What should the United States do with its future space policy? Available options range from hastening to develop and deploy space weapons that could destroy ballistic missiles, other satellites, or ground targets, to banning the weaponization of space altogether through international treaty. This chapter takes a middle path, not in the interest of triangulation or compromise for its own sake, but because the extreme options would poorly serve American security interests. At some point, a clearer decision in favor of one end of the weaponization/arms control spectrum or the other could be appropriate. But in light of strategic and technological realities, this is not the time.

Space systems were a focus of arms control debate during the Cold War, and many would still like outer space, the last physical frontier of the human experience, to be a sanctuary from military competition.¹ These proponents favor binding, permanent, multilateral bans on space weaponry. Beyond their philosophical motivation, American opponents of the weaponization of space make a practical national-interest argument: as the world's principal space power today, the United States stands to lose the most from weaponization, since it could jeopardize the communications and reconnaissance systems on which the U.S. military and economy so disproportionately depend.² Opponents of weaponizing space also point to the world's growing economic dependence on space assets and to the risk of damaging those assets should weaponry be based in or used outside of the atmosphere.

Non-American opponents of weaponizing space also worry about a unilateralist America pursuing its own military advantage at the expense of other countries, most of which do not favor putting weapons in space. This dispute has much of its origins and motivation in the history of the ballistic missile defense debate, as well as in the antisatellite weapons debate of the 1980s. But it has taken on a new tone in what many view as an era of American unipolarity or hegemony. In recent years, China and Russia have been consistent in their opposition to the weaponization of space and in their desire for a treaty banning the testing, deployment, and use of weapons in space.³ So have a number of U.S. allies, including Canada, which proposed in 1998 that the United Nations (UN) convene a committee on outer space during its conference on disarmament in Geneva.⁴ The UN General Assembly passed resolutions for more than 20 straight years opposing the weaponization of space.

In contrast, developing more military applications for outer space is an important imperative for most American defense planners today. Much thinking about the so-called revolution in military affairs and transformation of defense emphasizes space capabilities. Ensuring American military dominance in the coming years—something proponents tend to see as critical for global stability as well as for unilateral advantage—will require the United States to remain well ahead of its potential adversaries technologically. For some defense futurists, the key requirement will be to control space, denying its effective use to U.S. adversaries while preserving the unfettered operation of American satellites that help make up a "reconnaissance-strike complex." Others favor an even more ambitious approach. Given that fixed bases on land and large assets such as ships are increasingly vulnerable to precision-strike weaponry and other enemy capabilities—or to the political opposition of allies such as Turkey, Saudi Arabia, and France, which have sometimes opposed use of their territories or airspace for military operations (as in the 2003 war in Iraq and in the 1986 U.S. bombing of Libya)—these advocates favor greater U.S. reliance on long-range strike systems, including platforms in space.⁵

Advocates of space weaponry also argue that, in effect, space is already weaponized, at least in subtle ways. Most medium- and long-range rockets capable of carrying nuclear weapons already constitute latent anti-satellite (ASAT) weapons. Likewise, rockets and space-launch vehicles could probably be used to launch small homing satellites equipped with explosives and capable of approaching and destroying another satellite. Such capabilities may not even require testing, or at least testing that is not easily detectable from Earth. Advocates of weaponization further note that the United States is willing to use weapons to deny other countries' wartime use of the atmosphere, the oceans, and land, raising the question of why space should be a sanctuary when these other realms are not. As Barry Watts put it, "Satellites may have owners and operators, but, in contrast to sailors, they do not have mothers."⁶

