Credit: DLR (CC-BY 3.0)
Temperature measurement with the MASCOT radiometer MARA. The highlighted area on the surface is also observed by the MASCOT camera.
A radiometer is a device for determining the radiation emitted by a surface. Its objective is to measure the temperature of the surface without touching it. When MASCOT separates from the Hayabusa2 probe on 3 October 2018, the MASCOT radiometer MARA will already be switched on, and will measure the surface temperature of the asteroid Ryugu during the descent, landing and rest periods. At first glance, measuring surface temperature sounds rather mundane and not particularly exciting. But what can the temperature tell us about the asteroid? In order to gain a better understanding, we have to consider the factors that determine the surface temperature on a body that lacks an atmosphere. Naturally, sunlight is an important factor – as are the properties of the surface material, known as the regolith. The key factor here is the speed at which the heat dissipates into the ground, a property known as thermal inertia. read more