Publications

Things I've published and other work.

Selected Papers

Wavefront profiling via correlation of GLAO open loop telemetry

SPIE 2022 Proceeding - E. McEwen, R. Dungee, M. Chun, O. Lai, C. Barnec

Full Paper

Animated cross-correlation maps between wavefront sensor pairs from the imaka wind profiling paper Adaptive Optics (AO) used in ground based observatories can be strengthened in both design and algorithms by a more detailed understanding of the atmosphere they seek to correct. Nowhere is this more true than on Maunakea, where a clearer profile of the atmosphere informs AO system development from the small separations of Extreme AO (ExAO) to the wide field Ground Layer AO (GLAO). Employing telemetry obtained from the ımaka GLAO demonstrator on the University of Hawaii 2.2-meter telescope, we apply a wind profiling method that identifies turbulent layer velocities through spatial-temporal cross correlations of multiple wavefront sensors (WFSs). We compare the derived layer velocities with nearby wind anemometer data and meteorological model predictions of the upper wind speeds and discuss similarities and differences. The strengths and limitations of this profiling method are evaluated through successful recovery of injected, simulated layers into real telemetry. We detail the profilers’ results, including the percentage of data with viable estimates, on four characteristic ımaka observing runs on open loop telemetry throughout both winter and summer targets. We report on how similar layers are to external measures, the confidence of these results, and the potential for future use of this technique on other multi conjugate AO systems.

Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor

SPIE 2019 Proceeding - R. Jensen-Clem, C. Z. Bond, S. Cetre, E. McEwen, P. Wizinowich, S. Ragland, D. Mawet, J. Graham

Full Paper

Figure from the Keck II predictive wavefront control paperThe success of ground-based instruments for high contrast exoplanet imaging depends on the degree to which adaptive optics (AO) systems can mitigate atmospheric turbulence. While modern AO systems typically suffer from millisecond time lags between wavefront measurement and control, predictive wavefront control (pWFC) is a means of compensating for those time lags using previous wavefront measurements, thereby improving the raw contrast in the post-coronagraphic science focal plane. A method of predictive control based on Empirical Orthogonal Functions (EOF) has previously been proposed and demonstrated on Subaru/SCExAO. In this paper we present initial tests of this method for application to the near-infrared pyramid wavefront sensor (PYWFS) recently installed in the Keck II AO system. We demonstrate the expected root-mean-square (RMS) wavefront error and contrast benefits of pWFC based on simulations, applying pWFC to on-sky telemetry data saved during commissioning of the PYWFS. We discuss how the performance varies as different temporal and spatial scales are included in the computation of the predictive filter. We further describe the implementation of EOF pWFC within the PYWFS dedicated real-time controller (RTC), and, via daytime testing at the observatory, we demonstrate the performance of pWFC in real time when pre-computed phase screens are applied to the deformable mirror (DM).

The Keck Planet Imager and Characterizer: Demonstrating advanced exoplanet characterization techniques for future extremely large telescopes

SPIE 2019 Proceeding - N.Jovanovic, J. R. Delorme, C. Z. Bond, S. Cetre, D. Mawet, D. Echeverri, J. K. Wallace, R. Bartos, S. Lilley, S. Ragland, G. Ruane, P. Wizinowich, M. Chun, J. Wang, J. Wang, M. Fitzgerald, K. Matthews, J. Pezzato, B. Calvin, M. Millar-Blanchaer, E. C. Martin, E. Wetherell, E. Wang, S. Jacobson, E. Warmbier, C. Lockhart, D. Hall, R. Jensen-Clem, E. McEwen

Full Paper

The Keck Planet Imager and Characterizer instrumentThe Keck Planet Imager and Characterizer (KPIC) is an upgrade to the Keck II adaptive optics system enabling high contrast imaging and high-resolution spectroscopic characterization of giant exoplanets in the mid-infrared (2-5 microns). The KPIC instrument will be developed in phases. Phase I entails the installation of an infrared pyramid wavefront sensor (PyWFS) based on a fast, low-noise SAPHIRA IR-APD array. The ultra-sensitive infrared PyWFS will enable high contrast studies of infant exoplanets around cool, red, and/or obscured targets in star forming regions. In addition, the light downstream of the PyWFS will be coupled into an array of single-mode fibers with the aid of an active fiber injection unit (FIU). In turn, these fibers route light to Keck's high-resolution infrared spectrograph NIRSPEC, so that high dispersion coronagraphy (HDC) can be implemented for the first time. HDC optimally pairs high contrast imaging and high-resolution spectroscopy allowing detailed characterization of exoplanet atmospheres, including molecular composition, spin measurements, and Doppler imaging. Here we provide an overview of the instrument, its science scope, and report on recent results from on-sky commissioning of Phase I. The instrument design and techniques developed will be key for more advanced instrument concepts needed for the extremely large telescopes of the future.

