The one-of-a-kind Rosetta satellite that was developed to become the first spacecraft to rendezvous with a comet will need to chase a different comet than originally planned. The change in the $1 billion-plus mission was necessitated last week when officials at the European Space Agency and launch service provider Arianespace agreed to an extended launch delay.

The satellite had been scheduled to ride aboard an Ariane 5 rocket at the end of this month to reach the fast-moving Comet Wirtanen by 2012. However, a failed Dec. 11 launch of the heavy lifting 10-ton version of the Ariane 5 rocket led a team of experts to delay the Rosetta mission.

Questions Raised

The decision not to launch Rosetta on the Ariane 5 as scheduled raised questions among industry observers about whether there were problems with the baseline Ariane 5 as well as with the heavy lifting 10-ton version. Those doubts were fueled by a BBC report that said the launch failure inquiry board of the Dec. 11 mission found flaws with all versions of the Ariane 5.

Arianespace officials flatly denied that characterization of the board’s conclusions. None of the official findings released from the launch failure investigation have suggested the basic version of the Ariane 5 is at risk and only the 10-ton version has been grounded, they said.

The next mission of the Ariane 5 will not be identified until after a scheduled Feb. 12 liftoff of the last of the highly reliable Ariane 4 rockets. That rocket will carry the Intelsat 907 satellite.

Arianespace will announce its “action plan” for the 10-ton Ariane 5 on Jan. 20. That version will not be launched until further testing occurs, Arianespace officials said. The goal of Arianespace Chairman Jean-Yves Le Gall is to resume launching the 10-ton Ariane 5 in six months.

The Dec. 11 launch failure investigation traced the problem to the Vulcain 2 engine that is only used on the larger Ariane 5 model, not the basic version (SN, Jan. 13).

D.K. Sachdev, a satellite engineer who heads the SpaceTel Consultancy in Vienna, Va., said the delay of the Rosetta mission is a prudent step, despite the extra costs that will result.

“While the inquiry board highlighted the problem in the Vulcain 2 engine used only on the bigger Ariane 5, the postponement of the Rosetta mission appears to be a measure of abundant caution in order to make sure that there are no risk issues related to the basic Ariane 5,” Sachdev said. “This appears consistent with a report by the BBC that the inquiry board has identified several problems with all versions of the Ariane 5.”

Systemic Problems?

Mark Chartrand, a Baltimore-based satellite consultant, observed that “it is always better to be safe than sorry, especially since launch vehicles and satellites cost so much. It remains to be seen whether all the versions of the Ariane 5 will be called into question. The launch vehicle engineers could find more systemic problems with the Ariane 5. Any failure by a launch company’s vehicle raises concerns,” Chartrand said.

“We are going to take the time to make sure everything is fine,” said Suzy Chambers, director of external affairs with Arianespace Inc., the U.S. arm of the French launch company. “We owe that to our customers.”

The timing of the launch of the original Rosetta mission was critical. The satellite was scheduled to rendezvous with Comet Wirtanen in 2012 when the comet will be as far from the sun as Jupiter and traveling at speeds of up to 135,000 kilometers per hour. The launch of the Rosetta satellite needed to occur by the end of January for the planned encounter with the comet to take place, ESA and Arianespace officials said.

The Rosetta mission was complicated by the need for the spacecraft to perform several planetary swing-bys that would have allowed the satellite to approach the comet, enter into orbit around it and release a landing probe from a height of about 1 kilometer.

A new comet for the satellite to chase will be identified and a decision could occur as soon as this June, said Franco Bonacina, ESA’s head of media relations. ESA still plans to use an Ariane 5 for the Rosetta launch, he said.

“There is no hurry,” Bonacina said. The plan will be to target another comet that preserves the scientific value of the Rosetta satellite, limits the technical risks and minimizes the additional resources needed for a new mission, he added.

Big Investment

The high costs involved in the Rosetta mission heightened the need for a careful review of the planned launch to avoid taking unnecessary risks.

The Rosetta satellite, launch and operational costs total 700 million euros ($743 million). In addition, roughly 300 million euros ($318 million) was spent for additional instruments and payload, Bonacina said.

Scientific institutions in Germany, France, Italy and the United Kingdom mainly paid those costs. Additional financial support for the mission is coming from Sweden, Finland, Austria, Switzerland, Eastern European countries and the United States, Bonacina said.

There will be additional costs for ESA to find a new comet and to store the satellite until its launch, he added.

As a safeguard prior to the launch of the Rosetta, the review board that called for the launch delay last week also asked Arianespace and its partners to ensure that all Ariane 5 system qualification and review processes have been checked prior to future flights.

Arianespace and ESA are now going to consult with the parties involved to determine arrangements for the soonest possible launch of Rosetta, Bonacina said.

The satellite’s name was taken from the Rosetta Stone that was discovered roughly 200 years ago and enabled the mysteries of ancient Egyptian hieroglyphics to be unraveled. With that spirit of discovery, the Rosetta mission was developed to help scientists learn more about comets, the most primitive objects in the solar system, ESA officials said.

-Paul Dykewicz

(Franco Bonacina, European Space Agency, 33 1 5369 7713; D.K. Sachdev, SpaceTel Consultancy, 703/757-5880; Mark Chartrand, 410/ 235-6932; Suzy Chambers, Arianespace, 202/628- 3936)

Implications Of The Dec. 11 Failure For Ariane 5

• The design of the nozzles on the Vulcain 1 engine of the basic Ariane 5 and the Vulcain 2 engine on the 10-ton Ariane 5 differ primarily in the shape of the cooling tubes that form the structure of the nozzle and the technology of the nozzle’s stiffeners.
• In-flight performance of the Vulcain 1 engine with 12 successful flights did not identify any weaknesses concerning the functioning and resistance of its nozzle.
• Nevertheless, the inquiry board requested an exhaustive examination of the behavior of the Vulcain 1 engine nozzle, including precision modeling to demonstrate the correct behavior of the nozzle during flight. These checks are in progress.

Source: Arianespace