HENON - Main Challenges of a Space Weather Alerts CubeSat Mission

This paper highlights the main challenges encountered in the phase A and B design of a Space Weather Alerts mission performed by a 12U CubeSat, along with the proposed solutions and mitigation approaches. HENON (HEliospheric pioNeer for sOlar and interplanetary threats defeNce) mission phases A and B have been conducted by a consortium led by Argotec under European Space Agency contracts within the General Support Technology Programme through the financial support of the Italian Space Agency. HENON is mainly targeted at the provision of alerts upon detection of potentially harmful Space Weather phenomena, namely Solar Energetic Particles and interplanetary perturbations such as High-Speed Streams and Interplanetary Coronal Mass Ejections. HENON will be equipped with state-of-the-art miniaturized scientific payloads to measure energetic particles fluxes, solar wind parameters and interplanetary magnetic field. It will be operated in a Distant Retrograde Orbit (DRO) in the Sun-Earth system, which has never been explored before by any kind of spacecraft. This kind of orbit allows the CubeSat to be favorably placed for a significant period to perform both scientific measurements and alert provision. The transfer to such an orbit is planned to be performed autonomously, employing on-board electric propulsion, which will be another first time ever for a CubeSat in Deep Space. This ambitious mission brings significant technical challenges. The nature of the mission poses a major challenge, as HENON is supposed to achieve its main objective specifically during Solar Events, which are often a cause for satellites' failure or misbehavior, even for bigger class satellites. For a CubeSat-class spacecraft the challenge is even greater, as the classical mitigation strategies cannot be applied straightforwardly due to the limitations in available resources; hence a different approach based on sector analysis and radiation-driven subsystems placement must be used. To provide its Space Weather alert service, both Sun pointing of the instruments and Earth pointing of the antenna are required simultaneously for about a fourth of the orbit, leading to a trade-off between the ability to acquire relevant data and the ability to communicate alerts to Ground, also considering the long distance from Earth, which already imposes significant challenges for telecommunication. The autonomous transfer to the operative orbit brings supplementary challenges. The electric propulsion imposes a demanding requirement in terms of power generation, especially for a 12U CubeSat. This also implies prolonged thrusting arcs, without communication, with 1 year of transfer time to be added to the 1-year operational lifetime, for a total of at least 2 years in a harsh Deep Space environment where radiation single event effects need to be accounted for and mitigated. Furthermore, the extended mission lifetime and the continued thrusting arcs impose a high level of on-board autonomy, mainly to be implemented at On-board software level, to ease the burden of prolonged and costly Deep Space Ground station operations. HENON is going to be a unique mission, employing breakthrough technologies for a CubeSat in Deep Space. This paper presents the design approach to overcome these challenges and ensure a significant scientific return, reinforcing the path towards CubeSats able to achieve missions previously reserved to bigger-class satellites.