This month NASA’s JUNO spacecraft became the farthest solar powered spacecraft from the Sun.
Launched in August of 2011, JUNO used a gravity assist from Earth in October 2013 to develop sufficient momentum to glide to Jupiter.
JUNO’s on board power comes from three solar panels:
“Engineers designed Juno with three massive solar panels, each nearly 30 feet long. Combined, they provide Juno with 49.7 m2 of active solar cells. Once it reaches Jupiter, Juno will generate more than 400 watts of power, which may not sound like a lot, but it’s an impressive feat at so great a distance. For comparison, Juno’s solar panels can generate about 14 kilowatts near Earth, enough to power the average American home for a year.”
Once at Jupiter, JUNO will be approximately 483 million miles from the Sun. Until now spacecraft operating at that distance have used radioisotope thermoelectric generators (RTGs) to supply power.
JUNO will remain in orbit around Jupiter until February, 2018 when its orbit will decay and the probe will crash into the planet.
While there, JUNO will be providing information about the following:
– The composition of Jupiter’s atmosphere, particularly the amount of water present; water in the atmosphere will give scientists clues about Jupiter’s formation
– Map Jupiter’s magnetic and gravity fields which will reveal information about the planet’s structure
– Measure Jupiter’s magnetic force field by studying the magnetosphere are both poles
The spacecraft will close to within 3,100 miles of the surface.
While harnessing solar energy for power at that distance is undoubtedly a scientific and engineering feat, it is probably not scalable for larger missions, say, a crew of five humans on station for a year or more to explore Jupiter and its environs.
The same comment can be made about the gravity assist method of achieving enough momentum to fly to Jupiter. JUNO will arrive at Jupiter in July of this year, five years after launch.
These kinds of transit times to destinations in the solar system certainly preclude human exploration. They also ensure that the technology of the instruments on board is somewhat dated as well.