Autonomous Ion Mass Spectrometer Sentry (AIMSS)

Satellite measurements of plasma density and temperature help predict the intensity of geomagnetic storms, which can impact satellites, communications, and power systems. Accurate forecasting requires knowledge of plasma composition. However, typical orbital mass spectrometers have difficulty distinguishing between nitrogen (N+) and oxygen (O+) ions due to their similar masses. This limitation makes it difficult to validate modern space weather models, which depend on accurate knowledge of ion composition in near-Earth space. N+ and O+ ions behave differently in space due to differences in their origin, transport, and loss mechanisms. Improving our ability to distinguish between these ions is critical for understanding and predicting space weather.

Advantages

High mass resolution enables distinction between ion species that are typically unresolved in space-based measurements (e.g., N+ vs O+)
Simultaneous measurement of multiple ion species for improved data collection efficiency
Commandable ion throughput allows for high dynamic range without detector saturation
Flight-qualified design with near-term on-orbit demonstration on the ISS

Technology Description

The AIMSS instrument uses electric and magnetic fields to sort ions first by energy and then by mass. As ions move through the instrument, different species are separated and spread out across the detector as a spectrum, similar to how a prism separates white light into different colors.

First, incoming ions pass through two electrostatic energy filters (ESAs) located at the front of the sensor. These filters allow only ions within a selected energy range to continue through the instrument. By adjusting the voltage applied to each filter, AIMSS can control how many ions reach the detector and adapt to changing plasma density.

Next, the ions enter a magnetic field section that separates them by mass. Lighter ions are deflected more than heavier ions, causing different ion species to land at different...