RPO Activities: How they can be both the cause of and solution to instability in space

Rendezvous and proximity operations (RPO) – uncoordinated close approaches of different countries’ satellites – are being regularly undertaken by Chinese, Russian, and U.S. satellites. Given the complicated relationships amongst these space superpowers, RPOs have the possibility of leading to conflict in orbit. Alternatively, they could be the spurring factor for countries to come to a loose agreement as to what responsible military operations in space are and how to communicate concerns about these activities moving forward. It is important to understand what RPOs are and why they could be perceived as threatening in order to best contextualize what is occurring in space at present. Only then is it possible to identify pathways for progress to ensure that space is stable and usable for all over the long-term.

WHY RPO ACTIVITIES HAVE THE POTENTIAL TO BE DESTABILIZING

Proximity operations are a series of orbital maneuvers executed to place and maintain a spacecraft in the vicinity of another space object on a relative planned path for a specific time duration to accomplish mission objectives. Rendezvous is a process whereby two space objects are intentionally brought close together through a series of orbital maneuvers at a planned time and place. Taken together, rendezvous and proximity operations (RPO) technologies enable a wide range of capabilities to support civil and commercial space activities, such as on- orbit inspections, repair, refueling, assembly, and life extension. RPO capabilities can also be used for military and intelligence space activities such as intelligence, surveillance, and offensive weapons such as co-orbital anti-satellites. 1 SWF’s Global Counterspace Threat Assessment looks at co-orbital counterspace capabilities for 12 countries and defines this category as systems “that are placed into orbit and then maneuver to approach the target to attack it by various means, including destructive and non-destructive.” 2 The concern with RPOs, particularly those undertaken by military satellites, is that the otherside does not know what the final intention is of the maneuvering satellite. It might be getting up close to a satellite to inspect it, to listen to what it is listening to, to listen to what it is broadcasting, to jam communications coming from it, to interfere with its optical sensors, to release objects at a low velocity, to release objects at a high velocity, to grab the satellite, or simply just to see if it can. Hence these types of RPO activities can have harmful effects on space security, as they have the potential for (inadvertent) escalation, given that many of the technologies involved and even the actions have the potential to be dual-purpose. The Lexicon for Outer Space Security, which SWF worked on with the United Nations Institute for Disarmament Research (UNIDIR), clarifies that dual-purpose can be understood as referring to space objects or activities “that are designed to fulfil a benign objective (such as debris removal or on-orbit servicing), but they could potentially be repurposed to harm other space objects.” 3 One of the other challenges in regards to RPOs is that they are not as easy to make hard and fast requirements about. In other domains, it is possible to delineate how close other actors can get to each other; however, due to orbital dynamics, that does not automatically translate into the space domain. For example, it often is not necessarily distance but the amount of delta V (the amount of energy needed to change a spacecraft’s direction) that is needed to conduct an RPO that is the deciding factor as to whether the RPO could be considered to be a possible threat. Additionally, different actors in space have different risk assessments in terms of how they view RPOs near their spacecraft; these can be shaped by the mission of their spacecraft, how quickly it could be replaced if something happened to it, how confident they are in their situational awareness, etc. As well, there are very few hard rules about what is and is not allowed in orbit regarding RPOs; article 9 of the Outer Space Treaty talks about acting with “due regard” to others but how that is interpreted is left up to individual actors. 4 Finally, with RPO activities, given how they could be co-orbital counterspace capabilities, the satellite operators’ intentions are key, but how can that be demonstrated?

CURRENT RPO BY THE UNITED STATES, RUSSIA, AND CHINA

Over the last forty years, the United States has developed significant capabilities for conducting RPO to support military and intelligence-related space activities. Since the end of the Cold War, the U.S. Air Force, NASA, and DARPA have all conducted tests and demonstrations of RPO technologies in low and geosynchronous Earth orbits (LEO and GEO), most likely done to develop, practice, and utilize RPO technologies for close surveillance and inspection of other space objects, as well as collecting signals intelligence. Some of these missions have been publicly acknowledged but most remain shrouded in secrecy, with a few completely unacknowledged publicly. Since 2014, Russia has conducted multiple missions of RPO also in LEO and GEO, most of which are related to military or intelligence operations. Most of these missions have been publicly acknowledged by the Russian government but few have detailed public information available. None of the programs are thought to involve co-orbital ASAT testing or deployment, but there are still suspicions surrounding several of these events. Most of these missions are suspected to be part of the Nivelir program aiming to strengthen intelligence operations and space situational awareness capabilities. Since 2008, China has conducted multiple tests of satellite technologies for RPO to support surveillance and inspection of other space objects in both LEO and GEO, and most of which are related to military or intelligence operations. While these missions have been publicly acknowledged by China, most have few public details and several remain shrouded in secrecy.

