The Conceptual Design of CubeSat Based System for GNSS Radio Occultation/Reflective Mission

The Global Navigation Satellite System (GNSS) Radio Occultation/Reflective (RO/R) instrument collects global atmospheric data and oceanic wind speed data for weather prediction and climate researches. This paper proposes the conceptual design of the satellite constellation and the satellite to realize the GNSS-RO/R mission based on the cubesat platform, with the goal to achieve cost effectiveness and minimum deployed schedule. The cubesat considered in the study is 12U and within 20 kilogram. The proposed innovative constellation consists of 36 (with 6 backup) satellites on three 600 km altitude sun synchronous planes, 12 satellites even phasing on each plane. It is expected to have 20000 GNSS-RO profile measurements and on-demand GNSS-R profile measurements per day at minimum. The payload instrument will be able to collect RO/R measurements via GPS and GLONASS. The mission lifetime is 3 years. The on-orbit redundancy, instead of redundant satellite components, is adapted to increase system reliability. The satellite design of this study faces very tough challenging to meet the 10-kg mass constraint. The proposed solutions to lower down mass include the creative payload design, the plasma thruster based reaction control subsystem and attitude control subsystem, the use of special non-space grade made-inTaiwan components, and the creative mission scheduling among satellites to optimize daily global coverage with limited duty cycle of each satellite (the duty cycle can not be 100% because of mass saving on solar array and battery). The study demonstrates the feasibility to achieve the system design. The lessons learned of the system design study have also been introduced. The international cooperation and investment to realize this development is welcome. Design Philosophy  To develop quick and low cost COSMIC System, and establish capability of mass cubesat developer  Efforts to possibly improve some lessons learned with Formosat-7