Rosetta STM passes acceleration trials

Environmental tests on the Structural Thermal Model
(STM) of the Rosetta spacecraft are back in full swing after the long
break for Christmas and Millennium celebrations. The latest
endurance trial, known as a Sine (or Sinusoidal) Test, was
successfully completed today in the giant check-out room at the
European Space Research and Technology Centre (ESTEC) in the
Netherlands.

“We are delighted with the
progress made so far,” said
Rosetta Project manager,
Bruno Gardini. “We have a
very tight launch schedule to
meet, so every successful test is a bonus.”

The completed Sine Test is the latest in a series of vibration tests
designed to search for potential problems that could be encountered
during an Ariane 5 launch. The STM has already passed its Acoustic
Tests, which reproduce the spacecraft vibrations caused by the
tremendous noise generated during lift-off. Now, the STM has been
subjected to another session on the Multishaker platform in order to
simulate the effects of sudden acceleration as the rocket leaves the
launch pad.

The Multishaker allows technicians to move the 3 tonne spacecraft
at different speeds in three directions. At its fastest, the platform can
reproduce acceleration forces equal to three times normal gravity.
For a few minutes, this motion can cause the STM to weigh three
times as much as it would prior to lift-off. Sensors measure these
forces at different places on the body of the spacecraft.

By shaking the STM in this way, engineers can find out if the
spacecraft is behaving in line with their predictions. If the design
specifications are exceeded, they know that something is wrong and
further checks will have to be made.

The next major step will be the Thermal – Balance tests at the end of
February.