SEARCH · Engineering Papers
Results for “high contrast imaging”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758
We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one - possibly two - faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \textit{possible} detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 7588 has a H-L' color redder than nearly all known L-T8 dwarfs. 8ased on comparisons with the COND evolutionary models, GJ 7588 has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx.10-20 Mj if it is approx.1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 7588 is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 7588 is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.
High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758
We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one -- possibly two-- faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \textit(possible) detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 758B has a H-L'color redder than nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx. 10-20 Mj if it is approx. 1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 758B is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.
Occulting focal plane masks for Terrestrial Planet Finder Coronagraph: design, fabrication, simulations and test results
Occulting focal plane masks for the Terrestrial Planet Finder Coronagraph (TPF-C) could be designed with continuous gray scale profile of the occulting pattern such as 1-sinc2 on a suitable material or with micron-scale binary transparent and opaque structures of metallic pattern on glass. We have designed, fabricated and tested both kinds of masks. The fundamental characteristics of such masks and initial test results from the High Contrast Imaging Test bed (HCIT) at JPL are presented.
The Optical Design of CHARIS: An Exoplanet IFS for the Subaru Telescope
High-contrast imaging techniques now make possible both imaging and spectroscopy of planets around nearby stars. We present the optical design for the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph (IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide spectral information for 138×138 spatial elements over a 2.07 arcsec × 2.07 arcsec field of view (FOV). CHARIS will operate in the near infrared (lambda = 1.15 − 2.5 micrometers) and will feature two spectral resolution modes of R is approximately 18 (low-res mode) and R is approximately 73 (high-res mode). Taking advantage of the Subaru telescope adaptive optics systems and coronagraphs (AO188 and SCExAO), CHARIS will provide sufficient contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets. CHARIS will undergo CDR in October 2013 and is projected to have first light by the end of 2015. We report here on the current optical design of CHARIS and its unique innovations.
PISCES: An Integral Field Spectrograph Technology Demonstration for the WFIRST Coronagraph
We present the design, integration, and test of the Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) integral field spectrograph (IFS). The PISCES design meets the science requirements for the Wide-Field Infra Red Survey Telescope (WFIRST) Coronagraph Instrument (CGI). PISCES was integrated and tested in the integral field spectroscopy laboratory at NASA Goddard. In June 2016, PISCES was delivered to the Jet Propulsion Laboratory (JPL) where it was integrated with the Shaped Pupil Coronagraph (SPC) High Contrast Imaging Testbed (HCIT). The SPC/PISCES configuration will demonstrate high contrast integral field spectroscopy as part of the WFIRST CGI technology development program.
Model Validation of Phase-Induced Amplitude Apodization Complex Mask Coronagraph for LUVOIR-A in Vacuum
The Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is a coronagraph architecture for the next generation of large space telescopes optimized for habitable exoplanet imaging that can achieve attractive theoretical performance with high throughput at small inner working angles (IWA). PIAACMC designs are compatible with large, on-axis, segmented apertures such as the Large UV / Optical/ Infrared A (LUVOIR-A) concept currently being considered by the decadal survey review which would greatly enhance the possibility to achieve statistically significant scientific yields and signal quality for direct imaging exoplanet surveys. PIAACMC has been recently implemented for LUVOIR-A and is currently being tested in vacuum at JPL’s High-Contrast Imaging Testbed (HCIT). In this work, we review the theoretical performance of the PIAACMC instrument designed to meet a 1e-9 raw contrast goal in 10% broadband light in a region from 2-8 L/D both before and after the wavefront control loop. We use empirical measurements from the vacuum testbed to verify the instrument model and its performance including line-of-sight errors, instrument alignment, and fabricated components. In particular, the model verification includes measured sags of the manufactured PIAA mirrors by NuTek. The CMC mask was manufactured at JPL’s Microdevices Laboratory and we include surface profile characterization measurement. We assess the impact on performance of the different manufacturing and alignment errors.
Conceptual Design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) for the Subaru Telescope
Recent developments in high-contrast imaging techniques now make possible both imaging and spectroscopy of planets around nearby stars. We present the conceptual design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph (IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide spectral information for 140 x 140 spatial elements over a 1.75 arcsecs x 1.75 arcsecs field of view (FOV). CHARIS will operate in the near infrared (lambda = 0.9 - 2.5 micron) and provide a spectral resolution of R = 14, 33, and 65 in three separate observing modes. Taking advantage of the adaptive optics systems and advanced coronagraphs (AO188 and SCExAO) on the Subaru telescope, CHARIS will provide sufficient contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets. CHARIS is in the early design phases and is projected to have first light by the end of 2015. We report here on the current conceptual design of CHARIS and the design challenges.
