DS1 needs a way to get rid of that extra energy, and they do so by turning it into heat by passing it through a resistor. This is called conduction . This is unlikely to happen in space, because there is nothing in space to brush against most of the time. By radiating the heat as infrared light. This is how DS1 will lose most of its heat.
Infrared light consists of very long waves.
An object can absorb and emit infrared light. When an object absorbs infrared light, it heats up. Your car heats up in the Sun due to the same effect. Your dashboard absorbs energy emitted from the Sun, then re-emits it as infrared radiation. But, because this radiation cannot go through the glass, the car will become hotter since it cannot radiate the heat energy to the outside of the car.