Selection of extreme environmental conditions, albedo coefficient and Earth infrared radiation, for polar summer Long Duration Balloon missions

The selection of the extreme thermal environmental conditions -albedo coefficient and Earth infrared radiation- for the thermal design of stratospheric balloon missions is usually based on the methodologies applied in space missions. However, the particularities of stratospheric balloon missions, such as the much higher residence time of the balloon payload over a determined area, make necessary an approach centered in the actual environment the balloon is going to find, in terms of geographic area and season of flight. In this sense, this work is focussed on stratospheric balloon missions circumnavigating the North Pole during the summer period. Pairs of albedo and Earth infrared radiation satellite data restricted to this area and season of interest have been treated statistically. Furthermore, the environmental conditions leading to the extreme temperatures of the payload depend in turn on the surface finish, and more particularly on the ratio between the solar absorptance and the infrared emissivity α/ε. A simple but representative thermal model of a balloon and its payload has been set up in order to identify the pairs of albedo coefficient and Earth infrared radiation leading to extreme temperatures for each value of α/ε.