Orbital Debris

Small (< 10 cm) orbital debris are human-made objects that primarily reside in LEO with speeds that are typically < 11 km/s. Similar to meteoroids, we are interested in characterizing the small orbital debris population in order to assess the threat to orbiting spacecraft through impact damage. Our first approach includes data analysis using the EISCAT radar, located in Svalbard. A representative sample of data is contained in the image below, where each streak denotes a single piece of debris. These data, collected immediately after the Chinese ASAT event in 2007, are analyzed in order to determine debris flux as a function of localized latitude, longitude, altitude, and time. Concurrently, we are beginning to develop models to correlate measured radar-cross-section (RCS) with debris shape and to predict the evolution of debris orbits. These results allow us to extrapolate to sizes that cannot be measured with ground-based radar. Our current efforts are focused on determining the directionality and size of debris caused by fragmentation and collision, which directly addresses understanding and mitigating the runaway debris effect known as the “Kessler syndrome.”

Orbital debris data collected with the EISCAT radar in Svalbard.

We will compare our results with those obtained by NASA and ESA models, which have been shown to both under-predict and over-predict the threat, depending on the spatial and temporal parameters of the debris. Additionally, these models contain errors that increase as size decreases due to the difficulty in detection and characterization. Our deliverable to the FAA through the Commercialization of Space Center will be a new predictive capability to determine, before launch, the threat of debris collision throughout a mission. An initial prediction tool will be available by mid-2013, with improvements made available through implementation of more complex model components in the following years. Launch vehicles will benefit from the prediction tool by, for example, using it to address whether a spent rocket stage will be at risk of being catastrophically impacted before deorbiting.