NOAO >   Observing Info >   Approved Programs >   2018A-0389

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Program Information for 2018A-0389


PI: Anne Verbiscer, U. of Virginia, verbiscer@virginia.edu
Address: Department of Astronomy, PO Box 400325, Charlottesville, VA 22904 USA

CoI: David L Rabinowitz, Yale U.
CoI: Silvia Protopapa, U. of Maryland
CoI: Susan Benecchi, PSI

Title: Pluto and Charon At True Opposition: A Once in a Lifetime Opportunity

Abstract: At opposition in 2018, Pluto and Charon will be visible at the smallest solar phase angles in 87 years. They will be at ``true" opposition when Pluto crosses the line of nodes on UT 12 July, when, as seen from Pluto, Earth will transit the solar disk. Such rare planetary alignments enable the characterization of small-scale surface texture and porosity as well as the direct measurement of the geometric albedo, rather than an estimation of its value from photometric models. Here we propose to obtain broadband images of Pluto and Charon at the smallest possible phase angles from SOAR using the SOAR Optical Imager (SOI). Observations at this ``true opposition" configuration, when combined with observations at a larger phase angle, enable measurement of the opposition effect, or surge, which reveals the textural properties of the surface. These textural properties, including grain size, porosity, and grain opacity, are directly related to the evolution and collisional history of the body. Results from this program will enhance the scientific return from NASA's New Horizons mission, since {sl New Horizons} did not observe the Pluto system at phase angles smaller than $8^circ$. Observations at extreme phase angles, both small and large, are necessary to measure the single particle phase function and thus characterize the global scattering properties of particles on these icy bodies in the outer Solar System.

Program Type: Standard/Solar System

Scheduled Nights:
Run 1 (2018A):  SOAR/SOI -- 3.5n on Jul 10 - Jul 15 2018


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