GNSS-based hardware-in-the-loop simulations of spacecraft formation flying with the global ionospheric model TIEGCM

Abstract

Low-earth-orbit (LEO) spacecraft formation flying (SFF) simulated on the Virginia Tech Formation Flying Testbed (VTFFTB) demonstrated the feasibility of detecting simplified ionospheric electron density (Ne) structures (i.e., one-dimensional equatorial plasma bubbles/EPBs) utilizing a differential total electron content (TEC) method. The Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) is used to greatly enhance the ionospheric Ne simulation capability and fidelity (e.g., dimension, resolution, more realistic space weather processes) of GNSS-based hardware-in-the-loop (HIL) simulations in the current work. An algorithm is developed to incorporate TIEGCM 4D ionospheric Ne profiles into the VTFFTB HIL infrastructure by simulating the TEC impacts on multi-band GNSS signals. First, a series of first-principle analyses on ionospheric Ne retrieval accuracy are presented using software-based LEO SFF simulations in the TIEGCM ionosphere. Subsequently, two HIL ionospheric space weather observation simulation test cases, EPB and Tongues-of-Ionization (TOI), are simulated on the VTFFTB to demonstrate the enhanced 4D ionospheric simulation capability and evaluate the Ne retrieval characteristics. The Ne retrieval techniques are validated and characterized in the TIEGCM ionosphere via both software and HIL simulations. In principle, the technique developed is expected to be applicable to other similar simulation platforms, as well as other global or regional ionospheric models. This is advantageous for future GNSS testing, HIL simulations, and technology developments.