And of course, not all countries that publicly oppose putting weapons in space are true to their rhetoric in practice. The People's Republic of China (PRC) is the most notable example, with its early 2007 ASAT test destroying an old PRC weather satellite, increasing low Earth orbit space debris by 10 percent and shattering an effective moratorium on the testing of ASAT systems that was more than two decades old. In fairness to Beijing, it could be argued that it had a right to "catch up" with the United States— not only with the ASAT technology the Pentagon had developed in the 1970s and 1980s, but also with latent modern ASAT capabilities in the form of American ballistic missile defense systems. That said, it was China and only China that ended the effective international moratorium on actual testing of antisatellite systems, and it was the PRC that chose to take actions at blatant odds with its own official negotiating position in international talks over space weaponry. The point of this assessment is not to vilify China's behavior; in fact, in many ways, such a demonstration of capability is consistent with how a rising power historically would be expected to handle such a situation. Its behavior fits squarely within the trajectory that realists at least would predict. That is true even if it may have reflected poor coordination and communications within the PRC government (since the blow to China's international image may not be offset by the acquisition of useful new capabilities).⁷ But whatever one's views on that point, China's ASAT test would seem to reaffirm that the United States must fashion its military space policy based more on a hardheaded assessment of capabilities and potential capabilities than on ideological positions, be they of the pro–arms control or pro–space weaponization variety.

Specific military scenarios can bring these more abstract arguments into clearer focus. Consider just one possibility. If, in a future Taiwan Strait crisis, China could locate and target American aircraft carriers using satellite technology, the case for somehow countering those satellites through direct offensive action would be powerful. This decision might be made easier if China itself initiated the use of ASATs, perhaps against Taiwan, but it could be an option the United States would have to consider seriously even if China had not. If jamming or other means of temporary disruption could not be shown to reliably interrupt China's satellite activities, outright destruction would probably be seriously proposed. This scenario is investigated in greater detail below, not out of any conviction that the United States and China are headed for military rivalry or conflict, but out of the belief that such scenarios must concern American force planners as they think through the pros and cons of various policy options.

No space-based missile defense or antisatellite weapons (with the possible exception of an isolated experimental launcher or two) were deployed during the Cold War. That did not, however, reflect any decision to keep space forever free from weaponry. Nor do existing arms control treaties ban such weapons. Instead, they ban the deployment or use of nuclear weapons in outer space, prevent colonization of heavenly bodies for military purposes, and protect the rights of countries to use space to verify arms control accords and to conduct peaceful activities.⁸ In addition, in 2000, the United States and Russia agreed to notify each other of most space launches and ballistic missile tests in advance.⁹ Most other matters are still unresolved. And the concept of space as a sanctuary will be more difficult to defend or justify as the advanced targeting and communications capabilities of space systems are increasingly used to help deliver lethal ordnance on target.¹⁰

Some scholars do argue that the Strategic Arms Reduction, Interme-diate-Range Nuclear Forces, and Conventional Armed Forces in Europe treaties effectively ban the use of ASATs by one signatory of these treaties against any and all others, given the protection provided to satellite verification missions in the accords. But these treaties were signed before imaging satellites came into their own as targeting devices for tactical warfighting purposes, raising the legal and political question of whether a satellite originally protected for one generally nonprovocative and stabilizing purpose can be guaranteed protection when used in a more competitive fashion. Moreover, no one argues that these treaties ban the development, testing, production, or deployment of ASATs.¹¹ Nor do any involve China.

The United States currently conducts few space weapons activities, but that could change quickly. From time to time, a Pentagon official speaks of the need to be forward-leaning on the space weaponization issue, and periodically, the open press reports consideration of at least small amounts of research and development funding for dedicated antisatellite weapons. As best as one can tell from the outside, such programs do not appear to have much momentum as of now. Yet it is hard to be sure and very hard to predict the future.

In this light, should the United States agree to restraints on future military uses of outer space, in particular the weaponization of outer space? Any useful formal treaties would have to be multilateral in scope. It makes little sense to consider bilateral treaties because it is unclear what country should be the other party to a treaty. At this point, any space treaty worth the effort to negotiate would have to include as many other space-faring countries as possible, ranging from Russia and the European powers to China, India, and Japan. To be sure, that accords would be multilateral does not mean that they should be negotiated at the United Nations, where many space arms control discussions have occurred to date. There is a strong and perhaps ideological pro–arms control bias in the UN Conference on Disarmament, where these discussions have taken place. In addition, some countries may be using those fora to score political points against the United States rather than to genuinely pursue long-term accords for promoting international stability. The United Nations might ultimately be involved to bless any treaty, but it might be best to negotiate elsewhere.

