Goddard intern Billy Barrios performs an optical check on one of the NICER Optic’s mirrors. Image Credit: URC.
Student: Billy Barrios
California State University, Los Angeles
Major: Mechanical Engineering/Physics
Degree Level: Bachelor of Science
Internship Site: NASA Goddard Space Flight Center, Greenbelt, Maryland
Mentor: Dr. Keith C. Gendreau
Abstract: The Neutron Star Interior Composition ExploreR (NICER) will be a NASA Explorer Mission of Opportunity, dedicated to the study of neutron stars, the only places in the universe where all four fundamental forces of nature are simultaneously important. Answering the long-standing astrophysics question ÛÏHow big is a neutron star?,Û NICER will confront nuclear physics theory with unique observation constraints, exploring the exotic states of matter within neutron stars, and revealing their interior and surface compositions through rotation-resolved X-ray spectroscopy. NICER will feature 56 co-aligned X-ray concentrators and matching detectors with a 2,000 cm2 effective area. Each optic is roughly 6 inches in height and 4 inches in diameter, featuring 24 concentric aluminum foils which are individually coated with gold. The detectors which are located at the focal length of 1.085 meters behind the optics, each have a 2mm aperture. NICER will be the first X-Ray telescope utilizing mirrors in a ÛÏfull cylindricalÛ configuration, along with new manufacturing techniques on such a small scale. We began characterizing the effectiveness of the first assembled optics or engineering testing units (ETUs) by determining the point-spread function. The optics were placed inside a vacuum, where they received approximately parallel X-ray photons. The data is then picked up by the detector and analyzed with software. We find a 1.84 mm half-flux radius and a 3.49 mm 80% flux radius for the fully populated optic, and a 0.72 mm half-flux radius and a 1.64 mm 80 % flux radius for the sparsely populated optic. From these results we conclude that the optics are performing relatively well, and should meet design requirements with improvements in the manufacturing methods. (This project was co-authored by Billy Barrios, Steve Lentine, and Ceili Burdhimo).
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