On Thursday 3 October 2024, NASA announced the selection of two proposals for missions for further review to observe X-ray and far-infrared wavelengths of light from space, as part of its new Astrophysics Probe Explorers mission class.

Each proposal team will receive $5 million to conduct a 12-month mission concept study. After detailed evaluation of those studies, NASA expects to select one concept in 2026 to proceed with construction, for a launch in 2032.

The resulting mission will become the first in a new class of NASA astrophysics missions within the agency’s long-standing Explorers Program. The new Probe Explorers mission class was recommended by the 2020 Astrophysics Decadal Survey Report (Astro2020) to fill a gap between flagship and smaller-scale missions. Mission costs for the new Probe Explorers are capped at $1 billion each, not including the cost of the rocket, launch services, or any contributions.

NASA evaluated Probe Explorers proposals based on their scientific merit in alignment with the Astro2020 recommendations, feasibility of development plans, and use of technologies that could support the development of future large missions.

The two proposals selected for further study are:

• Advanced X-ray Imaging Satellite (AXIS) [Principal investigator: Christopher Reynolds, University of Maryland, College Park]: an X-ray imaging observatory with a large, flat field-of-view and high spatial resolution. AXIS would study the seeds of supermassive black holes; investigate the process of stellar feedback, which influences how galaxies evolve; and help determine the power sources of a variety of explosive phenomena in the cosmos. The observatory would build on the successes of previous X-ray observatories, capturing new capabilities for X-ray imaging and imaging spectroscopy.
• Probe far-Infrared Mission for Astrophysics (PRIMA) [Jason Glenn, NASA Goddard]: a 1.8-meter telescope studying far-infrared wavelengths, helping bridge the gap between existing infrared observatories, such as the James Webb Space Telescope, and radio telescopes. By studying radiant energy that only emerges in the far-infrared, the mission would address questions about the origins and growth of planets, supermassive black holes, stars, and cosmic dust.