Space Radiation Environment Tests on HOEs

1. Space Radiation Environment Tests on HOEs Geary Schwemmer* NASA GSFC Work Supported by NASA and IPO *new affiliation: Science and Engineering Services, Inc. Columbia, MD

2. Radiation Environment • Electron (gamma) radiation • Proton radiation • Ultraviolet

3. Five-HOE ShADOE Samples 5.7 mm PPG Starphire glass 10 µm DCG hologram 10 µm Epoxy 5.7 mm PPG Starphire glass

4. Optical Tests Before & After Exposure • Diffraction efficiency at 355 nm • 0° incidence transmission at 355 nm and 2-µm wavelengths • 355 nm absorption 30° 30°

5. Gamma Tests

6. Gamma exposure effect on diffraction efficiency, preliminary results

7. Gamma exposure effect on transmission at 355 nm, preliminary results

8. Co 60 1.25 MeV gamma ray exposures 0 KRad 3 KRad 30 KRad 300 KRad

9. Spectral Transmission

10. 254 nm UV exposure @ 100 nW/cm^2 for 12 min = 3.15 J/cm2 equivalent to ~ 1 year in orbit

11. 355 nm transmission loss vs. 254 nm exposure

12. Conclusions & future tests • Moderate 355 nm absorption due to gamma radiation over NPOESS mission life: ~25% thru 11.4 mm of glass. • Little to no hologram fading due to 254 nm or gamma radiation exposure. • No degradation at 2-microns. • Thinner glass will decrease absorption. • Proton radiation & high intensity 355nm UV tests TBD