PARIS — European space-science managers expressed a mixture of sadness and relief that their Rosetta comet-chaser satellite’s late-January launch aboard an Ariane 5 rocket was cancelled.
For some of them, Rosetta represented more than 10 years of preparations that now will continue for at least a year, and perhaps up to 30 months, as they seek a new target comet to replace the one whose rendezvous opportunity ended with the launch cancellation.
Rosetta’s mission is to orbit a small comet and then send a harpoon-equipped lander to its surface. The mission has cost the European Space Agency (ESA) 700 million euros ($740 million), including the launch and operation of the spacecraft through 2013. In addition, national space agencies, especially in Germany and Britain, provided between 200 million and 300 million euros in Rosetta experiment hardware and the lander.
ESA Science Director David Southwood said another 50 million to 100 million euros now would be spent storing Rosetta, finding another comet target and designing a new mission.
John Ellington, the Rosetta project head, said he would open negotiations immediately with the Arianespace commercial-launch consortium to secure an inexpensive storage fee that will keep Rosetta in an unused clean room at Europe’s Guiana Space Center spaceport.
Addressing a Jan. 15 press conference here, Southwood said he and other ESA science officials reluctantly concluded that canceling the launch was the best option given the increasing doubts about the reliability of the Ariane 5 rocket that have emerged since the rocket’s Dec. 11 launch failure.
"It’s a sad day for science, but it could have been far worse," Southwood said. "Knowing what we now know, I would not want to launch on Ariane 5 in any form until a full review of its systems has been completed. There can be no safe Ariane launch until the review is achieved."
Arianespace Chief Executive Officer Jean-Yves Le Gall said such a review would cover the basic Ariane 5 model as well as its enhanced versions such as the one Rosetta had been scheduled to use. But Le Gall said the basic Ariane 5, which has flown 13 times — 10 successfully — since 1996, will be fully cleared for flight in time for a late-February commercial launch of a telecommunications satellite for PanAmSat Corp. of Wilton, Conn.
Le Gall said in a Jan. 17 interview that it was Rosetta’s strict launch window — it had to launch by Jan. 31 — that forced a cancellation. Another factor, he said, was the fact that the launch sequence featured a ballistic-coast phase for the rocket’s upper stage – a first for Ariane.
Southwood went out of his way in the press briefing to express his faith in Arianespace and in Le Gall. But Southwood also said there appear to be deep problems with the credibility of certain test results from Ariane 5, and these problems need to be resolved.
"If we want to have the best launcher system in the world here in Europe, and to launch sophisticated satellites, we need to be able to respect strict launch windows," Southwood said.
Several Rosetta scientists privately expressed bitterness that Arianespace was scrapping their launch and then proceeding with a February commercial flight. These scientists said they suspected Arianespace of wanting to avoid a complicated launch so soon after a failure. "It’s a case of nerves," one said.
Southwood acknowledged that sentiment among some scientists but said he did not share it. "I know the Arianespace team are motivated by a desire to have the world’s best launch system and are simply being prudent."
John Credland, ESA’s outgoing head of science projects, recalled the days after the Ariane 5 maiden-flight failure in 1996, during which four ESA science satellites ended up in the Amazonian swamps following the rocket’s low-altitude explosion.
"I greatly prefer to be in the position we’re in today, with even a substantial delay, to where we were in 1996," Credland said. "I would not want to relive that experience."
Gerhard Schwehm, project scientist for Rosetta, said project teams have already identified five or six alternative comets for a revised Rosetta mission. One limiting factor is that any potential comet target must have a nucleus with a diameter of no more than about five kilometers to prevent the lander from being pulled to the surface by gravity at too great a speed.
Schwehm said no major systems of Rosetta or the lander would need to be replaced for a new mission.