On the other hand, should the United States accelerate any space weaponization programs? Here again, my conclusion is one of caution. Although opposed to most types of binding arms control (which would deprive the United States of options that may someday be necessary), I do not believe that the United States would benefit from exercising most of those options at present. Some additional capabilities, such as improved space situational awareness, make sense, as do more hardening for key satellites and more redundancy in communications and reconnaissance systems. But weapons, at present, do not make sense—with the exception of certain ballistic missile defense capabilities designed for a different purpose (even if they admittedly often have some inherent ASAT potential).

Before going into these issues in more detail, it is useful to provide clear strategic and military context to the discussion with a fuller examination of what a space-related military contingency could entail in the future. It is along these lines that a China scenario merits further study.

Scenario: Possible War Against China Over Taiwan

Given trends in military reconnaissance, information processing, and precision-strike technologies, large assets (such as aircraft carriers and land bases) on which the United States depends are likely to be increasingly vulnerable to attack in the years ahead. Land bases can to an extent be protected, hardened, and made more numerous and redundant, but ships are a different matter. How fast, and whether, China can exploit these trends remains unclear. But the trends are real nonetheless. As a recent example, China reportedly has tested an antiship cruise missile with a 155mile range—more than twice that originally expected by U.S. intelligence. And its space assets are surely growing in scope. Even if it does not have an extensive imaging satellite network in a decade or so, it may be able to orbit one or two reconnaissance satellites that could occasionally detect large ships near Taiwan. That might be good enough. If China could find major U.S. naval assets with satellites, it would only need to sneak a single airplane, ship, or submarine into the region east of Taiwan to have a good chance of sinking a ship.

Knowing the U.S. reluctance to risk casualties in combat, China might convince itself that its plausible ability to kill many hundreds or even thousands of U.S. military personnel in a single attack would deter the United States from entering the war in the first place. Such a perception by China might well be wrong (just as Argentina was wrong to think in 1982, in a somewhat analogous situation, that it could deter Britain from deciding to take back the Falkland Islands); but it could still be quite dangerous, given the resulting risks of deterrence failure and war.

China is certainly taking steps to improve its capabilities in space operations. According to a Pentagon assessment, "Exploitation of space and acquisition of related technologies remain high priorities in Beijing. China is placing major emphasis on improving space-based reconnaissance and surveillance. . . . China is cooperating with a number of countries, including Russia, Ukraine, Brazil, Great Britain, France, Germany, and Italy, in order to advance its objectives in space." China will also surely focus on trying to neutralize U.S. space assets in any future such conflict; no prudent military planner could do anything else, and the early 2007 ASAT test would seem to confirm this logic. According to the Pentagon, in language written before that 2007 test:

Publicly, China opposes the militarization of space, and seeks to prevent or slow the development of anti-satellite (ASAT) systems and space-based ballistic missile defenses. Privately, however, China's leaders probably view ASATs—and offensive counterspace systems, in general—as well as space-based missile defenses as inevitabilities. . . . Given China's current level of interest in laser technology, Beijing probably could develop a weapon that could destroy satellites in the future.¹²

Exactly how many U.S. satellites, and of what type, China might be able to damage or destroy is hard to predict. But it seems likely that low-altitude satellites as well as higher altitude commercial communications satellites would be vulnerable. Low-altitude imaging satellites are vulnerable to direct attack by nuclear-armed missiles, at a minimum, by high-energy lasers on the ground, and quite possibly by rapidly orbited or predeployed microsatellites as well. They are sufficiently hardened that they would have to be attacked one by one to ensure their rapid elimination. And they are sufficiently capable of transmitting signals through or around jamming that China probably could not stop their effective operation in that way. But they are few enough in number, and sufficiently valuable, that China might well find the means to go after each one.

