GNSS Radio Occultation Methods for CubeSat Missions: The University of Calgary and Spire Partnership

Abstract:

In 2008, the University of Calgary deployed a low-cost commercial-off-the-shelf dual frequency GPS receiver onboard the CanX-2 nanosatellite, with the goal of demonstrating single-antenna single-receiver GNSS radio occultation capabilities. The team successfully produced ionospheric electron density profiles and continues to operate the CanX-2 GPS payload and collect reliable data six years into the mission. Recently the University of Calgary partnered with Spire to develop low-cost atmospheric sounding methods based on GNSS radio occultations for nanosatellite platforms. The rapidly increasing capabilities on nanosatellites with regards to power production, pointing accuracy and antenna sensitivities provide an ever more attractive platform to create relevant solutions for space and terrestrial weather data.

This paper describes future mission concepts and capabilities for multi-GNSS methods to generate high-resolution atmospheric profiles. Building on lessons learned from CanX-2, the system requirements are defined and recommendations made for efficient GNSS payload operations. New methods are assessed for multi-frequency multi-constellation GNSS radio occultation approaches. Software and hardware simulations are conducted for validation of proposed methods using appropriate receiver architectures. Analyses include signal tracking for LEO trajectories (and Dopplers) and high-precision navigation solutions. Initial data analysis is also presented for a miniaturized, multi-frequency, software-­defined GNSS receiver currently operating onboard Spire’s innovative CubeSat platform.