Mission Design for the CubeSat OUFTI-1

CHAPTER 10.COMMUNICATION SYSTEMWe can see that the results are not so different from the simplified model.We also have the minimum required values of S and E bN N 0: the system is able toguarantee a good communication level with the available power in the assignedorbit.Obviously the most critical case is the downlink as the transmitting power isextremely limited, while the ground station can increase its power if it turnsout to be too low. Furthermore, the OUFTI-1 platform is supposed to used forthe next CubeSat of LEODIUM project with a payload on board which needspower too. Even if the orbits of the future missions are unknow, we performeda link budget for different value of power available on the satellite in case of thesame orbit as the one of OUFTI-1. We have the results represented in figure10.3.Figure 10.3: Downlink link budget for different values of transmitting power incase of 1200 Km altitude, 5 ◦ elevation.We see that the power can be partially reduced in order to use it for otherelements. Anyway, in case of use of the satellite by the amateur radio community,the margins on E bN 0and S have to be as bigger as possible in order to allowNthe communication even with ground antennas with mediocre performances.10.3 Backup telemetry and ground stationA CW beacon is also added on the CubeSat mainly for reliability reasons. Asthe D-STAR has never flown into space, a backup system is almost compulsory.In fact, if the main communication system fails, we would like to know whathappened in order to avoid the same problem in the future missions. This iseven more important if the D-STAR system don’t light up soon after launch.With the radio beacon, we will be able to pass some commands to the satellitetrying to fix the problem and, even if all the operations to save the missionwill be useless, anyway thanks to the housekeeping we hope to find out theGalli Stefania 103 University of Liège