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Rerouting Rosetta after a Rocket Explosion

The Rosetta spacecraft was scheduled to launch in February 2003 when its rocket rudely exploded while carrying a different satellite. The European Space Agency was stuck with an expensive craft, an approaching launch date, and no ride. It was time for new plan.

Illustration for article titled Rerouting Rosetta after a Rocket Explosion
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Rosetta was scheduled to catch a lift into orbit with the then-newly-designed Ariane 5 in February 2003, when another launch using the rocket went poorly and was remotely detonated to avoid a catastrophic crash. The European Space Agency wasn't about to risk their precious comet-explorer on a rocket before they understood what went wrong, so the launch date was shoved back to allow time for a thorough investigation. Rosetta was going to miss its window for a leisurely trajectory to intercept comet Wirtanen, leaving mission scientists scrambling to come up with a new plan.

The options were simple:

  1. Stick with comet Wirtanen, and go for more intense orbital maneuvers to catch up to it for the same intercept-date.
  2. Stick with comet Wirtanen, but delay launch by six years to intercept it at a later date.
  3. Redirect to comet Howell, taking a fuel-demanding trajectory.
  4. Redirect to comet Tempel 2, taking a trajectory through the inner solar system.
  5. Redirect to comet Churyumov-Gerasimenko, a larger comet.

In December 2002, mission designers and engineers debated the options. Getting to Wirtanen on the same timeline would require a far bigger and more expensive rocket, axing that plan. Mothballing a delicate piece of expensive equipment for years was too risky, even with careful high-tech storage options. Zipping over to comet Howell would require ridiculous amounts of fuel. Heading to comet Tempel 2 would bring the spacecraft dangerously close to the sun and outside of the designed heat-tolerance specifications. Comet Churyumov-Gerasimenko is larger than Wirtanen, complicating approach and rendezvous using hardware and software designed for a smaller nucleus, but was reachable with a sane rocket size and fuel capacity, and wouldn't bring the spacecraft painfully close to the sun.

Deciding that a complicated landing dance was the best option, the European Space Agency selected Churyumov-Gerasimenko. Figuring out how to get Rosetta from here to there was no easy task, requiring a complex decade-long trajectory using three Earth and one Mars flybys to get the spacecraft to the comet in an efficient manner. Rosetta made her revised launch date in March 2004, catching a ride on the now-approved Ariane 5 rocket. After a music video competition to wake up the spacecraft and its travelling-companion comet-lander Philae, Rosetta got a first peek at the destination comet. After a long wait, the spacecraft will encounter Churyumov-Gerasimenko in May of this year.

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Images credit: ESA. Read more about the complicated orbital dance necessary to get Rosetta to Churyumov-Gerasimenko.

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