P51A-2039
New Horizons approach photometry of Pluto and Charon: light curves and Solar phase curves
Friday, 18 December 2015
Poster Hall (Moscone South)
Amanda Marie Zangari1, Marc W Buie1, Bonnie J Buratti2, Anne Verbiscer3, Carly Howett1, Harold A Weaver Jr4, Catherine Olkin1, Kimberly Ennico Smith5, Leslie Ann Young1, S Alan Stern6 and The New Horizons Geology Geophysics and Imaging Science Theme Team, (1)Southwest Research Institute Boulder, Boulder, CO, United States, (2)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (3)University of Virginia Main Campus, Charlottesville, VA, United States, (4)Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, (5)NASA Ames Research Center, Moffett Field, CA, United States, (6)Southwest Research Institute Boulder, Dept Space Studies, Boulder, CO, United States
Abstract:
While the most captivating images of Pluto and Charon were shot by NASA's New Horizons probe on July 14, 2015, the spacecraft also imaged Pluto with its LOng Range Reconnaissance Imager ("LORRI") during its Annual Checkouts and Approach Phases, with campaigns in July 2013, July 2014, January 2015, March 2015, April 2015, May 2015 and June 2015. All but the first campaign provided full coverage of Pluto's 6.4 day rotation. Even though many of these images were taken when surface features on Pluto and Charon were unresolved, these data provide a unique opportunity to study Pluto over a timescale of several months. Earth-based data from an entire apparition must be combined to create a single light curve, as Pluto is never otherwise continuously available for observing due to daylight, weather and scheduling. From the spacecraft, Pluto's sub-observer latitude remained constant to within 0.05 degrees of 43.15 degrees, comparable to a week's worth of change as seen from Earth near opposition. During the July 2013 to June 2015 period, Pluto's solar phase curve increased from 11 degrees to 15 degrees, a small range, but large compared to Earth's 2 degree limit. The slope of the solar phase curve hints at properties such as surface roughness. Using PSF photometry that takes into account the ever-increasing sizes of Pluto and Charon as seen from New Horizons, as well as surface features discovered at closest approach, we present rotational light curves and solar phase curves of Pluto and Charon. We will connect these observations to previous measurements of the system from Earth.