Conference Proceedings

  1. E. McEwen, J. Males, O. Guyon, S. Haffert, et al. “Comparing realtime optical gain measurement and methods on MagAO-X,” 2026. Proc. SPIE 14150, Adaptive Optics Systems X.
  2. E. McEwen, J. Males, O. Guyon, S. Haffert, et al. “On-sky, real-time optical gain calibration on MagAO-X using incoherent speckles,” 2024. Proc. SPIE 13097-130970U, Adaptive Optics Systems IX.
  3. Skaf, N. et al. (E. McEwen 13 of 22) “Real-time control and data standardization on various telescopes and benches,” SPIE Astronomical Telescope and Instrumentation 2024, Art. no. arXiv:2409.13126, 2024. doi:10.48550/arXiv.2409.13126
  4. Kueny, J. K. (E. McEwen 8 of 17) “MagAO-X phase II upgrades: implementation and first on-sky results of a new post-AO 1000 actuator deformable mirror,” Proc. SPIE, 2024, vol. 13097, Art. no. 1309761. doi:10.1117/12.3018080
  5. Li, J. (E. McEwen 13 of 22) “Challenge of direct imaging of exoplanets within structures: disentangling real signal from point source from background light,” Proc. SPIE, 2024, vol. 13097, Art. no. 1309714. doi:10.1117/12.3020333
  6. Long, J. D. (E. McEwen 9 of 20) “More data than you want, fewer data than you need: machine learning approaches to starlight subtraction with MagAO-X,” Proc. SPIE, 2024, vol. 13097, Art. no. 130972X. doi:10.1117/12.3018424
  7. Males, J. R. (E. McEwen 7 of 23) “MagAO-X: commissioning results and status of ongoing upgrades,” Proc. SPIE, 2024, vol. 13097, Art. no. 1309709. doi:10.1117/12.3019464
  8. S. Haffert, J. Males, L. Close et al. (E. McEwen 11 of 18) “MagAO-X: a pathfinder for GMT to operate extreme adaptive optics at the photon noise limit,” 2023. Proc. SPIE 12680, Techniques and Instrumentation for Detection of Exoplanets XI, 1268008.
  9. J. A. Johnson, A. Vaz, et al. (E. McEwen 16 of 26) “MAPS Adaptive Secondary Mirror: First Light, Laboratory Work, and Achievements,” 2023 Proc. SPIE 12693-126930F.
  10. E. McEwen, R. Dungee, M. Chun, J. Lu, O. Lai, C. Baranec “Wavefront profiling via correlation of GLAO open loop telemetry,” 2022. Proc. SPIE 12185-121855U, Adaptive Optics Systems VII. doi:10.1117/12.2629613
  11. R. Jensen-Clem, C. Z. Bond, S. Cetre, E. McEwen, P. Wizinowich, S. Ragland, D. Mawet, J. Graham “Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor,” 2019, SPIE, Paper 11117-34. doi:10.1117/12.2529687
  12. N. Jovanovic et al. (E. McEwen 27 of 27) “The Keck Planet Imager and Characterizer: Demonstrating advanced exoplanet characterization techniques for future extremely large telescopes,” 2019, SPIE, Paper 11117-31. doi:10.48550/arXiv.1909.04541
  13. Pezzato, J., N. Jovanovic, D. Mawet et al. (E. McEwen 15 of 18) “Status of the Keck Planet Imager and Characterizer Phase II Development,” 2019, Proc. SPIE. 11117

Journal Articles

  1. Males, J. R., et al. (E. McEwen 7 of 19) “The eXtreme Wavefront Control Toolkit: High-Contrast Imaging Instrument Control for Ground and Space-Based Coronagraphs,” arXiv, Aug. 2026. doi:10.48550/arXiv.2608.10156
  2. Li, J., et al. (E. McEwen 23 of 35) “Discovery of Hα Emission from a Protoplanet Candidate around the Young Star 2MASS J16120668–3010270 with MagAO-X,” The Astrophysical Journal Letters, vol. 990, p. L70, Sep. 2025. doi:10.3847/2041-8213/adfcbd
  3. Close, L. M., et al. (E. McEwen 27 of 37) “Wide Separation Planets in Time (WISPIT): Discovery of a Gap Hα Protoplanet WISPIT 2b with MagAO-X,” The Astrophysical Journal Letters, vol. 990, p. L9, Sep. 2025. doi:10.3847/2041-8213/adf7a5
  4. Pearce, L. A., et al. (E. McEwen 6 of 23) “Five New Sirius-like White Dwarf–Main-sequence Star Systems with MagAO-X,” The Astronomical Journal, vol. 170, p. 58, Jul. 2025. doi:10.3847/1538-3881/addb50
  5. Liu, P. (E. McEwen 26 of 30) “The Young Suns Exoplanet Survey: An exoplanet candidate imaged around YSES 3,” Astronomy & Astrophysics, Volume 699, id.A78, 16 pp. July 2025. doi:10.1051/0004-6361/202449582
  6. Close, L. M. et al. (E. McEwen 19 of 26) “Three Years of High-Contrast Imaging of the PDS 70 b and c Exoplanets at Hα with MagAO-X: Evidence of Strong Protoplanet Hα,” The Astronomical Journal, Volume 169, Issue 1, id.35, 29 pp., (January 2025) doi:10.3847/1538-3881/ad8648
  7. Kautz, M., et al. (E. McEwen 19 of 24) “Phasing the Giant Magellan Telescope: Lab Experiments and First 2 On-sky Demonstration,” J. Astron. Telesc. Instrum. Syst. (October 2024)
  8. Landman, R., et al. (E. McEwen 13 of 15) “Making the unmodulated Pyramid wavefront sensor smart. Closed-loop demonstration of neural network wavefront reconstruction with MagAO-X,” Astronomy and Astrophysics, vol. 684, Art. no. A114, 2024. doi:10.1051/0004-6361/202348898