For higher altitude military satellite constellations, including the global positioning system (GPS), military communications, and electronic intelligence systems, China's task would be much harder. Such constellations often have greater numbers of satellites than do low-altitude imagery systems. They are probably out of range of most plausible laser weapons, as well as ballistic missiles carrying nuclear weapons. They might, however, be reached by microsatellites deployed as hunter-killer weapons, particularly if those microsatellites had been predeployed (a few might be orbited quickly just before a war, but launch constraints could limit their number, since microsatellites headed to different orbits would probably require different boosters). They might also be reachable by an ASAT similar to what China tested in 2007, once placed on a larger rocket.¹³

Finally, high-altitude commercial communications satellites are quite likely to be vulnerable. Their transmissions to Earth might well be interrupted for a critical period of hours or days by jamming or a nuclear burst in the atmosphere. For example, disruption of ultra-high-frequency radio signals due to a nuclear burst can last for many hours over a ground area of hundreds or even thousands of kilometers per dimension. Unhardened satellites might be damaged by a large nuclear weapon at distances of 20,000 to 30,000 kilometers.They might even be vulnerable to laser blinding.

So it appears that China will remain quite far behind the United States in military capability, relatively rudimentary in its space capabilities and lacking in sophisticated electronic warfare techniques and similar means of disrupting command and communications. But it could hamper some satellite operations, and it could have an "asymmetric capability" to find, target, and attack U.S. Navy ships (not to mention commercial ships trying to survive the postulated blockade of Taiwan).

Some might argue that the above analysis overstates the potential role of satellites. For example, even if China would have a hard time getting aircraft close enough to track U.S. ships, given American air supremacy, it might have other means. For example, it may be able to use a sea-based acoustic network. Such a system most likely would be deployed on the seabed, as with the U.S. sound surveillance system (SOSUS) array. On that logic, China may have so many options and capabilities that it need not depend on any one type, such as space assets.

Or China may not be able to make good use of any improvements it can achieve in its satellite capabilities. To use a reconnaissance-strike complex to attack a U.S. carrier, one needs not only periodic localization of the carrier, but also real-time tracking and dissemination of that information to a missile that is capable of reaching the carrier and defeating its defenses. The reconnaissance-strike complex must also be resilient in the face of enemy action. The PRC is not close to having such a capability either in its constituent parts or as part of an integrated real-time network.

But the case for concern in general, and for special concern about Chinese satellite capabilities in particular, is still rather strong. If China does improve its satellite capabilities for imaging and communications, the United States could be quite hard-pressed to defeat them without ASAT capabilities. Destroying ground stations could require deep inland strikes— and may not work if China builds mobile stations. The sheer size of the PRC also makes it difficult to jam downlinks; the United States cannot flood all of China continuously with high-energy radio waves. (Although the United States may be able to jam links to antiship cruise missiles already in flight, if it can detect them, it would be imprudent to count on this defense alone.) Jamming uplinks may be difficult as well if China anticipates the possibility and develops good encryption technology or a satellite mode of operations in which incoming signals are ignored for certain periods of time. Jamming any PRC radar-imaging satellites may work better, since such satellites must transmit and receive signals continuously to function. But that method would work only if China relied on radar, as opposed to optical, systems.

In regard to the argument that China could use SOSUS arrays or other such capabilities to target U.S. carriers, making satellites superfluous, it should be noted that the United States has potential means for countering any such efforts. To deploy a fixed sonar array in the vast waters east of Taiwan where U.S. ships would operate in wartime, China would need to pre-deploy sensors in a region many hundreds of kilometers on a lateral dimension at least. This could be technically quite difficult in such deep waters. Although the United States has laid sonar sensors in waters more than 10,000 feet deep, the procedure is usually carried out remotely from a ship or by a special submarine, and hence becomes more difficult as depth increases. In addition, the United States would have a very good chance of recognizing what China was doing. Even though peacetime protocols would prohibit preemptive attacks, the United States could be expected to know where many of China's underwater assets had been deployed, allowing attacks of one kind or another in wartime. The United States is devoting considerable assets to intelligence operations in the region already, for example, with its attack submarine force. It would similarly have a good chance of detecting and destroying Chinese airborne platforms, including even small unmanned aircraft systems, used for reconnaissance purposes.

