Physical properties of orbital debris from spectroscopic observations

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.