arXiv subjects

Jared R Males

Publications and source records attributed to Jared R Males.

3 recordsLinked to original sources

arXiv2024

High-contrast imaging at first-light of the GMT: the wavefront sensing and control architecture of GMagAO-X

The Giant Magellan Adaptive Optics eXtreme (GMagAO-X) instrument is a first-light high-contrast imaging instrument for the Giant Magellan Telescope (GMT). GMagAO-X's broad wavelength range and the large 25-meter aperture of the GMT creates new challenges: control of all 21.000 actuators; phasing GMT's segmented primary mirror to nm levels; active control of atmospheric dispersion to sub milli-arcsecond residuals; no chromatic pupil shear to minimize chromatic compensation errors; integrated focal plane wavefront sensing and control (WFSC). GMagAO-X will have simultaneous visible and infra-red WFS channels to control the 21.000 actuator DM. The infra-red arm will be flexible by incorporating switchable sensors such as the pyramid or Zernike WFS. One innovation that we developed for GMagAO-X is the Holographic Dispersed Fringe Sensor that measures differential piston. We have also developed several integrated coronagraphic wavefront sensors to control non-common path aberrations exactly where we need to sense them. We will discuss the key components of the WFSC strategies for GMagAO-X that address the challenges posed by the first high-contrast imaging system on the ELTs.

astro-ph.IM↗

arXiv2021

Millisecond Exoplanet Imaging, I: Method and Simulation Results

One of the top remaining science challenges in astronomical optics is the direct imaging and characterization of extrasolar planets and planetary systems. Directly imaging exoplanets from ground-based observatories requires combining high-order adaptive optics with a stellar coronagraph observing at wavelengths ranging from the visible to the mid-IR. A limiting factor in achieving the required contrast (planet-to-star intensity ratio) is quasi-static speckles, caused largely by non-common path aberrations (NCPA) in the coronagraph. Starting with a realistic simulator of a telescope with an AO system and a coronagraph, this article provides simulations of several closely related millisecond regression models requiring inputs of the measured wavefronts and science camera images. The simplest regression model, called the naive estimator, does not treat the noise and other sources of information loss in the WFS. The naive estimator provided a useful estimate of the NCPA of $\sim$ 0.5 radian RMS, with an accuracy of $\sim$ 0.06 radian RMS in one minute of simulated sky time on a magnitude 8 star. The bias-corrected estimator generalizes the regression model to account for the noise and information loss in the WFS. A simulation of the bias-corrected estimator with four minutes of sky time included an NCPA of $\sim 0.05 \,$ radian RMS and an extended exoplanet scene. The joint regression of the bias-corrected estimator simultaneously achieved an NCPA estimate with an accuracy of $\sim 5\times10^{-3} \,$radian and contrast of $\sim 10^{-5}$ on the exoplanet scene. In addition, the estimate of the exoplanet image was completely free of the subtraction artifacts that always plague differential imaging. The estimate of the exoplanet image obtained by the joint regression was nearly identical to the image obtained by subtraction of a perfectly known point-spread function.

astro-ph.IM↗

arXiv2017

Spatial Linear Dark Field Control: Stabilizing Deep Contrast for Exoplanet Imaging Using Bright Speckles

Direct imaging of exoplanets requires establishing and maintaining a high contrast dark field (DF) within the science image to a high degree of precision (10^-10). Current approaches aimed at establishing the DF, such as electric field conjugation (EFC), have been demonstrated in the lab and have proven capable of high contrast DF generation. The same approaches have been considered for the maintenance of the DF as well. However, these methods rely on phase diversity measurements which require field modulation; this interrupts the DF and consequently competes with the science acquisition. In this paper, we introduce and demonstrate spatial linear dark field control (LDFC) as an alternative technique by which the high contrast DF can be maintained without modulation. Once the DF has been established by conventional EFC, spatial LDFC locks the high contrast state of the DF by operating a closed-loop around the linear response of the bright field (BF) to wavefront variations that modify both the BF and the DF. We describe here the fundamental operating principles of spatial LDFC and provide numerical simulations of its operation as a DF stabilization technique that is capable of wavefront correction within the DF without interrupting science acquisition.

astro-ph.IM↗