Questions concerning the future of Europe's Rosetta comet probe are slowly being answered, but perhaps the biggest question of all -- that of funding -- is still left open after a high-level meeting last week.

An artist's concept of the Rosetta spacecraft and its tiny lander. Credit: Astrium

Officials last week confirmed plans to launch Rosetta in February 2004 to comet Churyumov-Gerasimenko aboard an Ariane 5G+ rocket at the meeting of the ESA science program committee.

The Ariane 5 flight will feature the first operational use of two burns of the storable propellant upper stage separated by an hour-long coast period.

For the past few months, the Hubble Space Telescope and the European Southern Observatory on Earth have studied Churyumov-Gerasimenko and determined it to be safe to land on, and that it presented a plausible mission scenario.

Rosetta was delayed from January after an upgraded version of the Ariane 5 booster failed to orbit its satellite payloads last December. Although the comet craft would fly on a different version of the heavy-lift rocket, ESA and Arianespace opted to postpone the Rosetta mission to fully verify the flightworthy status of all Ariane 5 configurations in the wake of the failure investigation earlier this year.

Rocket troubles with the Ariane 5 delayed Rosetta from its planned January 2003 launch. Photo: ESA/CNES/Arianespace

Rosetta only had several weeks to get off the ground due to strict orbital mechanics laws that govern the trajectory of the probe to its initial target -- comet Wirtanen.

Engineers and scientists then began a search for new options to allow Rosetta to complete its mission. Several baseline plans were formulated, and managers made the final selection last week at the regularly scheduled committee meeting.

Overall, officials told Spaceflight Now, the one-year delay is expected to add about $80 million more to the $1 billion cost of the Rosetta project for storage of the spacecraft, workforce commitments, and replanning of the revised mission.

Rosetta during its initial launch campaign at the Ariane launch site in South America. Photo: ESA/CNES/Arianespace

That additional cost is rigid and senior management does not expect it to change, an ESA spokesperson said on behalf of Rosetta program manager John Ellwood. "The project has been working on the cost definition during the last months and now has a very detailed assessment."

The ESA science program has a strict annual budget ceiling of about $430 million to spread around to a number of projects and missions both in development and in operation. "For the next two years it is already allocated for on-going programs with little contingency. Obviously, Rosetta needs most of its extra funding during the next two years."

In addition to the financial needs of Rosetta in the near-term timeframe, science program director David Southwood also has to juggle budgetary problems with the Herschel and Planck space telescopes. Both missions are experiencing cost overruns which further cloud the funding of Rosetta and other future projects in development.

The science program has since turned over the issue to a finance committee that is due to meet first this week to address the issue. Meanwhile, plans to launch Rosetta 9 months from now are "obviously dependent on the financial problem being sorted out," a spokesperson said.

An Ariane 5 rocket could launch Rosetta in February 2004. Photo: ESA/CNES/Arianespace

"ESA is committed to keeping all other approved projects on schedule. However, (we) will have to re-address the overall program once the present short term problems are resolved."

An ESA ministerial meeting May 27 could also play a role in the decision to earmark funds to save Rosetta, but the ESA administrative and finance committee this week will be first to deal with the issue.

Unless ESA can come up with funding to pay off the price of the delay, the space agency may be forced to scrap the Rosetta project altogether. Potential sources of money are unknown, but extensive reviews of all possibilities are sure to be occurring in the coming weeks with a crucial committee meeting and an ESA Council ministerial summit before the end of May.

Rosetta's mission will be the first to orbit a comet nucleus and will release a small lander to make the first controlled touchdown on the surface of a comet. Its complex suite of science instruments will take images and gather data on the environment around the nucleus and in the coma.