C.1.3 Earth shielding and flux enhancement from spacecraft motion

C.1.3.1. Earth Shielding

The Earth shielding factor, s_f, for a given surface depends on the spacecraft altitude above the Earth surface and on the relative orientation of the surface normal with respect to the Earth direction.

The average Earth shielding factor is given by:

(C-13)

with:

(C-14)

where

R_e is the Earth radius = 6 378 km;

h is the spacecraft altitude in km; 100 km accounts for the atmaosphere

The corrections for Earth shielding are taken from [RD.21]]

C.1.3.2. Flux enhancement from spacecraft motion

In addition to the Earth attraction and shielding, the spacecraft velocity causes the encountered flux to increase. The flux increase is given by v_rel/v where v is the (gravitational enhanced) meteoroid velocity and v_rel is the relative velocity of the meteoroid with respect to the spacecraft. When calculating fluxes using codes one generally considers each meteoroid velocity v_k bin separately. However, the outcome, which depends on the velocity distribution, is a single enhancement factor K.

The meteoroid flux to an Earth orbiting spacecraft is then given by:

(C-15)

Values of , s_f and K for typical Earth orbits are given in Table J-6.