On balance, growing Chinese satellite capabilities for targeting and communications could be an important ingredient in what Beijing might take (or mistake) for a war-winning capability in the future. China would not need to think it had matched the U.S. Armed Forces in most military categories, only that it had an asymmetric ability to pose greater risks to the United States than Washington might consider acceptable in the event of a future Taiwan Strait crisis.

China might also have the means to attack U.S. space assets, particularly lower-flying reconnaissance satellites, by 2010 (if it does not already). It is not entirely out of the question that China might use nuclear weapons to do so systematically, knowing that such a strike might greatly weaken U.S. military capabilities without killing many, if any, Americans. China attaches enough political importance to holding onto Taiwan that it might well prove quite willing to run some risk of escalation in order to do so—especially if its leaders thought they had deduced a clever way to escalate without inviting massive retaliation. Whether it could disrupt or destroy most satellites is unclear. Whether it could reach large numbers of GPS and communications assets in medium Earth orbit and geosynchronous orbit is doubtful. But for these and other reasons, it is also doubtful that the United States could operate its space assets with impunity, or count on completely dominating military space operations, in such a scenario.

The United States is not in danger of falling behind China, Iran, or any other country in military capability in the coming years and decades, and its own capabilities will probably grow, in absolute terms, faster than those of any other country. But its relative position could still suffer in a number of military spheres, including space-related activities. Its satellites will be less dependable in conflict than they are today or have been in recent years. Other countries may also mimic the U.S. ability to use satellites and accompanying ground assets for targeting and real-time attack missions. The trends are not so unfavorable or so rapid as to require urgent remedial action. Indeed, the United States has military and political reasons to show restraint in most areas of space weaponry. But passive defensive measures should be expanded and some potential offensive capabilities investigated so as to retain the option of weaponizing them in the future, if necessary.

Arms Control and Weaponization Options

Proposals for space arms control may be grouped into three broad categories. First are outright prohibitions of indefinite duration and broad scope. Second are confidence-building measures, such as requirements for advance notification of space launches and keep-out zones around deployed satellites. Third are informal understandings, worked out in talks or more likely established through the unilateral but mutual actions of major powers.

Overall, space arms control should not be a top priority for the United States in the future, contrary to what many arms control traditionalists have concluded. Some specific accords of limited scope, such as a treaty banning collisions or explosions that would produce debris above a certain (low) altitude, and confidence-building measures such as keep-out zones near deployed satellites, do make sense. But the inability to verify compliance with more sweeping prohibitions, the inherent antisatellite capabilities of many missile defense systems, and the military need to counter efforts by other countries to use satellites to target American military assets all suggest that comprehensive accords banning the weaponization of space are both impractical and undesirable. That said, the United States should not want to hasten the weaponization of space and indeed should want to avoid such an eventuality. It benefits from its own military uses of space greatly and disproportionately at present. It should take unilateral action, such as by declaring that it has no dedicated antisatellite weapons programs, to help buttress the status quo as much as possible.

