​​Satellite Spotting & Operations Handbook

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Solar power beyond earth orbit

The most distant spacecraft so far to use Solar Power is the current Juno Probe now orbiting Jupiter. On average, the solar arrays produce about 460 to 490 watts of power as it arrived at Jupiter. End of mission power is planned to be 420 watts. The individual solar arrays can be articulated by a small amount in flight to control the vehicle’s centre of gravity, which is important to vehicle stability. When making engine burns (made in the UK) Juno consumes fuel which changes the spacecraft’s mass properties and are balanced out by adjusting the solar array position. Two 55 amp/hour lithium-ion batteries are used to store electrical power that is used when the spacecraft is in eclipse or its solar arrays are off-sun. For the duration of its mission, except for 10 minutes of eclipse during the Earth Flyby, Juno will be in daylight. The electrical power subsystem manages the vehicle’s power bus and distribution to payloads and instruments. A central power distribution and drive unit monitors the power that is generated by the solar arrays, distributes it to instruments, heaters and experiment sensors as well as batteries that are charged when excess power is available.