Rosetta rises to meet the challenge
8 October 1999Thousands of scientists, students, industrialists and representatives ofspace agencies flocked to the RAI Congress Centre in Amsterdam this week to attend the 50th International Astronautical Congress. As ever, one of themain areas of interest for the visitors was an update on global unmannedspace exploration.
Among those giving presentations at a technical session about missions to visit small bodies (such as asteroids and comets) was Bruno Gardini, programme manager for ESA's Rosetta mission. Mr Gardini described to a packed room the technical and programmatic challenges arising from this exciting and unique project to visit two asteroids and fly alongside Comet Wirtanen.
From the 'warm' environment of our planet, Rosetta will travel more than five times the Earth's distance from the Sun, to a realm where levels of light and heat are 25 times lower than those to which we are accustomed. This means that the spacecraft has to be equipped with radiators and louvres to shed excess heat close to the Earth, while heaters and insulation are needed to prevent Rosetta from freezing when it is more than 800 million km from the Sun.
Low light levels beyond the orbit of Mars require specially designed solar arrays. Rosetta will carry the largest rigid solar arrays ever built by ESA in order to produce the necessary power to operate the science instruments, computers and other hardware during the comet rendezvous. Specially designed silicon cells will catch as much sunlight as possible and produce the 400W of power required. * Since the round trip time for radio signals between the Earth and Rosetta may last more than 90 minutes, four onboard computers will provide the spacecraft with sufficient 'intelligence' to operate autonomously, rather than rely on instructions from the distant home planet. In addition, a new 35 m antenna in Australia will be used for communications, while the spacecraft will be provided with newly developed deep space transponders (radio receivers / transmitters). * On an extended mission which will last more than 10 years, the spacecraft has to be designed for a high degree of reliability and durability, without costing an excessive amount. With a limited amount of time to prepare and a fixed launch date in January 2003, this means that testing of hardware has to begin as early as possible.
One of the most ambitious parts of the mission is the deployment and landing of a small probe on the pockmarked surface of the comet - something which has never before been attempted. Buffeted by jets of gas and dust, and far from home, the Rosetta lander will rely heavily on accurate monitoring and control from the European Space Operations Centre at Darmstadt in Germany.
So how is all of this to be accomplished in the short time available?
"With less than 4 years from the beginning of the development phase to launch, the programme requires a tight schedule control with highly efficient and motivated team work," said Bruno Gardini. "The challenge has been taken up by European industry and by hundreds of scientists around the world."
In case the audience had not grasped the magnitude of the task, he left them with a final, thought-provoking remark: "128 weeks to shipment - and counting."