What kind of testing does the Software Simulation Laboratory carry out?
The Laboratory simulates entire space missions on a virtual basis to see how the onboard software behaves in an operational context or for example to exercise the approach of a satellite to a comet in advance of the real encounter.
Take the example of untried flight software – the code written to fly onboard a satellite in space. This software is connected to a simulator which models the satellite and calculates its orbit, position and behaviour in space. The system is also linked to a simulated 'ground segment', the ground-based infrastructure that sends commands and receives data from the satellite. This “virtual” satellite is then operated using the same software interface used by real mission control teams.
To model a mission to a sufficiently realistic level is far from simple. The individual software models and software infrastructure involved might amount to hundreds of thousands of lines of code each, approaching or even surpassing a million lines in total. Multiple computers are linked and synchronised in real time in order to create such a complex simulation.
In order to facilitate this task, a 'Virtual Spacecraft Reference Facility' has been setup in the joint avionics systems laboratory, and shared between the Software and Simulation Laboratory and the adjacent Control and Data Systems Laboratories. It forms the basis of the ‘End-to-end Avionics Test Bench', which allows actual hardware to be plugged into the simulation to increase its representativity of a flight system.
In this way, also flight computer processors such as the ESA-developed LEON-2 FT can be included 'within the loop' and exercised in a realistic mission scenario.
Along with validating pre-flight software and selected flight hardware, the same set-up can be employed to replicate and solve software anomalies occurring during flight, a kind of detective work culminating in the upload of 'patches' to fix them.
The Laboratory also plays an important role in Electrical Ground Support Equipment (EGSE) used to check-out of satellites under construction and prior to being launched into space. EGSE involves making sure the completed satellite will work as planned by sending telecommands to the hardware in an appropriate format, to verify the correct responses, by checking tens of thousands of separate parameters being involved. The Laboratory maintains a database of telecommand definitions, so they can advise project teams on building customised EGSE procedures for each mission.
The Laboratory also allows experimentation with human-computer interface designs, computer tools enabling collaborative working between people, and systems to improve the reliability and efficiency of the software creation process.
Last update: 29 September 2009