Navigation and control systems of space vehicles can be tested on Earth only with restricted degrees of freedom and accuracy of the environmental dynamics before being flown. However, a vehicle’s dynamics can be simulated using numerical computer simulations. It has become general practice to use states from these simulations to stimulate sensors and flight systems for testing. The vehicle’s on-board hardware is used for these tests to verify the combination of sensors, computers and actuators.
The Department of Guidance, Navigation and Control Systems (GNC) runs several laboratories and testing facilities that can be used to test complete navigation and control systems of satellites and space vehicles or parts of GNC systems of space transportation systems.
These hardware-in-the-loop tests can be carried out in two steps:
Since most interfaces for sensors and actuators are standardized, it is possible to create a system that can test a variety of attitude and orbit control systems for space missions. To adapt the test and verification systems for a particular mission, the interfaces can be reconfigured and communications protocols can be implemented that allow to interact with the sensors and actuators used.