Why do we do full System Test?

8 January 2017

Schiaparelli module in ExoMars mission… lost in October 2016… a big blow to European Space Agency.  ESA announced on the 21st of October 2016 that its probe crashed on Mars soil; it was supposed to look for traces of life. ESA lost about 300 million euros.

What happened? From the information sent to the press it seems that the Inertial Measurement Unit (IMU) was overloaded with data and the erroneous information sent to the navigation system indicated a negative altitude (below ground level) and caused the parachute to detach prematurely. It was a free fall for about 3,7 km. The output of IMU was generally as predicted except for this situation which persisted for about one second. Of course accusations started to appear as usual but it is irrelevant now who is to blame.

I would like to get down to earth and look at it from a tester’s perspective. Even if I work in less expensive project, maybe with far smaller impact in European society I can learn from these examples and implement in our projects.

One thing I noticed from the articles released by the press, was that components were tested by different companies but there is no mention about one independent entity who conducted a full System Test with all components integrated. In our software projects, and here I get down to earth again, it is a must do perform a full system test. That means all components integrated. I wonder what was the estimated cost of this kind of test. More or less than 300M… I see quite often in the projects situations when there is a cutting off testing time or testing phases due to “budget constraints” or simply by miscalculating the total cost of failure. 

This is a very good example of risk that is assumed in these situations and underlines the importance of thorough testing.

One other fact noticeable is they did not have a “production like testing environment”. Why is that important? Because they would have seen the performance issue (overload of IMU) if the full landing of the module could have been simulated. This is more for us the testers who do performance tests; we must simulate the performance test in a production like environment. I am sure that in ExoMars project there are good motivations why these tests were not done. I am only using the example to underline the importance of respecting all testing phases and correct prerequisites for them, otherwise the total cost of failure could be unbearable. As for ExoMars … now the project managers are threatened to lose the financing for their launch in 2020.

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