One type of arms control accord on activities in space would be quite comprehensive, calling for no testing, production, or deployment of ASATs of any kind, based in space or on the ground, at any time; no Earth-attack weapons stationed in space, ever; and formal, permanent treaties codifying these prohibitions. These provisions are in line with those in proposals made by the Chinese and Russian delegations to the UN Conference on Disarmament in Geneva. They also are supported by some traditional arms control proponents who argue that space should be a sanctuary from weaponization and that the Outer Space Treaty already strongly suggests as much.¹⁴

These provisions suffer from three main flaws. To begin, it is difficult to be sure that other countries' satellite payloads are not ASATs. This is especially true in regard to microsatellites, which are hard to track. Some have proposed inspections of all payloads going into orbit, but this would not prevent a "breakout," in which a country on the verge of war would simply refuse to continue to abide by the provisions. Since microsats can be tested for maneuverability without making them look like ASATs and are being so tested, it will be difficult to preclude this scenario. A similar problem arises with the idea of banning specific types of experimentation, such as outdoor experiments or flight testing.¹⁵ A laser can be tested for beam strength and pointing accuracy as a ballistic missile defense device without being identified as an ASAT. A microsat can be tested for maneuverability as a scientific probe, even if its real purpose is different, since maneuvering microsats capable of colliding with other satellites may have no visible features clearly revealing their intended purpose. Bans on outdoor testing of declared ASAT devices would do little to impede their development.

Second, more broadly, it is not possible to prevent certain types of weapons designed for ballistic missile defense from being used as ASATs. This is in essence a problem of verification. However, the issue is less of verification per se than of knowing the intent of the country building a given system—and ensuring that its intent never changes. The latter goals are unrealistic. Some systems designed for missile defense have inherent ASAT capabilities and will retain them, due to the laws of physics, regardless of what arms control prohibitions are developed, and countries possessing these systems will recognize their latent capabilities.¹⁶ For example, the American midcourse missile defense system and the airborne laser would both have inherent capabilities against low Earth orbit (LEO) satellites, if given good information on a satellite's location—easy to obtain—and perhaps some software modifications. The United States could declare for the time being that it will not link these missile defense systems to satellite networks or give them the necessary communications and software capabilities to accept such data. But such restraints, while currently worthwhile as informal, nonbinding measures, are difficult to verify and easy to reverse. Thus, no robust, long-term formal treaty regime should be based on them. Indeed, the problem goes beyond missile defense systems. Even the space shuttle, with its ability to maneuver and approach satellites in low Earth orbit, has inherent ASAT potential. So do any country's nuclear weapons deployed atop ballistic missiles. Explicit testing in ASAT modes can be prohibited, but any prohibition could have limited meaning.

Third, it is not clear that the United States will benefit militarily from an ASAT ban forever. The scenario of a war in the Taiwan Strait is a good example of how, someday, the United States could be put at serious risk by another country's satellites.¹⁷ That day is not near, and there are many other possible ways to deal with the worry in the near term besides developing destructive ASATs. But over time, a possible need for such a weapon cannot be ruled out.

There is a stronger argument for banning Earth-attack weapons based in space. Most such weapons would probably require considerable testing. That means that testing might well be verifiable (especially if testing via ballistic missile were also prohibited). Furthermore, prohibitions on such weapons will cost the United States little, since it will retain other possible recourses to delivering weapons quickly over long distances (as may other countries). So a ban may make sense. The most powerful counterargument to banning ground-attack weapons in space is that the long-term need for them cannot be easily assessed now. But physical realities do suggest that the United States will be able to make do without them or to find alternatives.

A number of specific prohibitions, fairly narrowly construed, are worth considering as well. They could be carefully tailored so as not to preclude development of various capabilities in the future, given the realities and security requirements noted. But they nevertheless could help to reassure other countries about U.S. intentions at a time of still-unsettled great power relations and help protect space against the creation of excessive debris or other hazards to safe use over the longer term. Measures could include the following:

• temporary prohibitions, possibly renewable, on the development, testing, and deployment of ASATs, Earth-attack weapons, or both
• bans on testing or deployment of ASATs above set altitudes in space
• bans on debris-producing ASATs
• no first use of ASATs and space weapons.

Compliance with temporary formal treaty prohibitions would be no more verifiable than permanent bans. But they could make sense when future strategic and technological circumstances cannot easily be predicted.

