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NASA's New Horizons spacecraft observed (15810) 1994 JR$_1$, a 3:2 resonantKupier Belt Object (KBO), using the LOng Range Reconnaissance Imager (LORRI) onNovember 2, 2015 from a distance of 1.85 AU, and again on April 7, 2016 from adistance of 0.71 AU. These were the first close observations of any KBO otherthan Pluto. Combining ground-based and Hubble Space Telecope (HST) observationsat small phase angles and the LORRI observations at higher phase angles, weproduced the first disk-integrated solar phase curve of a typical KBO from$\alpha$=0.6-58$^\circ$. Observations at these geometries, attainable only froma spacecraft in the outer Solar System, constrain surface properties such asmacroscopic roughness and the single particle phase function. 1994 JR$_1$ has arough surface with a 37$\pm$5$^\circ$ mean topographic slope angle and has arelatively rapid rotation period of 5.47$\pm$0.33 hours. 1994 JR$_1$ iscurrently 2.7 AU from Pluto; our astrometric points enable high-precision orbitdetermination and integrations which show that it comes this close to Plutoevery 2.4 million years (10$^4$ heliocentric orbits), causing Pluto to perturb1994 JR$_1$. During the November spacecraft observation, the KBO wassimultaneously observed using HST in two colors, confirming its very redspectral slope. These observations have laid the groundwork for numerouspotential future distant KBO observations in the New Horizons-Kuiper BeltExtended Mission.

The First High-Phase Observations of a KBO: New Horizons Imaging of (15810) 1994 JR1 from the Kuiper Belt