Skip to main content

NASA Selects the Arcus X-Ray Mission for Phase A Study

Cambridge, MA -

NASA has announced that the Arcus X-ray mission concept has been selected for a "Phase A" study as part of the $250 million Medium-Class Explorer (MIDEX) program.

Arcus is a high-resolution grating spectrometer mission that combines X-ray optics and gratings to disperse the X-rays, much like how a prism separates sunlight into the colors of the rainbow. This allows for detailed study of the hot gas that is the dominant component of the normal matter in the Universe, much of which has not yet been directly seen. Arcus will measure the mass and velocity of gas accelerated by the gravitational force of black holes, discovering how this material impacts its host galaxy or beyond. Arcus will also study how stars like our Sun form and evolve. Arcus will conduct research on a wide range of astrophysical phenomena – from the tiniest dust grains to the largest black holes in the largest galaxies in the Universe – in X-ray light.

The selection of Arcus by NASA for this next phase means NASA will provide $2 million to fund a 9-month detailed study of the mission requirements. At the end of this period, the 3 missions selected for Phase A studies will be reviewed and a single mission selected for flight.

The Principal Investigator for Arcus is Randall Smith of the Smithsonian Astrophysical Observatory in Cambridge, Mass. The project also includes many hardware partners from US and European institutions including NASA's Ames Research Center and Goddard Space Flight Center, the Massachusetts Institute of Technology, Penn State University, and the Max Planck Institute for Extraterrestrial Physics. Orbital ATK, industry partner for Arcus, will manufacture the spacecraft itself.

Smithsonian Astrophysical Observatory scientist Gary Melnick is a Co-Investigator on SPHEREX, led by CalTech, also selected for Phase A ( More information on this and other NASA selections can be found in this announcement:

More information about Arcus can be found at:

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

Megan Watzke
Harvard-Smithsonian Center for Astrophysics
+1 617-496-7998

Peter Edmonds
Harvard-Smithsonian Center for Astrophysics
+1 617-571-7279