There are downsides to signing accords from which one might very well withdraw, of course. If and when the United States could no longer support the prohibitions involved, it would likely suffer in the court of international public opinion by its unwillingness to extend the accord, even if the accord was specifically designed to be nonpermanent. The experience of the United States in withdrawing from the Anti-Ballistic Missile Treaty suggests that the damage from such decisions can be limited. But that experience also suggests that it requires a great deal of effort to lay the diplomatic foundation for withdrawal, that bitterness about such a decision can persist thereafter, and that withdrawal from one treaty regimen— however outdated—might be used as a justification by other states to withdraw from more important and less outdated treaties that they find undesirable. On balance, accords of indefinite duration should not be entered into unless one expects to remain part of them indefinitely, so I tend to oppose most such accords.

Bans on testing or employing ASATs that produce debris make sense and could well be codified by binding international treaty. Destructive testing of weapons such as the Clinton administration's midcourse missile defense system or other hit-to-kill or explosive devices against objects in satellite orbital zones would not only increase the risks of an ASAT competition, it would also create debris in LEO regions that would remain in orbit indefinitely (that is, unless the testing occurred in what are effectively the higher parts of the Earth's atmosphere, where air resistance would ultimately bring down debris and where few if any satellites fly in any case). The U.S. military worries about this debris-producing effect of testing. To date, tests of the midcourse system have occurred at roughly 140 miles altitude, producing debris that deorbits within roughly 20 minutes, but future tests will be higher. A ceiling of 300 to 500 miles might be placed on such tests and a ban placed on using targets that are in orbit.

Another category of arms accords includes those that do not limit the weapons capabilities of states but instead seek to establish rules or guidelines for how states use their military assets. The goals would be to reduce tension, improve communications, and build safety mechanisms into how countries make military use of outer space. This arms control concept would build on some of the agreements that the nuclear superpowers signed to reduce the potential for unintentional nuclear confrontation during the Cold War, including the 1972 Incidents at Sea Agreement and agreements to set up communications hotlines.¹⁸ Here the stakes might not be so great, but they could still be great enough to justify some straightforward measures and rules of the road—as long as no great effort has to be expended to work out some commonly accepted practices.

One such idea is that of establishing keep-out zones around deployed satellites. There is no reason for a satellite to approach within a few tens of kilometers—or, in some orbits, within even hundreds of kilometers—of another satellite. Any close approach can thus be assumed to be hostile and ruled out as an acceptable action. States might consider formalizing this understanding of keep-out zones. The idea makes particularly good sense if there is a way to monitor compliance. Future American satellites are expected to have more sensors capable of surveying the environment around them, so this approach may work.¹⁹

What real strategic purpose would be served by such zones? Unless satellites were themselves given self-defense capabilities—making them difficult to distinguish from offensive ASATs—the zones could not be enforced. And any country wishing to develop a close-approach capability for the purpose of ultimately launching a large-scale ASAT surprise attack could develop that capability despite the existence of keep-out zones, by testing against its own space assets or even against empty points in space.

That said, the idea may still make sense, even though keep-out zones would not substantially limit military capabilities. First, creating such zones would add another step that any state planning an attack would have to address. ASATs could not easily be predeployed near other satellites without arousing suspicion (especially if the United States and other countries deployed satellites with sensors capable of monitoring their neighborhoods). Second, any state violating the keep-out zones would tend to tip off the targeted country about its likely intentions; conversely, respecting the zones would constitute a form of restraint that could calm nerves to some modest but perhaps worthwhile degree. And the United States has no need to place satellites near other countries' space assets in any case, so it would not be giving up anything to endorse such a rule of the road. On balance, this idea is a worthy one for a treaty regime, though not worth a great deal of top-level time to negotiate.

What of advance notice of space launches? Again, this type of accord, such as that reached between the United States and Russia during the Clinton administration, would not prevent a country from breaking out suddenly, nor would it place a meaningful constraint on capabilities. But as long as it was observed, countries would have additional reassurance that others were playing by the rules. They would also have time to prepare to observe the deployment of satellites from any launch, allowing slightly greater confidence that ASATs were not being deployed. As a peacetime rule of the road at least, it makes sense. Some have also suggested allowing international monitoring of space payloads prior to their launch.²⁰ This seems questionable, though, since satellites could be effective ASATs without carrying payloads that made that obvious.

