Optical design for an adaptive anastigmatic five-mirror
extremely large telescope

Délabre, Bernard

doi:10.1051/0004-6361:20078528

Cited by 17 publications

(10 citation statements)

References 9 publications

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“…The E-ELT project is a three mirror anastigmat including addition of a pupil transfer between a pair of flat mirrors, adaptive mirror M 4 and field stabilization mirror M 5 , which fold the beams along the elevation axis to the Nasmyth foci (Delabre [32], Vernet et al [33]). The ADM of a segment is minimized by an axial support system called a whiffletree -a superimposition of pivot trianglesmounted on the tripod frames.…”

Section: Segments Of Large Telescope Mirrorsmentioning

confidence: 99%

Active optics with a minimum number of actuators

Lemaitre

2014

Advanced Optical Technologies

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Optics for astronomy implies powerful developments of active and adaptive optics methods applied to instrumentation from X-rays to the near infrared for the design of telescopes, spectrographs, and coronagraph planet finders. This presentation particularly emphasizes the development of active optics methods. Highly accurate and remarkably smooth surfaces from active optics methods allow new optical systems that use highly aspheric and non-axisymmetric -freeform -surfaces. Depending on the goal and performance required for a deformable optical surface, elasticity theory analysis is carried out either with small deformation thin plate theory, large deformation thin plate theory, shallow spherical shell theory, or the weakly conical shell theory. A mirror thickness distribution is then determined as a function of associated bending actuators and boundary conditions. For a given optical shape to generate, one searches for optical solutions with a minimum number of actuators.

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Section: Segments Of Large Telescope Mirrorsmentioning

confidence: 99%

Active optics with a minimum number of actuators

Lemaitre

2014

Advanced Optical Technologies

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“…The European Extremely Large Telescope (E-ELT) is a ∼39 m optical/infrared telescope that will take ground-based astronomy to the next level (Delabre 2008;McPherson et al 2012). Its more than 970 m 2 of collecting area and unprecedented spatial resolving power will allow for revolutionary astronomical observations.…”

Section: Introductionmentioning

confidence: 99%

Instrumental polarisation at the Nasmyth focus of the E-ELT

Ovelar

Snik

Keller

et al. 2014

A&A

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The ∼39-m European Extremely Large Telescope (E-ELT) will be the largest telescope ever built. This makes it particularly suitable for sensitive polarimetric observations, as polarimetry is a photon-starved technique. However, the telescope mirrors may severely limit the polarimetric accuracy of instruments on the Nasmyth platforms by creating instrumental polarisation and/or modifying the polarisation signal of the object. In this paper we characterise the polarisation effects of the two currently considered designs for the E-ELT Nasmyth ports as well as the effect of ageing of the mirrors. By means of the Mueller matrix formalism, we compute the response matrices of each mirror arrangement for a range of zenith angles and wavelengths. We then present two techniques to correct for these effects that require the addition of a modulating device at the "polarisation-free" intermediate focus that acts either as a switch or as a part of a two-stage modulator. We find that the values of instrumental polarisation, Stokes transmission reduction and cross-talk vary significantly with wavelength, and with pointing, for the lateral Nasmyth case, often exceeding the accuracy requirements for proposed polarimetric instruments. Realistic ageing effects of the mirrors after perfect calibration of these effects may cause polarimetric errors beyond the requirements. We show that the modulation approach with a polarimetric element located in the intermediate focus reduces the instrumental polarisation effects down to tolerable values, or even removes them altogether. The E-ELT will be suitable for sensitive and accurate polarimetry, provided frequent calibrations are carried out, or a dedicated polarimetric element is installed at the intermediate focus.

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“…M4 is a 2.5-m deformable mirror designed to compensate the optical effects of atmospheric turbulence. M5 is intended for image stabilization (compensating for telescope vibrations) [7]. For a more detailed description of AO systems in the current ELT projects see Ref.…”

Section: Introductionmentioning

confidence: 99%

“…The linear size of the full field at F1 is about 0.6 m, whereas in the final focus F2 it is 1.95 m. Manufacturing lenses of this size is not possible and segmented lenses are not desirable in view of segmentation employed already for the primary mirror M1 and deformable mirror M4. In light of this, it has been suggested to use an LADC for the E-ELT close to F1, where the image scale is 3.5 times smaller than at F2 [7]. In spite of apparent simplicity of LADC it has some drawbacks, which are discussed in Section 2.…”

Section: Introductionmentioning

confidence: 99%

The achromatic design of an atmospheric dispersion corrector for extremely large telescopes

Bahrami¹,

Goncharov²

2011

Opt. Express

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Abstract:For off-zenith observations with ground-based astronomical telescopes, the effect of atmospheric dispersion relative to diffraction on image size increases with telescope diameter. Correction of atmospheric dispersion in extremely large telescopes (ELTs) might become critical. A common solution for ELTs is to use linear atmospheric dispersion correctors (ADCs). In spite of their simplicity, the intrinsic chromatic aberrations of linear ADCs could render diffraction-limited imaging impossible when used in a fast focus. The chromatic problems of the linear ADC in ELTs can be resolved by replacing the linear ADC by the achromatic ADC designs presented here, which provide diffraction-limited image quality and offer several opto-mechanical advantages over linear ADCs.

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Optical design for an adaptive anastigmatic five-mirror extremely large telescope

Cited by 17 publications

References 9 publications

Active optics with a minimum number of actuators

Active optics with a minimum number of actuators

Instrumental polarisation at the Nasmyth focus of the E-ELT

The achromatic design of an atmospheric dispersion corrector for extremely large telescopes

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