WASHINGTON — Juno, the $1.1 billion Jupiter orbiter slated to launch Aug. 5, could be a blueprint for doing planetary science as far out as Jupiter on a constrained budget, the project’s overseer said July 20.
“I think what Juno represents is a demonstration of something really complex and difficult to do [that] is able to be accomplished in a principal investigator mode,” said Scott Bolton, Juno principal investigator and director of space science and engineering at the Southwest Research Institute in San Antonio.
Juno is NASA’s second New Frontiers mission, responsibility for which is delegated to the principal investigator who proposed the mission, rather than a NASA field center, as is the case with flagship-class missions such as the Mars Science Laboratory and James Webb Space Telescope. New Frontiers missions are the biggest science missions — in terms of budget outlay — that NASA manages under the principal investigator approach.
Juno is being managed out of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.of Denver built the probe. It will launch on an Atlas 5 rocket from the Kennedy Space Center in Florida.
It will be the largest solar-powered craft to cruise beyond Mars.
To date, all NASA probes visiting the outer planets — where sunlight is in short supply — have relied on plutonium-fueled radioisotope power systems to run their on-board electronics.
In 2003, when Bolton and his colleagues were developing their Juno proposal, NASA was scrambling to secure enough plutonium for its inaugural New Frontiers mission, the Pluto-bound New Horizons probe currently on target to reach its destination in 2015.
“At the time we were putting together the mission, there were no [radioisotope thermoelectric generators] available and [NASA] would have had to develop a new one,” Bolton said in a July 19 interview.
As a result, the Juno team knew it would have to find a way to conduct an in-depth study of Jupiter on solar power alone.
“We’re the first solar-powered mission to go this far — five astronomical units,” said Bolton. An astronomical unit is the distance between the Earth and the sun — about 150 million kilometers.
Juno will have to travel five times that distance through space, keeping its three solar arrays pointed toward the sun the whole time, said Bolton. Given the distance of Jupiter from the sun, the solar arrays will provide only 400 to 500 watts of power once Juno reaches orbit, Bolton said. That is only enough to power “a couple of light bulbs,” but sufficient nonetheless to power the nine science instruments aboard the craft, he added.
The sensitive electronics that power these instruments have been encased in a titanium vault to protect them from the piercing radiation emanating from Jupiter.
“Juno is an armored tank” because “where we’re going is … one of the most hazardous regions in the solar system,” Bolton said.
When Juno locks into its planned polar orbit around Jupiter, the probe will peer into the jovian atmosphere and search for water.
“Our main science instruments to get at this are the microwave radiometers, which penetrate the atmosphere to see how much water is in it,” Bolton said.
Juno is also equipped with “a set of magnetometers … which tells us something about the interior structure” of the gas giant.
In particular, Juno will try to determine whether the solar system’s largest and oldest planet has a rocky or a gaseous core. Doing so will provide clues about how celestial bodies form, which in turn will provide insight into the conditions necessary for a planet like Earth to come into being, Bolton said.
The microwave radiometer was built at the Jet Propulsion Lab, the magnetometers at the Goddard Space Flight Center in Greenbelt, Md.
In 2003, when Juno was conceived, it had a $650 million price tag. In 2005, that figure rose to $842 million, reflecting an adjustment for inflation, said Jim Adams, deputy director of planetary science at NASA headquarters here. However, after Juno’s formal selection, budget reductions forced NASA to push Juno’s launch to 2011. It was originally slated to launch no later than June 30, 2010. The inflation-adjusted cost of the mission rose to the current $1.1 billion to reflect the launch delay, Adams said. .
NASA expects to spend about $180 million on Juno this year. That figure includes a $10 million boost over the 2011 appropriation. The cash injection “minimizes risk as the project continues toward launch in August 2011,” NASA said in its 2011 operating plan, a copy of which was obtained by Space News. Of the planetary science missions currently on NASA’s docket, only the Mars Science Laboratory (MSL), a $2.5 billion flagship-class mission designed to analyze the martian surface, is grander in scope than Juno. MSL is supposed to launch between Nov. 25 and Dec. 18.
New flagship-class missions could be out of the picture at NASA for years to come. Funding anticipated for planetary science over the next five years is below the level that would trigger recommendations to descope or delay flagship science, per the National Science Foundation’s latest decadal survey, “Vision and Voyages for Planetary Science in the Next Decade 2013-2022.”