The CANVAS Mission: Quantifying the Very-Low-Frequency Radio Energy Input from the Ground into the Earth's Magnetosphere

The CANVAS Mission: Quantifying the Very-Low-Frequency Radio Energy Input from the Ground into the Earth's Magnetosphere

Utah State University, Logan, UT

Very-low-frequency (VLF) electromagnetic waves, emitted by ground-based sources including lightning and VLF transmitters, can impact the lower ionosphere and magnetosphere through their interaction with the local plasma and energetic particle environments. Quantifying the impacts of these waves requires an accurate assessment of the propagation and attenuation of these waves. The Climatology of Anthropogenic and Natural VLF wave Activity in Space (CANVAS) mission is designed to measure VLF waves in low Earth orbit originating from these ground-based sources. The mission aims to characterize the VLF environment in low Earth orbit to address two main goals: i) constrain the VLF wave injection from the ground into the magnetosphere, and ii) improve models of VLF wave attenuation during propagation through the ionosphere.

CANVAS will measure VLF waves using three search coil magnetometers and two electric field dipole antennas that comprise its payload. The search coils are integrated into a 3D-printed Carbon PEEK holder, along with the magnetic field preamplifier board. The search coil system is deployed 1 meter from the spacecraft using a carbon fiber deployable boom, in order to isolate the sensitive search coils from spacecraft noise. The electric field system is composed of four 40 cm monopole antennas, making two orthogonal dipole antennas, integrated into the spacecraft “crown”, along with a custom preamplifier circuit for each monopole. The payload is completed by a custom analog receiver board, providing amplification, anti-alias filtering, and centering for the analog-to-digital converters (ADCs); and a custom digital board, which includes an FPGA for onboard signal processing. Spectral data spanning 0.3–40 kHz are saved at 1-second cadence, providing a continuous “fast survey” data mode for the duration of the mission.

The CANVAS spacecraft is a 4U CubeSat, 10 × 10 × 45 cm and under 6 kg. In addition to the 1-meter deployable carbon fiber boom and electric field antennas, the spacecraft incorporates deployable solar panels and a monopole antenna for UHF communications. Data is downlinked in S-band. The spacecraft structure and avionics are custom-designed and built at CU Boulder, while the radios and attitude determination and control system (ADCS) are vendor-supplied components.

The CANVAS mission is designed to operate at ∼500 km altitude in a moderate-inclination orbit (∼50 degrees), to ensure global coverage of lightning-generating regions; most lightning globally is confined to within ±50 degrees latitude. Spectra at 1-second cadence account for ∼424 MB of data per day, after housekeeping and encoding overhead. A one-year mission will ensure seasonal coverage to observe the Marshall 1 36th Annual Small Satellite Conference variability in global lightning activity.

This paper presents a detailed overview of the CANVAS science goals, payload, spacecraft, and mission. The instrument is now completed and undergoing functional testing and performance characterization, and the spacecraft is beginning integration, expected to be completed in Fall 2022. The CANVAS mission will be ready to launch in early 2023.