Consequence of Continued Growth in the GEO and GEO Disposal Orbital Regimes

To date more than 800 spacecraft, upper stages, and apogee kick motors are known to reside in geosynchronous and nearby orbits, including geosynchronous disposal orbits. An even larger number of debris greater than 10 em in diameter have been detected by U.S. and European groundbased sensors. Using projections of geosynchronous deployment characteristics and disposal rates, NASA and Kyushu University models of the geosynchronous and super-geosynchronous orbital regimes have examined the sensitivity of the long-term satellite population to various scenarios. Emphasis has been placed on the rate of collisions in the geosynchronous orbit and in the higher disposal orbits and on the significance of cross-regime contamination. The sensitivity of the long-term environment on low velocity (0-1 km/s) collision breakup model parameters and on the minimum height of disposal orbits has also been explored. Results are presented in terms of both satellite population and spatial density

Using NASA Standard Breakup Model to Describe Low-Velocity Impacts on Spacecraft

The applicability is examined of the hypervelocity collision model included in the NASA standard breakup model 2000 revision to low-velocity collisions possible in space, especially in the geosynchronous regime. The analytic method used in the standard breakup model is applied to experimental data from low-velocity impact experiments previously performed at Kyushu University at a velocity range less than 300 m/s. The projectiles and target specimens used were stainless steel balls and aluminum honeycomb sandwich panels with face sheets of carbon fiber reinforced plastic, respectively. It is concluded that the hypervelocity collision model in the standard breakup model can be applied to low-velocity collisions with some simple modifications

New Orbit Propagator to Be Used in Orbital Debris Evolutionary Models

An orbital environment debris evolutionary model for low Earth orbit has been developed at Kyushu University. A fast orbit propagator is essentially needed in such an evolutionary model because the number of space debris larger than 1 cm in low earth orbit is very large and it takes much time to compute long-term orbital changes of space debris. The effects of orbital perturbations are investigated for hundreds of years, and the rate of change in orbital elements were invented by earlier publications. New expressions of the rate of change in orbital elements are presented to account for gravitational forces of the Sun and Moon. This paper analyzes the long-term effects of orbital perturbations based on the new analytic models of third body forces and conventional analytical models of atmospheric drag, solar radiation pressure, and zonal harmonics. Some results are shown that can predict the changes of the orbit. The models shown in this paper will be useful for long-term calculation of the satellite orbits

Outcome of Recent Satellite Impact Experiments

This paper summarizes three satellite impact tests completed in early 2007 through collaboration between Kyushu University and the NASA Orbital Debris Program Office. The previous experiments completed in late 2005 aimed to compare low- and hyper-velocity impacts on identical target satellites, whereas the new tests used larger satellites as targets and aimed to investigate the effects of impact directions. Three identical micro satellites equipped with fully-functional electronic devices were prepared as targets. Their dimensions were 20 cm by 20 cm by 20 cm, and the mass of each was approximately 1.3 kilograms. Aluminum alloy solid spheres, with diameters of 3 cm and masses of 39 grams were prepared as projectiles. The impact velocity was approximately 1.7 km/s. The impact tests were carried out at the two-stage light gas gun facility at the Kyushu Institute of Technology. All three target satellites were completely fragmented, but there were noticeable differences among the three sets of fragments due to the different impact directions. More than 1000 fragments from each test were collected, measured, photographed, and documented with material descriptions. The analysis of the fragments is currently in progress. Preliminary results of the new data and comparisons with previous data will be included in the paper