Observations of a successive stellar occultation by Charon and graze by Pluto in 2011

Introduction: Since the late 1980s, stellar occultations have provided snapshots of the Pluto system and specifically of Pluto’s atmospheric evolution. The lower atmosphere, below roughly half-light level in an occultation light curve, has changed distinctly over time (e.g. [1, 2]). Theorized explanations for the lower atmospheric structure include a steep thermal gradient and/or extinction, the latter of which can be characterized as a dependence between occultation flux and wavelength. Pluto’s upper atmosphere has remained consistent. However, in 2007, a grazing occultation revealed waves in the upper atmosphere [3-5]. Data: Observations were made at NASA’s 3-m Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, for a predicted occultation of a UCAC2 14.43 magnitude star by Pluto on 23 June 2011. The stellar magnitude is 11.0, 10.1, and 9.7 in J, H, and K, respectively. The star was observed simultaneously with and SpeX [6] and MORIS (the MIT Optical Rapid Imaging System [7]). MORIS recorded visible images of a 1arcmin by 1-arcmin field of view, with an effective cen-