Constrained Reference Star Differential Imaging: Enabling High-fidelity Imagery of Highly Structured Circumstellar Disks
High-contrast imaging presents us with the opportunity to study circumstellar disks and the planets still embedded within them, providing key insights into the formation and evolution of planetary systems. However, the postprocessing techniques that are often needed to suppress stellar halo light typically result in significant and variable loss of circumstellar light, even when using relatively conservative approaches like reference star differential imaging (RDI). We introduce “constrained reference star differential imaging” (constrained RDI), a new class of RDI point-spread-function (PSF) subtraction techniques for systems with circumstellar disks. Constrained RDI utilizes either high-resolution polarized-intensity (PI) images or disk models to severely limit or even eliminate the signal loss due to oversubtraction that is common to RDI. We demonstrate the ability of constrained RDI utilizing polarimetric data to yield an oversubtraction-free detection of the AB Aurigae protoplanetary disk in total intensity. PI-constrained RDI allows us to decisively recover the spectral signature of the confirmed, recently discovered protoplanet, AB Aurigae b. We further demonstrate that constrained RDI can be a powerful analysis tool for soon-to-be-acquired James Webb Space Telescope coronagraphic imaging of disks. In both cases, constrained RDI provides analysis-ready products that enable more detailed studies of disks and more robust verification of embedded exoplanets.
Laboratory Demonstration of Phase Induced Amplitude Apodization (PIAA) Coronagraph with Better than 10(exp -9) Contrast
We present coronagraphic images from the Phase Induced Amplitude Apodization (PIAA) coronagraph on NASA's High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Lab, showing contrasts of 5x10(exp -1) averaged from 2-4 lambda/D, in monochromatic light at 808 nm. In parallel with the coronagraph and its deformable mirror and coronagraphic wavefront control, we also demonstrate a low-order wavefront control system, giving 100 x rms suppression of introduced tip/tilt disturbances down to residual levels of 10(exp -3) lambda/D. Current limitations, as well as broadband (10% fractional bandpass) preliminary results are discussed.
Adjustable collimation for dark-field proton radiography contrast enhancement
A dark-field imaging condition established through pre- and post-object beam collimation has been tested for a variety of different settings at the proton radiography facility (pRad) at Los Alamos National Laboratory. This technique facilitates imaging of thin samples and materials with small areal density changes with 800 MeV protons that would otherwise appear nearly transparent for high energy protons. In the configuration that was examined, the pre-object (upstream) collimator is utilized to remove protons with large scattering angles prior to the target object. The post-object collimation entails a combination of a conventional collimator, which eliminates protons with large scattering angles after target interaction, and an inverse collimator. The inverse collimator removes unscattered protons traveling on the beam axis and those with smaller scattering angles up to a desired angle. This establishes a dark-field condition by permitting solely protons that exhibit scattering angles from target interaction within a designated range to contribute to the image. This study explores the potential of combining different sized collimators for pre- and post-object collimation. The objective is to optimize contrast for a range of samples with minimal areal density variations. A series of dark-field conditions are explored employing a remote-controlled collimator wheel and the contrast-to-noise ratio, spatial resolution, and proton transmission are compared for those combinations. It is found that the contrast-to-noise ratio can be substantially enhanced for thin samples and low areal density objects, thereby facilitating capturing high-contrast images of objects that were previously invisible to high energy protons.
Coronagraph Focal-Plane Phase Masks Based on Photonic Crystal Technology: Recent Progress and Observational Strategy
Photonic crystal, an artificial periodic nanostructure of refractive indices, is one of the attractive technologies for coronagraph focal-plane masks aiming at direct imaging and characterization of terrestrial extrasolar planets. We manufactured the eight-octant phase mask (8OPM) and the vector vortex mask (VVM) very precisely using the photonic crystal technology. Fully achromatic phase-mask coronagraphs can be realized by applying appropriate polarization filters to the masks. We carried out laboratory experiments of the polarization-filtered 8OPM coronagraph using the High-Contrast Imaging Testbed (HCIT), a state-of-the-art coronagraph simulator at the Jet Propulsion Laboratory (JPL). We report the experimental results of 10-8-level contrast across several wavelengths over 10% bandwidth around 800nm. In addition, we present future prospects and observational strategy for the photonic-crystal mask coronagraphs combined with differential imaging techniques to reach higher contrast. We proposed to apply a polarization-differential imaging (PDI) technique to the VVM coronagraph, in which we built a two-channel coronagraph using polarizing beam splitters to avoid a loss of intensity due to the polarization filters. We also proposed to apply an angular-differential imaging (ADI) technique to the 8OPM coronagraph. The 8OPM/ADI mode avoids an intensity loss due to a phase transition of the mask and provides a full field of view around central stars. We present results of preliminary laboratory demonstrations of the PDI and ADI observational modes with the phase-mask coronagraphs.
