REFLECTIVE COATING OF 834 ANGSTROM FOR IMAGING O+ IONS

Imaging upflowing O+ ions of ionospheric origin and plasmaspheric O+ c an be achieved through solar resonance scattering at 834 Angstrom. Unf ortunately, several strong background emissions, including the ones at 1025 and 1216 Angstrom due to geocoronal hydrogen atoms, pose serious problems. Most common optical coatings have higher reflectivity at 10 25 and 1216 Angstrom than at 834 Angstrom. After examining a number of options, we have designed a multiple-layer coating that selectively r eflects 834-Angstrom radiation and suppresses 1025- and 1216-Angstrom radiation The structure oi the coating material consists of a very thi n (50 to 150 Angstrom) metal (nickel) layer on top of a semitransparen t dielectric material (magnesium fluoride) over an aluminum substrate. Three such coatings were produced at NASA Goddard Space Flight Center using an existing coating facility that is not optimized for thin coa tings. in spite of such fabrication difficulties, we have obtained enc ouraging results.