THE ALBEDO, EFFECTIVE TEMPERATURE, AND ENERGY-BALANCE OF NEPTUNE, AS DETERMINED FROM VOYAGER DATA

Data from the Voyager infrared spectrometer and radiometer (IRIS) investigation are used in determining the albedo, effective temperature, and energy balance of Neptune. From broadband radiometric observations made at phase angles of 14-degrees and 134-degrees, together with measurements at intermediate phase angles from the literature, an orbital mean value for the bolometric Bond albedo, ABAR = 0.290 +/- 0.067, is obtained; this yields an equilibrium temperature T(eq) = 46.6 +/- 1.1 K. From thermal spectra obtained over latitudes from pole to pole an effective temperature T(eff) = 59.3 +/- 0.8 K is derived. This represents a substantial improvement over previously determined values. The energy balance of Neptune is therefore E = 2.61 +/- 0.28, which is in agreement with previous results. The reduced uncertainty in this value is due to the improved determination of the effective temperature.