Instructions: In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.
Input: Spacecraft operating in the inner Solar System usually rely on the use of photovoltaic solar panels to derive electricity from sunlight. In the outer solar system, where the sunlight is too weak to produce sufficient power, radioisotope thermoelectric generators (RTGs) are used as a power source.
Output:
space satellites rely on this type of energy