10.2.4           The meteoroid model

10.2.4.1          Meteoroid flux model

a.              The total average meteoroid flux (sporadic + stream average) given in terms of the integral flux Fmet,0 shall be used:

(10‑1)

where

Fmet,0           is the unshielded isotropic interplanetary flux at 1 AU distance from the Sun. It gives the number of particles with mass m or larger per m2 per year impacting a single-sided randomly­oriented flat plate.

and

F1(m) =      (2,2 ⨉ 103m0,306 + 15) -4,38;

F2(m) =      1,3 ⨉ 10-9 (m + 1011 m2 + 1027m4) -0,36;

F3(m) =      1,3 ⨉ 10-16 (m + 106 m2) -0,85;

with m in g

NOTE              The meteoroid flux model specified in 10.2.4.1 is taken from [RD.22].

10.2.4.2          Velocity distribution

a.              The meteoroid model given in 10.2.4.1 shall be used together with the normalised velocity distribution of meteoroids at 1 AU given in Table C-1 in Annex C.

10.2.4.3          Flux enhancement and altitude dependent velocity distribution

a.              The velocity distribution in Table C-1 shall be adjusted according to the procedure given in Annex C.1.2 to reflect its altitude dependence.

NOTE              The velocity correction which is used to increase the flux with decreasing distance from the Earth is used to adjust the velocity distribution which is then re-binned accordingly.

10.2.4.4          Earth attraction and shielding

a.              For Earth orbits, the unshielded flux Fmet,0 specified in 10.2.4.1 shall be modified as specified in Annex C.1.3 to account for the gravitational attraction (which enhances the meteoroid flux in the Earth proximity) and the geometrical shielding of the Earth (which reduces the flux).

b.              If applied near the Moon, Venus or Mars the corresponding attraction and shielding factors of Annex C.1.2 and C.1.3 shall be modified by exchanging the parameters for Earth by the corresponding ones for Moon, Venus and Mars.

10.2.4.5          Meteoroid streams fluxes

a.              For the calculation of meteoroid stream fluxes, the meteor stream parameters given in Table C-2 shall be used together with the flux calculation procedure given in Annex C.1.4.2 and C.1.4.3.

b.              For each meteoroid stream the specific particle velocity shall be considered.

c.               For meteoroid stream particles a mass density of 1,0 g cm-3 shall be used.

NOTE              This meteoroid stream model is also implemented in MASTER-2005