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The central problem to be addressed is the threat of interference posed by the inherent vulnerability of all space assets. Protecting them against the natural hazards of the environment is difficult enough. Providing physically assured protection against deliberate assault is unfeasibly expensive and, thus, for practical purposes all but impossible. Because the capacity to do damage is conferred by the capacity to launch any object or to project any significant energy source to orbital altitude, protective rules cannot preclude destructive potential in space while also allowing legitimate use. Any space asset could be used as a weapon against others within reach of its maneuvering or illuminating capability. Therefore, practical protective rules would have to focus more on behavior than on capability. Most of the proposals that have been advanced for additional regulation of military space activities feature a prohibition on deliberate acts of interference and on dedicated preparations to undertake them. Some realization of that idea would undoubtedly be a basic objective of any formal negotiation.

The principle of prohibiting acts of interference in space can be expected to command widespread but not uncontested adherence. The history of accommodation between the original Cold War protagonists and the more recent infusion of space services into daily activities throughout the world have set a presumption that space is a venue for common use rather than antagonistic competition—more like a network of highways than a battleground. The contrary assertion by space warfare advocates that conflicts of national interest will inevitably dominate is not supported by the historical record and is not the prevailing public impression. Nonetheless, a candidate agreement prohibiting acts of interference in space and the testing and deployment of the means to undertake them would face demanding burdens of defining both the acts and means in question, of setting restrictions that would provide meaningful protection, and of demonstrating how compliance is to be determined.

A ban on interference would begin with a prohibition on any further tests or operational deployment of dedicated anti-satellite systems. Additional protection against direct acts of interference would address proximity and illumination. An acceptable agreement would presumably have to set buffer zones around space assets and prohibit any incursion into the zones by controlled orbiting objects not specifically authorized; it would also have to set tolerably low thresholds for illumination of space assets by remote energy sources, and it would have to prohibit interference with the communications channels to and from satellites as the basic rule but would probably have to tolerate some degree of functional denial or disruption during wartime. Any legal exemptions for wartime interference with communications or imagery satellites should be of minimal duration and area of application, and their military value should be weighed against the increased difficulty of keeping the war limited once such attacks had occurred.²¹⁰

The working out of agreed details for these provisions would undoubtedly be contentious but is feasible in principle. Exclusion zones and illumination thresholds can be defined that would prevent interference if they are honored. Deliberate violation could be detected and responsibility attributed by the methods used to monitor space launches and to track orbiting objects. The same features of the environment that impose inherent vulnerability— predictable orbits, cost of maneuver, and exposure to observation—also complicate stealthy attack by kinetic or explosive means, and satellites could be equipped with sensors that would detect and report destructive illumination.²¹¹ The question is whether a regime of enforced transparency designed to prevent undetected or unattributed interference could overcome the legacy of secrecy originally imposed to hide the capacity for electromagnetic observation and electronic intercept. That is a matter of preference rather than technical feasibility, and the trade-offs involved are not severe under current circumstances. Concealing the exact capabilities of current satellites might be possible, but concealing their existence or basic purposes is not. If parties to an agreement prohibiting acts of interference wish to set a high standard for verifying compliance, they could do so without having to reveal much if anything not otherwise known. They would have to reveal, however, the existence and ownership of all satellites.

ENDNOTES

210. One reason attacks on military support satellites were avoided during the Cold War was the belief that U.S. and Soviet leaders could do a better job of keeping a crisis from spinning out of control and keeping a limited war from escalating to an all-out nuclear exchange if they had good information about what was happening and could easily communicate with each other and with their military commanders. Another reason is that many satellites that provide military support services for one country also provide important services for many other customers who might not be involved in the initial hostilities but who could be drawn in if interference with that satellite threatened their national interests.

211. A space-based ASAT could be secretly attached to its target (a parasitic ASAT), it could trail close behind its target in the same orbit, it could be placed in a distant part of the same orbit, or it could be placed in a crossing orbit. Given current satellite sizes and launch detection and space surveillance capabilities, the United States might be able to hide a space-based ASAT, but whether any other country could do so with confidence is doubtful. Over time, the prospects for stealthy space-based ASAT attacks will depend on the progress of satellite miniaturization compared with the development and spread of launch monitoring and space surveillance capabilities. See Wright, Grego, and Gronlund, The Physics of Space Security, 151–154.