Size-dependent space debris density distribution and implications for size to mass conversion

Over the past 15 years, modelling of the near-Earth space environment has become a prime tool in assessing satellite reliability and survivability. Using the available data sources on tracked space debris objects, a density distribution for orbital spacecraft and large fragments rho = 1.29 d-0-49 has been derived. Although this is somewhat different from previous models, the range of densities for individual objects of a given size is so large that the relationship is only of statistical significance. In addition, uncertainties in debris mass derived from observation are at least a factor of 4 and can be larger than 10. An assessment of the accuracy of sizes derived from observations and consequent errors in derived mass is made.