Sparks fly on Rosetta orbiter
6 April 2001From time to time, something may happen to bring home the fact that people are not compatible. At such times, it becomes obvious that there is a breakdown in a relationship with a partner or work colleague.
However, it is not only humans who suffer from such problems. Regular air travellers will be familiar with the pilot's instructions to shut down laptop computers and mobile phones before take off. Similar difficulties may arise with incompatible spacecraft components, leading to disastrous systems failures.
With this in mind, engineers spent 8 days recently subjecting the electrical qualification model (EQM) of ESA's Rosetta spacecraft to a series of electromagnetic compatibility tests inside the giant clean room at Alenia Spazio in Turin.
Surrounded by cables and test equipment, this was the first time that the box-shaped EQM and its full complement of EQM payloads had undergone such an intensive electromagnetic check-out.
"Previously, all of the electromagnetic tests were done at unit or subsystem level," said Bodo Gramkow, principal payload systems engineer for Rosetta. "For this test we had to put it all together in order to demonstrate that the spacecraft and the individual units are compatible. We put many more loads on the system to see whether all the spacecraft subsystems are singing and dancing together. This was an important rehearsal for the main event (the actual operation of Rosetta in orbit) and we needed to be sure that all subsystems were performing in harmony."
"We measured electrical emissions and injected signals into the spacecraft in order to determine the susceptibility of the spacecraft and its payload to electromagnetic interference," he explained. "Once the spacecraft was powered up, we went through a sequence of tests to monitor different parameters and to find out if any problems needed to be investigated."
"The 'noise' on the experiment output was measured as we swept the signal frequency from 30 kHz to 100 MHz at the power input lines," he added. "By increasing the signal level in this way, we verified the robustness and safety margins on the spacecraft."
Towards the end of the eight-day programme, the engineers introduced a test that had a little more spark than usual.
"We carried out an electrostatic discharge test," said Mr. Gramkow. "It's like a controlled flash of artificial lightning that is sent to the spacecraft."
This may seem a harsh way to treat a multimillion Euro spacecraft, but Mr. Gramkow was not concerned about the outcome.
"We were confident that the spacecraft would be immune to this threat," he said. "Nevertheless it certainly added an extra spark to the tension felt during this week! We had encountered many complicated problems in the course of this test campaign. It meant we all had to work late into the night. But, with the dedication and support of all those involved - the experimenters and our colleagues from industry - we met these goals. At the end, we too were singing and dancing together!"