Blanketed spacecraft ready for balance tests
14 December 1999After its safe delivery to the European Space Research and TechnologyCentre (ESTEC) in the Netherlands, the Structural Thermal Model (STM) ofthe Rosetta spacecraft is ready to start an exhaustive series ofenvironmental tests.
Since its dish-shaped high gain antenna and thermal blanket were attached late last week, the STM now closely resembles the flight model which will be launched towards Comet Wirtanen in January 2003.
When it is in deep space, beyond the planet Mars and the asteroid belt, fast, reliable communications between the Rosetta spacecraft and the Earth will be vital for the success of the mission. In order to achieve this, a 2 metre diameter antenna, which can be manoeuvred up, down and sideways, must be located on the opposite side of the spacecraft to the lander.
A test model of this high gain antenna has recently passed its initial environmental tests after being placed on a platform known as a Multishaker. On 9 December, after the antenna was attached to the main body of the spacecraft, a thermal blanket was then wrapped around the STM. In deep space, this multi-layer shroud of aluminised kapton will be needed to reduce heat loss and protect Rosetta from the cold when it travels far from the Sun.
With all of this added bulk and weight, the next stage is to examine the STM's mass properties, in order to measure its balance, centre of gravity, and moment of inertia. If all goes well, the fuel tanks on the STM will then be filled with water and the spacecraft will be ready for its acoustic tests.
This time, the entire 3 tonne spacecraft will be blasted by waves of sound to simulate an Ariane 5 launch. Hopefully, the ESTEC engineers will be able to leave for their Christmas break knowing that the Rosetta spacecraft was shaken, but not stirred.