ARD GPS Post-Flight Analysis

In the frame of the Atmospheric Re-entry Demonstrator (ARD) flight, a GPS experiment has been conducted to support future designs of autonomous navigation systems for Space and atmospheric flight. GPS in re-entry is faced to a large set of environment conditions, from orbital flight at high altitude and orbital velocity, to landing conditions at Earth surface. Performance and adaptability of the GPS system, in its capacity to acquire and track rapidly varying low level RF signals in a large frequency range, is of main interest to Navigation design. In addition, as a RF system, the GPS study offers opportunities to study the black-out phenomenon arising from atmosphere ionisation. A systematic data analysis has been conducted at ASTRIUM, following the experience gained in such activity for Space in-flight GPS characterisation. The main results presented in this paper concern the following analyses : geometric visibility analysis, C/No characterisation and black-out effect identification, sensitivity and dynamics performance assessment through acquisition time and threshold characterisation, measurement performances. Key performances are confronted to prediction to identify design drivers and improvement directions. The GPS tracked nearly permanently nine satellites in distributed directions, thus offering in addition ionisation anisotropy qualitative indications.