Why We Need to Avoid More Anti-Satellite Tests

India announced three weeks ago that it had joined an "elite club of space powers," having destroyed one of its own satellites with a hit-to-kill missile defense interceptor. With "Mission Shakti," India became the fourth country to intentionally destroy a satellite on orbit.

Only three other states—the Soviet Union, the United States, and China—have deliberately destroyed orbiting satellites. No state has destroyed another state's satellite. This extraordinary restraint is worth preserving and expanding.

While India's rationale for the test undoubtedly included pleasing domestic audiences and signaling military strength, India's decision to use its missile defense interceptor against a satellite rather than a missile has wider ranging implications. Because midcourse missile defense systems are intended to destroy long-range ballistic missile warheads, which travel at speeds and altitudes comparable to those of satellites, they also have inherent anti-satellite (ASAT) capabilities. This test again makes that inherent capability explicit. Indeed, China used a hit-to-kill interceptor to destroy the Fengyun-1C satellite in 2007, and thereafter tested the system against missile targets. The United States followed suit the next year by destroying the USA-193 satellite with an interceptor from the Aegis missile defense program.

 Related:  India's Anti-Satellite Missile Test Is a Big Deal. Here's Why. 

The Indian government characterized the Mission Shakti test as responsible because its target was at such a low altitude that all the debris would flush out "within weeks." However, the kinetic energy of hit-to-kill intercepts can kick debris pieces into new, higher orbits, which increases the debris lifetime and allows it to threaten other satellites. So far, around 50 pieces of trackable debris from Mission Shakti have been identified as reaching apogees at or above the International Space Station. These are certain to be accompanied by smaller debris that are not trackable but could still be deadly in a collision. On April 1, NASA Administrator Jim Bridenstine decried the test and stated that this kind of activity is "not compatible with the future of human spaceflight." Even "responsible" tests put other space users at risk.

The bigger concern, however, is that the use of destructive anti-satellite weapons in more typical orbits can create dangerous amounts of persistent space debris that can threaten the secure use of space for all users. Commercial and civil interests dominate even in low earth orbit, where eighty-five percent of satellites are nonmilitary.

Unlike at the low altitude of the Shakti test, destroying satellites at higher altitudes—which is likely if ASAT weapons are used in a military conflict—can create very large amounts of debris that persists for decades, or indefinitely. China's destruction of the Fengyun-1C satellite in 2007 created thousands of pieces of catalogued debris, most of which remains in orbit. The Fengyun-1C satellite was modestly sized, about 750 kilograms. The destruction of a large satellite, such as a 10-ton military reconnaissance satellite, could easily double the amount of dangerous debris in low earth orbit at altitudes that are heavily used.

For these reasons, space-faring countries have incentives not to test or use debris-creating weapons. But self-interest is not an effective long-term strategy to deal with a growing arsenal of ASAT-ready technologies against a backdrop of increasing strategic competition in space. How big is the problem? Even setting aside other means of interfering with satellites, and looking solely at missile defenses, it is clear this is a serious issue.

India's test highlighted what was already evident: that missile defenses can be effective anti-satellite weapons. In fact, while the technologies being developed for long-range missile defenses might not prove very effective against ballistic missiles, they could be far more effective against satellites. Missiles launch with little or no notice and may be accompanied by decoys and other countermeasures. Satellites travel in trackable, predictable orbits and an attacker could potentially attempt multiple intercepts if the first try fails.

The global inventory of missile defenses with the range to target satellites is significant and growing. Congress has approved adding 20 more interceptors to the existing 44 U.S. Ground-based Midcourse Defense System's fleet — these interceptors can reach any satellite in low earth orbit. Current U.S. plans call for hundreds of Aegis ship-based SM-3 Block 2 interceptors which can reach the vast majority of low-earth-orbiting satellites. China, Russia, India and Israel continue to develop their own hit-to-kill interceptors.

Testing, developing and stockpiling anti-satellite weapons without limits is problematic not only because of the potential for creating debris that would make space inhospitable and expensive to use, but because attacks on satellites can create or escalate terrestrial crises in potentially difficult to predict ways. For example, a space environment that is perceived as too dangerous and threatening may create an incentive to "use or lose" military capabilities enabled by space-based assets as a crisis approaches. And of course, as more states build and test these weapons, more states may decide to join the "elite" club.

We all would be better off with legal and normative constraints on conduct in space and on particularly dangerous technologies, including hit-to-kill missiles. This could augment stability in crises, avoid the drive to arms race, and provide guardrails to preserve the space environment. The international community has struggled to overcome ideological divisions meet this challenge. Under the European Union's proposed International Code of Conduct for Outer Space Activities — in which states resolved not to damage or destroy any satellite except for reasons of safety, self-defense or to avoid debris production — Mission Shakti would have clearly been identified as outside internationally agreed norms. However, this effort foundered in 2015. Moreover, the United Nations Conference on Disarmament has not been functional in 20 years, and the Russia- and China-sponsored Draft Treaty on Prevention of the Placement of Weapons in Outer Space has failed to establish widespread support. And just recently on March 29, the United Nations Group of Governmental Experts process tasked with looking at space arms control concluded without coming to consensus recommendations.

A lot has changed in the decade since China and the United States destroyed satellites. The commercial space sector has grown in size and scope, and the number of operational satellites in orbit has more than doubled. It's possible that Mission Shakti will serve as a wake-up call rather than another step in an avoidable process of weaponizing the space environment, particularly if it gets the attention of commercial space actors whose investments and visions will be at risk. Sensible, effective, verifiable norms and limits that provide for a more secure and sustainable future in space are possible given sufficient will.  

Laura Grego is a senior scientist in the Global Security Program at the Union of Concerned Scientists. She focuses her analysis and advocacy on the technology and security dimensions of ballistic missile defense and outer space security.

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