Trio of stellar occultations by Pluto One Year Prior to New Horizons' Arrival

Our campaign in July 2014 yielded three successful stellar occultations (~m=15, 17, and 18) of Pluto (~m=14), observed from telescopes in New Zealand, Australia, and Chile. Telescopes involved included Chile: Magellan's Clay (6.5 m), SOAR (4.1 m), Carnegie's DuPont (2.4 m); Australia: AAT (4 m); and Canterbury's Mt. John McLellan (1-m); as well as various smaller telescopes in Australia and Chile. One of the events was also observed, with negative results, from GROND on La Silla (2.2 m) and SMARTS's ANDICAM at CTIO (1.3 m). Though our observations were coordinated across continents, each successfully observed event was seen from only one site because of bad weather at the other sites. Two of the events were uniquely observed from Mt. John (Pasachoff et al., DPS 2014) and one, with only Chile sites in the predicted path, from the Clay (Person et al., DPS 2014). This last event was expected to be of the brightest star with the largest telescope we have ever observed for a Pluto occultation, but clouds arrived at the 6.5-m Clay 90 s before the predicted time; a 1% occultation was nonetheless seen and eventually, confirmed by Keck AO observations, to be of a 15th magnitude star previously hidden in the brightness of the 12th mag star. Our scientific conclusion is that as of these observations, one year before New Horizons' passage of Pluto, the atmosphere of Pluto remained robust and of the same size. Details on our analysis of the three events will be presented.Acknowledgments: This work was supported in part by NASA Planetary Astronomy grants to Williams College (NNX12AJ29G) and to MIT (NNX10AB27G), as well as grants from USRA (#8500-98-003) and Ames Research (#NAS2-97-01) to Lowell Observatory. A.R.S. was supported by NSF grant AST-1005024 for the Keck Northeast Astronomy Consortium REU, with partial support from U.S. DoD's ASSURE program. P.R. acknowledges support from FONDECYT through grant 1120299. J.M.P. thanks Andrew Ingersoll and Caltech Planetary Astronomy for hospitality.