This work presents the design and prototyping of two 1U standard CubeSats for the First Brazilian MCTI Satellite Olympiad, launching one in a stratospheric helium-filled balloon. The nanosatellites were designed for two missions: Internet of Things connectivity in remote areas based on CubeSat (IoSat) and low-orbit harmful gamma radiation mapping (LOHGRM). The IoSat mission aimed to provide server connectivity for a remote sensor network. The LOHGRM CubeSat was designed for sensing and mapping gamma radiation power levels in the satellite’s orbit to construct a heat map to study the gamma radiation effect on the equipment. The prototype’s performance was evaluated based on physical, mechanical, magnetic, thermal, and transmission characterization, with satisfactory results under test conditions. The LOHGRM mission test was carried out on the ground as proof of concept without flying while a stratospheric balloon launched the IoSat prototype. Due to restrictions imposed by the competition, the IoSat nanosatellite only captured and registered altitude, pressure, and temperature data without testing the communication payload. Instead, this data was sent to the ground station through the competition communication system and stored in a memory card to assess its operation during the flying. The satellite’s maximum altitude was 22.6 km, operating under –23.5 °C