Mars Express comes alive
17 Aug 2000Europe's mission to Mars is assuming a tangible form at the Astrium SAS (formerly MMS) integration facilities in Toulouse, France. "We're down to the real work. It's not paperwork anymore - it's a real spacecraft," says Vincent Poinsignon, Mars Express project manager at Astrium SAS.
Astrium SAS has built, exactly on schedule, the test bench to help ensure that all the components of the Mars Express spacecraft operate in unison. "We've kept to the schedule for one year. This is a real milestone which shows that the new working methods with industry being pioneered by Mars Express are working well," says Rudi Schmidt, Mars Express project manager at ESTEC.
Don McCoy who is responsible for Mars Express Assembly, Integration and Verification (AIV) at ESTEC explains what the new facility is. "The test bench is really like the spacecraft opened out. It consists of four tables which are equivalent to the four sides of the spacecraft (see image). The gap in the middle is where the base should be. The boxes attached to the tables represent scientific instruments and spacecraft equipment. They are in the positions they will occupy on the real spacecraft sides."
The test bench provides about 8000 connections between more than 30 units resulting in about 13 km of wiring. "The completion on time of such a complex facility is a credit to the team at Astrium. Everybody is very enthusiastic about their achievement," says McCoy.
The test bench will remain in continual use for the next fifteen months while models of the instruments and other equipment are plugged into their rightful places and tested in a simulation of the electrical environment they will experience on the spacecraft. "We will be following a sequence of integration," says McCoy. "First we're testing the spacecraft's brains, that's the CDMU (Control and Data Management Unit) or on-board computer (silver box in middle of image). Then we'll test the remote terminal unit and other spacecraft units before adding the instruments." Overall, this assembly will verify the cooperative operation of about 30 processors, equivalent to 30 interconnected portable PCs.
The models under test will range from breadboards, that is basic models of the electrical design, through more sophisticated engineering models right through to flight models. "Astrium SAS is taking a novel approach to a test bench in that they will be using it to assemble the entire spacecraft to ensure correct function before finally integrating the units into the flight structure," says McCoy.
While the test bench activities are going on, the spacecraft flight structure and propulsion systems are being built and subjected to dynamical mechanical tests. When the test bench and flight structure tests are complete, the units will be integrated into the flight spacecraft and the whole system will undergo final testing before being shipped to Baikonur for mating to the Soyuz Fregat launcher in time for launch on 1 June 2003.