SPECTRAL GEOMETRIC ALBEDO AND BOLOMETRIC BOND ALBEDO OF NEPTUNE'S SATELLITE TRITON FROM VOYAGER OBSERVATIONS

Abstract

We have calculated the spectral geometric albedo and bolometric Bond albedo of Triton by combining the published data from the Voyager spacecraft Photopolarimeter (PPS) experiment and the Voyager imaging science (ISS) experiment. We have used the PPS ultraviolet (0.25 μm) and infrared (0.75 μm) filter data and the ISS violet (0.41 μm) and green (0.56 μm) filter data to produce geometric albedos and phase integrals at each of the four wavelengths. The resulting spectral geometric albedo is not inconsistent with the presence of weak absorption feature in Triton's spectrum near 0.75 μm. The phase integrals were determined by Russell's approximation and by 2‐point Gaussian quadrature. The geometric albedo at the uv, v, g and ir filters is 0.59, 0.68, 0.81, and 0.75 respectively. The resulting bolometric Bond albedo (∼0.65) is· consistent with the 38 K, unit emissivity, daytime surface temperature for Triton reported as a best fit to the data of the Voyager Infrared Specrotrometer and Radiometer (IRIS). Our results are also in agreement with the 37.5 K temperature of nitrogen at an inferred basal pressure of 14 μbar as reported by the Voyager Ultraviolet Spectrometer (UVS) investigation.The bolometric Bond albedo that is determined from tile phase integral and spherical albedo reported originally by the ISS investigation yields a surface temperature which is consistent with the PPS, IRIS and UVS temperatures only for a surface with a substantially lower emissivity. There are differences between the PPS and the ÎSS phase curves which cause the differences in bolometric bond albedo reported in the two studies.