An Introduction to the Radio Frequency Sensor (RFS) and Its Upcoming Geosynchronous Mission

Through a partnership between the United States Department of Energy’s National Nuclear Security Administration, Los Alamos National Laboratory, and Sandia National Laboratories, Space and Endo-atmospheric Nuclear detonation detection Surveillance Experimentation and Risk-reduction (SENSER) is a set of flight experiments destined to fly in a western hemisphere geosynchronous orbit, with vehicle integration, launch, and data distribution supported through the United States Department of Defense’s Space Test Program, mission STP-3. The SENSER system comprises three research and development experiments, one each focused on: optical, hard radiation, and radio frequency sensing technologies. SENSER’s mission lifetime is targeted for at least one year, with possible follow on activities beyond that; launch is expected in early- to mid-2019.

Of particular interest to the lightning community will be the Radio Frequency Sensor (RFS). Many of RFS’s goals are focused around verifying and validating next-generation technologies for future operational missions, but RFS will also support fundamental sensor research and development, as well as basic science missions. RFS will have an active crossed-dipole receiving antenna (one “horizontal” and one “vertical” dipole co-located and mounted orthogonally), with the linear feeds from each dipole fed into a direct-conversion software-defined radio. RFS will operate simultaneously in two different detection bands: the low band will cover frequencies from approximately 5-55 MHz, and the second band will be selectable as either 120-140 MHz or 325-350 MHz. With the flexible software-defined radio design (as well as the ability to upload modified flight firmware and software applications on-orbit), algorithm implementations for noise-riding impulsive triggering modes, as well as digital circular polarization synthesis, will be verified throughout the mission lifetime. In addition to design validation and improvement, RFS’s mission will provide an excellent opportunity for in-situ evaluation of the natural signal background, as well as the opportunity to observe lightning transients, on-board electrostatic discharges (discharges that occur across dielectrics on the space vehicle as a result of charging gradients from the dynamic charged particle environment), and ionospheric scintillation effects. RFS will explore the exploitation of polarization information in lightning event-type identification and characterization, as well as the potential for single-satellite event source location capabilities. Most importantly, RFS will collect persistent, hemisphere-scale, lightning activity that will allow for the study of the entire lifetime of a storm (rather than intermittent, lower-orbit, snapshots) to allow for large-scale and seasonal total lightning climatology. We will present an overview of both the RFS design and hardware, as well as expected system capabilities in this presentation.