STEPHEI: Revolutionizing Space Plasma Measurements with CubeSat Instrumentation
- Scott Thaller
- Aug 28
- 2 min read
Scott Thaller, Research Scientist
The invisible forces propelling particles through space, energizing plasma and generating waves in the magnetosphere all stem from one key player: the electric field. Understanding this field is essential for decoding Earth's space environment dynamics, including particle movement, energy transfer and magnetosphere-ionosphere connections.
Orion scientists have recently conceptualized a groundbreaking space science tool that we’re calling STEPHEI, short for Small Tenuous Plasma Heliophysics Electric Field Instrument. The concept envisions STEPHEI operating aboard a CubeSat to measure electric fields in space—potentially transforming how researchers study tenuous plasma environments where particle densities remain extraordinarily low.
WHY ELECTRIC FIELD MEASUREMENTS MATTER
Electric fields play a crucial role in our understanding of space weather and plasma physics. These measurements help scientists decode:
Particle transport and energization processes
Wave phenomena in space
Magnetosphere-ionosphere coupling mechanisms
Other dynamic plasma behaviors
Many of these phenomena occur at spatial distance scales that scientists call the "meso-scale" - a range where traditional single-point measurements fall short. To truly understand these complex systems, we need simultaneous measurements from multiple locations that can distinguish between spatial and temporal changes.
THE CUBESAT SOLUTION
This is where STEPHEI and CubeSat technology create perfect matches. CubeSats provide a compact, cost-effective platform for deploying multiple measurement points throughout the magnetosphere, offering the spatial coverage needed to capture these elusive phenomena.
OVERCOMING TECHNICAL CHALLENGES
Traditional electric field instruments use what's called a "double probe" system with bias currents to reduce plasma sheaths between the ambient plasma and sensors. However, on small CubeSats, this approach can cause the spacecraft to charge to high electric potentials, creating artificial electric fields that contaminate the measurements.
We’ve addressed this fundamental challenge through innovative engineering, developing high-impedance, low-leakage current frontend electronics that maintain measurement integrity while operating on a compact CubeSat platform.
LOOKING FORWARD
The concept of STEPHEI represents an exciting new direction in space plasma instrumentation that could enable multi-point measurement capabilities that were previously cost-prohibitive with larger spacecraft. If developed, such technology would open new possibilities for understanding space plasma dynamics with unprecedented detail and creating more accurate space weather models.
Click the link below to view the poster presentation of this work.