Browsing by Author "Groff, Tyler D."
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Item Design and modeling of the off-axis parabolic deformable mirror laboratory(SPIE, 2019-09-09) Subedi, Hari B.; Juanola-Parramon, Roser; Groff, Tyler D.Coronagraph-equipped direct imaging missions need an active wavefront control system to cancel out the optical aberrations that degrade the performance of the coronagraphs. A fast steering mirror is used to control Line-of- Sight (LoS) pointing error caused by the telescope jitter. In addition to controlling other low-order aberrations such as astigmatism and coma, high stroke, high actuator density deformable mirrors (DMs) are also used to control the electric field at the required high spatial frequencies. We are designing a testbed to verify a different deformable architecture, where the powered optic in the optical train are controllable and have lower actuator count compared to the existing DMs with nominal surfaces. This simplifies the packaging issue for space missions and reduces both cost and risk of having the entire coronagraph instrument's performance depending on one or two high-actuator count DMs. The testbed would also be capable of testing different low-order wavefront sensing algorithms, which focuses in the near-term on a new adaptive Kalman filtering and gradient decent method to estimate the harmonic LoS errors that affect space telescopes. In the long run, we would test different machine learning techniques to estimate low-order aberrations and non-linear algorithms for digging the region of high contrast called the dark holes (DH).Item First generation parabolic deformable mirror for the ExoSpec project(SPIE, 2023-10-05) Subedi, Hari B.; Groff, Tyler D.; Will, Scott; Juanola-Parramon, RoserThe Exoplanet Spectroscopy (ExoSpec) project links four different tasks at Goddard Space Flight Center (GSFC) to facilitate efficient imaging and characterization of exoplanets. One of the tasks is the development of parabolic deformable mirrors to improve on the current state-of-the-art wavefront sensing and control implementations that are baselined to have two high-actuator count flat Deformable Mirrors (DMs). The current baseline has two DMs at a considerable separation distance to effectively control both amplitude and phase aberrations. This significant separation poses packaging challenges to the direct imaging missions. We can mitigate this issue by making the off-axis imaging elements in the optical train controllable. Besides addressing the packaging challenges, this technique reduces the risk of having the entire coronagraph instrument’s performance depend on two high-actuator count DMs. Simulations show that making imaging elements deformable increases the overall controllable bandwidth - it would be possible to control wavefront aberrations up to 35% bandwidth over a 5 - 12 λ|D. GSFC has worked with a commercial vendor to produce a first-generation parabolic DM and built a testbed in an environmentally controlled cleanroom to experimentally demonstrate the use of a parabolic DM in a coronagraph instrument. This versatile testbed is designed to test different DM architectures and various low-order wavefront schemes. This provides us with a basis for comparison with different DM configurations: 1) flat DM, 2) parabolic DMs, and 3) flat DM and parabolic DMs. In this paper, we will provide an update on our parabolic DM work.