Photometry of Kuiper belt object (486958) Arrokoth from New Horizons LORRI

On January 1st 2019, the New Horizons spacecraft flew by the classical Kuiper belt object (486958) Armkoth (provisionally designated 2014 MU69), possibly the most primitive object ever explored by a spacecraft. The I/F of ArMkoth is analyzed and fit with a photometric function that is a linear combination of the Lommel-Seeliger (lunar) and Lambert photometric functions. Armkoth has a geometric albedo of p(y) = 0.2(-0.04)(+0.05) at a wavelength of 550 nm and ti0.24 at 610 nm. Arrokoth's geometric albedo is greater than the median but consistent with a distribution of cold classical Kuiper belt objects whose geometric albedos were determined by fitting a thermal model to radiometric observations. Thus, Arrokoth's geometric albedo adds to the orbital and spectral evidence that it is a cold classical Kuiper belt object. Maps of the normal reflectance and hemispherical albedo of Armkoth are presented. The normal reflectance of Arrokoth's surface varies with location, ranging from approximate to 0.10-0.40 at 610 nm with an approximately Gaussian distribution. Both Arrokoth's extrema dark and extrema bright surfaces are correlated to topographic depressions. Armkoth has a bilobate shape and the two lobes have similar normal reflectance distributions: both are approximately Gaussian, peak at approximate to 0.25 at 610 nm, and range from approximate to 0.10-0.40, which is consistent with co-formation and co-evolution of the two lobes. The hemispherical albedo of Armkoth varies substantially with both incidence angle and location, the average hemispherical albedo at 610 nm is 0.063 +/- 0.015. The Bond albedo of Arrokoth at 610 nm is 0.062 +/- 0.015.