The SEEDS Direct Imaging Survey for Planets and Scattered Dust Emission in Debris Disk Systems
Debris disks around young main-sequence stars often have gaps and cavities which for a long time have been interpreted as possibly being caused by planets. In recent years, several giant planet discoveries have been made in systems hosting disks of precisely this nature, further implying that interactions with planets could be a common cause of such disk structures. As part of the SEEDS high-contrast imaging survey, we are surveying a population of debris disk-hosting stars with gaps and cavities implied by their spectral energy distributions, in order to attempt to spatially resolve the disk as well as to detect any planets that may be responsible for the disk structure. Here we report on intermediate results from this survey. Five debris disks have been spatially resolved, and a number of faint point sources have been discovered, most of which have been tested for common proper motion, which in each case has excluded physical companionship with the target stars. From the detection limits of the 50 targets that have been observed, we find that beta Pic b-like planets (approximately 10M(sub jup) planets around G-A-type stars) near the gap edges are less frequent than 15-30%, implying that if giant planets are the dominant cause of these wide (27 AU on average) gaps, they are generally less massive than beta Pic b.
Studies of the Effects of Actuator Errors on the HCIT/PIAA Contrast Performance
The High Contrast Imaging Testbed Phase Induced Amplitude Apodization (HCIT/PIAA) coronagraph system at JPL relies on an Electric-Field Conjugation (EFC) wavefront correction algorithm to obtain the required high contrast. This algorithm works with one deformable mirror (DM) to estimate the electric-field to be controlled, and with one or multiple DM's to create a "dark-hole" in the image plane. We have investigated the effects of DM actuator errors on the efficiency of the EFC algorithm. The structural design of the optical system as well as the parameters of various optical elements used in the analysis are drawn from those of the HCIT/PIAA system that have been and will be implemented with one or two DM's. The simulation takes into account the surface errors of various optical elements. In this paper, we report our findings in the case of narrowband wavelength light.
High-Contrast Coronagraph Performance in the Presence of DM Actuator Defects
Deformable Mirrors (DMs) are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Occasionally DM actuators or their associated cables or electronics fail, requiring a wavefront control algorithm to compensate for actuators that may be displaced from their neighbors by hundreds of nanometers. We have carried out experiments on our High-Contrast Imaging Testbed (HCIT) to study the impact of failed actuators in partial fulfillment of the Terrestrial Planet Finder Coronagraph optical model validation milestone. We show that the wavefront control algorithm adapts to several broken actuators and maintains dark-hole contrast in broadband light.
High-Order Coronagraphic Wavefront Control With Algorithmic Differentiation: First Experimental Demonstration
Future space-based coronagraphs will rely critically on focal-plane wavefront sensing and control with deformable mirrors to reach deep contrast by mitigating optical aberrations in the primary beam path. Until now, most focal-plane wavefront control algorithms have been formulated in terms of Jacobian matrices, which encode the predicted effect of each deformable mirror actuator on the focal-plane electric field. A disadvantage of these methods is that Jacobian matrices can be cumbersome to compute and manipulate, particularly when the number of deformable mirror actuators is large. Recently, we proposed a new class of focal-plane wavefront control algorithms that utilize gradient-based optimization with algorithmic differentiation to compute wavefront control solutions while avoiding the explicit computation and manipulation of Jacobian matrices entirely. In simulations using a coronagraph design for the proposed Large UV/Optical/Infrared Surveyor (LUVOIR), we showed that our approach reduces overall CPU time and memory consumption compared to a Jacobian-based algorithm. Here, we expand on these results by implementing the proposed algorithm on the High Contrast Imager for Complex Aperture Telescopes (HiCAT) testbed at the Space Telescope Science Institute (STScI) and present initial experimental results, demonstrating contrast suppression capabilities equivalent to Jacobian-based methods.
Image Formation in High Contrast Optical Systems: The Role of Polarization
To find evidence of life in the Universe outside our solar system is one of the most compelling and visionary adventures of the 21st century. The technologies to create the telescopes and instruments that will enable this discovery are now within the grasp of mankind. Direct imaging of a very faint planet around a neighboring bright star requires high contrast or a hypercontrast optical imaging system capable of controlling unwanted radiation within the system to one part in ten to the 11th. This paper identifies several physical phenomena that affect image quality in high contrast imaging systems. Polarization induced at curved metallic surfaces and by anisotropy in the deposition process (Smith-Purcell effect) along with beam shifts introduced by the Goos-Hachen effect are discussed. A typical configuration is analyzed, and technical risk mitigation concepts are discussed.