ESA considers three mission scenarios for delayed Rosetta comet chaser
The European Space Agency (ESA) has announced that the Rosetta satellite may still attempt to land on Comet Wirtanen, its original target before the first launch was cancelled in January. Following that decision, Rosetta scientists and engineers have been examining several alternative mission scenarios based on scientific return, technical risks and the containment of costs. Out of nine alternative plans studied by the Rosetta science working team, three have been short listed for further detailed study. Two of these would see Rosetta attempt to rendezvous with a new target comet, Churyumov-Gerasimenko, while the third would take it Wirtanen, its original target. Of the three options, the Wirtanen mission would be the earliest to blast off in January 2004, with the first possible Churyumov-Gerasimenko chase starting in February 2004, and the second a year later in February 2005. While ESA scientists have a relatively good understanding of the Wirtanen Comet, a series of observations will be carried out using the Hubble space telescope and the European Southern Observatory in order to characterise Churyumov-Gerasimenko. This will allow scientists to identify landing scenarios and assess whether hardware modifications to Rosetta will be necessary. The original Rosetta mission in January was cancelled following the loss of an enhanced Ariane 5 rocket soon after its launch from the ESA spaceport in Kourou in French Guyana in December 2002. In order to minimise the possibility of a further cancellation, ESA is looking at back-up options to Ariane, including the Russian Proton rocket. The final decision on Rosetta's new mission scenario will be made by the ESA science programme committee in May.