The test programme of the Rosetta Structural Thermal
Model (STM) continues to go with a bang. At the end of last week,
the STM underwent a series of shocking experiences in order to
check its ability to survive the rough treatment that will be meted out
during launch. This was followed today by a deployment test of a
giant solar array.

The first of the STM’s trials to
be carried out last week was
the so-called ‘shogun’ test.
This was a joint operation by
technicians from CNES,
Arianespace, and ESA’s European Space Research and
Technology Centre (ESTEC) in The Netherlands. (Arianespace
operates the Ariane 5 launch vehicle that will send Rosetta on its
way to Comet Wirtanen in 2003.)

The shogun test was a simulation of the shock transmitted to the
spacecraft when its protective fairing separates from the rocket’s
upper stage. Using a copy of the actual spacecraft adapter which will
attach Rosetta to the upper stage, a set of pyrotechnic devices was
attached around the underside of the adapter. With all staff
withdrawn to safe positions behind protective glass, these explosive
charges were set off instantaneously to rupture the aluminium plate
on the adapter.

“It only lasted a millisecond, but it went off with quite a loud crack,”
commented Rosetta Assembly and Integration Verification Engineer
Alan Moseley.

The next day, the STM was subjected to a ‘clamp band separation
test’. The clamp band is a metal strip that attaches the launch
adapter to the spacecraft. After checking that the clamp band fitted
properly, technicians once again had to discover whether its
explosive separation would damage Rosetta. This time, two
pyrotechnic charges were set off. As the band was split in two, both
sections were pushed away from the spacecraft interface by springs
and caught by special ‘catcher’ brackets.

“Although the tests themselves were extremely short, the shocks
imparted to the STM were quite severe. The detailed analysis of the
impact on the spacecraft’s units will data take several days, to come
to a realistic conclusion,” said J. C. Salvignol, Rosetta mechanical
systems engineer.

“I’m pleased to say that the STM passed both tests without any
damage,” added his colleague, Jacques Candé.

Today saw the deployment test for one of Rosetta’s 16 metre-long
solar arrays. These enormous arrays are needed because Rosetta
will be operating at five times the Earth’s distance from the Sun,
where levels of sunlight are only 4% those on our planet. Rosetta will
be making history as the first spacecraft ever to use solar arrays to
generate electrical power during a deep space mission beyond the
asteroid belt.

The check-out began when six ‘thermal knives’ were used to melt
through the attachments which held the array to the side of the
spacecraft. Using a special jig, springs on the giant panel caused it
to slowly open out to its full, impressive length. After 3 minutes 47
seconds, the array was fully extended, allowing engineers to check
its alignment and condition.

Later in the day, yet another shock test took place. This time, the
dish-shaped high-gain antenna was shaken by three pyrotechnic
devices which exploded one after another. During a subsequent
performance check of the antenna motor, the dish was successfully
moved more than 40 degrees from its fixed position.

“Once again, everything was nominal,” declared a highly satisfied
Alan Moseley.