For engineers, designing and building systems is an exciting and dynamic learning experience. Testing, however, is often thought of as drudgery, left for the last minute, and done in an ad hoc “OK this works let’s move on” manner. This all but guarantees a system prone to failures. For most systems, this is acceptable because we can simply fix the failures and move on. For space systems, a single failure often means your multi-year, possibly multi-million dollar space mission has totally, irrecoverably failed.
Industry combats this problem by using expensive hardware-in-the-loop test jigs and extensive day-in-the-life testing. We are bringing this to small CubeSat builders by providing Flatsat-based Hardware-In-the-Loop Simulator (FlatHILS), an inexpensive and open source system integration and test infrastructure. Inspired by the catchphrase “test like you fly”, FlatHILS brings an industrial-strength test environment to CubeSats. FlatHILS runs Basilisk, an open source satellite simulation program running on a PC that simulates, in real time, the satellite’s position in orbit, its attitude (direction it’s pointed), whether there are any ground stations within communication range, sun exposure, the visible star field, and Earth’s magnetic field vector. This simulation data is then used to test the “flatsat”, a development satellite laid flat on a test bench. FlatHILS directly powers the satellite’s solar panels using an LED-based solar simulator, runs the satellite’s magnetometers using a Helmholtz Cage, operates star trackers using LCD panels, and even simulates ground passes using a computer-controlled RF attenuator between the FlatSat and the development ground station (a bench testing version of the University Class Open Ground Station (UniClOGS) called, of course, “FlatClOGS”.
FlatHILS allows CubeSat operators to run hardware-in-the-loop day-in-the-life tests of their entire CubeSat system, including a satellite and a ground station, including full tests of power and communications, and limited testing of attitude determination and control subsystems.