A team at Los Alamos National Laboratory is leveraging SMD-funded technology developments to design a novel sensor that examines the interactions between space plasma and the plumes generated by the thrusters of spacecraft delivering supplies and crew members to the International Space Station. Not only will this sensor monitor conditions at the space station, but it will also provide information to enable more accurate space weather prediction for other locations in space.
Space weather describes the environmental conditions between Earth and the Sun, including particles, fields, and plasma that can affect assets in space and on Earth. Weather on Earth has many components including rain, temperature, extreme wind, ice, lightning, etc., and can be extreme. Weather in space is complicated because the environment consists of a complex collection of charged particles, sparse numbers of neutral molecules, along with ever changing magnetic and electric fields. Satellites in space are subject to this extremely harsh environment, and space weather is studied in part because of the disruptions it can cause to electronics systems in space satellites.
A longstanding goal of the space weather community is to advance our capability to predict space weather events days in advance, in the same way that terrestrial weather forecasting enables one to anticipate a week of sunshine or snow. Improved space weather prediction could enable potential cost savings in areas such as spacecraft operations, aviation, and ground-based power grids.
One of the primary inhibitors to advancing our space weather forecasting capability is lack of knowledge and measurements of the constituent ion populations in space. There are two sources for ions in near-Earth space: the solar wind and the polar wind. The solar wind steadily emanates from the Sun and is composed of predominantly hydrogen, alpha particles, and high charge-state heavy ions. The polar wind emanates from Earth’s upper atmosphere (the ionosphere) and is composed of singly ionized atoms and molecules including atomic hydrogen (H+), atomic helium (He+), and atomic oxygen (O+) (see Figure 2 below), as well as atomic nitrogen (N+), molecular nitrogen (N2+), molecular oxygen (O2+), and nitrogen oxide (NO+). The process by which these low-energy ions leave Earth’s atmosphere and enter near-Earth space is called ionospheric outflow and is an area of significant study.
Satellite measurements of O+ are often used to indicate geomagnetic storms—space weather disturbances that have broad, deleterious impacts on space and ground assets. These negative influences include enhanced radiation effects on satellites due to intensified radiation belt fluxes; increased upper atmospheric scintillation that distorts radar, radio, and GPS signals; and geomagnetically induced currents that can damage or disrupt ground-based electrical power grids.
However, typical mass spectrometers flown today cannot distinguish between N+ and O+ ions due to their similar masses. Ambiguity between N+ and O+ is problematic, as measurements and models show that these ions behave differently in space due to differences in their upper atmospheric source (different scale heights and photoionization), transport (different behaviors in electric and magnetic fields), and loss mechanisms (e.g., neutralization via charge exchange with ambient neutral hydrogen, or geocoronal H0). Our poor knowledge about the differences in source, transport, and loss of N+ and O+ in the space environment makes it impossible to validate modern space weather models and hinders our ability to predict space weather.
The Autonomous Ion Mass Spectrometer Sentry (AIMSS) is designed to make high mass resolution observations of the ionospheric plasma and to measure man-made contamination caused by the interaction of the ionospheric plasma with the thruster plumes from spacecraft delivering supplies and crew to the International Space Station (ISS). The particles expelled by these thruster systems contaminate space station surfaces, causing degradation of optical and thermal surfaces and resulting in increased charging of the spacecraft surface.
AIMSS is also capable of distinguishing ions of ionospheric origin, including N+, O+, N2+, O2+, and NO+. As mentioned, most modern space plasma mass spectrometers are typically incapable of these measurements. Furthermore, AIMSS will measure these ionospheric ions and molecular ions from a pallet mounted onboard the space station, which resides in the Earth’s ionosphere. The resulting measurements will provide important inputs and validation for space weather forecasting models. AIMSS will also serve as a testbed for future missions targeting cold magnetospheric plasma.
The AIMSS payload is a double focusing mass spectrometer and utilizes electric and magnetic field geometries to focus in both direction and energy. The AIMSS instrument design and operation are illustrated in Figure 3. This design allows for multiple ion species to become spatially distributed by mass-to-charge ratio (M/q) along the focal plane. Specifically, lighter ions entering the analyzer will have a shorter path length than heavier ions, creating a series of concentric paths almost like a rainbow, as shown in Figure 3 (right). The instrument is comprised of: (1) a laminated collimator to set the field-of-view (FOV); (2) a laminated electrostatic analyzer (ESA) to selectively filter ions by the energy-to-charge ratio (E/q); (3) a magnetic sector analyzer (designed and built by Plasma Controls at Colorado State University) to separate ions by M/q; and (4) a microchannel plate (MCP) followed by position sensitive cross delay anode (XDL) assembly to detect the location of the ions on the detector plane.
The ability of AIMSS to distinguish between ion populations found in various planetary ionospheres and regions of the solar system was modeled and is shown in Figure 4. Various ion species were modeled as they entered the instrument and travelled through the detector sections, shown in Figure 3, to be recorded as measured counts. The locations and species of the ions landing on the detection plane are shown in Figure 4 for a variety of possible locations: (A) Earth, (B) Venus, (C) Jupiter, (D) Saturn, and (E) the pristine solar wind (i.e., there is no interaction with a nearby planet). These end-to-end electro-optic modeling results indicate that the AIMSS detector can provide high mass resolution observations of planetary ionospheres critical for advancing space plasma science.
The NASA Heliophysics Technology and Instrument Development for Science (H-TIDeS) Program funded early AIMSS efforts to refine the design concept, conduct prototype testing of subsystems, and advance the technology readiness level (TRL). The instrument was subsequently proposed to, and selected by, the Los Alamos National Laboratory (LANL) Laboratory Directed Research and Development (LDRD) Program Office and is currently being built, tested, and calibrated at LANL. The payload containing AIMSS will fly on the Space Test Program – Houston 11 (STP-H11) mission to the International Space Station in early 2026. This flight will provide on-orbit data to validate the instrument performance and inform future design improvements for instruments destined for the magnetosphere.
Project Leads: Dr. Carlos A. Maldonado, Los Alamos National Laboratory (LANL), Dr. Matthew G. McHarg, United States Air Force Academy (USAFA)
Sponsoring Organizations: NASA H-TIDeS and LANL Laboratory Directed Research and Development (LDRD) Program Office, DoD Space Test Program.
