Ground segment

The ground segment consists in two main elements: (1) a ground station (GS) for controlling the satellite (plus a duplicate, distant backup GS at EuroSpace Center of Redu), and (2) an interface/extension to a standard (ground-based) D-STAR repeater.

The first element (GS) consists of a control computer (possibly a tablet or a smart phone), radio equipment, and (steerable,) tracking x-quad antennas, located at our institute. The “brain” of the GS is the control computer's “mission control center (MCC)” software tool, which manages the sending of telecommands (TC's) and the receiving of telemetry (TM's) to & from the satellite, using the standard, amateur-radio AX.25 protocol.

The second element (interface/extension) routes the communications from the worldwide D-STAR network to & from the satellite, and thus to & from a user located at the intersection of the transmit and receive footprints of the satellite antennas (VHF and UHF). However, two users located in the intersection footprint can also communicate directly via the satellite. Our ground-based D-STAR repeater consists of a control computer, radio equipment, and a dual-band, vertical antenna located about 1.5 km from our GS. The interface/extension consists in a control computer, a standard UHF D-STAR repeater transceiver, a home-made, computer-controlled VHF-to-UHF frequency converter - allowing (1) the uplink and downlink signals to both go through this transceiver, and (2) the application of the appropriate Doppler frequency corrections to the uplink signal -, and a tracking antenna, all at the same location as the DSTAR repeater. (The downlink Doppler corrections are done on-board – according to uplinked, precomputed correction tables - so that users can use standard, unmodified D-STAR transceivers.) The ground-based repeater has been operational for several years, and has been regularly upgraded and improved. It was the first Belgian D-STAR repeater connected to the internet.

We designed our GS (and MCC) so that it could be integrated into the worldwide GENSO satellite tracking network. This will be invaluable to control the satellite when it is not in view of our OUFTI-1 facilities.