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New "Juno" Mission To Jupiter Announced
Riding with Robots writes "Today NASA announced it is officially proceeding with the Juno robotic mission to Jupiter. Scheduled to launch in August 2011 and reach the largest planet in 2016, the spacecraft will orbit the planet 32 times, skimming about 4,800 kilometers over the planet's cloud tops for about a year. The mission will focus on Jupiter's structure and evolution, and not on Europa or the other icy moons that may hide oceans under their surfaces — a disappointment if you ask me. Then again, all planetary missions so far have turned up amazing images and surprising scientific discoveries, and I doubt this expedition will be any different." We discussed NASA's deliberation of its short list a few days back.
That's not how orbits work. After the 32nd orbit, Juno will enter its 33rd orbit. Orbits are inertial, and only require fuel for station-keeping. On this orbit, however, no orbital perturbations will cleverly keep Juno out of the worst of Jupiter's tremendous magnetic fields, which trap cosmic rays, solar wind particles, and other ionizing radiation, and so Juno's electronics will begin to degrade. No longer able to speak to us, Juno will keep orbiting until the orbital trajectory itself begins to degrade and it spirals down into the planet to burn up in the atmosphere.
So I took a few seconds to RTFA and I found (or didn't find):
It uses SOLAR PANELS to power this thing all the way to Jupiter. That'll beat the previous record holder (I think the DAWN mission to Vesta and Ceres) for use of solar power away from the sun. TFA says that other than a 10 min period in earth's shadow during a flyby it will always be in sunlight.
1) So does that mean it will be in a sun synchronous polar orbit at Jupiter? Won't that compromise the data collection opportunities it has? (It'll never be able to look "straight down" with the sun at its back).
I couldn't find any details about how it intends to enter and then adjust its jupiter-centric polar orbit. I see no mention of using gravity assist WITHIN the jupiter system using any of the galilean satellites to reduce the amount of delta V for insertion (and adjustments). Is this because they are going into a polar orbit and won't be in the plane of the satellite's orbits? Nor did I see any mention of some fancy aero-braking (like the Mars orbiters use). (Of course I guess ion drives (like those used in DAWN) wouldn't be practical because the probe would have to "linger" too long in Jupiter's radiation belts while it slowly shed velocity).
2) So will they be using some standard chemical propellents with a long storage time (like Cassini)? Will a large part of the spacecraft be fuel or does its "unique highly elliptical" orbit not require too much delta V to enter?
Anyway, sounds like a cool mission, that won't cost too much or take too long to get there (uses solar power so no expensive nukes, uses 1 gravity assist and a medium size Atlas booster). Hopefully the camera has a high enough resolution to take a picture of Medusa! (Please see Arthur C. Clarke's "Meeting with Medusa").