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Abstract: The intentional break-up of the Fengyun-1C spacecraft on 11 January 2007 via a hypervelocity collision with a ballistic object created the most severe artificial debris cloud in Earth orbit since the beginning of space exploration. More than 2000 debris of the order of 10cm or greater in size have been identified by the US Space Surveillance Network. The majority of these debris reside in long-lived orbits. The NASA Orbital Debris Program Office has conducted a thorough examination of the nature of the Fengyun-1C debris cloud, using Space Surveillance Network (SSN) data for larger debris and special Haystack radar observations for smaller debris. These data have been compared with the NASA standard satellite break-up model for collisions, and the results are presented in this paper. The orbital longevity of the debris have also been evaluated for both small and large debris. The consequent long-term spatial density effects on the low Earth orbit regime and the potential effect of the debris cloud on the growth of the near-Earth satellite population have been addressed. [Copyright &y& Elsevier]

Abstract: This paper summarizes three micro-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 hypervelocity impacts on identical target micro-satellites, whereas the new tests used larger micro-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 20cm by 20cm by 20cm, and the mass of each was approximately 1.3kg. Aluminum alloy solid spheres, with a diameter of 3cm and a mass of 39g, were prepared as projectiles. The impact velocity was approximately 1.7km/s. The impact tests were carried out using the two-stage light gas gun at the Kyushu Institute of Technology. All target micro-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. Preliminary results of the new data and comparisons with the previous data will be presented in the paper. [Copyright &y& Elsevier]

Results will be presented from a new NASA optical survey of objects at geosynchronous orbit (GEO). The goal is to determine the total population of debris objects at GEO to as small a limiting size as possible. This survey uses the University of Michigan''s 0.6/0.9 m Schmidt telescope Michigan Orbital Debris Survey Telescope (MODEST). Located at Cerro Tololo Inter-American Observatory in Chile, the system is equipped with a scanning CCD with a field of view of 1.3° × 1.3°, and can detect objects smaller than 20 cm diameter at GEO. Each night the telescope scans a strip of sky 100° long × 1.3° high. Up to eight independent detections are made of each candidate GEO object in a 5 min time span, yielding measurements of brightness, position, and angular motion. Since February 2001, an extensive series of observations of the GEO regime has been carried out with this system, revealing a considerable population of objects smaller than 1 m in diameter. [Copyright &y& Elsevier]