An International Environmental Agreement for space debris mitigation among asymmetric nations

We investigate how ideas from the International Environmental Agreement (IEA) literature can be applied to the problem of space debris mitigation. Space debris pollution is similar to other international environmental problems in that there is a potential for a ‘‘tragedy of the commons’’ effect: individual nations bear all the cost of their mitigation measures but share only a fraction of the benefit. As a consequence, nations have a tendency to underinvest in mitigation. Coalitions of nations, brought together by IEAs, have the potential to lessen the tragedy of the commons effect by pooling the costs and benefits of mitigation. This work brings together two recent modeling advances: (i) a game theoretic model for studying the potential gains from IEA cooperation between nations with asymmetric costs and benefits, (ii) an orbital debris model that gives the societal cost that specific actions, such as failing to deorbit an inactive spacecraft, have on the environment. We combine these two models with empirical launch-share data for a ‘‘proof of concept’’ of an IEA for a single mitigation measure—deorbiting spacecraft at the end of operational lifetime. Simulations of empirically derived and theoretical launch distributions among nations suggest the possibility that voluntary coalitions can provide significant deorbiting gains relative to nations acting in the absence of an IEA agreement. & 2010 Elsevier Ltd. All rights reserved. 1. Problem statement When actions of individuals affect a shared resource, there is potential for a tragedy of the commons consequence: individual decision-makers under-invest in protection if they see only a fraction of the benefits from the investment. Consequently, a stream of recent literature has sought to understand how nations can form coalitions to counter the potential for tragedy of the commons effects in protecting the environment. Game-theoretic models in the greenhouse gas (GHG), ozone depletion, and acid rain arenas have shown that when nations (1) recognize asymmetries of marginal costs and benefits of mitigation and (2) establish coalitions that adjust abatement rates through transfer payments, there can be a substantial increase in global levels of pollution abatement. The size of the increase is a function of the number of parties, the nature of the transfer scheme, and the size and nature of the asymmetries. (See, for example, [1–4].) Our initial focus applies the International Environmental Agreement (IEA) framework to one debris mitigation measure: post-mission deorbiting of spacecraft. We derive marginal benefits from the lifetime-risk metric provided by Bradley and Wein [5], marginal costs from deorbit cost estimates given by Wiedemann [6], and spacecraft ownership data from the Union of Concerned Scientists (UCS) database [7].