Utilizing Open Loop Reception to Assess the Impact of Solar Interference on the Transmission of Spacecraft Telemetry

On November 18, 2023, Mars reached solar conjunction as viewed from Earth, with a minimum Sun-Earth-Mars (SEM) angle of 0.1 degrees. With the SEM angle smaller than usual, this geometry presented a unique opportunity to study the effects of solar plasma on radio signals sent from Mars assets to the Deep Space Network (DSN) on Earth. For a period of two weeks before and after the event, we utilized the Open Loop Receivers (OLRs) at the DSN to record the radio signal from three Mars orbiters: Mars Odyssey (56 tracks), Mars Reconnaissance Orbiter (56 tracks), and MAVEN (24 tracks). The OLR recordings were completely opportunistic in nature—no modifications were made to any of the spacecrafts’ configurations or to the DSN ground stations. As the SEM angle decreased, telemetry from the three orbiters was increasingly corrupted, while the OLR continued to capture a spectrum containing the degraded signal. Additionally, a coronal mass ejection was observed during the study period, with the impact evident in the OLR data. By correlating phase noise from the OLR data with the SEM angle, we map the impact of solar plasma on the transmission of data through the Sun’s corona. The OLRs were also configured to record wide frequency bands, offering a path for telemetry recovery even as the closed loop receiver data were degraded at low SEM angles.