Assembly of Rosetta STM starts in Turin
20 September 1999Assembling a spacecraft by taking it to pieces may sound rather illogical,but that is exactly what has happened to the Rosetta Structural and ThermalModel (STM). Since its delivery to the Alenia Aerospazio plant in Turinduring August, the STM was separated into two sections - the payload module(PM), which will carry the scientific experiments, and the service module(SM) which will house the satellite's main subsystems. Over the next fewmonths, engineers will be working in two shifts in order to carry out theassembly, integration and test programmes on each module before they are once again united in late October.
The first stage of the assembly process involves installation of the spacecraft's reaction control (propulsion) system. This means adding two fuel tanks and a very intricate network of Titanium pipes to the service module. Several kilometres of harness - electrical cable - is also being built into the heart of each module before it is buried beneath other hardware units.
The most recent step has been to begin installation of the scientific payload. All of the 'dummy' experiments, including the Rosetta Lander, have been delivered to Alenia on time and will be fitted to the payload module in the coming weeks.
If all goes well, the spacecraft's major subsystems, including the power, data handling and attitude control systems, will be added after 5 October. The final stages of assembling the giant jigsaw puzzle will involve installation of the Lander STM, the solar arrays and booms. The target date for this is the end of November.
The STM is a high-fidelity mock-up of the spacecraft. It is used to iron out any major problems in the design and assembly of the final operational version. Although it has similar structural and thermal properties to the flight model, the experiments and other systems it carries are 'dummies' i.e. non-functional.
The main skeleton of the 200 kg STM structure comprises two sections. The service module at its heart is a 3 metre high central cylinder which is divided into quarters by vertical shear panels. The payload module, a box-shaped structure which will carry the solar panels and scientific instruments, will eventually be attached to the outside of the service module.