Scientific and technical teams from NASA and the European Space Agency (ESA) are fleshing out ideas for the next mission to fly to an outer planet
– either to Jupiter or Saturn. A decision on which of those two exploration targets will be the destination for the space agency’s next
billion-dollar flagship mission is expected by year’s end.


“We have the outer planet flagship mission in the [NASA] budget … I do believe it will happen,” said Fran Bagenal, a professor of astrophysical and planetary sciences at the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. “I couldn’t have said that four years ago … now I have great confidence that this will happen.”


Bagenal is chair of the Outer Planets Assessment Group (OPAG), which was established by NASA in late 2004 to identify scientific priorities and pathways for exploration in the outer solar system.


In 2007, NASA completed a series of studies for flagship missions, honing down the list to the two candidate missions that now are under further study by both NASA and ESA.


Down-selection this year


During a two-day OPAG meeting that began
here March 31,
officials provided a status report on the two outer planet exploration concepts now on the table: a Europa-Jupiter System Mission and a Titan-Saturn System Mission. Each of those mission scenarios has multiple components with both ESA and NASA contributing to whichever outer planet investigation is down-selected.


The Europa-Jupiter mission involves two orbiters with instruments designed to operate in the severe radiation environment of Jupiter. In addition to ESA and NASA, Russia also has expressed interest in the mission, proposing a Europa lander.


The Titan-Saturn flagship entails a main spacecraft that would orbit Saturn and
deployment of
secondary spacecraft to the surface of
Titan. For the secondary spacecraft, there are proposals that would include
such as a balloon for exploring the atmosphere, surface probes and
even a mini-submarine for exploring lakes on Titan


“We are no longer doing studies … we are now getting ready for a mission,” said Curt Niebur, program officer for outer planets research at NASA
headquarters in Washington. Money to push forward on an outer planets flagship, he said, is contained in NASA’s
2009 budget – with ESA conducting a down-select process through its Cosmic Vision process.


Potential partners


“There are between one and five different spacecraft elements that comprise these missions,” Niebur noted, along with potential contributions from the Japan Aerospace Exploration Agency, as well the Russian space agency, Roscosmos.


“At this point we have firm agreement with ESA. We don’t have firm agreements with other potential partners,” Niebur added.


For NASA, the outer planet flagship mission is cost-capped at $2.1 billion, Niebur said. “That’s all the money we have … that’s all the money NASA has to put towards this.”


NASA and ESA will both down-select to one outer planet mission this fall, Niebur explained. The mission to the outer planet would be launched via an Atlas 5, a Delta 4 Heavy
or an Ares 5 no later than 2017. The launch would be designed to send the spacecraft
on a lengthy cruise toward its destination but one that would be no longer
than seven years.

Leonard Dudzinski, NASA’s program officer for radioisotope power capability, said
the outer planet flagship would make use of Multi-Mission Radioisotope Thermoelectric Generators.


At present, there is enough plutonium-238 dioxide allocated for 800 watts of power for an outer planet flagship mission – although due to the shortfall of the nuclear fuel, “we’ve encouraged studies this year to look at reduced power requirements to save some of that plutonium,” Dudzinski advised the OPAG attendees.


Eyes wide open


NASA and ESA also are planning to issue a joint Announcement of Opportunity for scientific experiments to fly on the mission. The first of three NASA-hosted Outer Planet Flagship Mission Instrument Workshops is to be held June 3-5 in Pasadena, Calif.
, Niebur said.


“Whether or not it’s Europa or Titan as the major target isn’t at all clear,” Bagenal said
. Two large science definition teams are working hard to make these missions happen, she said.


Bagenal emphasized that by careful, early study of these missions it is hoped that any cost overrun can be short-circuited.


“There’s no point in having an outer planet flagship mission
that ends up costing so much that we can’t afford to go to another target in the outer solar system for another 15 years or 20 years,” Bagenal pointed out. “So we really have the pressure on us to make sure that we can do something that is technically and fiscally responsible.”


Whatever outer planet target is chosen – likely to occur this November – getting to that locale is tough, Bagenal told Space News, be it taking a payload to the surface of Titan or going into orbit around Europa.


“The technologies are being worked … they are being lined up,” Bagenal said.


“It’s just an issue of can you be clever and squeeze things down and do things very efficiently to save money. And it’s money, money, money,” Bagenal said. “All these studies are being done to make sure we’re going in carefully … with our eyes wide open