Two methods for determining the temperature on the surface of the cometary nucleus based on spectroscopic measurements

Abstract

The paper presents two methods that can be used to determine the surface temperature of a cometary nucleus. The key role in this approach is played by the measurement of hemispherical albedo for selected dust analogues, which was performed using a Cary 5000 spectrometer. To most accurately reflect the actual structure of the dust layer present on the surface of the cometary nucleus under Earth's conditions, selected dust analogues were used in laboratory research. In the first method, bolometric albedo (Bond albedo) was used, and in the second method, hemispherical albedo was used, which comes directly from the measurement. Comparing both methods, it was found that the average value of the temperature difference for a given analogue is 0.47 K. Due to the small temperature differences between these approaches, both methods can be treated as equivalent. Based on the measurements and calculations performed, it was found that the most representative analogue of the actual dust present on the surface of comet 67P/Churyumov–Gerasimenko is a sample consisting of a mixture of sand with a volume fraction of about 10% and charcoal with a volume fraction of about 90%.