POSSIBLE PATHWAYS FORWARD

As a starting point, nations should discuss definitions of agreed behavior for military activities in space, in particular the interactions between their military satellites in space, akin to the discussions that led to the Incidents at Sea Agreement during the Cold War. As in the case of maritime operations, clarifying norms of behavior for noncooperative RPOs and, where possible, providing notifications of upcoming activities can help reduce the chances of misperceptions that could increase tensions or spark conflict. It would be helpful to have an understanding as what sorts of RPOs are deemed threatening. For example, US Space Force officials have repeatedly described RPOs conducted by a series of five Chinese satellites with each other over the course of 2024 as “dog-fighting in space.” 5 While this is not a technically accurate way to describe the actions of the Chinese satellites in question, it does demonstrate how these sorts of actions are viewed by the United States. Space situational awareness (SSA) plays an important role here as well. SSA, in this case defined as knowledge about the space environment and human space activities that enables both offensive and defense counterspace operations, can be a key factor in verifying actions in orbit and limiting how escalatory they are perceived. However, as pointed out in the August 2024 Report of the Group of Governmental Experts on further practical measures for the prevention of an arms race in outer space, verifying dual-use systems – which RPO technologies could be considered – can be “challenging due to their inherent characteristics and might involve monitoring their actual use rather than only assessing their characteristics, which may provide options for certain types of verification measures. Consideration could be given to characteristics and activities where there is greater risk.” 6 So in terms of RPOs, this might mean focusing on actions around militarily sensitive satellites in GEO, for example. There is also a need for being able to quickly communicate amongst actors when anomalous behavior is detected. The question is, how is anomalous behavior determined? This is where discussions about what is considered normal behavior would be helpful, as they can aid in identifying when there are actions that are outside the norm. In addition to these track two conversations, these sorts of dialogues can be reinforced at the multilateral level. The UN open-ended working group (OEWG) on the prevention of an arms race in outer space (PAROS) in all its aspects is starting year two of its four-year mandate to develop rules of responsible behavior and consider legally binding agreements to prevent an arms race in outer space and is also a good venue for tackling the complexity of space security. The most recent session in July 2025 resulted in an agreement to move forward with a two- track structure: one track considering possible legally binding obligations, the other considering voluntary measures such as norms, rules and principles of responsible behavior. 7 Looking ahead at the indicative timetable that was agreed upon at the July meeting, RPOs that could increase the risk of misunderstanding and miscalculation that are on the agenda to be discussed at the 3rd session of the OEWG (July 2026) and the 6th session (end of 2027). 8 RPOs are here to stay, but that does not mean that they have to be destabilizing. There are multiple opportunities for progress to be made on clarifying intent, understanding what is anomalous behavior, and improving communication between space actors. It is crucial that the international community prioritizes these issues so that space can be a predictable and stable domain for all.

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Footnotes

1. For information about specific military RPO activities by China, Russia, and the United States, please see SWF’s fact sheets available here: https://swfound.org/counterspace
2. Victoria Samson and Laetitia Cesari, Global Counterspace Capabilities: An Open Source Assessment, Secure World Foundation, April 2025, p. xii, https://www.swfound.org/publications-and-reports/2025-global-counterspace-capabilities-report
3. Almudena Azcárate Ortega and Victoria Samson, eds., A Lexicon for Outer Space Security, UNIDIR, Geneva, 2023, https://spacesecuritylexicon.org
4. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, January 27, 1967, 18 UST 2410, 610 UNTS 205, 6 ILM 386 (entered into force October 10, 1967), https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/outerspacetreaty.html
5. Chris Gordon, “China Practicing ‘Dogfighting in Space,’ US Space Force Says,” Air and Space Forces Magazine, March 18, 2025, https://www.airandspaceforces.com/china-practicing-dogfighting-space-force
6. Report of the Group of Governmental Experts on Further Practical Measures for the Prevention of an Arms Race in Outer Space, Group of Governmental Experts, Final Reports, August 23, 2024, GE-PAROS/2024/CRP.4, https://docs-library.unoda.org/Group_of_governmental_experts_on_further_practical_measures_for_the_prevention_of_an_arms_race_in_outer_space_-_(2023)/GE-PAROS-2024-CRP.4.pdf
7. Victoria Samson and Jessica West, “Space Security in Geneva: Between Constraint and Convergence,” CIGI, September 9, 2025, https://www.cigionline.org/articles/space-security-in-geneva-between-constraint-and-convergence
8. “Indicative Timetable 2025–2028,” Open-ended Working Group on the Prevention of an Arms Race in Outer Space in All Its Aspects, Second Session, Geneva, A/AC.297/2025/CRP.2/Rev.5, July 22, 2025, https://docs-library.unoda.org/Open-ended_Working_Group_on_Prevention_of_an_Arms_Race_in_Outer_Space_-_(2025)/A.AC_.297.2025.CRP_.2.Rev_.5.pdf