Cosmic rays observed in successful test of Fermilab's prototype X-ray detector

This past week, in an aerospace engineering lab at the University of Illinois Urbana-Champaign dark matter detection took a significant step forward. Fermilab scientist Juan Estrada brought his novel Skipper detector technology to run a thermal vacuum test interfaced to its future satellite bus. The test successfully demonstrated the crucial thermal control capabilities required for the detector operation at 170 degrees Kelvin, which is -153.67 Fahrenheit.

“This test not only validated our detector's ability to operate under flight-like conditions but also captured cosmic rays, demonstrating our readiness to move toward a milestone test using a faint X-ray source. Milestone tests such as the one performed today bring us closer to the detection of the ethereal signals of dark matter,” said Phoenix Merrick Alpine, who is one of Michael Lembeck’s Ph.D. students in the Department of Aerospace Engineering at Illinois.

Alpine is the lead systems engineer for the DarkNESS mission, which stands for Dark matter Nano-satellite Equipped with Skipper Sensors.  The work is part of a collaboration between Fermilab, a particle physics and accelerator laboratory near Batavia, and the Laboratory for Advanced Space Systems at Illinois, which is directed by Lembeck.

“We first presented our capabilities to Fermilab in 2019,” Lembeck said. “We showed them a mission concept for how DarkNESS could expose an x-ray sensor to the galactic center to look for dark matter particle decay signatures in the received x-rays.

“This week’s test marks the first integration of the detector with its thermal control system operating in the 6U CubeSat platform. A small, fist-sized cryocooler was able to chill the Skipper CCDs to their operational temperature. X-ray data successfully extracted from the detectors is the result of two years of Alpine’s dedicated effort on the project.”

What’s next for DarkNESS?

DarkNESS has recently entered the critical design phase, Alpine said.

“In partnership with Kongsberg NanoAvionics, the focus now shifts toward bringing the thermal control system to flight configuration. This thermal control system is a characteristic feature of the DarkNESS satellite, which is responsible for maintaining the detector's operational temperature in the space environment,” Alpine said.

Firefly’s DREAM 2.0 initiative recently selected the DarkNESS mission for a launch opportunity targeted for October 2025. DarkNESS will go into a near polar orbit where it will collect x-ray data emanating from Sagittarius A*, the black hole at the center of the Milky Way. The mission should remain in orbit for a year.