Design, Manufacturing and Test of the CubeSat Ursa Maior

URSA MAIOR (University of Rome la SApienza Micro Attitude In ORbit testing) is a 3U CubeSat realized in the framework of QB50. an FP7 Project led by the Von Karman Institute for Fluid Dynamics, with the aim to carry out atmospheric research within the lower thermosphere, between 200 km and 380 km altitude, which is the least explored layer of the atmosphere. The project has also an educational aim and it is intended for those university students who want to deal with the complete realization of a CubeSat, in order to gain experience and become confident with the problems related to a real project. Several PhD and Master students in Space Engineering are involved in the CubeSat design, manufacturing and testing, supported by a staff of professors, at S5I.ab (Sapienza Space Systems and Space Surveillance Laboratory) of University of Rome La Sapienza. Since the main objective of QB50 mission is to carry out a multi-point in-situ atmospheric research in the lower thermosphere, URSA MAIOR carries a multi-Needle Langmuir Probe (mNLP) science unit. This CubeSat is a platform for technology demonstration. It will board two other payloads: ART1CA, a passive and independent deorbiting system for nanosatellites based on a polymeric drag sail designed, manufactured and tested at NPC SpaceMind, and MEMIT, a micro-Thruster experiment for nano-satellite attitude control developed at CRAS (Sapienza Aerospace Research Center) whose main goal is testing a new integrated MEMS (Micro Electro Mechanical System) valve-nozzle. Taking care of the educational goal, almost all the subsystem are developed in-house, such as the structure, the OBDH/OBCs, UHF and VHF antennas. All the required validation tests are performed in the local facilities. The ADCS is provided by Surrey Space Center. It uses a combination of MEMS rate sensor, a magnetometer, and sun and nadir sensors to estimate attitude and angular velocity. A pitch momentum wheel and three magnctorquers are devoted to the attitude control of the satellite. The paper describes the design, manufacturing and testing of the URSA MAIOR CubeSat, discussing the satellite subsystems architecture and highlighting the on-ground test results.