Solar scintillation study during planetary conjunction

During superior solar conjunction of a spacecraft, the spacecraft has limited communication with the ground station due to the effect of the Sun on RF signal transmission. Our analysis of data that has been obtained during several MESSENGER (MErcury Surface, Space ENivornment, GEochmeisty, and Ranging) conjunctions has revealed that the spacecraft can operate at smaller SEP angles than was reported in prior studies. Operating at smaller SEP angles can substantially reduce the down time of a communication link during solar conjunction. While the general trend is for the performance to degrade with decreasing SEP angles, we have found instances where the performance deviates from this behavior. Our analysis of the data has revealed a short-term amplitude scintillation and a long-term phase scintillation. Amplitude scintillation produces up to 3 dB of degradation of carrier signal strength over a short time scale (< 1 s). Phase scintillation occurs on a longer time scale than amplitude scintillation — 10 s to 100 s of seconds — and can cause deeper fades.