End to end optical design and wavefront error simulation of METIS

Agócs, Tibor; Zuccon, Sara; Jellema, Willem; Born, Joost van den; Horst, Rik ter; Bizenberger, Peter; Vázquez, M.; Todd, Stephen; Baccichet, Nicola; Straubmeier, C.

doi:10.1117/12.2313434

Cited by 6 publications

(9 citation statements)

References 2 publications

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“…The SFE were generated according to the description of Agócs. 9 Random Zernike polynomials are used to model the low and mid spatial frequency components. These can be caused by surface manufacturing, printthrough errors, and other low order contributors such as mechanical mounting stresses and errors, thermal gradients, and gravitational sagging.…”

Section: Generating a Randomized Surface Form Errormentioning

confidence: 99%

The Talbot effect's impact on the high contrast imaging modes of METIS

Boné

Agócs

Absil

et al. 2020

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV

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The ELT, Europe's Extremely Large Telescope, with its 39m main mirror will be the largest optical/infrared telescope in the world, able to work at the diffraction limit. METIS is one of its first light instruments with powerful imaging and spectroscopic capabilities in the thermal wavelengths. It contains several high contrast imaging (HCI) modes, which allow it to detect and characterize exoplanets amongst others. The HCI performance is highly dependent on pupil stabilization mechanisms and a closed loop compensation of non-common path aberrations degrading the wavefront error of the instrument.The Talbot effect is a near-field effect on collimated light, where spatial frequencies of the wavefront are re-imaged periodically along the optical path. The periodicity is known as the Talbot length, which is a function of the wavelength and the wavefront's spatial frequencies with the latter being a result of the wavefront errors caused by the surface form errors of optical elements. The aberrations oscillate from amplitude to phase, in the spatial scale of one Talbot length, which can have an impact on the performance of the HCI modes. We evaluate the impact of the Talbot effect with respect to the METIS phase aberration budget by assuming representative power spectral density profile for the surface form error of each optical surface. We propagate the errors to the subsequent pupil plane and finally investigate the resulting point spread function profile. Simulations are fed back into the HCI error budget and if necessary, the specifications regarding instrument surface form are adjusted.

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Section: Generating a Randomized Surface Form Errormentioning

confidence: 99%

The Talbot effect's impact on the high contrast imaging modes of METIS

Boné

Agócs

Absil

et al. 2020

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation IV

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“…Optical overview of METIS taken from [18]. Light from the telescope enters the METIS cryostat from the left.…”

Section: Figmentioning

confidence: 99%

“…The components of the WCU (red colored box) as well as the spectrograph and imager are irrelevant for further consideration. More details can be found in [18,19] At the very end, all factors that have an impact on the AO performance have to be considered to come to a sound decision for the wavefront sensor's spectral band. We tried to narrow down this rather extensive task by looking at the signal to noise ratio (SNR) per sub-aperture of a generic wavefront sensor with 2 types of real-world detectors, an electron multiplying CCD (EMCCD [21]) and an electron avalanche photodiode near-infrared detector (SAPHIRA [22,23]).…”

Section: Figmentioning

confidence: 99%

Single conjugate adaptive optics for the ELT instrument METIS

et al. 2018

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The European Extremely Large Telescope (ELT) is a 39 m large, ground-based optical and near-to mid-infrared telescope under construction in the Chilean Atacama desert. Operation is planned to start around the middle of the next decade. All first light instruments will come with wavefront sensing devices that allow control of the ELT's intrinsic M4 and M5 wavefront correction units, thus building an adaptive optics (AO) system. To take advantage of the ELT's optical performance, full diffraction-limited operation is required and only a high performance AO system can deliver this. Further technically challenging requirements for the AO come from the exoplanet research field, where the task to resolve the very small angular separations between host star and planet, has also to take into account the high-contrast ratio between the two objects. We present in detail the results of our simulations and their impact on high-contrast imaging in order to find the optimal wavefront sensing device for the METIS instrument. METIS is the mid-infrared imager and spectrograph for the ELT with specialised high-contrast, coronagraphic imaging capabilities, whose performance strongly depends on the AO residual wavefront errors. We examined the sky and target sample coverage of a generic wavefront sensor in two spectral regimes, visible and near-infrared, to pre-select the spectral range for the more detailed wavefront sensor type analysis. We find that the near-infrared regime is the most suitable for METIS. We then analysed the performance of Shack-Hartmann and pyramid wavefront sensors under realistic conditions at the ELT, did a balancing with our scientific requirements, and concluded that a pyramid wavefront sensor is the best choice for METIS. For this choice we additionally examined the impact of noncommon path aberrations, of vibrations, and the long-term stability of the SCAO system including high-contrast imaging performance.Keywords Single conjugate adaptive optics · SCAO · ELT · Pyramid wavefront sensor · Shack-Hartmann wavefront sensor · Fragmented pupil · Low wind effect · Non-common path aberrations · High-contrast imaging

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“…Like most other subsystems, the SCAO module resides inside the METIS cryostat. Its location in the optical path 15 is the result of a number of design considerations:…”

Section: Wavefront Sensing Within Metismentioning

confidence: 99%

Single conjugate adaptive optics for METIS

Bertram

Absil

Bizenberger

et al. 2018

Adaptive Optics Systems VI

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METIS is the Mid-infrared Extremely large Telescope Imager and Spectrograph, one of the first generation instruments of ESO's 39m ELT. All scientific observing modes of METIS require adaptive optics (AO) correction close to the diffraction limit. Demanding constraints are introduced by the foreseen coronagraphy modes, which require highest angular resolution and PSF stability. Further design drivers for METIS and its AO system are imposed by the wavelength regime: observations in the thermal infrared require an elaborate thermal, baffling and masking concept.METIS will be equipped with a Single-Conjugate Adaptive Optics (SCAO) system. An integral part of the instrument is the SCAO module. It will host a pyramid type wavefront sensor, operating in the near-IR and located inside the cryogenic environment of the METIS instrument. The wavefront control loop as well as secondary control tasks will be realized within the AO Control System, as part of the instrument. Its main actuators will be the adaptive quaternary mirror and the field stabilization mirror of the ELT.In this paper we report on the phase B design work for the METIS SCAO system; the opto-mechanical design of the SCAO module as well as the control loop concepts and analyses. Simulations were carried out to address a number of important aspects, such as the impact of the fragmented pupil of the ELT on wavefront reconstruction. The trade-off that led to the decision for a pyramid wavefront sensor will be explained, as well as the additional control tasks such as pupil stabilization and compensation of non-common path aberrations.

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End to end optical design and wavefront error simulation of METIS

Cited by 6 publications

References 2 publications

The Talbot effect's impact on the high contrast imaging modes of METIS

The Talbot effect's impact on the high contrast imaging modes of METIS

Single conjugate adaptive optics for the ELT instrument METIS

Single conjugate adaptive optics for METIS

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