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Gordon, Brian

Publications and source records attributed to Gordon, Brian.

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Hybrid Lyot Coronagraph for WFIRST: High Contrast Testbed Demonstration in Flight-like Low Flux Environment

In order to validate required operation of the proposed Wide-Field InfraRed Survey Telescope (WFIRST) coronagraph instrument, we have built a testbed in Jet Propulsion Laboratory (JPL), which is analogous to the baseline WFIRST coronagraph instrument architecture. Since its birth in 2016, this testbed, named as Occulting Mask Coronagraph (OMC) testbed, has demonstrated several crucial technological milestones: Broadband high contrast demonstration in both Hybrid Lyot Coronagraph (HLC) and Shape Pupil Coronagraph (SPC) modes while the Low Order Wavefront Sensing and Control (LOWFS/C) subsystem senses and corrects the dynamic flight-like wavefront disturbances. In this paper, we present up-to-date progress of HLC mode demonstration in the OMC testbed. While injecting the flight-like low photon flux starlight with expected Line of Sight (LoS) and Wavefront Error (WFE) perturbation to the OMC testbed, we demonstrate generating high contrast dark hole images. We first study the expected photon flux in actual flight environment, and estimate detection noise and estimation accuracy of the complex electric field if the wavefront sensing algorithm is used based on the pair-wise difference imaging. Then, we introduce our improved scheme to mitigate this photon-starved flight-like low flux environment. As a result, we generate a dark hole that meets the WFIRST raw contrast requirements using the 2nd magnitude star light. We establish the key ideas, describe test setups, and demonstrate test results with data analysis.

Wilson, Daniel↗
NASA NTRS2011

A Hybrid Lyot Coronagraph for the Direct Imaging and Spectroscopy of Exoplanet Systems: Recent Results and Prospects

We report our best laboratory contrast demonstrations achieved to date. We review the design, fabrication, performance, and future prospects of a hybrid focal plane occulter for exoplanet coronagraphy. Composed of thickness-profiled metallic and dielectric thin films vacuum deposited on a fused silica substrate, the hybrid occulter uses two superimposed thin films for control over both the real and imaginary parts of the complex attenuation pattern. Together with a deformable mirror for adjustment of wavefront phase, the hybrid Lyot coronagraph potentially exceeds billion-to one contrast over dark fields extending to within angular separations of 3 lambda/D (3 x the cosmological constant / diameter of the telescope) from the central star, over spectral bandwidths of 20 percent or more, and with throughput efficiencies up to 60 percent. We report laboratory contrasts of 3 x 10 (sup -10) degrees over 2 percent bandwidths, 6 x 10 (sup -10) degrees over 10 percent bandwidths, and 2 x 10 (sup -9) over 20 percent bandwidths, achieved across high contrast fields extending from an inner working angle of 3 lambda/D to a radius of 15 lambda/D. Occulter performance is analyzed in light of recent experiments and optical models, and prospects for further improvements are summarized. The science capabilities of the hybrid Lyot coronagraph are compared with requirements of the ACCESS mission, a representative exoplanet space telescope concept study for the direct imaging and spectroscopy of exoplanet systems. This work has been supported by NASA's Technology Demonstration for Exoplanet Missions (TDEM) program.

coronagraph↗
NASA NTRS2008

Laboratory Demonstrations of High-contrast Imaging for Space Coronagraphy

This slide presentation reviews the use of the High Contrast Imaging Testbed (HCIT) in the design and improvement of space coronagraphs. The objectives of the work are to: (1) Advance the technology readiness of space coronagraph hardware, techniques, algorithms, and predictive models; (2) Provide proof-of-concept demonstrations of coronagraph techniques; and (3) Support collaborations across the exoplanet community in pursuit of the optimal space coronagraph architecture.

High Contrast Imaging Testbed (HCIT)↗
NASA NTRS2004

High Contrast Imaging Testbed for the Terrestrial Planet Finder Coronagraph

The Terrestrial Planet Finder (TPF) mission is planning to launch a visible coronagraphic space telescope in 2014. To achieve TPF science goals, the coronagraph must have extreme levels of wavefront correction (less than 1 Angstrom rms over controllable spatial frequencies) and stability to get the necessary suppression of diffracted starlight (approximately l0(exp -10)) contrast at an angular separation approximately 4 (lamda)/D). TPF Coronagraph's primary platform for experimentation is the High Contrast Imaging Testbed, which will provide laboratory validation of key technologies as well as demonstration of a flight-traceable approach to implementation. Precision wavefront control in the testbed is provided by a high actuator density deformable mirror. Diffracted light control is achieved through use of occulting or apodizing masks and stops. Contrast measurements will establish the technical feasibility of TPF requirements, while model and error budget validation will demonstrate implementation viability. This paper describes the current testbed design, development approach, and recent experimental results.

coronagraph↗