Abstract :
In order to validate space debris environment models they have to be compared with measurement data. US radars and the German FGAN radar are used since some years to measure the debris environment in the centimetre size range. In 1999, two 24-hour beam-park experiments were performed at FGAN in the framework of the Inter-Agency Space Debris Coordination Committee (IADC). The observed detection rates can be evaluated to derive a confidence interval for the total number of objects in specified altitude bins which can be directly compared with the models. The difficulty consists in the fact that a radar does not have a uniform detection sensitivity within the radar beam. Thus, the concept of “average detection threshold” is described and used in this paper. For the FGAN TIRA system this average detection threshold is 1.6 cm for objects at 500 km range and 2.5 cm at 1100 km range. The analysis shows that the ESA MASTER (Meteoroid And Space debris Terrestrial Environment Reference) model, the DERA IDES (Integrated Debris Evolution Suite) model, the NASA/JSC EVOLVE model and the CNUCE Orbital Debris Reference Model (CODRM) are at the lower end or even below the measurement derived confidence intervals at most altitudes which means an underestimation of the current space debris environment.
