Design and test of the automatic Morse beacon system of the OUFTI-2 nanosatellite

Abstract

OUFTI-2 is an educational satellite under development at the University of Liège. It is a 1 liter CubeSat, the main payload of which is a homemade radio repeater featuring D-STAR digital, amateur-radio communications. A main secondary payload is dedicated to the test of an innovative type of shielding that can protect electronic systems against space radiations. OUFTI-2 is expected to be deployed from the ISS, with a mission duration of about 6 months.

One important subsystem of the nanosatellite OUFTI-2 is the beacon system. The beacon continuously emits successive frames which describe the satellite state. These frames are emitted at both a low and a high rate, which are respectively 12 wpm and 2400 bauds. In the case where other subsystems of the satellite might be damaged, in particular the communication subsystem, the beacon is a diagnostic tool which informs of the essential parameters of the satellite. The beacon is also really helpful in normal operation since its low rate Morse signal can easily be captured and decoded by worldwide amateur radio operators. These operators can therefore send decoded signals to the OUFTI-2 team, which is extremely useful in order to have a permanent monitoring of the satellite, especially when it is not above Liège. Regarding the high rate signal, it is a great tool to acquire updated satellite information faster, however, no decoding system of this frame was designed yet.

The first contribution of this work is to assess the correct functioning of the beacon by measuring its RF parameters. The paper will describe the procedure followed to measure the RF parameters and why they will eventually need a reviewing. The second contribution is to implement a system that can decode the 2400 bauds frame, based on different devices. Results will show that the implemented system is able to decode signals of which power might get down to -100 dBm.