Three months after it cancelled its mission to Pluto because of dramatic cost increases, NASA has turned to an open competition in a bid to develop an affordable alternative.

This month the agency will invite competitive bids for a mission to the Pluto-Charon system and the Kuiper Belt beyond, which it says will cost not more than $500 million including launch. Work on the NASA Jet Propulsion Laboratory's (JPL) Pluto/Kuiper Express mission was stopped last September after cost projections ballooned from $650 million to $1.5 billion.

NASA is not committed to selecting or executing a Pluto mission, says associate administrator for space science Ed Weiler. "But we want to make sure we have all the options on the table."

Proposals are due by 19 March. Two or more proposals will be selected for more detailed studies leading to selection of the winning mission in August this year.

The new Pluto/Kuiper Express mission will be modelled on the NASA Discovery programme, which has resulted in lower cost, more focused scientific missions using rapidly developed spacecraft. "Competition has worked quite well in other NASA space science programmes," says Weiler.

NASA had planned to launch JPL's Pluto/Kuiper Express in 2004 to take advantage of a Jupiter gravity-assisted trajectory available only every 12 or so years. No launch date has been specified for the new mission, but NASA's goal is to reach Pluto by 2015, suggesting a 2004-6 launch.

Before the stop-work order, "unacceptable" cost increases on JPL's Pluto probe were endangering a higher-priority mission to Jupiter's moon Europa, pushing its launch back from 2003 to 2011. Under the new plan, the Europa orbiter, also being developed by JPL, will be launched in 2008.

Source: Flight International