Design considerations in predicting energy needs of spacecraft

Multiple modes of power are available to spacecraft ranging from solar to nuclear thermoelectric. But, how do we select between the different power sources for reliability and long duration power? To this end, understanding the amount of solar energy available at the designated locale for the mission on a per unit surface area basis is critical for designing the power management function of the spacecraft. Specifically, once the amount of solar power available at the designated orbit is estimated, and together with the amount of energy required for the various instrument package onboard the spacecraft, estimates of the surface area of the solar panels could be calculated. If the required surface area is larger than that supportable by the spacecraft structure as well as launch constraints, nuclear thermoelectric power source would be needed instead of solar power. More importantly, integrated power management is required to titrate the amount of energy generated against that required by the spacecraft and instruments; thereby, presenting scenarios where the engineers at mission control would need to switch off specific instruments for conserving power to maintain safe flight control of the spacecraft. Hence, energy management of spacecraft runs through the design phase of the mission through to daily operation of the spacecraft, for example, in orbit around another planet, and is critically important to the overall success of the mission. While solar energy is desirable for most missions, lack of insolation at distances far away from the Sun meant that either the mission is deficient in science payload or a nuclear thermoelectric power source is required for powering all necessary scientific instruments onboard.