Exposure of Restore-L camera optical elements to a simulated orbital radiation environment

This paper reports on the exposure of visible wavelength camera optical elements to a simulated orbital radiation environment in support of the Restore-L flight project at NASA’s Goddard Space Flight Center. Borosilicate glasses with various metal oxide dopants - S-LAL8, S-LAL18, N-SF1, and the polycarbonate material Makrolon GP were exposed to electrons and protons of varying energies. Low energy (E ≤ 10keV) charged particles were used primarily to assess degradation to the antireflective coatings of the optical elements. High energy (E ~ 1 MeV) charged particles were used to evaluate degradation to the bulk material. Elements of S-LAL18, N-SF1, LaK9G15, and Makrolon GP were exposed to a representative atomic oxygen rich environment. Elements of S-LAL8 and Makrolon GP were exposed to intense ultraviolet radiation. Pre- and post-exposure transmittance measurements were used to quantify the effects on the elements tested in the simulated environment over the 0.3 to 1.2 micron wavelength range. Our measurement results will be discussed in the context of their robustness to the orbital environment and the known chemical constituents of the materials tested.