Exoplanets imaging with a Phase-Induced Amplitude Apodization Coronagraph - I. Principle

Using 2 aspheric mirrors, it is possible to apodize a telescope beam without losing light or angular resolution: the output beam is produced by ``remapping'' the entrance beam to produce the desired light intensity distribution in a new pupil. We present the Phase-Induced Amplitude Apodization Coronagraph (PIAAC) concept, which uses this technique, and we show that it allows efficient direct imaging of extrasolar terrestrial planets with a small-size telescope in space. The suitability of the PIAAC for exoplanet imaging is due to a unique combination of achromaticity, small inner working angle (about 1.5 $\lambda/d$), high throughput, high angular resolution and large field of view. 3D geometrical raytracing is used to investigate the off-axis aberrations of PIAAC configurations, and show that a field of view of more than 100 $\lambda/d$ in radius is available thanks to the correcting optics of the PIAAC. Angular diameter of the star and tip-tilt errors can be compensated for by slightly increasing the size of the occulting mask in the focal plane, with minimal impact on the system performance. Earth-size planets at 10 pc can be detected in less than 30s with a 4m telescope. Wavefront quality requirements are similar to classical techniques.Comment: 35 pages, 16 figures, Accepted for publication in Ap

Telescope to Observe Planetary Systems (TOPS): a high throughput 1.2-m visible telescope with a small inner working angle

The Telescope to Observe Planetary Systems (TOPS) is a proposed space mission to image in the visible (0.4-0.9 micron) planetary systems of nearby stars simultaneously in 16 spectral bands (resolution R~20). For the ~10 most favorable stars, it will have the sensitivity to discover 2 R_E rocky planets within habitable zones and characterize their surfaces or atmospheres through spectrophotometry. Many more massive planets and debris discs will be imaged and characterized for the first time. With a 1.2m visible telescope, the proposed mission achieves its power by exploiting the most efficient and robust coronagraphic and wavefront control techniques. The Phase-Induced Amplitude Apodization (PIAA) coronagraph used by TOPS allows planet detection at 2 lambda/d with nearly 100% throughput and preserves the telescope angular resolution. An efficient focal plane wavefront sensing scheme accurately measures wavefront aberrations which are fed back to the telescope active primary mirror. Fine wavefront control is also performed independently in each of 4 spectral channels, resulting in a system that is robust to wavefront chromaticity.Comment: 12 pages, SPIE conference proceeding, May 2006, Orlando, Florid

TOPS: a small space telescope using phase induced-amplitude apodization (PIAA) to image rocky and giant exo-planets

The Telescope to Observe Planetary Systems (TOPS) is a proposed space mission to image planetary systems of nearby stars simultaneously in a few wide spectral bands covering the visible light (0.4-0.9 μm). It achieves its power by combining a high accuracy wavefront control system with a highly efficient Phase-Induced Amplitude Apodization (PIAA) coronagraph which provides strong suppression very close to the star (within 2 λ/D). The PIAA coronagraphic technique opens the possibility of imaging Earthlike planets in visible light with a smaller telescope than previously supposed. If sized at 1.2-m, TOPS would image and characterize many Jupiter-sized planets, and discover 2 RE rocky planets within habitable zones of the ≈10 most favorable stars. With a larger 2-m aperture, TOPS would have the sensitivity to reveal Earth-like planets in the habitable zone around ≈20 stars, and to characterize any found with low resolution spectroscopy. Unless the occurrence of Earth-like planets is very low (η⊕ <~ 0.2), a useful fraction of the TPF-C scientific program would be possible with aperture much smaller than the baselined 8 by 3.5m for TPF, with its more conventional coronagraph. An ongoing laboratory experiment has successfully demonstrated high contrast coronagraphic imaging within 2 λ/d with the PIAA coronagraph / focal plane wavefront sensing scheme envisioned for TOPS

The Phase Induced Amplitude Apodization Coronagraph: an overview of simulations and laboratory effort.

International audienc

The Phase-Induced Amplitude Coronagraph (PIAA)

International audienc

Sparse wavefront control: A new approach to high-contrast imaging

Current high-contrast imaging systems implement wavefront control using traditional deformable mirrors developed for atmospheric turbulence correction, which require large strokes, high-speed, and continuous phase correction. However, high-contrast imaging has different requirements. Thus, developing a specialized deformable mirror for this application able to meet the demanding requirements of future exoplanet imaging flagship missions is valuable for the exoplanet scientific community. In this paper, we propose a novel wavefront control approach, called Sparse Wave-Front Control (SWFC), which enables high-contrast imaging using sparse phase changes on the active surface re-directing coherent starlight to null speckles. To validate SWFC, we simulated a telescope equipped with a Phase Induced Amplitude Apodization (PIAA) coronagraph and a 100 by 100 actuator sparse Deformable Mirror to null speckles caused by the optical system aberrations. We modeled the mirror as a flat surface where narrow gaussian influence functions represent actuators. We performed wavefront control utilizing Electric Field Conjugation achieving 6.7e-11 mean contrast between 3 to 35 lambda/D in monochromatic light and 7.4e-11 in 10% broadband light. In the second part of this paper, we propose an approach to manufacture Sparse Deformable Mirrors utilizing photosensitive polymers, which could be placed below the mirror coating and can be photonically actuated by back illumination through the mirror substrate.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Results of the astrometry and direct imaging testbed for exoplanet detection

Measuring masses of long-period planets around F, G, and K stars is necessary to characterize exoplanets and assess their habitability. Imaging stellar astrometry offers a unique opportunity to solve radial velocity system inclination ambiguity and determine exoplanet masses. The main limiting factor in sparse-field astrometry, besides photon noise, is the non-systematic dynamic distortions that arise from perturbations in the optical train. Even space optics suffer from dynamic distortions in the optical system at the sub-mu as level. To overcome this limitation we propose a diffractive pupil that uses an array of dots on the primary mirror creating polychromatic diffraction spikes in the focal plane, which are used to calibrate the distortions in the optical system. By combining this technology with a high-performance coronagraph, measurements of planetary systems orbits and masses can be obtained faster and more accurately than by applying traditional techniques separately. In this paper, we present the results of the combined astrometry and and high-contrast imaging experiments performed at NASA Ames Research Center as part of a Technology Development for Exoplanet Missions program. We demonstrated 2.38x10(-5) lambda/D astrometric accuracy per axis and 1.72x10(-7) raw contrast from 1.6 to 4.5 lambda/D. In addition, using a simple average subtraction post-processing we demonstrated no contamination of the coronagraph field down to 4.79x10(-9) raw contrast.NASA's Technology Development for Exoplanet Missions program; JPL's Exoplanet Exploration ProgramThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]