Potential radio frequency interference with the GPS L5 band for radio occultation measurements

Abstract. Future radio occultation (RO) receivers are planned to utilize the newly implemented Global Positioning System (GPS) L5 band centered at 1176.45 MHz. Since there are currently no operational GPS L5 receivers used for space-based RO applications, the interference environment is unclear. Distance measuring equipment (DME) and tactical air navigation (TACAN) stations share the same frequency band as GPS L5. The signals from these stations have been identified as possible sources of interference for any GPS L5 receiver, including those used in RO applications. This study utilizes Systems Tools Kit (STK) simulations to gain insight into the power received by a RO satellite in low Earth orbit (LEO) from a DME–TACAN transmission as well as the amount of interfering stations. In order to confirm the validity of utilizing STK for communication purposes, a theoretical scenario was recreated as a simulation and the results were confirmed. Once the method was validated, STK was used to output a received power level aboard a RO satellite from a DME–TACAN station as well as a tool to detail the number of interfering DME–TACAN stations witnessed by a space-based RO receiver over time. The results indicated a large number of DME–TACAN stations transmitting at similar orientations as a receiving RO satellite, thereby leading to the possibility of signal degradation in an unclear interference environment.