Juno Ready for Launch

The Juno mission to Jupiter is on schedule and on budget according to NASA Planetary Science Division Director Jim Green. The $1.107 billion probe is scheduled for launch next week.

The spacecraft, enclosed in its payload fairing, was mated with its Atlas V rocket this morning. Launch will be from SLC 41 at Cape Canaveral Air Force Station on August 5. The launch window remains open through August 26.

Reporters at NASA’s press conference today focused on why the spacecraft uses solar power instead of nuclear power. All the spacecraft that have travelled beyond the asteroid belt so far used nuclear Radioisotope Power Systems (RPSs) because the density of sunlight diminishes rapidly as one moves further from the Sun. Juno’s three solar arrays are each the length and width of a tractor trailer, said Juno project manager Jan Chodas from the Jet Propulsion Laboratory. Because solar energy is 25 times less at Jupiter’s distance than at Earth, they will generate only 400 watts of power – akin to four 100 watt light bulbs — despite their size.

The orbit of Juno will go between Jupiter’s radiation belts and 5,000 kilometers above the surface of the clouds. Over time the radiation will degrade solar array performance, but principal investigator Scott Bolton from the Southwest Research Institute said that the mission’s scientific investigations will be completed in one year, so it is not a mission limiting factor.

Bolton explained scientists’ fascination with Jupiter. He said that after the Sun formed, Jupiter got the rest of the “leftovers” and “we want the ingredient list” to learn the “recipe” for making planets.

What is at the center of Jupiter remains unknown. Bolton wants to know if it has a core of heavy elements or if the gas in the atmosphere just keeps getting compressed the further down one goes. The pressure at the center is thought to be 400 megabars (one bar is equivalent to the pressure on the surface of the Earth). Whatever is there is “not like what we have on Earth,” he said, which is why he does not like to use the term “rock” to describe what may be there.

Kaelyn Badura, a high school student from Deltona, FL, talked about her involvement in the project along with other high school students. They are using NASA’s Goldstone Apple Valley Radio Telescope to make baseline observations of Jupiter. Bolton added that NASA has been working with students in this manner for some years, including for the Galileo and Cassini missions. The students get to “do science first hand,” calibrating and analyzing data taken with the radio telescope from their classrooms via the Internet. Badura said that she was learning not only about science, but how to work as part of a team. Her school has been involved since 2006.

Juno will take five years to reach Jupiter, returning to Earth’s vicinity in 2013 to get a gravity boost. It will be placed into an 11-day polar orbit around the planet – the first spacecraft to orbit the planet’s poles. Italy, Belgium, France and Denmark are participating in the project. Juno is the second of NASA’s “New Frontiers” series of competed missions. The New Horizons spacecraft enroute to Pluto was the first. Green said that NASA’s goal is to do two New Frontiers missions per decade.