Success for Rosetta's transatlantic link
28 October 2002
With less than three months to go before Rosetta lifts off from Kourou spaceport in French Guiana, engineers from ESA, Alenia and Astrium are working feverishly to ensure that Europe's comet chaser meets its narrow launch window in January 2003.Two major milestones in the extended Rosetta launch campaign have been successfully completed in recent weeks, and the project team is delighted with the progress that has been made since the 3-tonne spacecraft was delivered to Kourou in early September.
Once Rosetta had been set up in its launch configuration (without the solar arrays and high-gain antenna) and passed a leak test of its propulsion system, experts installed the final versions of the flight software and validated its electrical systems.
This was followed by the Final Acceptance Test, in which engineers in the payload preparation facility at Kourou worked around the clock for eight days to carry out extensive checks of Rosetta's computer 'brain' to verify that the spacecraft was responding as it should.
"This was the last full functional test of the spacecraft, including its payload, before liftoff," said Claude Berner, Rosetta Payload and Operations Manager. "It was a critical moment, but the test was successfully completed on schedule. We will not carry out another full functional test until after the launch."
Confident that all was well with their deep-space explorer, the Rosetta team then conducted a complex system validation test with colleagues at the European Space Operations Centre (ESOC) in Darmstadt, Germany.
During a transatlantic link up that lasted almost round-the-clock for 96 hours, specialists at ESOC checked that they could communicate with the spacecraft in real time as Rosetta responded to a series of commands.
"The test was extremely successful," commented Paolo Ferri, Rosetta Operations Manager at ESOC. "We spent about 78 hours out of the 96 hour period sending commands, and every day we finished within half an hour of the scheduled time."
"We tried to operate the spacecraft in a realistic manner," he explained. "Members of the experiment teams were present in ESOC to study the results as we commanded all of the experiments both in sequence - one after the other - and then several at a time."
One of the most important aspects of the long-distance trial was the attempt to simulate the operations that would take place immediately after launch.
"At the beginning of the test, we asked the Kourou crew to put the spacecraft into the configuration it will have just before launch," said Ferri. "Immediately after they manually triggered the separation switches (simulating the spacecraft separation from the Ariane launcher) we took control and ran through the same sequence that we will follow on 13 January. It was a very real simulation of the first day and a half of Rosetta's mission."
"Although this was a very important test, it is just part of the training and validation procedures we have been practising since September 2002 and that we will continue until launch," he added. "This involves simulating all of the early phases of the mission and rehearsing possible failure situations."
With these two potential stumbling blocks out of the way, Rosetta's launch campaign is well on the way towards completion. Over the next few weeks, the spacecraft will assume its final flight configuration as the huge solar arrays and dish-shaped high gain antenna are installed. In late November, after a final 'go-no go' test, the spacecraft will be fuelled and placed under wraps prior to mating with its Ariane 5 upper stage.
