New Low-Cost Stratospheric Balloon Flight Opportunities with Pisa University’s MicroHAPS Platform

Since 2018, the Space Systems Laboratory at the University of Pisa carries out research and development activities on low cost stratospheric platforms, focusing on the use of COTS sounding balloon technology to lift a scientific or technological payload into the stratosphere. With about 2000 units launched every day from locations all over the world since decades, the weather/sounding balloon is a very mature and extremely reliable technology. Together with the availability of inexpensive microcontrollers, miniaturized sensors and GNSS receivers, it enables the realization of highly cost effective stratospheric missions. This paper presents an overview of the activities carried out so far and a discussion of the innovative technical characteristics of the MicroHAPS (µHAPS) platform, specifically designed to host a 2 - 3 kg payload on short and medium duration flights up to 38 km altitude. With 11 operational flights of the present UniPi HAB platform already successfully completed, the basic functionalities of the system are validated, including payload location for recovery through satellite tracking, onboard photovoltaic power generation and telemetry and telecommand with half-duplex LoRa over long distances. In its present form, UniPi HAB and the forthcoming µHAPS represent viable opportunities for scientific investigation and technology testing in the stratosphere. The paper also outlines the main issues related to future developments of µHAPS such as autonomous payload landing via paraglider and the implementation of a reinforcement learning control strategy to provide station keeping / area permanence capability through exploitation of wind direction variability with altitude.