In May 2013, the Pentagon suggested that a high altitude Chinese sub-orbital space launch—claimed to be a scientific mission by China—was in reality the first test of an anti-satellite (ASAT) interceptor that would reach all the way to geo-synchronous earth orbit. Previously, on January 11, 2007, China had successfully launched an ASAT missile against one of its own low earth orbit (LEO) weather satellites.
These and other Chinese actions have provoked strong concerns within the U.S. about China’s motivations. James R. Clapper, the U.S. Director of National Intelligence, for example, recently told a Senate hearing that: “Chinese and Russian military leaders understand the unique information advantages afforded by space systems and are developing capabilities to disrupt U.S. use of space in conflict. Chinese military writings highlight the need to interfere with, damage, and destroy reconnaissance, navigation, and communication satellites.”
While these concerns have some validity, all U.S. military satellites are not equally vulnerable to a Chinese ASAT attack. Furthermore, the benefits from an ASAT attack are limited and would not confer decisive military advantage in every plausible conflict.
Limits of the Possible
The substantial range of orbital altitude—1,000 kilometers to 36,000 kilometers—across which satellites operate from poses a challenge to China’s ability to attack U.S. military satellites. U.S. intelligence, surveillance and reconnaissance (ISR) satellite that operate at altitudes less than 1,000 kilometers are theoretically most vulnerable to an ASAT attack by China’s Intermediate Range Ballistic Missiles (IRBMs). Although the 2007 Chinese ASAT test demonstrated an intercept of this type, there is no publicly available data on the conditions under which the test occurred. How long was the target satellite tracked? Was it transmitting telemetry data providing its orbital location information? These conditions matter. If the U.S. slightly changed the parameters of a satellite’s orbit (for example, its inclination), will China still be able to track, target and intercept the satellite?
Unlike the U.S., China has a very limited satellite tracking capability, most of which are based in its territory and possibly a few ships. A first order technical analysis—assuming China cannot pre-determine a point of intercept—suggests it would be extremely difficult for China to successfully execute an ASAT operation without extensive tracking capability. This is due to the difference between the velocity of the target satellite and the ASAT missile. The satellite is traveling at approximately 7.5 km/s. In the approximately three minutes of boost available to the missile, the satellite travels a distance of 1,350 km. For a successful intercept, in the same three minutes the ASAT missile will have to travel up to the altitude of the satellite (say 800 km) and, at the same time, compensate for the 1,350 km the satellite traverses using its lateral acceleration forces.
Unlike ISR satellites, GPS and military communication satellites are completely invulnerable to China’s current missile arsenal. Even China’s most powerful missiles, its solid-fueled Inter-Continental Ballistic Missiles (ICBMs) would not be able to reach an altitude of 20,000 km where GPS satellites operate, much less the 36,000 km where U.S. military communications satellites operate. In order to reach higher orbit satellites, China would have to build new and more powerful ICBMs. Even if China manages to develop such an ICBM, it certainly will not be able to easily proliferate a large number of them without imposing substantial financial strain on itself. Alternatively, China can use its liquid-fueled space launch vehicles.
However, even if Chinese space launch vehicles could reach these higher orbits in time to intercept U.S. satellites, executing a number of these launches in quick succession is close to impossible. Its infrastructure limits such a venture. For example, China launched a total of eight annual space launches to orbits higher than LEO in 2012, nine in 2011, eight in 2010, two in 2009 (with one failure), and four in 2008. In the last five years the two quickest back-to-back launches to orbits higher than LEO occurred with a gap of 15 days. Finally, unlike the ICBMs which can be quickly fired, liquid-fueled space launch vehicles take time to fuel and these preparations are very visible. If the U.S. anticipates and observes China preparing for an ASAT attack, it could destroy the launch vehicles during the preparation stages.
Alternate Platforms and Redundancies
Furthermore, the presence of alternate platforms and built-in redundancies substantially limit the advantages that China can obtain from anti-satellite operation against the U.S. For example, in the case ISR satellites, the U.S. possesses an extensive array of airborne platforms that can duplicate and likely outperform many missions that are also performed by satellites. A few of these airborne platforms are: U-2, E-8C Joint Surveillance and Target Attack Radar System (JSTARS), RC-135 Rivet Joint, EP-3 (Aries II), E-3 Sentry and E-2C Hawkeye. In addition, America possesses a number of UAVs like the RQ-4 Global Hawk, MQ-1 Predator, MQ-SX, MQ-9 Reaper, MQ-1C Grey Eagle, MQ-5 Hunter, MQ-8 Firescout and RQ-7. All recent U.S. military operations have extensively employed these airborne ISR systems. In the 2003 Operation Iraqi Freedom, for example, coalition Air Forces employed 80 aircraft that flew nearly 1,000 ISR sorties during the initial weeks, collecting 42,000 battlefield images and more than 3,000 hours of full motion video. They also provided 2,400 hours of SIGINT coverage and 1,700 hours of moving target indicator data.
These airborne platforms also have standoff capability and should be able to operate safely outside of China’s inland air defense systems in a hypothetical conflict in the 180 kilometer long Taiwan Straits. All of these platforms will be used in a conflict in the Taiwan Straits, raising questions about the unique value of attacking U.S. ISR satellites. Why would China choose to focus on attacking ISR satellites when airborne platforms probably pose a much greater threat and would be easier to attack?
