ABSORBED DOSE MEASUREMENTS ON LDEF AND COMPARISONS WITH PREDICTIONS

The radiation environment on LDEF was monitored by cumulative absorbed dose measurements made with TLDs at different locations and shielding depths: The TLDs were included in four experiments: A0015(a) Biostack , P0004 Seeds in Space and P0006 Linear Energy Transfer Spectrum Measu rements at the trailing edge (west side) of the satellite; M0004 Fiber Optics Data Link at the leading edge (east side); and A0015(b) Biosta ck at the Earth side. The shielding depths varied between 0.48 and 15. 4 g/cm(2), Al equivalent. Both the directional dependence of trapped p rotons incident on the satellite and the shielding thickness were refl ected in absorbed dose values. The trapped proton anisotropy was measu red by TLDs at the east and west sides of LDEF. At the east side doses ranged from 2.10 to 2.58 Gy under shielding of 2.90 to 1.37 g/cm(2) ( M0004) while on the west side doses ranged from 2.66 to 6.48 Gy under shielding of 15.4 to 0.48 g/cm(2) (P0006). The west side doses were mo le than a factor of two higher, where the vertical shielding thickness es to space were equal. Other west side doses of 3.04 to 4.49 Gy under shielding of 11.7 to 3.85 g/cm(2) (A0015(a)) and 2.91 to 6.64 Gy unde r shielding of 11.1 to 0.48 g/cm(2) (P0004) generally agreed with the P0006 results; The Earth side doses of 2.41 to 3.93 Gy under shielding of 10.0 to 1.66 g/cm(2) (A0015(b))were intermediate between the east side and west side doses. Calculations utilizing a model of trapped pr oton spectra were performed by Watts et al. (1993) and comparisons of dose measurement and calculations may be found in a companion paper (A rmstrong et al., 1996). Copyright (C) 1996 Elsevier Science Ltd