The Psyche Spacecraft: The Solar System’s Newest Interplanetary Meteorologist?

David Lawrence, GRNS Instrument Lead

Patrick Peplowski, GRNS Instrument Scientist

Most people don’t think about weather in space (or that space may even have weather!), but the effects of space weather were hard to miss in early May 2024. The Sun is currently in an agitated state known as “solar maximum”, and this state is known to lead to an increase in solar activity. On May 7, 2024 a location on the Sun’s surface known as Active Region 3664 (or AR3664; see pictures from NASA’s Astronomy Picture of the Day here, here and here) released a massive storm that rained high-speed particles on Earth’s atmosphere. These particles generated aurora displays seen all over the world, including the nighttime skies near Arizona State University, the home base of NASA’s Psyche mission (see Figure 1). People all over the world enjoyed these vivid displays of space weather, which normally are only visible from high northern latitude locations.

Figure 1. Photograph of the sky above Sedona, Arizona take by the first author’s son, Benjamin Lawrence, on May 10, 2024 at 11pm local time.

While the Psyche spacecraft was designed to study a metallic asteroid, its scientific sensors also make it an excellent space-weather station. These sensors include a magnetometer that measures interplanetary magnetic fields, and detectors from the Gamma-Ray and Neutron Spectrometer that measure the presence and character of high-speed (or energetic) particles. The recent solar storm provided an excellent test case to demonstrate how the Psyche spacecraft can serve as an interplanetary space-weather station.

This test case is illustrated in Figure 2. The top three panels show a space-weather “storm tracker” (actually a space-weather prediction model from the NOAA Space Weather Prediction Center), as seen from above the Sun-Earth system. The bottom panel shows “weather station” measurements from the Psyche spacecraft (top three panels) and NOAA’s Earth-orbiting GOES spacecraft (bottom panel). The GOES spacecraft are designed to monitor the space weather at Earth, and the information they provide is a key part of our effort to understand the space environment.

Figure 2. Top three panels show a space-weather “storm tracker” produced by NOAA Space Weather Prediction Center. The bottom four panels show “weather station” data provided by the Psyche GRNS and the Earth-orbiting GOES spacecraft (i.e., “Particles@Earth”). Particle data from the three “storm tracker” times are indicated by the numbers 1, 2, and 3. “Time 1” occurs soon after AR3664 releases particles towards the Earth, but before they are seen at Earth. “Time 2” is when these particles hit the Earth, but are not yet at the Psyche spacecraft. “Time 3” is just prior to when the Psyche spacecraft sees a particle enhancement, but much less intense than what was seen at the Earth.

A key aspect of Figure 2 is that on May 9–13, the Psyche spacecraft was in a completely different region of space from the Earth and GOES, and therefore saw a unique space environment compared to what we all experienced.

The numbers 1, 2 and 3 in Figure 2 mark three distinct periods for both the space-weather model and Psyche/GOES data:

1. This shows two well-developed storms (seen as two reverse ‘C’ shapes) soon after they lifted off from the Sun.

2. The now-merged storms, along with their high-speed particles (now in the shape of a single reverse ‘C’) hit the Earth. The large jump in GOES data (bottom panel) corresponds to the same charged particles that triggered the May 10–11 aurorae.

3. The remnant of the storm (now spread out into a large reverse ‘C’ shape expanded to the extreme edge of the storm tracker model) approaches the Psyche spacecraft.

While the space-weather model does not quite reach the Psyche spacecraft’s location, it predicts that instead of a massive hit, the spacecraft would rather experience a glancing blow. The Psyche data show this is indeed the case. Whereas the Earth saw a two-order-of-magnitude (or greater) particle enhancement, at the Psyche spacecraft we only saw a moderate increase in count rates that correspond to the charged particles hitting our detectors. Thus, the Psyche space-weather station confirmed the predictions reported in the solar “storm tracker” model.

The Psyche spacecraft still has five years in space before it reaches its ultimate destination, the metal-rich asteroid Psyche. Throughout this journey to the asteroid belt, our spacecraft will continue to travel through isolated regions of space not occupied by other spacecraft. Along the way, it will make observations of space weather that we hope may contribute to improved space-weather predictions. If so, the Psyche mission can expand its long list of accomplishments to include being an interplanetary meteorologist.