global optimization based on the zero-order optimization method for the support of primary mirror with a large tolerance; (3) based on the optimization results of the second step, further optimization with first-order optimization method in dense mesh areas by a small tolerance. HOMVDMM exploits the complementary merits of both the zero-and first-order optimizations, with the former in global scale and the latter in small scale. As an application, the axial support of the primary mirror of the 2.5-m wide-field survey telescope (WFST) is optimized by HOMVDMM. These three designs are obtained via a comparative study of different supporting points including 27 supporting points, 39 supporting points, and 54 supporting points. Their residual half-path length errors are 28. 78, 9.32, and 5.29 nm. The latter two designs both meet the specification of WFST. In each of the three designs, a global optimization value with high accuracy will be obtained in an hour on an ordinary PC. As the results suggest, the overall performance of HOMVDMM is superior to the first-order optimization method as well as the zero-order optimization method.

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Active optics primary mirror support system for the 26m VST telescope

Cited by 40 publications

References 28 publications

A forming wide polar-ring galaxy at z ~ 0.05 in the VST Deep Field of the Fornax cluster

A forming wide polar-ring galaxy at z ~ 0.05 in the VST Deep Field of the Fornax cluster

A simulation model for a telescope earthquake analysis: the VST primary mirror safety system

Hybrid optimization methodology of variable densities mesh model for the axial supporting design of wide-field survey telescope

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