How to build a satellite - ESA's Integral
28 May 1999
To have a look at ESA's Integral spacecraft you have to travel to Turin,Italy. At Alenia Aerospazio engineers are running electrical tests on thegamma-ray observatory that will be launched in 2001.In the large clean room the experts are working on the engineering model of the satellite. This model is specially built for the extensive electrical test campaign. Hundreds of cables of different colours protrude from the spectrometer, one of the main instruments of Integral, already mounted on the platform of the payload module. Another important part, the imager, has just arrived and still lies alongside. The service module is placed separately. In three weeks the two modules will be mated.
In the back of the clean room is another model that looks exactly like the acutal spacecraft - an impressively complex, five meter high construction covered with glittering, gold-coloured foil. This is the payload model, built for mechanical and thermal testing.
"To build a satellite is easy, but it's very hard to make sure that nothing will go wrong at launch or in orbit", says Kai Clausen, Project Manager of Integral. Only elaborate test campaigns can reduce the risk of failure. With the mechanical and thermal tests sucessfully completed last Autumn, the engineers now have to guarantee that all electrical and software interfaces operate well.
In monthly progress meetings the experts report on completed tasks and open issues. Will there be enough power from the solar panels and batteries to meet the instruments and all the satellite's other needs? This was one of the questions brought up at the recent progress meeting at the end of May in Turin. Together with Kai Clausen some 20 experts from ESTEC, ESOC and Alenia Aerospazio sat around a large table in lively discussion on the satellite's power budget. It is not yet completely clear exactly how much power will be generated and consumed - these figures have to be supplied in the coming weeks.
Good news came from the experts who reported on the analysis of the pointing and alignment of the instruments. The calculations show that the imager will have an astonishing source location accuracy of 20 arcseconds. "This is what the scientists wanted, and here we are", said Kai Clausen. His current concern is that the instruments are delivered in time. Only then can the spacecraft be launched as planned in September 2001. Any delay would increase the costs considerably. But so far everybody is confident that no substantial problems will arise.
In the clean room at Alenia Aerospazio, in addition to the models, the first part of the real satellite is already waiting for the next phase of the project, the flight model programme. The H-shaped black structure delivered by the Swiss company Contraves is the backbone of the payload module. It is made of strong and stiff composite material and ensures that the instruments will have the structural stability necessary for their accurate pointing.
