An assessment of CubeSat collision risk

In their 2011 paper, Oltrogge and Leveque encouraged the CubeSat community to take leadership roles in space debris assessment, ensuring that debris guidelines and standards are met and by implementing effective debris mitigation strategies. However, common misconceptions about the role of CubeSats in the evolution of the space debris environment remain today. For example, up to two-thirds of all CubeSats launched to-date are predicted to remain on-orbit for more than 25 years. In addition, CubeSats have contributed more than 360,000 unique events since November 2005 to the record of satellite conjunctions produced by Celestrak's Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES). To provide some clarity on this issue, a database of CubeSats containing their launch history and relevant physical parameters has been developed for use within the Debris Analysis and Monitoring Architecture to the Geosynchronous Environment (DAMAGE), which has been employed to assess the future collision risk from CubeSats. The probability and likely characteristics of conjunctions involving CubeSats have been estimated for a 30-year projection from 1 January 2013 of the low Earth orbit (LEO) population of objects ≥ 10 cm. Three CubeSat launch traffic scenarios were modelled using Gompertz logistic functions with maximum launch rates of 205, 560 and 700 CubeSats per year. These CubeSat launches were added to regular launch traffic, which was based on historical launches from the period 2005 to 2012. Further, calibration of DAMAGE conjunction predictions for the historical period 2005 to 2013 with those recorded by SOCRATES enabled the true number of conjunctions involving CubeSats to be estimated for the future projections. Results show that, even for a relatively low launch rate, CubeSats are anticipated to be involved in 16.5 to 165 million conjunctions in the next 30 years and, potentially, catastrophic collisions as early as 2014. Whilst CubeSats are relatively small, they are nevertheless involved in high-speed conjunctions with large, resident LEO spacecraft and debris in SOCRATES and DAMAGE predictions. To reduce the risks, some effort is needed to engage with the growing small satellite community, and to encourage them to contribute to and, ultimately, lead on sustainable practices and debris mitigation activities.