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Increasing the raw contrast of VLT/SPHERE with the dark hole technique
- Source :
- Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, EDP Sciences, 2020, 638, pp.A117. ⟨10.1051/0004-6361/202038010⟩, Astronomy and Astrophysics-A&A, 2020, 638, pp.A117. ⟨10.1051/0004-6361/202038010⟩
- Publication Year :
- 2020
- Publisher :
- HAL CCSD, 2020.
-
Abstract
- Context. Since 1995 and the first discovery of an exoplanet orbiting a main-sequence star, 4000 exoplanets have been discovered using several techniques. However, only a few of these exoplanets were detected through direct imaging. Indeed, the imaging of circumstellar environments requires high-contrast imaging facilities and accurate control of wavefront aberrations. Ground-based planet imagers such as VLT/SPHERE or Gemini/GPI have already demonstrated great performance. However, their limit of detection is hampered by suboptimal correction of aberrations unseen by adaptive optics (AO). Aims. Instead of focusing on the phase minimization of the pupil plane as in standard AO, we aim to directly minimize the stellar residual light in the SPHERE science camera behind the coronagraph to improve the contrast as close as possible to the inner working angle. Methods. We propose a dark hole (DH) strategy optimized for SPHERE. We used a numerical simulation to predict the global improvement of such a strategy on the overall performance of the instrument for different AO capabilities and particularly in the context of a SPHERE upgrade. Then, we tested our algorithm on the internal source with the AO in closed loop. Results. We demonstrate that our DH strategy can correct for aberrations of phase and amplitude. Moreover, this approach has the ability to strongly reduce the diffraction pattern induced by the telescope pupil and the coronagraph, unlike methods operating at the pupil plane. Our strategy enables us to reach a contrast of 5e-7 at 150 mas from the optical axis in a few minutes using the SPHERE internal source. This experiment establishes the grounds for implementing the algorithm on sky in the near future.<br />Comment: Accepted for publication in Astronomy & Astrophysics
- Subjects :
- media_common.quotation_subject
FOS: Physical sciences
Context (language use)
Astrophysics
instrumentation: adaptive optics
01 natural sciences
law.invention
Telescope
Optics
law
instrumentation: high angular resolution
0103 physical sciences
Adaptive optics
010303 astronomy & astrophysics
Coronagraph
Instrumentation and Methods for Astrophysics (astro-ph.IM)
media_common
Wavefront
Physics
010308 nuclear & particles physics
business.industry
Plane (geometry)
Astrophysics::Instrumentation and Methods for Astrophysics
techniques: high angular resolution
Astronomy and Astrophysics
Exoplanet
Space and Planetary Science
Sky
Astrophysics::Earth and Planetary Astrophysics
business
Astrophysics - Instrumentation and Methods for Astrophysics
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Subjects
Details
- Language :
- English
- ISSN :
- 00046361
- Database :
- OpenAIRE
- Journal :
- Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, EDP Sciences, 2020, 638, pp.A117. ⟨10.1051/0004-6361/202038010⟩, Astronomy and Astrophysics-A&A, 2020, 638, pp.A117. ⟨10.1051/0004-6361/202038010⟩
- Accession number :
- edsair.doi.dedup.....84128ed5ee3b5a408c631cf9d4d2a111