Artist's concept of Rosetta orbiting a comet with its lander on the surface. Credit: Astrium/Erik Viktor

After the initial disappointment of postponing the Rosetta mission, ESA's Director of Science David Southwood expressed his firm determination to accept the delay and take it on as a galvanising challenge.

Speaking about the scientists, engineers, and industrial teams attached to the mission, he says "If one is going to be stuck anywhere, these are the guys to be with. They have the pioneering spirit and dedication that is worthy of space explorers."

Rosetta is and stays one of the most challenging interplanetary missions ever undertaken. It is the major space mission to a comet, and the only lander and orbiter of its kind.

The decision to postpone the launch of Rosetta - which was ready well time for the expected launch window - was taken jointly by ESA and Arianespace. The Rosetta launch is not expected for at least one year at the earliest.

The Ariane-5 programme is now under thorough reexamination. ESA expects Arianespace to provide the necessary guarantees regarding the Ariane-5 system qualification procedures and review process.

Rosetta can no longer catch its original target, Comet Wirtanen. However, the Rosetta team is now at work finding alternative target comets for the spaceprobe to explore. The team will identify several comets as targets that Rosetta could reach, within the timeframe for launch of the next two-and-a-half-years.

It will select new targets on the basis of three main criteria: striving for the maximum scientific return possible, minimising the technical risks to the spacecraft, and carefully estimating the extra funding needed.

For the time being, the costs of grounding the mission are likely to be somewhere between Euro 50 and 100 million.

The comet shortlist will be presented to the Science Programme Committee (SPC) at their meeting on 25-26 February 2003. The SPC will discuss their suitability and viability. A final decision on the new target and mission profile is expected for May 2003 at the latest.

So, the Rosetta mission takes a new direction. Rosetta's Project Scientist, Gerhard Schwehm, is undaunted by this new twist in the spacecraft's story. He says, "During the decade it has taken us to develop and build Rosetta, we have faced many challenges and overcome them all. This new challenge will be met with the same energy, enthusiasm and, ultimately, success."

As for the spacecraft itself, it must now be stored away, safely and cleanly, until it is called upon. Engineers will remove its batteries, take off the lander harpoons, and drain its fuel tanks.

"The same care that went into building the spacecraft will now be applied to storing it and making sure that it will be in perfect shape for us to launch it when the date comes," says John Ellwood, Rosetta's Project Manager.

Although Rosetta will no longer meet Comet Wirtanen, it will rendezvous with a new comet that will soon become as well-known to the European comet-chasing community as the name Wirtanen is now.