Tumbling Stone 24 - Special Issue - Rosett'a launch

Special Issue : 15/03/2004
A scientific publication by SGF and NEODyS

Rosetta's launch

The launch overivew

Rosetta's mission began at 08:17 CET (07:17 GMT) on the 2nd of March 2004, when a european Ariane lifted off from the Guiana Space Centre, in Kourou, French Guiana, starting a 790 million kilometres and 10 years long journey to rendezvous, orbit, and land on the comet Churyumov-Gerasimenko. To launch the Rosetta spacecraft, Arianespace used an Ariane-5 G, a modified version of the basic model of the new Ariane-5 launcher.

In the days just before the launch, two delays took place: the first on the 26th, due to meteorological reasons, while the second, one day later, for a minor technical problem, a piece of insulating foam that became detached from the Ariane 5 rocket's main stage.

An image of Ariane 5: you can see the missing piece in the image below, just on the right of the esa sign. Copyright ESA
After the launch (to have a complete report of the launch, you can visit the webpage http://www.spaceflightnow.com/ariane/v158/status.html), the Ariane 5 reached an altitude of 173,4 Km before turning its engine off. Then, the launcher successfully placed its upper stage and payload into an eccentric coast orbit (200 x 4000 km). About two hours later, at 10:14 CET (09:14 GMT), after a tour and a half of the Earth had been made, the upper stage ignited its own engine to reach an escape velocity in order to leave the Earth's gravity field at an altitude of 1300Km and enter heliocentric orbit. The Rosetta probe was released 18 minutes later.

Speaking from Paris, European Space Agency Director Jean-Jacques Dordain said signals from the Rosetta spacecraft were quickly acquired by the agency's operations center in Darmstadt, Germany, confirming that the deep-space probe was well on its way.

During the next eight months, the spacecraft's onboard systems will be checked and its science payload will be commissioned. Then, it will be placed into hibernation mode for most of the 10 years of its journey through the Solar System.

Rosetta's launch, initially scheduled for mid January 2003, had been postponed by ESA a first time, about one year ago, due to an accident that happened on the 11th of December 2002, to the very first 10 tons version of the Ariane-5, carrying a commercial mission. On the whole, it was the fourth Ariane 5 failure in 16 attempts since the model's inauguration in the mid-1990s.

The flight had to be destroyed just a few minutes after its launch, since it hadn't followed its original trajectory, probably because of a leakage in the cooling system of the Vulcain 2 engine. After this accident, ESA took the difficult decision to postpone the launch, abandoning the scheduled target, comet Wirtanen.

The decision was taken as a precaution, to give to Arianespace the time to analyze the launch procedures and the accident. Rosetta stayed on earth for a year, while scientists calculated a trajectory for a new target, Churyumov-Gerasimenko, a comet that became a major target of the HST and of researchers and observatories from all over the world.

Of course, changing target was not so easy, and many problems had to be faced by scientists. For example, the flybys of the two asteroids, 4979 Otawara and 140 Siwa, initially planned on the way to the comet Wirtanen, had to be rescheduled, and today, during the two excursions into the main asteroid belt, scientists have identified a number of possible target asteroids along Rosetta's path. But they still don't know the name of the one (or more) that will be selected in the course of the mission for a close fly-by.

The delay may also pose some problems for the technical aspects of the mission: for example, being the new comet bigger than the previous one, the landing will be at 1m/s, much faster than it was initially calculated, and scientists wonder if the module will have problems during this

A phtoreportage of Rosetta's launch click here to read it