J.2.3 Model uncertainties

J.2.3.1. General

The meteoroid and space debris environment flux models given in 10 and Annex C contain several known approximations and other uncertainties.

J.2.3.2. Meteoroids

According to [RD.21] uncertainties in the meteoroid models mainly result from uncertainties in particle densities and masses. Fluxes for meteoroids larger than 10^-6 g are well defined, but the associated masses are quite uncertain. The mass density of meteoroids spans a wide range, from about 0,15 g cm^-3 to values as large as 8 g cm^-3. For meteoroids flux uncertainties at a given mass are estimated to be at least a factor of 0,33 to 3.

J.2.3.3. Space debris

The space debris flux models were developed as a best estimate rather than a conservative one. In [RD.89] the spatial density distributions as predicted by various space debris models are compared. Model predictions are not always consistent, in particular in terms of quantity and for lower debris sizes. Significant modelling related deviations can also occur between model versions_.

Fluxes of sub-mm size objects in orbits below 1 000 km have short lifetimes of weeks or months. Their population depends heavily on individual generation events and can vary by an order of magnitude.

Other uncertainties of debris models are the debris density and shape.

A more detailed discussion of model uncertainties is given in [RD.21] and [RD.90].

Considering all these factors, flux uncertainties for space debris at a given diameter are estimated to be on average at least a factor of 0,33 to 3 (as for meteoroids), and in certain size ranges even larger.