This is a prototype of the outer shell of the first imaging X-ray telescope mirror flown on a rocket. Designed and constructed by a group working under Riccardo Giacconi at American Science & Engineering, Inc., and under John C. Lindsay at the Goddard Space Flight Center, it was the basis for a flight model in 1965 that obtained an X-ray picture of the sun. Its paraboloid-hyperboloid design utilizes grazing incidence optics to reflect x-rays onto specially sensitized photographic film or electronic detectors. X-rays will normally pass right through a regular mirror, but they will glance off smooth surfaces if they strike at a shallow angle, beyond the "critical angle" of reflection. This system's sensitivity allowed for shorter exposure times and thicker filters and increased resolution over other forms of collimation.

Three identical telescopes based on this prototype were flown on an Aerobee sounding rocket from the White Sands Missile Range on March 17, 1965. A specially designed "pointing control" locked the telescopes onto the Sun to provide a stabilized image. The images obtained from that flight were compared with optical images to correlate regions of solar activity with X-ray emission.

The artifact was donated to NASM in August 2000 by Dr. Riccardo and Mirella Giacconi. (see A20000793001 for the core optical baffle system).