Space exploration has expanded dramatically in scope, actors, and applications. This growth has fueled innovation for humanity but also produced congestion, competition, and rising security concerns. As more States rely on satellites for national security and civilian needs, counterspace capabilities have evolved in parallel. Secure World Foundation declared co-orbital weapons as one of the counterspace capabilities in its Global Counterspace Threat Assessment (2026). It defines a co-orbital weapon as “weapons that are placed into orbit and then maneuver to approach the target to attack it by various means, including destructive and non-destructive.” 

Rendezvous and Proximity Operations (RPOs) technologies are inherently dual-use and come under the umbrella of co-orbital weapons. Rendezvous is the process of intentionally bringing two or more space objects into an orbit by orbital maneuvers such as “matching the plane altitude and phasing.” Proximity operations are a series of maneuvers a satellite does in the same or nearly the same orbit in the vicinity of another space object for a specific time duration to accomplish mission objectives. 

RPOs have civilian and commercial uses such as refueling, repairing, on-orbit inspection, and life extension. However, RPO technologies can come under counterspace capabilities, as the intention of maneuvering a satellite can be misinterpreted. States’ risk assessment plays a key role in perceiving an RPO satellite as a threat or not. Moreover, RPO satellites can perform functions such as surveillance, disruption, or decryption of signals, jamming communication, interference with optical sensors, grabbing a satellite, and releasing high- or low-velocity co-orbital kinetic anti-satellite weapons.  

RPOs are not a new phenomenon. However, States are increasingly building sophisticated RPO technologies amid today’s space competition. The U.S., Russia, and China have conducted multiple RPOs and exhibited their capabilities. The U.S. does not have any dedicated program for developing co-orbital counterspace weapons; however, it conducted multiple RPOs in both Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO). These activities included targeting, tracking, and hit-to-kill (HTK) intercept technologies that can be potential co-orbital anti-satellite capabilities. The U.S. conducted 5 RPOs in 2025 in GEO that maneuvered closely to their own satellites and Chinese satellites as well. Moreover, the Delta 180 mission was a showcase of offensive capabilities such as physical collision to destroy a satellite. 

Russia has actively invested in and performed various RPOs in recent decades in both LEO and GEO. Russia is building its anti-satellite (ASAT) capabilities out of the mothballs of the Cold War. Many satellites of the Cosmos series and Luch satellites were launched under RPOs for purposes such as co-orbit inspection, intelligence collection, and surveillance. Some of these satellites, such the Cosmos series, were co-planar with U.S. satellites. Such RPOs can result in supporting target identification and tracking, intercepting broadcasts, or jamming radio waves, thus hampering satellite communications. Russia did not explicitly test co-orbit hit-to-kill (HTK) weapons. However, it has assessed deployment of aerosol or cloud, and multiple subsatellites or payloads at low and high velocities. There are speculations that the Burevestnik program may have been launched by Russia to develop a co-orbital ASAT program. Russia can develop a co-orbital ASAT weapon by deploying a high-velocity payload. 

China is also a major actor in space. It has conducted various RPOs in both LEO and GEO. The first RPO by China was conducted in 2010 that involved SJ-12 and SJ-06F satellites. In 2025, China launched SJ-21 and SJ-12 02 for RPOs. The latter came within 60 km of the U.S. satellite USA336. The closest RPO was conducted by SJ-17, which had a robotic arm, which approached the target satellite within 1 km for detailed inspection. The potential military utility of Chinese RPOs is to demonstrate on-orbit space situational awareness (SSA), satellite servicing, inspection, and imaging capability. There is no publicly known evidence that China has tested any offensive co-orbital weapons to destroy any space object. 

RPOs of major powers tighten the security dilemma as States perceive others’ actions as offensive. There is a legal loophole in the Outer Space Treaty (OST) (1967) on RPOs. Some general clauses explain how a State should conduct an RPO, however, it is largely founded in the basic guidelines. For instance, Article XI of OST obligates States to inform the UN Secretary-General, the public, and the international scientific community. However, States only provide generic descriptions and avoid transparency. Similarly, Article IV (Registration Convention) requires States to register specific details, but they can register information that meets a general function to avoid revealing potential dual uses. Article XI (OST) suggests that States shall act with “due regard” to the other States’ interests. “Due regard” is vague, as inspecting and surveilling a satellite might not be considered as offensive as kinetic ASATs. There is no legal way to limit the extent of proximity between two satellites involved in RPO. Another problem that international space law cannot address is the intent of an RPO. States can undertake RPO for military purposes but publicly project it as peaceful uses. The absence of baseline norms increases the risk of misreading intent, which can prompt sudden escalation. 