On balance, several of these confidence-building measures are marginally useful. They will not prevent the United States from retaining its hedges against a future need for ASATs, whether in the form of dual-purpose ballistic missile defense programs or even dedicated antisatellite systems. They will not prevent China or another country from quietly building inherent ASAT capability either. But they will add an extra step or two that other countries choosing to weaponize space would need to deal with before threatening American interests.

A final category of measures would not involve arms control at all— in the formal sense of signed treaties and binding commitments—but rather unofficial and unilateral restraints. Such restraints would not force the United States to tie one hand behind its back and leave other countries free to develop space weapons; rather, by adopting the restraints and thereby setting a precedent and a tone, the United States would aim to encourage other countries to reciprocate. To the extent others did not show restraint, the policy could be reconsidered. This approach has several precedents in international affairs. For example, during the first Bush administration, the United States reduced the alert levels of some nuclear forces and took tactical nuclear weapons off naval vessels in part to encourage similar Soviet actions, which followed.²¹ This approach can work more quickly than formal arms control; it can also preserve flexibility should circumstances change. It is perhaps most useful when it is not absolutely critical that all countries immediately comply with a given set of rules or restraints. In other words, if the United States would have ample time to change its policy in the event that other countries failed to cooperate, without doing harm to its security interests in the interim, there is much to be said for this approach.

Since the United States is not presently building or deploying space weapons, informal restraint would presumably apply to research and development and testing activities. As one example, if a treaty to accomplish this goal could not be quickly negotiated, the United States could make a unilateral pledge not to create space debris through testing of any ASAT.²² The flexibility associated with such a pledge might permit it to go further and also pledge not to produce any ASAT that would ever create debris, given that even if the United States needs a future ASAT, it would have alternative technological options.

The United States might also consider making a clear statement that it has no dedicated ASAT programs and no intention of initiating development or deployment of any, if that is true. It could also declare that it will not test any systems, including high-powered lasers, microsatellites, and ballistic missile defenses, in an ASAT mode. The latter approach would have the greatest chance of eliciting verifiable reciprocation by other countries.

The downsides to such statements are that if and when U.S. policy requirements changed, the statements would have to be repudiated, raising alarms abroad and risking a greater diplomatic problem than would occur if the United States had never held itself to informal restraints. The advantages are that they might buy the United States some time, allowing it to play its part in stigmatizing space weapons it has no strategic interest in developing or seeing developed any time soon.

Conclusion

While I have spent considerable time on arms control options, it is worth concluding with an observation on which military measures do make some sense now (even as options are preserved for considering others in the future). First, improved American space surveillance is needed, largely to know what other countries are doing with their microsatellites. Second, individual American satellites would also benefit from local situational awareness so that Department of Defense officials will know if satellites are approached closely. Third, and most of all, the vulnerability of key U.S. satellites to a Rumsfeldian Space Pearl Harbor—admittedly a melodramatic and exaggerated image, but still a useful caution and reminder—should be mitigated. This requires hardening against electromagnetic pulse and shielding optical components against blinding lasers. Someday, it could require creating mechanisms to deal with excess heat from lasers with prolonged dwell times. It also argues strongly in favor of redundancy. That need not mean rapid-launch satellite replenishment capability. But it does argue for a portfolio of reconnaissance capabilities, including airbreathing capabilities.

Military space policy is and will remain complex, with judgments constantly required about which programs make strategic sense and serve American national security objectives. To be sure, that argument is frustrating for those who would prefer the analytical and rhetorical simplicity of the argument that space must remain man's last unmilitarized frontier or that space, like all other frontiers, will eventually be militarized, so we may as well get on with it first. But a balanced approach reflects reality and the complex web of interests that the United States needs to advance in the years ahead.

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