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A number of optical instruments are involved in making systematic surveys of the geosynchronous Earth orbit (GEO) region. Because of the limited field of view of an optical instrument, it is impossible at any one time to observe objects in all orbit planes in the region. Therefore, the orbit distributions seen are biased relative to the true populations of orbits in space. Because the observations represent a statistical sample of the population, statistical variations must be accounted for. The full procedure to remove the biases is extremely difficult with the limited orbit data measured because objects in GEO can have a wide spectrum of possible orbits. The measurements themselves are often insufficient to distinguish whether the object is in an elliptical or circular orbit. However, by limiting the range of possible orbit types it is possible to simplify the problem and obtain reasonable orbit distribution estimates. These distributions can in turn be used to identify interesting groupings of objects that may be part of an unrecognized breakup event. This paper describes the methods used to remove observational biases, and presents estimates of orbit distributions of uncatalogued objects at GEO visible to the instruments. [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]

Currently, certain physical properties, such as material type and albedo, of orbital debris are assumed when used to determine the size of the objects. A study to ascertain whether or not the assumed values are valid has begun using reflectance spectroscopy as a means of determining the material type of the object. What appears to some as a squiggly line is actually the reflectance of sunlight from the object. By comparing the location, depth, and width of the absorption features on the squiggly lines, the material type of the debris object is identified. Once the material type is known, the albedo of the object can be determined. This paper discusses the results from observations of large rocket bodies and satellites in both lower and geosynchronous Earth orbits (LEO and GEO, respectively) taken at the air force maui optical and supercomputing (AMOS) site located in Maui, Hawaii. Using the 1.6-m telescope and a spectral range of 0.3–0.9 μm, differences between rocket bodies of different types and launch dates, as well as satellites of different types and launch dates are determined. Variations seen in the squiggle lines are due to colors of paint, space weathering, and for the satellites, orientation and size of the solar panels. Future direction of the project will be discussed as well as plans for future observations. [Copyright &y& Elsevier]