Have a look at the design of the Psyche spacecraft now being built by Space Systems Loral in Palo Alto. What’s intriguing here is the five-panel x-shaped design of the solar array, reconfigured from a four-panel array on either side of the spacecraft. The juiced up array offers this asteroid-bound spacecraft higher power capabilities for its solar electric propulsion system, helping to support the recently adjusted higher velocity requirements of its journey.


Image: This artist’s-concept illustration depicts the spacecraft of NASA’s Psyche mission near the mission’s target, the metal asteroid Psyche. The artwork was created in May 2017 to show the five-panel solar arrays planned for the spacecraft. Credit: NASA/JPL-Caltech/Arizona State Univ./Space Systems Loral/Peter Rubin.

For the Psyche mission has been re-thought, with the interesting result that arrival at the unusual metal asteroid will take place a full four years earlier than the original timeline.

“We challenged the mission design team to explore if an earlier launch date could provide a more efficient trajectory to the asteroid Psyche, and they came through in a big way,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. “This will enable us to fulfill our science objectives sooner and at a reduced cost.”

Expected to launch in 2023, the Psyche spacecraft will now launch in the summer of 2022, with arrival at Psyche, after a much faster journey, in 2026, four years ahead of the earlier schedule. The shortened travel time is all about trajectory, as Jim Green mentions above. The new plan calls for eliminating the Earth gravity assist, which dramatically shortens cruise time. The spacecraft also benefits from maintaining a greater distance from the Sun, reducing the need for heat protection. A Mars gravity assist is still planned for the mission in 2023.

A Discovery-class mission selected in 2017, the spacecraft is headed for one of the more exotic objects in the Solar System. The most massive M-type asteroid, 16 Psyche is thought to be made up of metallic iron and nickel, similar to the core of the Earth, rather than silicate rock or ice. About 200 kilometers in diameter, It is evidently the exposed core of a larger differentiated body that lost its rocky outer layers due to collisions in the distant past. The mission will study the asteroid’s geology, composition, magnetic field and mass distribution.

The Psyche team, led by Lindy Elkins-Tanton (Arizona State University) presented an overview of the mission at the 45th Lunar and Planetary Science Conference in 2014, seeing it as a journey back to the period of planetary accretion, when larger bodies had begun differentiating but were also being reshaped by collisions. And as the team points out, 16 Psyche gives us a way to see the interior of a rocky planet, the only way we can visit a metallic core. The team’s presentation included these key issues to address:

1. Is Psyche the stripped core of a differentiated planetesimal, or was it formed as an iron-rich body?

  • What were the building blocks of planets?
  • Did planetesimals that formed close to the Sun have very different bulk compositions?

2. If Psyche was stripped of its mantle, when and how did that occur?

3. If Psyche was once molten, did it solidify from the inside out, or the outside in?

4. Did Psyche produce a magnetic dynamo as it cooled?

5. What are the major alloying elements that coexist in the iron metal of the core?

6. What are the key characteristics of the geologic surface and global topography?

  • This is a new field: geology of metal objects.
  •  Does Psyche look radically different from known stony and icy bodies?

7. How do craters on a metal body differ from those in rock or ice?

Seeking answers to these questions, the spacecraft will have an instrument payload that includes magnetometers, multi-spectral imagers, and a gamma ray and neutron spectrometer.


Image: Deep within the terrestrial planets, including Earth, scientists infer the presence of metallic cores, but these lie unreachably far below the planets’ rocky mantles and crusts. Because we cannot see or measure Earth’s core directly, asteroid Psyche offers a unique window into the violent history of collisions and accretion that created the terrestrial planets. Credit: University of Arizona.

For more, see Elkins-Tanton et al., “Journey to a Metal World: Concept for a Discovery Mission to Psyche,” available here. This JPL news release is also helpful.