Technical description and performance of the phase II version of the Keck Planet Imager and Characterizer
Nemanja Jovanovic, Daniel Echeverri, Jacques-Robert Delorme, Luke Finnerty, Tobias Schofield, Jason Wang, Yinzi Xin, Jerry W. Xuan, J. Kent Wallace, Dimitri Mawet, Aniket Sanghi, Ashley Baker, Randall Bartos, Charlotte Z. Bond, Benjamin Calvin, Sylvain Cetre, Greg Doppmann, Michael P. Fitzgerald, Jason Fucik, Maodong Gao, J. Ge, Charlotte Guthery, Katelyn Horstman, Chih-Chun Hsu, Joshua Liberman, Stephanie Leifer, Scott Lilley, Ronald López, Eduardo Marín, Emily C. Martin, Bertrand Mennesson, Evan Morris, Reston Nash, Jacklyn Pezzato, Michael Porter, Mitsuko Roberts, Garreth Ruane, Jean-Baptiste Ruffio, Ben Sappey, Eugene Serabyn, Boqiang Shen, Andrew Skemer, Ji Wang, Edward Wetherell, Peter Wizinowich, Maïssa Salama, Vincent Chambouleyron, Rebecca Jensen-Clem, Charles Beichman
Abstract
The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for the Keck II Adaptive Optics (AO) system and the NIRSPEC spectrograph to enable diffraction-limited, high-resolution (R>30,000) spectroscopy of exoplanets and low-mass companions in the K and L bands. Phase I consisted of single-mode fiber injection/extraction units (FIU/FEU) used in conjunction with an H band pyramid wavefront sensor. The use of single-mode fibers provides a gain in stellar rejection, a substantial reduction in sky background, and an extremely stable line-spread function in the spectrograph. Phase II, deployed and commissioned in 2022, brought a 1000-actuator deformable mirror, beam-shaping optics, a vortex mask, and other upgrades to the FIU/FEU. An additional service mission in 2024 extended operations down to the y band, delivered an atmospheric dispersion corrector, and provided access to two laser frequency combs. KPIC phase II brings higher planet throughput, lower stellar leakage, and many new observing modes which extend its ability to characterize exoplanets at high spectral resolution, building on the successes of phase I. We present a description of the final phase II version of KPIC, along with results of system-level laboratory testing and characterization showing the instrument’s phase II throughput, stability, repeatability, and other key performance metrics prior to delivery and during installation at Keck. We outline the capabilities of the various observing modes enabled by the new modules as well as efforts to compensate for static aberrations and non-common path errors at Keck, which were issues that plagued phase I. Finally, we show results from commissioning.