 Conclusion 

Addressing RPO-related risks requires a multi-pronged approach centered on dialogue, transparency, and verification. States should begin by discussing agreed definitions of behavior for military space activities, as the phrase “peaceful exploration” is vague. A shared definition of threatening RPOs will help avoid any misinterpretation by any country. States shall make pre-notifications and avoid going into others’ “keep-out” zones, i.e., high-value GEO assets. A multilateral Space Situational Awareness mechanism would reduce the threat for States with weaker tracker systems. Defining an escalation framework for RPOs using clear vocab, for example, “likely benign,” “warrants inquiry,” and “imminent threatening, will avoid any offensive response based on perceived worst-case scenarios. Direct, fast-channel, bilateral crisis hotlines should be established to reduce miscalculation risk. 

Ultimately, RPOs are dual‑use technologies that can quickly be perceived as offensive. All major powers use them for inspection and imaging, yet proximity to another State’s satellites will always raise alarms. Without norms and transparency, RPOs risk triggering dangerous episodes in outer space. Major powers must prioritize stability and take concrete steps to prevent escalation and preserve peace in an increasingly contested domain. 

Areesha Manzoor is a Research Assistant at the Centre for International Strategic Studies, Islamabad, researching space politics. Her authorship includes articles and research papers on space politics. The views of the author are her own. 

Rendezvous and Proximity Operations in the Legal Grey Zone of International Space Law was originally published on Global Security Review.

The fundamental aim of Golden Dome is to protect the United States from air or space-based missiles armed with a variety of warheads: nuclear, chemical, biological, or conventional. Golden Dome will be made available to key allies should they deem it necessary for their own defenses in an increasingly complex global security environment. However, the level of interest these allies have in negotiating the terms of missile defenses from the U.S. remains to be seen.

While moving beyond the technical development of SDI, Golden Dome is not ushering a new age of missile defense strategy. A national missile defense policy has been in place since the 1990s following a hotly debated period in Congress where a “placebo defense” was finally deployed. The term “placebo defense” was coined by prolific political strategist Dr. William Van Cleave, who advocated for a layered concept of missile defense while he was a member of “Team B.” Team B was commissioned by the-then Director of Central Intelligence, President George H.W. Bush for the purpose of providing the government with alternative intelligence assessments and policy guidance regarding the Soviet strategic threat.

Dr. Van Cleave first used the term “placebo defense” in lectures at the Department of Defense & Strategic Studies at Missouri State University in 1996. While not officially defined in any academic paper, “placebo defense” describes the U.S. policy of deploying limited missile defenses incapable of defending against significant ballistic missile attack from either Russia or China. Rather, such limited missile defenses instead minimize the threat by rogue states like North Korea and Iran. The goal in part was to silence the critics who claim the U.S. must at least be able to defend itself from those rogue nations more likely to launch one or two missiles at U.S. forces overseas, or key coastal areas of the country.

The Team B concept of layered missile defense was supported by former SDI officials who advocated for a space-based laser (SBL) system to provide the most effective method of intercepting ballistic missiles. While this would be ideal for balancing technical feasibility and overall program cost, SBLs were not supported by Congress and follow-on administrations. Valuable research and development have since been neglected, making SBLs unlikely achievable anytime soon.

Golden Dome is now poised to move forward with some of the Team B concepts and additional strategists since the 1990s. To move Golden Dome forward rapidly, it is time to reconsider Brilliant Pebbles, which is also referred to as Future Space-Based Interceptors. Designed by Lawerence Livermore National Laboratory, Brilliant Pebbles envisioned placing small space-based interceptors (weighing around 10 kilograms) in Low Earth Orbit (LEO) capable of colliding with intercontinental ballistic missiles during the boost-phase of their trajectory. These interceptors would remain in orbit for only 18 months. Brilliant Pebbles was cancelled in 1993 due to a lack of political support in Congress despite some strategists arguing the technical feasibility of the program and its technical readiness for deployment in the near term.

Since the program’s end, the technical efficiency of small pump-fed engines and the impulse of solid axial engines, the areas of technological development that limited the concept in the late 1980s, have improved. It is now possible for an interceptor to reach 20g acceleration and cover a range of 800 km, well beyond the capabilities in the original project. Further mission analysis is still needed to determine the number of Brilliant Pebbles required to provide adequate missile defenses within the Golden Dome strategy. Furthermore, the cost to deploy Brilliant Pebbles using this concept will also be vastly reduced using current U.S. space launch capabilities provides by companies such as SpaceX and Blue Origin.

The ability of Golden Dome to effectively protect the U.S. from air and space missile threats fundamentally relies on selecting the most effective space-based missile defense system. Brilliant Pebbles is a system whose maturity can be advanced quickly and cost effectively to provide a boost-phase intercept capability. This could finally put to an end to the “placebo” missile defense system which leaves the U.S. insufficiently defended.

Dr. Matthew Mowthorpe is currently working at BAE Systems where he is responsible for space control. Views expressed are the author’s own. 

Brilliant Pebbles Can Provide a Real Space-Based Missile Defense for Golden Dome was originally published on Global Security Review.