A Cubesat Receiver For The Study Of Vlf-Waves At Leo

We describe the design of the mu BBR (micro Broad Band Receiver), a VLF receiver for the VPM mission. VPM is an AFRL CubeSat mission that will be launched into a 500 km circular orbit with a 51 degrees inclination where it will continuously sample the VLF electromagnetic spectrum from 300 Hz to 30 kHz. These waves largely control the state of the radiation belts and improved understanding of them will lead to improved radiation belt predictive models. The mu BBR consists of a single-axis electric dipole antenna, or dipole antenna assembly (DAA), a single-axis magnetic field search coil antenna, or search coil boom assembly (SCBA) and a payload electronics module (PEM). It is designed for high reliability by using radiation-tolerant components. The dipole antenna and search coil are aligned perpendicular to each other and the spacecraft is operated so as to keep both perpendicular to the background magnetic field as much as possible. All signal processing is implemented in an FPGA, using fixed-point arithmetic, without any volatile on-board firmware. Data is sampled at 80 kHz using a GPS-disciplined clock. Two date products are delivered: a reduced-bandwidth survey mode with 6.5, 13.1, or 26.2 second resolution, and a commandable full-resolution burst mode. Burst data can be taken in the time or frequency domain, can be selectively windowed along the time or frequency axes, and can be decimated by a factor of 2, 4, 8, or 16. Such capability is included because of anticipated data download rate limitations. The VPM spacecraft is scheduled for launch before the end of 2019.