In the case of GPS satellites, the redundancy of the constellation limits what China can achieve. The GPS constellation consists of around 30 satellites in six orbital planes. This orbital arrangement guarantees that the navigation signal of at least four satellites can be received at any time all over the world. To meaningfully impact U.S. performance—for example, force U.S. ships to operate without access to accurate GPS navigation signals in the Taiwan Straits region—China would have to successfully attack and disable at least six GPS satellites. Even if six GPS satellites are destroyed in an elaborate ASAT operation, the degradation in navigation signals lasts only for a period of 95 minutes. What would China gain from 95 minutes of GPS degradation? U.S. ships and aircraft have accurate inertial navigation systems that would still permit them to operate in the region. As for the ability to use GPS-guided bombs, the U.S. could shift to laser-guided bombs. In fact, between Operations Enduring Freedom and Iraqi Freedom, DOD decreased the use of GPS-guided bombs by about 13 percent and increased the use of laser-guided bombs by about 10 percent.
Finally, in the case of communication satellites, a Chinese ASAT operation has its own problem: escalation control. The Naval Telecommunications System (NTS) that would be supporting the U.S. Navy in a conflict is very elaborate. It is comprised of three elements: (1) tactical communications among afloat units around a battle group, (2) long-haul communications between the shore-based forward Naval Communications Stations (NAVCOMSTAs) and forward-deployed afloat units, and (3) strategic communication connecting NAVCOMSTAs with National Command Authorities (NCA).
The first element consists of tactical communication between close formations (25-30 kilometers) using “line-of-sight” radio. For communication with picket ships and between formed groups (300-500 kilometers) “extended line-of-sight” radio are used. Satellites do not play a major role here.
In contrast, the third element, consisting of strategic communications, is largely dependent on satellites. Therefore, the component of NTS that China would be able to disrupt with its ASATs is strategic communications that would connect the NCA with the forward-deployed battle group. This poses a unique problem. Normally, China should prefer to disable the communication capabilities within the forward-deployed battle group and then negotiate with the NCA to have the battle group withdraw or stand down. However, it can only accomplish the opposite. By using ASATs, China would cut off the forward-deployed battle group from its NCA but not be able to significantly disable the battle group’s ability to execute its naval mission. China could hope that such an attack might force the battle group to stand down. However, it will also have to contend with the possibility that the battle group commander would act more rashly in the absence of direct guidance from the NCA, particularly if combat maneuvers have been initiated. Would China be willing to take such risk? Arguably, the risk might not be worth the potential escalation it might trigger.
The various arguments expounded above paint a nuanced picture on American vulnerabilities in space and China’s potential to exploit it. Just because the U.S. armed forces use satellites more than any other military does not make these satellites immediate and obvious targets. Convincing the Chinese of this might be the best way to dissuade their anti-satellite activities. There are a number of steps the U.S. can take to do that:
- The presence of alternate systems gives a large measure of operational security to U.S. forces—enabling them to operate in an environment with degraded satellite services. Such systems should be more effectively integrated into U.S. military operations.
- The U.S. should demonstrate its ability to use measures like satellite sensor shielding and collision avoidance maneuvers for satellites that would dilute an adversary’s ASAT potential.
- Monitoring mechanisms that provide long warning times and the ability to definitively identify an attacker in real time should be a priority. Examples of these include the ground based Rapid Attack, Identification, Detection, and Reporting System (RAIDRS), which is used to identify, characterize and geo-locate attacks against U.S. satellites, and the upcoming Geosynchronous Space Situational Awareness (SSA) that would provide a continuous monitoring of satellites.
These military-technical solutions might provide some relief, however, it is important to acknowledge and address legitimate Chinese concerns about U.S. weapons programs, including missile defenses in order dissuade China. Central to the threat of China’s ASAT is the incongruence Beijing perceives between the capabilities of U.S. and PLA forces. While it may not be politically possible to address all Chinese concerns, engaging and addressing some of them is a sensible way to build a stable and cooperative regime in space.
Such inducements will require more cooperative ventures that integrate China more deeply into the global space community. The U.S. could, for example, make available U.S. data on satellite traffic and collisions that would help China streamline its space operations. Such gestures will demonstrate a modicum of goodwill, which can encourage further cooperation. However, the U.S. has been more forthcoming and willing to ink data sharing arrangements with allies than with China. Although there may be security reasons behind this preference to engage primarily with allies, it is important to realize that China is the nation that needs to be most induced to contribute to the peaceful development of space operations. Any coherent plan to dissuade and deter China from employing an ASAT attack will also have to include bilateral discussions.
Discussions over possible space arms control will provide opportunities to convince China of important thresholds. For example, as Micah Zenko of the Council of Foreign Relations suggests, if China believes shooting down U.S. early-warning satellites would be de-escalatory and stabilizing in a naval encounter with the U.S., it should be told clearly that is not the case. U.S. military satellites that provide missile early-warning have a tactical utility but, more importantly, they also serve to maintain the stability of nuclear deterrence between the U.S. and China. China should be convinced that attacking these satellites will provoke swift reprisal attacks. Finally, engaging in negotiations over space security and demonstrating leadership with such measures will help characterize the U.S. as a responsible actor; and therefore render it with the authority to respond with force when an attack is made on its own or allied space assets.
Jaganath Sankaran is an Associate with the International Security Program/Project on Managing the Atom Project at the Belfer Center for Science and International Affairs at Harvard University’s Kennedy School of Government. He was previously a Stanton Nuclear Security Fellow at the RAND Corp. He wrote his doctoral dissertation on the topic of space security. A more detailed version of this op-ed will be published in a forthcoming article in the Strategic Studies Quarterly.